Nutritional Qualities of Range Forage Plants in Relation

flèâ^'/Te TECHNICAL BULLETIN NO. 943

^

DECEMBER 1947

Nutritional Qualities of Range Forage Plants in Relation to

Grazing With Beef Cattle on the Southern Plains

Experimental Range

By D. A. SAVAGE

Senior agronomist, Division of Forage Crops and Diseases

Bureau of Plant Industry, Soils, and Agricultural Engineering Agricultural Research Administration

and

V. G. HELLER Head, Department of Agricultural Chemistry Research

Oklahoma Agricultural Experiment Station

UNITED STATES bEPARTiafeNT OF A^HICULTURE, WASHINGTON, D. C.

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Technical Bulletin No. 943 • December 1947

Nutritional Qualities of Range Forage Plants in Relation to Grazing With Beef Cattle on the Southern Plains Experimental Range '

By D. A. SAVAGE, senior agronomist, Division of Forage Crops and Diseases Bureau of Plant Industry, Soils, and Agricultural Engineering, Agricultural Research Administration, and V. G. HELLER, head, Department of Agricultural Chemistry Research, Oklahoma Agricultural Eaêriment Station ""

CONTENTS

Page Summary _ _ 2 Purpose and scope of the investigation""!!" 5 Location of area and vegetation studied I.I 6

Climatic conditions... _ I.I g Soil types and composition 6 Native vegetation IIIIII 8

Experimental procedures . 11 Forage sampling 11 Blood sampling '_ n Analyses "IIH" 12

Analytical results of native range forage. IIIII 12 Minerals _ 12

Calcium content IIIIIIIIII 14 Phosphorus content I'.lllll 16 Phosphorus-calcium relationship - IIIIII" 19

Protein.. _._.__ 21 Warm-weather grasses -IIIIIII 21 Cool-weather grasses "IIIIII 25 Winter-annual grasses IIIIIII" 26 Palatable forbs II"" 26 Browse plants IIIIIII 27

Fat content 1 27

Page Analytical results of native range forage—Con-

tinued ^ Nitrogen-free extract 07 Crude fiber ^ Ash content ot Moisture content I" 31 Introduced grasses compared with'leading

native grasses 31 Carotene content " 35

Grazing results related to nutrientV'in ran¿¿

Trend in cattle gains äs'related to"fôrâëë composition... _ ^ ^6

Effect of cool-weather grasses on cattle gains mwmter 3g

E fleet of mineral supplements on cattie gains' 40 Minerals consumed by cattle " 42 Effect of mineral supplements on blood

plasma 43 Effect of cottonseed cake on cattie'gains' 45 Carotene in cattle blood and range forage 47

Literature cited ""' 40 Appendix... 52

p ONCÉETE information on the chemical composition of native V>i and introduced grasses and other range forage plants is urgently needed m the southern Great Plains to provide reliable indications of the nutritional quality of the plants, of their palatability and utilization by cattle, and of their effect on beef production. These quali-

n^l^^n^^^,^^!^'' publication February 1947. Based on cooperative investigations conducted by the Bureau of Plant Industry, Soils, and Agricultural Engineering and the Oldahoma Agricultural Experiment Station. The work coveii^ anäytica! and related phases of a comprehensive grazing investigation conductercoopera- tively by these agencies, the Bureau of Animal Industry, and the Soil Gonserva- «TnlT'^^ ""^ ^^^ ^°^^^^ ^^^^^' Department of Agriculture! and by other dgencies. .1^^^ writers gratefully acknowledge their indebtedness for advisory assistance in planning and conducting these investigations to W. H. Black, Bureau of Animal Industry, and M. A. Hein, O. S. Aamodt, and M. A. Bell, Bureau of Haut Industry, Soils, and Agricultural Engineering; for assistance in collecting forage

2 TECHNICAL BULLETIN 9 4 3, U. S. DEPT. OF AGRICULTURE

tative characters are more important than forage yields in evaluating plants for grazing purposes.

This information can serve as a guide in selecting species for the extensive revegetation work now in progress in the region and in developing sound management practices. Knowledge as to how much food the various plants contain at different seasons is extremely helpful in planning grazing operations to obtain maximum beef production consistent with sustained forage growth and in deciding upon the kind and quantity of extra feed required to supplement the native range. Increased meat production combined with recurring shortage of protein feeds, cereal grains, and mineral supplements creates an urgent need for information on the feeding value of pasture plants.

This bulletin, presenting the results (1) of analytical work as inter- preted in relation to plant palatability and use by beef cattle, (2) of blood analyses of the cattle, and (3) of special grazing and supplementary feeding tests having a bearing on the food value of the pasture plants, may be summarized as follows.

SUMMARY

The forage from 29 species of native and introduced grasses, forbs, and browse plants was collected on the United States Southern Plains Experimental Range at monthly or less frequent intervals during the 6-year period 1940-45 and analyzed to determine the more important chemical constituents, including crude protein, calcium, phosphorus, fat, nitrogen-free extract, crude fiber, ash, and moisture. Carotene determinations were added to the studies during the last 2 years of the period.

Factors other than the chemical composition considered included (1) the mineral and carotene content of the blood plasma of beef cattle receiving various mineral supplements on the experimental range, (2) the gain in weight of almost 500 head of yearling Hereford steers used annually in conducting comprehensive grazing and range management investigations on the range, (3) the relative quantities of different minerals consumed by the livestock, (4) the comparative quantities of each species of plant available to and eaten by the cattle, (5) the type of soil and its composition, and (6) the wide diversity of plants represented in the vegetational association.

During the 6-year period the climatic conditions prevailing on the experimental range were similar in nearly every respect to those occurring generally in drier parts of the southern Great Plains. The

and blood samples, to Cecü G. Armstrong and E. H. Mcllvain, Jr., Bureau of Plant Industry, Soils, and Agricultural Engineering; for assistance in collecting blood samples and making the palatabUity determinations, to J. R. Harlan, of the same Bureau; for seed and other assistance in conducting regrassing studies, to J. E. Smith, Soil Conservation Service ; for assistance in analyzing the forage and blood samples, to W. G. Gross, Frances Moyer, and other technicians, Oklahoma Agricultural Experiment Station; for help in making economic analyses of grazing results in 1945, to Peter Nelson, of the same station, and W F Lagrone and D. W. Blackburn, Bureau of Agricultural Economics; for assistance in grading and allotting cattle, to W. H. Black, Bureau of Animal Industry, Charles Gardner, R. L. Ross, and J. D. Edmonson, Oklahoma Extension Service, and John Nelson, Soil Conservation Service; for advice in interpreting data, to N. R. ElUs, Bureau of Animal Industry ; and to ranchers for supplying cattle, to appraisers on sales value of cattle in 1945, and to others for locating sources of cottonseed cake.

KUTRíTIONAL QUALITIES of^ RANGE FORAGE PLANTS 3

experimental area represents that type of land most subject to wind erosion and least suited to farming in the region and is typical of land most likely to remain in or to be restored to grass. The nutritional results are therefore considered to have direct application to the drier parts of the region and broad application to the area as a whole.

During each month nearly every species of range forage occurring on the experimental range contained calcium greatly in excess of the minimum requirement (0.23 percent of dry matter) for beef cattle. All grasses showed a calcium average 68 percent above this minimum, and all forbs (nongrassy herbaceous plants) and shrubs contained even more.

The 5-year average (spring of 1940 to spring of 1945) monthly phosphorus content of all grasses combined was in excess of the minimum needs of beef cattle (0.13 percent of dry matter) from April to October, inclusive, although a few species exhibited phosphorus deficiencies late in summer and early in fall. Nearly all warm-weather grasses, which include species most typical of vegetation in the southern Great Plains, were deficient in phosphorus while dormant from November to March.

Most of the palatable forbs contained more phosphorus in summer and less in winter than the grasses. The quantity of phosphorus in the forbs declined successively from early growth to maturity and dormancy—from spring to fall and througn the winter.

The calcium content of nearly all range forage species was more than double the phosphorus content, especially in winter when some of the plants showed phosphorus deficiency.

The monthly trend in average protein content of 14 native grasses was directly related to the monthly changes in phosphorus, ash, and moisture, and inversely correlated with the trend in fiber and nitrogen- free extract. The trend of protein in most range forage species was also directly related to successive changes in plant development, season of growth, and quantity and distribution of precipitation.

The average protein content of the cool-weather grasses exceeded that of the warm-weather species every month except July, although the cool-weather types are often dormant, dry, woody, and relatively unpalatable much of the summer.

Palatable forbs that are eaten to some extent by cattle when the plants are young usually contain more protein than the warm-weather grasses at that time. These forbs include bush morning-glory, sand pea, and horseweed.

Skunkbush (or skunkbrush) and sand sagebrush, which are browsed to a very limited extent by cattle late in winter, especially when other forage is lacking or wholly covered with snow, contain more protein at that time than the dormant summer grasses. The woody, resinous nature of these plants greatly reduces their palatability and makes them of little use for grazing purposes.

Fat is an excellent source of energy, but its content in the grasses was usually low and not greatly significant.

Jiitrogen-free extract, which represented the greatest proportion of the grasses (47.5), was higher in winter than in summer and showed variations during the year opposite to those recorded for protein, phosphorus, and fat.

Crude fiber represented about one-third of the average composition of the dry range grasses and varied inversely with the more valuable

4 TECHNICAL BULLETIN 943, U. S. DEPT. OF AGRICULTURE

chemical constituents in the forage. In general, the larger the quantity of fiber in the grasses, the lower their palatability and nutritional quality.

In the case of most range forage species, the ash content, containing the essential minerals and inert material, varied in a manner analogous to that recorded for protein, fat, and phosphorus—^the trend being inversely related to that of fiber.

Monthly trends in moisture content showed a fairly close and positive correlation with changes in the more valuable chemical constituents, indicating the close relation between succulence and food value of forage.

No introduced grass consistently superior to the principal native species of the southern Great Plains has thus far been discovered, although three introductions have shown promise—Caucasian bluestem, Turkestan bluestem (yellow beardgrass), and weeping lovegrass. These grasses exhibited about the same trend in content of the different chemical constituents during the 2-year period 1944-45 as the native grasses of the warm-weather class.

The carotene, or provitamin A, content of 10 species of grass was extremely high during the spring and decreased successively thereafter in a trend similar to that recorded for protein.

The comparatively high grazing value of native range forage in the southern Great Plains is indicated by average weight gains of yearling Hereford steers on the experimental range. These gains amounted to 304 pounds per head for the summer and 52 pounds for the winter. The cattle included in these averages received nothing but range forage and salt in summer and 256 pounds of protein concentrates per head in addition to the range forage and salt m winter. The monthly gains of yearling steers were fairly direct in their relation to changes in the quantity of protein, phosphorus, ash, and moisture in the forage. The rate of gain decreased from April to September.

Yearling steers fed a mineral mixture of steamed bonemeal and salt or steamed bonemeal, lime, and salt showed no advantage in summer or winter gains over similar steers receiving salt alone. These results indicate that no minerals other than salt are required to supplement the range forage in this area, especially when the forage supply is augmented with cottonseed cake in winter.

The phosphorus and calcium content of the blood plasma from the salt-fed cattle were equally as high as in the blood from cattle that received a mineral mixture. Throughout the year, the quantities of these elements in the blood were in excess of those needed by the steers.

Cattle having access to a considerable quantity of the cool-weather grasses in winter in addition to the dry-range forage, and others confined solely to a reseeded pasture of a cool-weather grass, made much more winter gain with less protein concentrates than comparable cattle grazed entirely on the dormant range.

During the last half of the 1945 summer-grazing season the feeding of cottonseed cake to yearling steers in sufficient quantity to overcome the protein deficiency in the range forage resulted in maintaining the gains at rates almost as high as those recorded on more nutritious grass during the first 3 months. The additional weight gains recorded for the cattle receiving the supplement and their greater finish and

NUTRITIONAL QUALITIES OF RANGE FORAGE PLANTS 5

higher market value left a substantial profit after defraying the cost of buying and feeding the concentrate. The increased gains resulting from feeding daily rations of 1 and 2 pounds of cottonseed cake to each steer late in summer were in approximate proportion to the quantity of supplement fed.

The trend in the content of carotene in the blood plasma ot yearling steers showed a direct but delayed relation to that contained in the forage. An increase in the carotene content of the forage, caused by the revival of growth in March, was reflected in an April increase of this constituent in the blood. Successive decreases in the quantity of this constituent in the forage from May to the following February were responsible for corresponding but delayed decreases in the blood carotene.

PURPOSE AND SCOPE OF THE INVESTIGATION

Some analytical work with range forage plants has been done by other investigators in the West, but very little within the confines of the region that includes western Kansas, western Oklahoma, eastern Colorado, northeastern New Mexico, and the Texas Panhandle. Val- uable contributions to the subject include the report by McMillen and Williams (<^^) ^ on two grasses for a 3-year period in the Oklahoma Panhandle and that by Fudge and Fraps {16) on a variety of grasses for a 3-year period in the southeastern part of the Texas Panhandle.

In this study the writers conducted experiments on palatability and grazing use by beef cattle under different systems and intensities of grazing to determine the nutritional qualities and relative grazing values of the various plants at different stages and seasons of growth. Other factors considered in evaluating the feeding quality of the vegetation included (1) the mineral and carotene content of the blood plasma of beef cattle receiving various mineral supplements on the range, (2) the gain in weight of the cattle, (3) the relative quantities of different minerals consumed by the livestock, (4) the comparative quantities of each species available to and eaten by the cattle, (5) the chemical composition and type of soil, and (6) the wide diversity of plant species represented in the vegetation. The plant collections and other range studies were made under the direction of the senior author and the chemical analyses under the supervision of the junior author.

The forage from 29 species of native and introduced grasses, forbs, and browse shrubs was collected on the experimental range during the 6-year period 1940-45 and analyzed completely to determine the more important chemical constituents. Nineteen of the more important species with an occasional month excepted, were analyzed each month during the 5-year period from April 1940 to April 1945. Seven of the principal native grasses were analyzed every month throughout the 6 years. Three introduced passes were added to the study in 1944 and compared with seven native grasses at monthly or bimonthly intervals during 1944 and 1945. Carotene, or provitamin A, determinations were added to the studies during this period. Other plants, most of which were available for grazing for only a limited period, were analyzed at less frequent intervals during the first 5 years.

' Italic numbers in parentheses refer to Literature Cited, p. 48.


LOCATION OF AREA AND VEGETATION STUDIED

The Southern Plains Experimental Range, a part of the United States Southern Great Plains Station, at Woodward, Okla., contains 4,315 acres of native range land and long-abandoned farm land of a highly variable but generally sandy texture. It is located near old Fort Supply in northwestern Oklahoma, at an altitude ranging from 1,975 to 2,300 feet above sea level and near longitude 99° 30' E. and lati- tude 36° 30' N. The native vegetation, soils, and climatic conditions are fairly typical of considerable areas of land in the drier part of the central and southern Great Plains.

The area represents that type of land most subject to wind erosion and least suited to farming. It is typical of land that is most likely to remain in grass or to be restored to grass. For these reasons the nutritional results reported here have direct application to much of the range lands that have never been farmed and to most of the farm land that is being returned to permanent pasture grasses in the drier parts of the region. In addition to these specific applications, many of the more fundamental j)rinciples resulting from this study are expected to have broad application to the region as a whole.

CLIMATIC CONDITIONS

Climatic conditions in the vicinity of the experimental range are similar to those prevailing generally in the southern Great Plains. The annual precipitation for the 73-year period 1873-1945 averages 23.08 inches, of which 71 percent occurs during the growing season, i. e., April to September, inclusive. The summer rains usually, but not always, occur in the form of sporadic, localized, torrential show- ers, frequently interspersed with high temperatures and occasionally with hot winds of high velocity. Drought periods occur nearly every year and infrequently persist for several seasons or years. The winters are usually mild, open, and fairly dry, with an occasional light shower or snowstorm and sharp ñuctuations in temperature. Severe blizzards are infrequent. Protracted cold rarely occurs, and the ground is seldom covered with snow for many days at a time. High winds often intensify the eifect of cold weather during the winter and early spring. Low humidity is common to the region.

The average annual precipitation for the 6-year period of these investigations, as determined from two locations on the experimental range, was only 1.37 inches below the 73-year average (table 1). The growing season of 1940 was the driest recorded in the locality since 1886. The next 5 years were characterized by annual precipitation that varied little from the average and by conditions generally favorable for range forage production.

SOIL TYPES AND COMPOSITION

Most of the soils of the experimental range are of a sandy nature, but nearly every regional type from Lincoln silty clay loam to Tivoli sand (dune phase) is represented on the area, according to a recon- naissance soil survey of the experimental range by K. L. KoUmorgen ^ in 1939 and a detailed soil survey of the same range by E. G. Fitz-

* Assistant soil conservationist, Soil Conservation Service,

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An informal report by Fitzpatrick shows that most of the soils on the experimental range and in the region generally are well supplied with minerals and other essential elements in available form. These soils were developed mainly from materials originally washed out from the Eocky Mountains and contain a wide variety of minerals that have not been leached below the depth of plant roots, except in some of the very sandy soils. The higher sagebrush-clad dunes are fairly low in content of available phosphorus but contain ample supplies of calcium and other minerals. Most of the heavier soils between the dunes are high in all minerals, including phosphorus.

Fitzpatrick states that most soils of the drier parts of the region are well supplied with available minerals. He adds, however, that the Miles series of loamy fine sand, which is characterized by a natural covering of shinnery oak {Quercus havardi Eydb.) and occurs in comparatively restricted areas along the cap rock in parts of Oklahoma, Texas, and New Mexico, is usually deficient in minerals. Since this soil type is not represented on the experimental range, the analytical results of range forage and the data from mineral feeding studies with range cattle are not likely to apply directly to the shinnery areas. Soils of the region that are developed from Permian Eed Beds or reddish shales and limestones may exhibit iodine deficiency. Such soils rarely occur on the experimental range, and symptoms of iodine deficiency are infrequent among human beings or livestock of the region.

NATIVE VEGETATION

Nearly all the principal grasses and other range forage plants of the Great Plains region are represented in the plant association on the experimental range and were included in the analytical studies. The sand-dune sage type of vegetation that characterizes the area consists mostly of gently rolling stabilized dunes frequently interspersed with areas of heavier soil and clad with highly variable quantities of sand sagebrush, grass, and other vegetation, according to Parker and Savage {36), Nearly everv square rod of land supports from one to a dozen or more plants of sand sagebrush, which gives the landscape a gray appearance.

Eepresented on the area are 51 species of grass and more than 216 species of forbs and shrubs. Most of the grasses are bunch types, which usually present a thin open stand associated with other species of vegetation. A dense short-grass turf predominates to the exclusion of brush only on small areas of heavy soil between the dunes. The density of brush and forbs usually increases and that of grass declines with successive increases in slope and depth of sand. The vegetation, therefore, constantly changes with topography throughout the area, but when considered as a whole is fairly uniform within different sets of pastures.

The 29 species of grasses, forbs, and shrubs included in these studies are listed, together with their common and scientific names, soil habi- tat, and customary period of growth, in table 2.

' Formerly soil scientist, Division of Soil Survey, Bureau of Plant Industry Soils, and Agricultural Engineering.

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EXPERIMENTAL PROCEDURES

FORAGE SAMPLING

The forage samples of grasses and forbs were obtained by hand clipping all of the surface growth above a 1-inch stubble. The shrub samples were limited to the 4-inch tips of the plant. In this manner the samples represented nearly all of the surface growth of herbaceous plants and the browse tips of woody species. Since the samples included more of the coarser basal portion of the grasses and forbs than is customarily grazed by livestock under proper management, the analytical data provide a conservative account of the food materials or- dinarily consumed. The samples were obtained from moderately grazed pastures and represented plants that had not been grazed or clipped during the current season but had been subjected to comparable grazing treatments in the past.

Each sample included sufficient plants to be fully representative of the species for the range as a whole. All samples were not collected on the same soil type because many of the species are restrictive in their soil requirements. This may account for some of the reported differences in the chemical composition of different species that undoubtedly reflects natural differences in the mineral content of the various soil habitats. Starting in April, when the young leaves of most grasses were 3 to 6 inches long and in optimum development to start grazing, every sample for a given year was limited to growth produced that year. Exceptions were samples of shrubs and cool-weather grasses, which frequently included some of the growth produced during the previous fall and winter. Most of the samples obtained from Janu- ary to March represented the winter-dormant growth of the previous year, except for collections of shrubs and cool-weather grasses, which often included some new growth produced during the sampling year.

Stage of plant development, average height of plant, and percentage of green material present in the forage were recorded in the field for every sample. Representative parts of the many plants obtained for each species collection were weighed on the range immediately after the material was collected. The samples to be analyzed for carotene were collected late in the afternoon, and representative portions of the bulk material from each species were put in airtight containers, weighed green, placed in cold storage overnight, and transported to Stillwater early the next morning, where they were analyzed immediately. The rest of these and all other samples were air-dried, the moisture calculated, and the material analyzed.

BLOOD SAMPLING

A study of the effect of mineral supplements on the mineral content of the blood plasma of yearling steers was conducted by periodical analyses in 1942 and 1943 and was expanded in 1944 to include monthly or bimonthly analyses for both minerals and carotene. The results of these studies and of similar analyses of the range forage provided data for comparisons of seasonal changes in the composition of the forage and blood with monthly trends in the gains of beef cattle through the year. In these comparisons the blood samples were obtained in the evening from 12- to 18-head lots of yearling steers receiving different


mineral supplements on the range, placed in airtight flasks containing anticoagulant material, stored in a refrigerator overnight, and transported to the laboratory the next morning.

ANALYSES

The green grasses, ground dry samples, and the blood from the cattle were analyzed by standard and accepted procedures that may be briefly described as follows : Proximate analyses of dry feed. Official and Tentative Methods of Analysis of the Association of Official Agri- cultural Chemists (1) ; carotene of the green plant. Wall and Kelley (^) ; carotene of the blood samples, Kimble (^J) ; calcium of the plasma, Clark and CoUip (9) ; and phosphorus, Youngburg and Youngburg (^), the colors being determined spectrophotometrically in the last three methods. The air-dry forage samples were ground through the fine screen of a Wiley mill and stored in sealed containers until analyzed for moisture, ash, crude protein, nitrogen-free extracts, fats, crude fiber, calcium, and phosphorus. Magnesium, lignin, cellu- lose, and hemicellulose were also determined for a part of the samples. The rest of the moisture left in the air-dried material was determined by oven-drying to permit an expression of moisture on both the field and dry basis.

ANALYTICAL RESULTS OF NATIVE RANGE FORAGE

The general chemical nature and carotene content of five classes of native range forage occurring on the experimental range are best indicated by a comparison of the various chemical constituents contained on an average in the forage (tables 10-19, in Appendix). Four- teen of the leading perennial grasses, when analyzed by months throughout the 5-year period, spring of 1940 to spring of 1945, showed the following average annual chemical content : Moisture, 37.7 percent ; nitrogen-free extract, 47.5 percent; crude fiber, 34.6 percent; crude protem, 7.7 percent ; ash, 7.6 percent ; fat, 2.6 percent ; calcium, 0.38 percent; and phosphorus, O.lf percent. The monthly averages presented in figure 1 show a fairly close correlation between the trends in moisture and those in protein, phosphorus, and ash, and an equally close correlation between changes in nitrogen-free extract and those in crude fiber. The more valuable constituents of the plants, i. e., the protein, calcium, and phosphorus, represent rather small proportions of the total composition. The nitrogen-free extract and crude fiber, which are the less valuable constituents in the plants, constitute 82.1 percent of the total dry matter.

MINERALS

Calcium and phosphorus are of first importance among the minerals needed for bone structure and development of beef cattle. They rank with common salt as basic essentials in livestock diet. These elements should be present in a well-balanced ration in the approximate proportion of 2 parts of calcium to 1 part of phosphorus. Mitchell and McClure {S4) and others report a preference for a somewhat narrower ratio, i. e., about 1.71 to 1. Most nutritionists agree that an oversupply of calcium in proportion to phosphorus, which often occurs in range


FAT

4- 4 ^ --PJfl^g^Ji^.gZrfii-Jîl'j^.L 1 APR. MAY JUNE JULY AUG. SEPT. OCT NOV. DEC. JAN. FEB. MAR.

FiGUKE 1.—Average monthly trend in chemical composition of 14 perennial grasses for a 5-year period, spring of 1940 to spring of 1945.

forage, may reduce the efficiency of the phosphorus by causing its loss through the feces. N. E. Ellis ^ reports informally that the proportion of these elements may vary from the ideal ratio if each element is present in sufficient quantity to meet livestock requirements. He stated, however, that an excess of calcium is objectionable when the quantity of phosphorus is deficient. This is verified by Guilbert and Kockford

•* Principal chemist, in charge of nutrition investigations, Bureau of Animal Industry.


(i<^), who report that a high quantity of calcium with low phosphorus is unfavorable to phosphorus utilization and intensifies deficiency. Mitchell and McClure {Slf.) also substantiated this conclusion by stat- ing that malnutrition may result from feeding rations containing dis- proportionate quantities of calcium and phosphorus.

Black, Tash, Jones, sCnd Kleberg (4) report that a phosphorus content of 0.13 percent and a calcium content of 0.23 of the dry matter of the vegetation consumed are generally accepted as the minimum quantities of these elements required by range cattle. This conclusion is confirmed by Watkins {Jf6) and many other investigators. Gastier and Moxon ^ state that forages containing less than 0.11 percent of phosphorus and less than 0.20 percent of calcium are deficient in these elements. The minimum requirements wêre recently set at slightly different levels by Guilbert, Gerlaugh, and Madsen {17). Deducting the 25-percent margin of safety from their figures, forage containing 90 percent dry matter must possess 0.16 percent of calcium and 0.14 percent of phosphorus for wintering 1,000-pound cows, 0.19 and 0.14, respectively, for nursing cows, 0.22 and 0.16 for wintering 500-pound weanling calves, 0.20 and 0.17 for the normal growth of 600-pound heifers and steers, and 0.15 and 0.14 for the normal growth of 800- pound heifers and steers.

CALCIUM CONTENT

It is obvious from the calcium data in table 10 (in the Appendix) that nearly every species of range forage occurring on the experimental range contains this element in quantities greatly in excess of the minimal requirements of beef cattle every month in the year. The only species that fell below the prescribed minimum of 0.23 percent calcium at any time in the year were little bluestem in December and January and sand bluestem and blue grama in January. The 5-year average annual calcium content of all grass was 68 percent higher than the minimum of 0.23 percent specified for beef cattle. The palatable forbs included in this study averaged three times as much calcium as the grasses. For nearly every month in the year, the quantity of calcium present in all grasses and forbs combined was double the minimum requirement. The browse tips of skunkbush and sand sagebrush are also excellent sources of calcium and contained this element in quantities greatly in excess of those present in grasses. This is not important, however, since cattle seldom eat the brush except late in winter or early in spring, unless the grass supplies are wholly consumed or covered with snow. Cattle occasionally browse on the new growth of skunkbush and to a more limited extent on that of sand sagebrush late in winter.

The leading grasses in terms of calcium content during the 5-year period, spring of 1940 to spring of 1945, were sand paspalum, purple sandgrass, blowout grass, Texas bluegrass, switchgrass, buffalo grass, and western wheatgrass. The dust and sand that cling to the pubescent leaves of four of these species may account in part for their high calcium content. The plants were shaken but not washed to remove the

^ GASTLEE, G. F., and MOXON, A. L. CALCIUM AND PHOSPHORUS CONTENT OF GRASSES AT DIFFERENT STAGES OF GROWTH. S. Dak. Agr. Expt. Sta. Mimeog. Pam. 2, 4 pp. 1944. [Processed.]


earthen particles before the analyses were made. These particles were not wholly removed from the samples, partly because of the difficulties involved in doing so and partly because the inert material constitutes a part of the mass eaten by cattle in the normal process of grazing.

The warm-weather grasses that remain dormant most of the winter possessed the most calcium during the summer, whereas the cool- weather grasses that are usually dormant during late summer contained the most calcium during the winter. The difference in seasonal quantity of this element, however, was not great in either case. Al- though most of the grasses possessed slightly more calcium during their active period of growth than when they were dormant, no sharp positive correlation was found between calcium content and stage of growth or time of the year (table 10, fig. 2). The analytical results, when studied by years or seasons, showed no correlation between the calcium

s .8 3 Ü -I < 7

\

yi/ WARM-WEATHER GRASSES ■■ COOL-WEATHER GRASSES — PALATABLE FORBS (WEEDS) ——

SAGEBRUSH AND SKUNKBUSH

\

APR. MAY JUNE JULY AUG. SEPT OGT NOV. DEC. JAN. FEB. MAR.

FiGUBE 2.—Average monthly trend in calcium content of 4 classes of range forage for a 5-year period, spring of 1940 to spring of 1945.

759473"—47- 3


content of the forage and seasonal or annual precipitation. This observation agrees with that of Black, Tash, Jones, and Kleberg (^), who found that changes in the calcium content of range forage in southern Texas was not related to the quantity of annual rainfall. Harper and Daniel,« however, reported that prairie hay produced in Oklahoma during a season of heavy rainfall was low in'calcium.

In contrast to the results with grasses, the calcium in forbs and shrubs on the experimental range was considerably influenced by stage of growth and time of the year. The calcium content usually increased as the plants developed and approached maturity. The yearly average calcium content of sand sagebrush was nearly three times greater than the annual average for all grasses. The average for skunkbush was more tjian twice that in the grass. These results agree with those reported by Watkins (i?) for browse plants in New Mexico. The superabundance of calcium in the forbs and shrubs lends no special significance to their value as grazing plants in this region where the grasses contain sufficient quantities of this element. The calcium superiority of the forbs and shrubs, however, might indicate their increased value as pasture plants in localities where a calcium deficiency is known to exist in the grass.

PHOSPHORUS CONTENT

Information regarding the phosphorus content of range forage is extremely important, because this element is often deficient in grasses and IS so limited in some parts of the world that faulty bone development and other forms of malnutrition are frequently'evident. Most investigators in the West consider the feeding of phosphorus supplements on the range as an axiomatic requirement in the proper nutrition and development of beef cattle.

All 20 species of range forage plants analyzed from the experimental range through the 5-year period showed a phosphorus content in April May, and June greatly in excess of the minimum requirement of 0.13 percent (table 11, p. 52). Similar results were recorded for the 7 native species that were analyzed in comparison with three introduced grasses through the fifth and sixth years of the study.

In nearly every instance the phosphorus content decreased gradually with the growth of the plants (fig. 3). The highest phosphorus content, nearly three times the minimum needed by beef cattle, was recorded m April when the plants were young, tender, and growing Nearly every plant showed a slight decrease in phosphorus in May and a further decrease m June, but all possessed during these months much more than the quantity needed for the proper development of beef cattle. The close correlation between phosphorus content and greenness or rapidity of growth in relation to rainfall corroborates the findings of McCreary (SO) in Wyoming. ^

Further reductions in content of phosphorus usually occurred as the plants approached maturity in midsummer, entered dormancy in fall and weathered during winter. Exceptions were noted among the

^ HARPER, H. J., and DANIEL, H. A. RAINFALL AFFECTS MINERALS IN HAY Okla Agr. News Serv., Mimeog. Rpt., 2 pp. 1934. [Processed.]


.02 APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC. JAN. FEB. MAR.

FIGURE 3.—Average monthly trend in phosphorus content of 4 classes of range forage for a 5-year period, spring of 1940 to spring of 1945.


warm-weather grasses when growth was occasionally revived by late summer rains and phosphorus increased. In contrast with some of the results reported for calcium, changes in the phosphorus content were directly and positively related to the occurrence and distribution of ramfall. The growth of revived plants always contained more phosphorus than the older, drier, or more dormant forage. Other exceptions to the tendency for phosphorus to decrease during the fall and winter included the cool-weather grasses that usually renew growth in the fall and continue active development of new leaves most of the winter.

A few of both the cool-weather and warm-weather grasses exhibited phosphorus deficiency late in summer and early in fall. However, the monthly averages for all warm-weather grasses combined or of all warm- and cool-weather grasses combined showed the content of phosphorus to be in excess of minimum needs from April to October inclusive. It seems obvious from the results presented in this report that no minerals other than common salt would be required to supplement the local range forage during these 7 months.

Nearly all the warm-weather grasses, which include species most typical of native vegetation in the southern Great Plains region, were deficient in phosphorus from November to March, inclusive. The phosphorus content declined as a result of weathering during the dormant winter period. An average minimum content of 0.07 percent was reached in January and February. It is evident from these data that stockmen who have nothing but these dormant warm-weather grasses available for winter grazing should feed a phosphorus supplement to range cattle or provide cottonseed cake or other feeds containing extra phosphorus.

In direct contrast to the summer grasses, the cool-weather grasses on the experimental range contained a superabundance of phosphorus every month from October to early July. Although these grasses occur sparingly, they are widely distributed over the experimental range and undoubtedly contribute green forage to the winter diet in sufficient quantities to compensate for deficiencies in phosphorus and provitamin A in the other vegetation. The data clearly indicate that cattle grazed on a pure stand of these cool-weather grasses would require no extra phosphorus, except possibly late in July and August. A pasture composed of a mixture of the two classes of grass, or separate pastures of each grazed in rotation when the respective grasses are in optimum condition for use, should wholly eliminate the necessity of feeding phosphorus supplements to beef cattle under conditions similar to those prevailing on the experimental range.

The leading grasses in average phosphorus content on a yearly basis and for the winter 6 months were the cool-weather grasses, Texas bluegrass, Canada wild-rye, and western wheatgrass, in the order listed. The outstanding warm-weather grasses during the dormant winter period were giant reedgrass, blowout grass, sand paspalum, sand lovegrass, sand dropseed, buffalo grass, and blue grama. Since all of these warm-weather grasses except sand lovegrass, buffalo grass, and blue grama are seriously lacking in palatability during the winter months, it is evident that the three exceptions constitute the most valuable dormant grasses for winter grazing.


Most investigators in the Great Plains region have long been im- pressed with the fact that the leading native grasses of the area are not only outstanding in food values during the summer but usually retain more of these values in the dormant condition than do the grasses of humid, subhumid, or mountainous regions. These general observations are attested by the fact that sand lovegrass and buffalo grass lose only about 50 percent of their summer phosphorus content during the winter; sand dropseed, 55; switchgrass and blue grama, about 60 ; and the bluestems, about 62.

Most of the palatable f orbs analyzed in connection with these studies contained more phosphorus during the growing season and less during the winter months than did the grasses. The trend in phosphorus content of these nongrassy herbaceous plants was closely analogous to that in the warm-weather grasses. The quantity of phosphorus declined successively from early growth to maturity and dormancy. These forbs were much more palatable to beef cattle when the plants were young and tender and high in food value.

The phosphorus content of skunkbush and sand sagebrush rarely fell below the minimum stipulated for beef cattle. This element in the shrubs equaled or slightly exceeded that in most grasses during the summer 6 months and was much higher than the quantity contained in most dormant grasses during the winter months. In respect to the yearly average phosphorus content, sand sagebrush exceeded the average for all grasses by a margin of 24.6 percent; skunkbush, to the extent of 6.0 percent. Although the quantity of these shrubs grazed by beef cattle during the winter is comparatively small, it undoubtedly assists in overcoming phosphorus deficiencies in some of the grasses.

PHOSPHORUS-CALCIUM RELATIONSHIP

The relative quantities of phosphorus and calcium in the forage for 14 perennial grasses during four seasons of the year are compared with the averages for three other classes of vegetation (fig. 4). The results show that none of the species were deficient in calcium at any time and that none fell below the average phosphorus content during the summer, although many of the leading species had less than the minimum requirement during the winter. Of special significance is the consistency with which the calcium content of all species much more than doubled the phosphorus content, especially when there was a deficiency of the latter element. Under these conditions it would be useless and probably a serious mistake to feed calcium or mineral supplements containing much calcium to beef cattle consuming the forage. To do so would add to the abundance of calcium already present in the forage and tend to reduce the efficiency of the phosphorus present in the grass or added through the use of cottonseed cake as a supplement. These observations are verified from the following report by Knox and Watkins {28), of New Mexico :

Mineral substances such as limestone and oystershell should not be used on the range, for they provide only calcium and are entirely lacking in phosphorus, for which there is a much greater need. Neither is it advisable to mix these substances with the high-phosphorus minerals such as bonemeal, bone black, and di-calcium phosphate, for these products themselves furnish ample calcium.


MINERALS (PERCENT OF OVEN-DRY FORAGE)

.20 .30 40 .50 60 .70 .80 90 100 1.10 120

^C^^CN5

^^^^

^^^ ^^ ^^ se f

^

SAND SAGEBRUSH PALATABLE FORBS LITTLE BLUESTEM SAND OROPSEED SWITCHGRASS SKUNKBUSH SAND PASPALUM CANADA WILD-RYE BLOWOUT GRASS SAND BLUESTEM WESTERN WHEATGRASS SAND LOVEGRASS TEXAS BLUEGRASS GIANT REEDGRASS BLUE GRAMA BUFFALO GRASS SIDE-OATS GRAMA

SAND SAGEBRUSH SAND LOVEGRASS BLUE GRAMA BLOWOUT GRASS SAND PASPALUM SAND DROPSEED TEXAS BLUEGRASS PALATABLE FORBS BUFFALO GRASS LITTLE BLUESTEM GIANT REEDGRASS SKUNKBUSH SWITCHGRASS WESTERN WHEATGRASS SAND BLUESTEM CANADA WILD-RYE SIDE-OATS GRAMA

WESTERN WHEATGRASS CANADA WILD-RYE TEXAS BLUEGRASS SAND SAGEBRUSH BLOWOUT GRASS SAND LOVEGRASS SKUNKBUSH SAND DROPSEED SAND PASPALUM LITTLE BLUESTEM BUFFALO GRASS GIANT REEDGRASS BLUE GRAMA SWITCHGRASS SAND BLUESTEM PALATABLE FORBS SIDE-OATS GRAMA

TEXAS BLUEGRASS CANADA WILD-RYE WESTERN WHEATGRASS GIANT REEDGRASS SKUNKBUSH SAND SAGEBRUSH SAND PASPALUM BLOWOUT GRASS SAND LOVEGRASS SAND DROPSEED BUFFALO GRASS BLUE GRAMA SWITCHGRASS LITTLE BLUESTEM PALATABLE FORBS SAND BLUESTEM SIDE-OATS GRAMA

PHOSPHORLS E^â CALCIUM

FiöUÄE 4.—Five-year average phosphorus and calcium content of 17 species or classes of range forage during 4 grazing seasons of the year.


PROTEIN

Protein ranks first in importance among the chemical constituents needed in the growth and development of beef cattle. The proteins are composed of amino acids that are essential to the normal growth of animals. In many areas and during the greater part of the year the protein of most grasses is so limited that cattle cannot make profit- able growth without a supplementary supply in the form of protein concentrates or other feeds high in this constituent.

The different grasses and other forage plants occurring on the experimental range can be best evaluated as to protein content by comparing the analytical data with the known requirements of beef cattle. The relative quantities of digestible protein needed in a ration for different classes, ages, and weights of cattle are presented in detail in a recent report prepared by Guilbert, Gerlaugh, and Madsen (17) for the Animal Nutrition Committee of the National Research Coun- cil. They recommended 8.5 percent digestible protein as the proper allowance for normal growth of 400-pound heifers and steers, 5.7 for 600-pound animals of this class, 4.7 for 800-pound animals, and 4.3 for 1,000-pound animals. The digestible protein content of a feed usually averages about two-thirds of its crude protein content. There- fore, the above-listed requirements, when converted into crude protein for comparison with the analytical data from the experimental range forage, total 12.8, 8.6, 7.1, and 6.5 percent of crude protein, respec- Ûvely, for the different weights of heifers and steers.

The committee's recommendations for wintering yearling steers of the kind used in tests on the experimental range would require a feed containing crude protein ranging from 7.5 percent for 600-pound steers to 6.8 percent for 900-pound animals. The lower figure constitutes the requirement for wintering pregnant cows and heifers. The protein needs for fattening beef cattle are usually 40 to 50 percent higher than the requirements for wintering. Eations for fattening yearling steers to obtain daily gains of 2.2 pounds per head should contain a crude protein content ranging from about 10.8 percent for 600-pound animals to 9.6 percent for 800-pound steers.

The 5-year average crude protein content of 20 species and 5 classes of range forage are given in table 12, page 53. Monthly protein data for four general classes of the vegetation are illustrated in figure 5 in comparison with the gains of yearling steers for the same months. In figure 6, the average protein content of every important species is compared with the fiber and fat content for the four grazing seasons.

WARM-WEATHER GRASSES

The bulk of range forage in this region is composed of warm-weather grasses that usually dry up fairly early in fall, remain dormant most of the winter, and renew growth rather late in spring. The trend in the monthly protein content of most of these species was directly related to successive changes in plant development, season of growth, precipitation, moisture content, and phosphorus content, and affected the rate of gain of beef cattle. All of these grasses ran extremely high in protein content in April when the plants were young, tender, and growing actively. The quantity of this constituent present in the grass decreased slightly in May and considerably more in June, but was maintained during this month at a level well above that required for the normal growth of most classes of beef cattle.


MAR.

-Average monthly trend in the protein content of 4 classes of range forage for a 5-year period, spring of 1940 to spring of 1945, compared with monthly changes in the rate of gain of yearling steers.

The average protein content of all warm-weather grasses was 18 percent in April, 12.4 in May, and 8.1 in June. The average for the 3 months was 12.9 percent, which repi'esents an allowance more than sufficient for the rapid fattening of beef cattle. Thereafter, the protein content usually decreased as the plants approached maturity in midsummer, ripened, entered dormancy in the fall, and weathered during the winter. Similar trends were reported by Brennen and Fleming (S) and Fleming, Shipley, and Miller (IS) for four Nevada range grasses; by Kik (^^) for four grasses in Arkansas; by Sarvis (S7) for five grasses in North Dakota; and by Wasser (^5) for two grasses in Colorado.

NUTRITIONAL QUALITIES OF RANGE FORAGE PLANTS 23 PERCENT OF CRUDE FIBER IN OVEN-DRIEÜ FORAGE

0 4 8 12 16 20 24 28 32 36 40 44 I 1 \ \ 1 \ \ 1 \ 1 1 r-

PERCENT OF FAT AND CRUDE PROTEIN IN OVEN-DRIED FORAGE

2 4 6 8 10 12 14 16 18 20 22 24 26 —I 1 1 r

SAND SAGEBRUSH

SAND DROPSEED WESTERN WHEAT6RASS PALATABLE FORBS SAND PASPALUM

CANADA WILD-RYE SKUNKBUSH

SAND BLUESTEM SWITCHGRASS BLUE GRAMA

BLOWOUT GRASS

LITTLE BLUESTEM

TEXAS BLUEGRASS

GIANT REEDGRASS SAND LOVEGRASS

SIDE-OATS GRAMA

BUFFALO GRASS

PALATABLE FORBS

SAND SAGEBRUSH

TEXAS BLUEGRASS

SKUNKBUSH

BLUE GRAMA

SAND DROPSEED

BUFFALO GRASS

WESTERN WHEAT6RASS

SAND PASPALUM

BLOWOUT GRASS

SAND LOVEGRASS

GIANT REEDGRASS SIDE-OATS GRAMA

SAND BLUESTEM

SWITCHGRASS LITTLE BLUESTEM CANADA WÍLD-RYE

WESTERN WHEATGRAS5

CANADA WILD-RYE

TEXAS BLUEGRASS SAND SAGEBRUSH

SKUNKBUSH

PALATABLE FORBS

BLOWOUT GRASS

SANDDROPSEED BLUE GRAMA

SAND PASPALUM

BUFFALO GRASS

SAND LOVEGRASS

SIDE-OATS GRAMA "

GIANT REEDGRASS LITTLE BLUESTEM

SAND BLUESTEM SWITCHGRASS

CANADA WILD-RYE WESTERN WHEATGRASS

TEXAS BLUEGRASS SAND SAGEBRUSH

PALATABLE FORBS

SKUNKBUSH

SAND PASPALUM

BUFFALO GRASS BLOWOUT GRASS

SAND DROPSEED SIDE-OATS GRAMA BLUE GRAMA

SAND LOVEGRASS

SAND BLUESTEM

SWITCHGRASS

LITTLE BLUESTEM GIANT REEDGRASS

CRUDE PROTEIN ^S^ CRUDE FIBER

FiGUBB 6.—Five-year average fat, protein, and fiber content of 17 species or classes of range forage for the 4 grazing seasons.

759473**—47 4


September rains often caused a revival of growth and accounted for a slight increase in protein content over the summer minimum of 4.7 percent, recorded for August. The average protein content of 5.2 percent for these warm-weather grasses during the last 3 months of the growing season insured a substantial continuation in the gains of beef cattle, although the quantity of protein was not sufScient to maintain gains at the rapid fattening rate recorded during the early summer. The effect of supplementing the range forage with cottonseed cake kte in sunimer is reported elsewhere in this bulletin.

During the winter 6 months these grasses declined in average content of crude protein from 4.5 percent in October to slightly more than 3 percent in February. The low winter average of 3.7 percent, recorded for this class of vegetation, shows clearly that it requires some protein supplement for the winter maintenance of beef cattle and considerably more for fattening purposes. These grasses lost during the winter 58.8 percent of their average summer protein content. The average rate of decline was from 9 percent in the summer to 3.7 during the winter. The extreme rate of decrease amounted to a drop from 18 percent in April to 3 in February.

The principal warm-weather grasses in terms of average protein content during the summer 6 months were sand dropseed, sand paspalum, blue grama, blowout ^rass, buffalo grass, sand bluestem, switchgrass, and sand lovegrass, m the order listed. The high protein content of sand dropseed and blowout grass is of little importance, however, when other grazing values are considered. These two grasses are much higher in fiber and much lower in palatability than most of the other species and, therefore, are rarely eaten by cattle in moderately grazed pastures where other grasses are available. It is evident that cattle confined exclusively to sand dropseed would obtain greater quantities of protein during the summer months than could be procured from pure stands of other warm-weather grasses, but it seems likely that cattle gains would be affected adversely by the relative harshness of the sand dropseed plants and the higher quantities of fiber the animals would have to assimilate in grazing them.

A consideration of chemical composition, palatability, and other factors involved in evaluating plants for grazing purposes leads to the conclusion that the following warm-weather grasses are of superior value for summer grazing and rank in somewhat the order hsted: Blue grama, buffalo grass, sand lovegrass, side-oats grama, sand bluestem, and switchgrass.

The dormant summer grasses that ran highest in protein content during the winter months included blowout grass, sand paspalum purple sandgrass, sand dropseed, buffalo grass, blue grama, side-oats grama, and sand lovegrass, in the order listed. The first three are distinctly unpalatable to cattle during the winter and the fourth is decidedly less palatable than the others, which it exceeds in protein content. Therefore, because of these considerations and the advantage of superiority in phosphorus content, it may be concluded that buffalo grass, blue grama, and sand lovegrass are the most valuable dormant grasses for winter grazing. Side-oats grama, sand bluestem, and switchgrass rank next to these species. The slight advantage reported u ^TiT Sr^^^ ^^^^ ^^^^ ^^^^ grama in winter grazing value is verified by McMiUen, WiUiams, and Langham (SS), who stated that buffalo


grass proved to be superior to blue grama for winter pasture in the Oklahoma Panhandle. The leading grasses of the Great Plains are generally recognized

as being outstanding in their ability to retain much of the high food values in their dormant condition that they possess in the green stage of growth. A comparison of the average protein content for the growing season, April to September, inclusive, with that for the 6 months of winter dormancy affords a simple means of expressing the winter loss of summer protein. Thus, buffalo grass is found to have lost during the winter only 47.3 percent of its average summer protein ; side-oats grama, 52.7 ; sand lovegrass, 56.3 ; and blue grama, 57.1. The taller grasses show greater summer-to-winter losses of protein, amounting to 74.1 percent for sand bluestem and 75.5 for switchgrass.

Grasses that were outstanding in year-long grazing value among the warm-weather species were blue grama, buffalo grass, and sand lovegrass. Sand lovegrass was highly relished by cattle during the summer and was eaten more readily in winter than other tall grasses. It often constitutes much of the winter diet to the near exclusion of other available species when the supplies of short grasses are ex- hausted or wholly covered Tyith snow.

Other characters that contribute to the superlative qualities of these and other leading grasses of the Great Plains region were described in a recent report by Savage {39^ pp, 161-168), which was published in Great Britain. Further and more specific agronomic characters of these grasses have been described in considerable detail by Hoover {21), Wenger {J,B), Savage {38), and Savage and Smith.^

Other warm-weather grasses that were analyzed periodically during the first 5 years of this study, but not tabulated herein because of in- sufficient data to afford a continuity of monthly comparisons, included fall witchgrass and hairy grama. The first is fairly palatable to beef cattle. It ranked intermediate among the other warm-weather species in protein content and exceeded most of them in content of minerals. Hairy grama proved to be one of the least palatable grasses on the experimental range and usually ranked with little bluestem in being comparatively low in protein content.

COOL-WEATHER GRASSES

Native vegetation on the experimental range is characterized by a wide variety of plants, including the three cool-weather grasses that remain green most of the winter and run extremely high in content of protein, minerals, and provitamin A at that time. One or more of these grasses occurs sparsely but generally distributed on nearly all soil types throughout the range. The quantity of forage contributed by tifíese species to the winter diet of beef cattle is not sufficient to provide fully for all inadequacies of food elements in the dormant winter forage. The small quantity of green forage produced, however, is sought out and eaten with relish by cattle and undoubtedly serves in a large measure to compensate for deficiencies in protein, minerals, and carotene in other winter forage.

• SAVAGE, D. A., and SMITH, J. E. REGRASSING METHODS FOR THE SOUTHERN GREAT PLAINS. U. S. Southem Great Plains Field Sta. Mimeog. Oir., 16 pp. 1944. [Processed.]


These grasses usually possess as much protein and other essential nutrients from October to April as the winter-dormant grasses do early in summer when it would never be considered necessary to feed protein concentrates on native range of this area; therefore, the presence of large quantities of these grasses on a winter range would insure a better-balanced diet for beef cattle than would be obtainable with dry roughage and cottonseed cake alone. An increase in the quantity of these cool-weather grasses, through the establishment of reseeded pastures for exclusive winter use in rotation with other grasses during the summer, would undoubtedly increase cattle gains and greatly reduce the winter requirement for protein concentrates.

The average protein content of the cool-weather grasses exceeds that of the warm-weather species everv month in the year except July, which agrees in general with a Nebraska report {35^ pp, 12-16) that "cool-weather grasses attain higher percentages of protein than do warm-weather grasses." Despite these advantages in composition, the cool-weather grasses are often dry, woody, and dormant much of the summer and are of secondary value for grazing purposes at that time. Their high feeding value when young and relatively low nutritive value when mature are analogous to the results reported for the warm- weather grasses and agree with the trend reported for Kentucky bluegrass by Buckner and Henry {S) and Brown (7).

The maximum development of these cool-weather grasses usually requires more moisture in the fall, winter, and early spring than is commonly received in this region. Reseeded stands of western wheatgrass have survived 10 years of climatic conditions at Woodward, Okla., however, and usually produced more total pasturage than was obtainable from wheat in this area. Furthermore, these grasses are believed to represent a better balanced diet than wheat pasture, since they have never been reported as causing death losses from grass tetany, the ailment commonly referred to as wheat poisoning. Western wheatgrass usually contains more protein than the other cool-weather grasses, which is fortunate because seed of this grass is more plentiful and easier to harvest and drill with ordinary farm machinery.

WINTER-ANNUAL GRASSES

Other cool-weather grasses that were analyzed during the brief periods they were available for grazing included little barley and sixweeks fescue. These winter annuals, locally referred to as winter grass, occur periodically during seasons of heavy winter precipitation. They often provide considerable green forage for a few weeks early in spring and are fairly palatable to livestock at that time. They usually contain less protein than the perennial grasses ; however, they compete seriously with the better grasses for early spring moisture, and then dry up to form a worthless mixture of forage among the new growth of the more permanent grasses.

PALATABLE FORBS

Several of the forbs or nongrassy herbaceous plants that occur on the experimental range contain a higher percentage of protein through the year than do the warm-weather grasses. These plants include bush morning-glory, sand pea, horseweed, partridge-pea, and slender


scurf-pea. The first three species are palatable to cattle when the plants are young and are also eaten to a limited extent at other seasons. Although these species constitute a small part of the ration, they no doubt help materially to balance the diet.

BROWSE PLANTS

Skunkbush and sand sagebrush, which are eaten to a very limited extent by cattle late in winter, contain more protein at that time than do the dormant summer grasses, although they do not have the composition of a concentrate reported by McCreary {SI) for sagebrush leaves in Wyoming. The high protein and mineral content found for sand sagebrush agrees with the results reported by Watkins (^7) in New Mexico.

The woody, resinous nature and high camphor content of skunkbush and sand sagebrush, as determined by analyses for the experimental range, greatly reduces their palatability to beef cattle and makes them of strictly negligible value for grazing purposes. In fact, their serious detrimental effect in competition with the better classes of range forage far exceeds in importance any minor browse value they may exhibit when other forage is lacking or entirely covered with snow.

FAT CONTENT

Fat is an excellent source of energy, but its content is usually low in grasses and, therefore, not greatly significant (table 13, p. 54). This constituent is worthy of some consideration, however, since its energy value is 2.25 times that of protein and nitrogen-free extract. The fat content of warm-weather grasses changes less than protein during the year but shows about the same trend. These grasses usually decreased gradually in fat content from about 3 percent in April to 1.8 percent the following February, with an average of 2.7 percent for the summer 6 months and 2 percent for the winter period (fig. 7). The two shrubs contained greater quantities of fat than the cool- weather grasses, which, in turn, exceeded the warm-weather species in this respect. Most of the palatable forbs possessed more fat than the warm-weather grasses but less than the cool-weather grasses.

The leading species in terms of fat content during the winter, when this constituent is most needed by livestock, were sand sagebrush, Texas bluegrass, skunkbush, Canada wild-rye, western wheatgrass, little bluestem, purple sandgrass, sand paspalum, and side-oats grama.

NITROGEN-FREE EXTRACT

Nitrogen-free extract is the principal source of heat and energy in plants. This carbohydrate fraction is composed chiefly of starches, sugars, and pentosans that are easily digestible. This constituent, which constitutes the greater portion of grass, ranged from an average content of 46.9 percent of the dry matter of all grass during the summer to 48.1 percent during the winter (table 14, p. 55). The trend in monthly content of this constituent in most grasses varied in a manner opposite that reported for protein, phosphorus, and fat (tables 12,11, and 13). The content of nitrogen-free extract showed a sharp


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APR. MAY JUNE JULY AUG. SEPT. GOT NOV. DEC. JAN. FEB. MAR.

FIGURE 7.—Average monthly fat content of 4 classes of range forage for a 5-year period, spring of 1940 to spring of 1945.

increase from the young growth in April to the older plants in July, after which time it usually fluctuated at a high level until the following March, when a decrease occurred with the revival of new growth in the spring (fig. 8). The cool-weather grasses usually possessed slightly and consistently less of this constituent than the warm- weather types. The leading species in terms of average nitrogen-free extract content on a year-long basis were skunkbush, buffalo grass, sand lovegrass, side-oats grama, switchgrass, and blue grama.

CRUDE FIBER

Crude fiber represents about one-third of the composition of dry range grasses and constitutes much of the woody, structural part of the plant. Appreciable portions of this material are utilized through the action of fermentation and the presence of bactei'ia in the multi-unit stomach of ruminants. In general, the larger the quantity of fiber present in a forage crop the lower is its food value. The fiber content


APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC. JAN. FEB. MAR.

FIGURE 8.—Average monthly content of nitrogen-free extract in 4 classes of range forage for a 5-year period, spring of 1940 to spring of 1945.


APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC. JAN. FEB. MAR

FiGUEE 9.—Average monthly trend in fiber content of 4 classes of range forage for a 5-year period, spring of 1940 to spring of 1945.


of most plants increases with maturity (fig. 9) and usually varies inversely with changes in the content of the more desirable constituents, i. e., protein, phosphorus, fat, and carotene.

Buffalo grass, side-oats grama, blue grama, and sand lovegrass were lowest in fiber content and highest in palatability among the warm- weather grasses on a year-long basis for the 5 years (table 15, p. 56). Grasses that were highest in fiber content on a year-long average were giant reedgrass, sand dropseed, sand bluestem, little bluestem, switchgrass, sand paspalum, and blowout grass, in descending order as listed. Only three of these fibrous grasses—sand bluestem, switchgrass, and sand paspalum—are highly palatable for summer grazing. None of the highly fibrous grasses, however, are eaten readily by cattle during the winter. Therefore it appears that palatability is inversely related to fiber.

ASH CONTENT

The ash content of range plants contains such essential minerals as phosphorus and calcium and also considerable inert material in the form of dust and sand that clings to the forage. The quantity of this inert material is particularly high in such pubescent, or hirsute, species as sand paspalum, buffalo grass, and purple sandgrass. Despite the presence of these earthen particles, the content of ash in the native forage showed a seasonal trend closely comparable with that recorded for phosphorus alone and for other essential food constituents, including protein (table 16, p. 57). The ash content of most classes of range forage declined successively from April to September ; from green growth in spring to mature growth in fall (fig. 10). The cool- weather grasses showed a marked increase in ash content as they revived growth in fall and continued active development during the winter. The warm-weather grasses fluctuated somewhat in ash content during the winter but showed a rapid increase in this constituent as they revived growth early in spring.

MOISTURE CONTENT

The results of all analytical work conducted with native range plants on the experimental range show that a fairly consistent and positive correlation exists between the relative quantities of moisture in the field-collected material and the comparative content of essential food constituents on an oven-dry basis. The moisture content usually decreased with increases in stage of development of the plants (fig. 11 and table 17, p. 58) and, therefore, showed a trend comparable to that recorded for protein, phosphorus, fat, and ash. It seerns apparent from these results that the food value of a plant is indicated in a general manner, at least, by the quantity of succulence and green material that it contains.

INTRODUCED GRASSCS COMPARED WITH LEADING NATIVE GRASSES

Many native grasses from all parts of the world have been tested extensively at the United States Southern Great Plains Field Station at Woodward, Okla., and elsewhere in the region in an effort to find an introduced perennial adapted to the area. To date, no introduc-


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FIGURE 10.- MAY JUNE JULY AUG. SEPT OCT NOV. DEC. JAN. FEB. MAR.

-Average monthly trend in ash content of 4 classes of range forage during a 5-year period, spring of 1940 to spring of 1945.

tion consistently superior to the principal native grasses of the region has been discovered. Three introductions have shown some promise, however, Caucasian bluestem, Turkestan bluestem, and weeping lovegrass. The Turkestan bluestem is referred to as "yellow beardgrass" in southern Texas, where it has shown considerable promise.

The two introduced bluestems are the only exotic species that are fully adapted to the hot summers and cold winters of this region. These grasses were obtained from southwestern Asia where climatic conditions are closely comparable to those prevailing in the southern

NUTßlTIONAL QUALITIES OF RAUGË FOtíAGE PLANTS 3â

APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC. JAN. FEB. MAR.

FIGURE 11.—Average monthly trend in moisture content of the field-collected forage from 4 classes of range plants for a 5-year period, spring of 1940 to spring of 1945.

Great Plains. These two bluestems are similar in growth habits but difl'er markedly in forage yield and palatability to beef cattle. They produce more and finer stems than the native Andropogon species, bear more viable seed, and usually reseed themselves more readily.

Caucasian bluestem has been consistently more productive and more palatable to beef cattle than the Turkestan bluestem. It has been slightly less palatable, however, than such leading native species as sand lovegrass, sand paspalum, blue grama, side-oats grama,


switchgrass, and buffalo grass. The similarity in growth of Turkestan and Caucasian bluestem and the superiority of the Caucasian species with respect to production and palatability lead to the conclusion that it is the better forage grass.

Weeping lovegrass, an introduction from South Africa, shows some promise for the region because of its prompt germination, strong seedling vigor, ease of establishment, rapid and vigorous growth on a wide range of soil types, resistance to heat and moderate cold, and heavy forage production for at least a few years. This species is shorter lived, however, than the native species and distinctly less palatable. The value of this grass for erosion control and other purposes has been reported by Crider {11) and Staten and Elwell {JÎ).

These three introductions were analyzed with respect to the principal chemical constituents at monthly or bimonthly intervals during 1944 and 1945. Seven of the leading native grasses were collected on the same dates and analyzed for comparison. All were also analyzed for carotene, or provitamin A, for comparison with similar analyses of carotene and minerals in the blood plasma of beef cattle grazing on the range.

The monthly averages of all constituents, except carotene, for each of the three introduced grasses, compared with averages for two classes of native grasses, are shown in table 18, page 59. The detailed monthly averages for each of the native grasses during this 2-year period are not presented in this report, because they agree closely with the data and trends already reported for the same species during the first 5 years of this study. The principal exception was that during the first 5 years sand dropseed led all other warm-weather grasses in protein content but during the last 2 years fell below blue grama, buffalo grass, and sand paspalum in this respect. During the shorter period, these last three species ranked in average protein content in descending order as listed.

The three introduced grasses exhibited about the same trend in content of the different chemical constituents during the year, as was previously reported for native grasses of the warm-weather class. Each of the introductions, as well as the averages for all of the warm- weather grasses, declined successively in protein content from April to January, but exhibited a slight increase during the following March. Similar trends occurred with respect to the varying content of phosphorus, fat, and ash, but with opposite trends in the case of fiber.

Texas bluegrass, the cool-weather species used in these comparisons, exceeded every other grass in average protein content for the year. Weeping lovegrass contained slightly more protein than the average for all warm-weather native grasses but possessed considerably less phosphorus. This introduction, however, contained less protein than did blue grama or buffalo grass when the annual average for the 2-year period is considered. Turkestan bluestem contained more protein than Caucasian bluestem but less than weeping lovegrass and most of the native species. The advantage that Turkestan bluestem exhibited over Caucasian bluestem in respect to protein, phosphorus, calcium, and fat is counterbalanced by the superiority in palatability and forage production of the Caucasian bluestem.

Weeping lovegrass usually contained more protein than four of the seven native grasses, but this advantage is overcome by its lower content of phosphorus and much lower palatability. It contained less


fiber than sand dropseed and sand bluestem but more than most other species. The small quantity of additional crude fiber that it contains in comparison with most other grasses, however, does not fully explain its low palatability nor reflect the high breaking strength of its leayes and stems. This grass proved to be the least palatable species m grazing tests conducted for the past 2 years in which cattle grazed free choice on 40 different grasses in one pasture and on 57 different grasses in another. Its inferiority in comparison with the other grasses was less noticeable during the winter than during the summer. This was due to the fact that the introduced grass greens up earher m spring and continues growth later in fall than other warm-weather grasses.

CAROTENE CONTENT

The only vitamins definitely known to be required by beef cattle are A and D, according to Guilbert and Eockford {18). They add, however, that there is very little likelihood of a vitamin D deficiency occurring in range forage because it is present m sun-cured teeds and is developed in the animal body when exposed to sunlight. Vitamin A is therefore of primary importance among the vitamins needed by livestock A prolonged deficiency of this vitamin results m lower gams, less efficient use of feeds, more sick animals, greater mortality, a lower OTade of finished stock, and night blindness, according to WaU {Uh Kemmerer, Fudge, and Fraps {23), and Jones and others (^^). i he principal source of this vitamin is the carotene or yellow pigment found in all green-plant tissue. The content of this material declines rapidly in the decomposition of forage upon exposure to sun and air.

The average monthly or bimonthly carotene content of three introduced grasses and seven native species for the 2-year period 1944-45 is shown in table 19, page 61. These analyses were weighed m micro- fframs of carotene per gram of dry forage and then expressed m the equivalent of parts per million. The relative importance of this constituent in the different kinds of forage at various times m the year can be evaluated best by first considering the minimum requirements for beef cattle. Kemmerer, Fudge, and Fraps {28) report that 4 p. p. m. may be needed in dry-range forage for cattle. They indicated, however that as low as 1.7 p. p. m. would be sufficient m green teed. Con- sidering the higher figure as representing minimum requirements, Texas bluegrass, buffalo grass, weeping lovegrass, and Caucasian blue^ stem had an excess of carotene at all times. Five other species fell below the minimum requirement in January, and one species m Janu- ary and March. . . -, ^ i. j -A

The limited period m which these grasses showed a minor deficiency of carotene is not considered sufficient for any deleterious effect on beef cattle, and none was observed. Cattle grazing on forage hiffh in carotene are capable of storing ample supplies of this constituent for use over rather extensive periods when the forage is deficient. Jones and others {22) report that short yearlings required an average of 142 days on a carotene-deficient diet to deplete their previous storage of this constituent to a degree sufficient to exhibit deficiency symptoms. The comparatively low carotene content of dry- range forage late in winter was no doubt compensated for by an excess of this constituent in the cool-weather grasses. . . .i

Every native species of warm-weather grass decreased consistently and successively in carotene content from April to the following Jan-


uary. All of them exhibited a slight increase with the revival of growth m March. The decreasing trend in carotene content was directly related to successive stages in the growth development of the plants. The older, drier, and less active the growth, the lower the content of carotene. These results agree closely with those reported by Langham, McMillen, and Walker (29), Smith and Stanley (40), Hathaway, Davis, and Keim (W), and Wall (U), except that Wall found an increase from the young growth to the flowering stage. This constituent showed the same trend noted for protein and phosphorus and was also related directly to the rate of gain of beef cattle.

The trend in carotene content of Caucasian bluestem was the same as that recorded for the warm-weather native grasses, but with Turkestan bluestem and weeping lovegrass there was a slight increase in Septem- ber correlated with a temporary revival of growth at that time. The cool-weather grass decreased in carotene content from the active green stage of growth in March to maturity in July. Favorable conditions for regrowth caused an increase in the carotene in September and again m January. The average carotene content for all grasses decreased successively from 462 p. p. m. in April to 16 in January.

GRAZING RESULTS RELATED TO NUTRIENTS IN RANGE FORAGE

The comparatively high grazing value of native range forage in the southern Great Plains is clearly indicated by the relatively large gams recorded for yearling Hereford steers on the experimental range during the last 8 grazing seasons, 4 summers and 4 winters. The 4- year average live-weight gains per head was 304 pounds for the summer and 52 for the winter. The cattle included in these averages received nothing but the range forage and salt during the summer and 256 pounds of protein concentrates per head in addition to these feeds during the winter. Cottonseed pellets constituted the protein supplement used for all winters except one, when sovbean pellets were used most of the time. The grazing seasons averaged 170 days in length during the summer and 160 days during the winter.

TREND IN CATTLE GAINS AS RELATED TO FORAGE COMPOSITION

All steers used in the grazing tests on the experimental range were weighed individually and the gains recorded at monthly intervals throughout the year. Three-day weighings constituted the basis for determining initial and final weights for each semiannual grazing season. These procedures afforded a reliable means of comparing monthly changes in rate of gain with the trend in chemical composition of the forage plants. The average results of these comparisons for the last four summer grazing seasons are given in table 3. The trends m monthly rate of gain were fairly direct in their positive relationship to changes in the content of protein, phosphorus, ash, and moisture m the grass. There was a less positive correlation between the seasonal changes in calcium content and the trend in cattle gains, home tendency was noted for the content of fiber and nitrogen-free extract to be related inversely to livestock gains.

The cattle made the greatest rate of gam in April and May when the grasses were young, lush, and tender. During this period the grasses contained the greatest quantities of protein, phosphorus, cal-


TABLE 3.—Average trends in monthly gains of yearling steers and nutritional qualities of range grasses for the L-uear veriod 19Jß-Ji5 ^^ t^

Gain data and forage analyzed

Gain data: Total per head pounds. Average daily do Monthly percentage of total Accumulated by end of each

month : Pounds per head Percentage of total

Grazing period _days_ Composition of grasses (in percent,

oven-dry) : Warm-weather grasses:

Crude protein Phosphorus Calcium _ Ash Moisture (in field) Fat Nitrogen-free extract Crude fiber

All grasses (including annuals and cool-weather types) :

Crude protein Phosphorus Calcium Ash Moisture (in field) Fat._- Nitrogen-free extract Crude fiber

Trend in summer gain and forage composition

Apr.- May

106. 7 2. 31

35. 1

106. 7 35. 1 46.7

15.2 . 30 . 42

8.9 69. 7 2.9

43.2 29.5

15. 5 . 30 . 41

8. 9 70.2 3.0

42. 5 29. 7

June

66.0 2. 20

21. 7

172. 7 56.8 30

8. 1 .21 .38

7.9 63. 0 2.4

46. 7 34. 5

8.3 .21 .37

7.6 61.6 2.5

47. 1 34.3

July

50. 4 1.63

16. 5

Aug.

223. 1 73.3 31

5.6 . 16 .39

6.8 45. 6 2.8

50. 9 33. 6

5. 6 . 16 .37

6. 7 43. 5

3. 1 50.5 33.9

42. 6 1.38

14. 0

Sept.- Oct.

265. 7 87.3 31

4.7 . 17 .33

6.7 47.9 2.3

49.8 36. 2

5. 1 . 16 .33

6.6 46. 3 2.5

49. 8 35.6

38.4 1. 21

12. 7

304. 1 100 3L 5

4.9 . 14 .39

6.5 38. 2 2.5

49. 6 36.2

6. 1 . 15 .39

6.7 37.9

2. 9 48. 7 35. 8

Sum- mer

Calcu- lated 1

304.1 1.79

100

170. 25

Weighted^ 8.4 .20 .39

7.4 53. 2

2. 6 47. 6 33.6

8.9 .20 .38

7.5 52.5 2.8

47.1 33.6

Í Calculated on the basis oí a season of 170.25 days. 2 Obtained by dividing totals by 7.

cium, ash, fat, and moisture, and the least fiber and nitrogen-free extract. All of the valuable food constituents showed a decrease in June, but they were suiBcient during that month to maintain average daily gains of 2.2 pounds per head, which is comparable with some of the better gains obtained on a full-grain ration in a feed lot.

The rates of gain continued to decline in July and August in direct proportion to successive decreases in the nutritional qualities of the grass. The gains showed a further slight decrease in Sep- tember, in contrast to a small increase in food content of the grass at that time. This lack of correlation between gains and food constituents may have been due to the collection of fall samples containing more revived growth from late rains than was typical of the entire forage for that period. Moreover, September gains of the cattle were reduced to some extent by the additional shrinkage in weights caused by the 3-day weighings at the end of the season, as contrasted with a 1-day weighing for previous months.

The close correlation between monthly changes in the principal chemical constituents and the trend in livestock gains agrees with


a recent report by Clarke and Tisdale {10) for similar investigations on the plains of southern Alberta and Saskatchewan.

The gain data on the experimental range showed that the steers made 87.3 percent of their total summer gain by the end of August. A practical suggestion would be for stockmen to take advantage of this fact by selling their fatter steers at that time when prices are usually higher than later in the season. This would leave more forage for the remaining cattle, build up the vigor of the grass, and avoid overgrazing that has proved to be especially damaging to the vegetation late in summer and early in fall.

In direct contrast with the summer data, the trend in winter gains, as illustrated in figure 5 in connection with the previous discussion of protein, showed no direct relation to changes in the food content of the grasses. The winter gains were influenced more by weather conditions than by any other factor.

EFFECT OF COOL-WEATHER GRASSES ON CATTLE GAINS IN WINTER

The value of cool-weather grasses in providing green forage extremely high in nutritional qualities during the winter has been mentioned in connection with the discussions of chemical composition. The importance of this type of grass for winter grazing has been studied by comparative grazing tests conducted during the winters of 1944-45 and 1945-46. The first test involved the use of heavy yearlings 18 to 20 months of age grazed on the dormant winter range in comparison with almost identical cattle grazed on similar range supplemented with reseeded areas of Texaá bluegrass and western wheatgrass. The proportion of these green winter grasses in this pasture was not sufficient to satisfy all protein requirements but contributed much more protein, minerals, and carotene (provitamin A) than were obtainable on the adjacent dormant range. Starting in the fall with cattle of equal weight and feeder grade in each pasture, the lot that had access to the cool-weather grasses weighed 69.3 pounds more per head in the spring.

A similar but more complete test of the winter grazing value of cool-weather and warm-weather grasses was conducted during the second winter. A 50-acre reseeded field of western wheatgrass was used in a grazing comparison with the dormant grasses on eight native range pastures. The forage available to the cattle on the western wheatgrass pasture consisted of considerable dry residue from the previous summer, together with the continued growth of green leaves at the base of the plants all winter.

The steers on this pasture, stocked at the rate of one animal to 4.2 acres, gained 158.5 pounds per head during the 147-day winter grazing season extending from November 16, 1945, to April 12, 1946. Comparable steers, allotted 7.3 acres of dormant range per head, gained only 96.8 pounds per head during the same period. In both cases the pastures were grazed moderately but there was more unused forage left at the end of the season on the reseeded pasture than on the native range. The western wheatgrass had a carrying capacity 73 percent greater than the native range. Therefore, since the cattle on western wheatgrass made 64 percent more gain per head during the winter, this pasture produced nearly three times as much gain per acre (tableé).

NUTRITIONAL QUALITIES OP RANGE FORAGE PLANTS 39

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The superiority of the western wheatgrass for winter grazing is proved further by the saving it afforded in the use of protein concentrates. The cattle on this pasture received a total of only 148 pounds of cottonseed cake per head during the winter, as compared with 267 pounds for the cattle on native range. Of special significance is the fact that this pasture provided ample green pasturage all winter, whereas adjacent wheatñelds failed much of the time to produce sufficient growth for grazing purposes.

The steers on this pasture, stocked at the rate of one animal to 4.2 acres, gained at the average daily rate of 1.08 pounds per head during the winter season. Comparable steers allotted 7.3 acres of dormant native range per head averaged only 0.66 pound per head during the same period. The steers on native range received an average daily ration of 1.7 pounds of cottonseed pellets per head, the rate being mcreased from 1 pound in November to 2 pounds on December 15. The rate of feeding the protein supplement to the cattle on western wheatgrass was the same as for the other cattle in November and December but was reduced to 1 pound daily in January without any reduction in gain. It is evident from these data that the western wheatgrass supported 73 percent more cattle per section of land, produced 64 percent more gain per head, and returned nearly three times as much beef per acre as the dry winter range.

The quality of feed and rate of gain on the western wheatgrass would undoubtedly have been much higher if the old growth had been removed in advance and nothing but the new growth had been available. It also seems logical to believe that if the cattle on western wheatgrass had been fed no protein supplement they would have made gains closely comparable to those of the cattle that were fed heavily with the supplement on dry range. Under such conditions both lots would have received about the same quantity of protein in their respective diets.

EFFECT OF MINERAL SUPPLEMENTS ON CATTLE GAINS

Early in the course of the analytical studies the chemical data showed that there was little likelihood of a serious mineral deficiency occurring in local range forage, especially when a number of plant types were available on the range and cottonseed cake was fed during the winter. Feeding trials with beef cattle on the range were conducted, however, during favorable and unfavorable growing seasons to obtain more conclusive information. This work was started in the spring of 1943 and has been continued, modified, and expanded since that time. Gain data are now available for 3 summers and 2 winters. Each semiannual grazing season covered a period of approximately 6 months. The studies were conducted with 16- to 24-head lots of yearling Hereford steers of uniform age, breeding, initial weight, and initial feeder grade. An excess of range forage was available to the steers at all times, since lightly grazed pastures containing essentially the same kind and quantity of vegetation were used for the comparisons.

During the first two semiannual grazing periods a mineral mixture consisting of steamed bonemeal, lime, and granulated salt, in the ratio of 1-1-2 by weight, was fed to one lot of steers in comparison with another lot that received salt alone. Since early analyses of the forage


showed no evidence of a calcium deficiency at any time, the lime was eliminated from the mixture in the spring of 1944 and thereafter. This was done to avoid an overbalance of calcium that would reduce the effectiveness of the phosphorus. The mineral mixture fed thereafter consisted of 1 part of steamed bonemeal to 3 parts of salt by weight. The studies were augmented during the winter of 1944-45 and the summer of 1945 by adding a comparable pasture lot in which the cattle had free access to separate bunks of steamed bonemeal and salt. The work was further expanded during the winter of 1945-46 to include comparisons of the mineral mixture with salt alone under three rates of stocking and degrees of grazing use.

The yearling gain data, as summarized for the five grazing seasons in table 5, were essentially the same for the lots that received salt alone as they were for the lots that were fed other minerals in addition to salt. The steamed bonemeal, when fed separately with salt or in mixtures with salt, caused no significant increase or decrease in steer gains, as compared with salt alone. Similar results were obtained in the winter use of weanling calves for the sixth grazing season, com- pleted April 12, 1946. These results indicate that no minerals other than salt are required to supplement the local range forage for these classes of beef cattle, especially when the forage is supplemented with 3ottonseed cake during the winter. Similar results were reported by Brouse (6) for wintering calves in the Nebraska sand hills. He found that there was no significant benefit from feeding minerals other than salt to calves fed a daily ration of 1 pound of cottonseed cake.

TABLE 5.—Five-season average live-ioeight gain each of yearling steers fed different mineral supplements on native range

Gain per head

Supplemental mineral treatment Two-winter average

Three-summer average

Five-season average 1

Total Daily Total Daily Total Daily

Bonemeal and salt Pounds 49. 7 49.8

Pounds 0. 31 .31

Pounds 318. 8 323.5

Pounds L89 1. 92

Pounds 368.5 373.3

Pounds I. 11

Salt alone _ i.- L 12

Gain in favor of salt. . 1 0 4.7 .03 4.8 .01

1 Yearly total on basis of 5 seasons.

The inability of the steamed bonemeal to effect an increase in steer gains during the winters, despite reported deficiencies in phosphorus among some of the grasses at that time, may be explained as follows. The winter shortage of this element in some grasses was no doubt fully compensated for (1) by ah excess of phosphorus in other grasses and forage plants and (2) by the winter feeding of protein concentrates containing phosphorus.

All steers used in these tests were fed equal daily quantities of protein supplements during the winters. Each steer received 22 pounds of cottonseed pellets, containing 43 percent protein, and 193 pounds of soybean pellets, containing 41 percent protein, during the first winter


and 312 pounds of cottonseed pellets during the second winter. The f)hosphorus content of these supplements was 1.19 percent for the cottonseed pellets and 0.69 for the soybean pellets, which agrees closely with the averages reported for these products by Ellis, Kauffman, and Miller {13,j)p, 106Ô-1074). Since 1 pound of the cottonseed pellets provided slightly more than 5 gm. of phosphorus, it is evident that this material helped greatly to satisfy the phosphorus requirement. The conclusion is that the phosphorus needs of cattle on local range forage will be met by the winter feeding of sufficient cottonseed cake to satisfy minimum protein requirements for normal growth.

MINERALS CONSUMED BY CATTLE

Further evidence that range forage used in these experiments contains sufficient phosphorus for beef cattle, especially when supplemented during the winter with cottonseed cake, is presented by the fact that the steers showed a definite reluctance to eat the mineral mixtures unless forced to do so by the absence of salt on the side, and even then the consumption of the mixture was much less than that of salt alone in adjacent pastures. When salt was fed exclusive of other minerals, the average quantity consumed was 18.1 pounds per head during the summer and 26.6 pounds during the winter, or a total of 44.7 for the year (table 6). When a mineral mixture of salt and bonemeal was fed,

TABLE 6.—Average seasonal consumption of minerals iy yearling steers on native range

Minerals consumed per head

Mineral supplements fed Average, 2 winters

Average, 3 summers

Total, 5 seasons i

Mineral mixture Pounds

22. 6 26.6

Pounds n. 8 18.1

Pounds 34 4

Salt alone _ _ 44 7

1 Yearly total on basis of 5 seasons.

the average used per steer was 11.8 pounds in the summer and 22.6 in the winter. Cattle having access to separate bunks of the two minerals ate 2.6 times as much salt as they did bonemeal during the winter and 7.8 times as much during the summer. These results indicate that the cattle had no craving for phosphorus, and are in direct contrast to those recorded in such phosphorus-deficient areas as southern New Mexico, where the cattle eat more of a mineral mixture than they do of salt alone. Keporting informally for that area, W. E. Watkins,^^ of the New Mexico Agricultural Experiment Station, stated that the average mineral-mixture consumption for a considerable period was 52 pounds per year while salt alone was 35. His mineral mixture contained equal parts of special steamed bonemeal or spent bone black and salt. These results were confirmed for the same area by Knox and Neale {27), who reported that the cattle ate about the same quantity of salt regardless of the quantity of mineral it contained. Barnes, Smith, and Jones (^) of Texas reported that there is good evidence that cattle

'"Nutrition chemist and associate in Animal Husbandry, in a letter dated February 10, 1945.


consume appreciable quantities of bonemeal only when they need phos- Çihorus in addition to that which they receive from the forage or other eeds. A good grade of granulated salt was used in the studies on the

experimental range, and all minerals were fed in roofed watertight bunks to avoid leaching and to facilitate records of consumption. Cattle trailed to the experimental range from adjacent ranches where block salt was fed ate the loose salt voraciously and for several days, indicating that in previously licking the blocks they had failed to obtain sufficient salt to satisfy their appetites. Another observation of interest is the fact that the cattle consumed more minerals during the winter months, when the forage was lower in minerals, than during the summer, when the vegetation contained greater quantities of such elements.

EFFECT OF MINERAL SUPPLEMENTS ON BLOOD PLASMA

The question as to whether or not phosphorus is needed to supplement the local range forage was further studied through a series of analyses of the blood plasma from the salt-fed cattle and from those fed both phosphorus and salt. This is an excellent means of determining the need for mineral supplements, according to Black, Tash, Jones, and Kleberg (^) and Theiler, Green, and Du Toit {42). These investigators showed that the inorganic phosphorus content of the blood of an animal indicates whether it is receiving adequate phosphorus. In South Africa and southern Texas, where serious phosphorus deficiencies occur in the range forage, the whole blood of cattle receiving no phosphorus supplements often contained as little as 2.5 milligrams (mg.) of inorganic phosphorus per 100 cc. Cattle fed bonemeal under the same conditions maintained what wâs referred to as a normal inorganic phosphorus content of 4 to 5 mg. per 100 cc. of whole blood. W. H. Black,^^ however, stated informally that the 4-mg. level is considered about the danger point for either yearlings or 2-year-olds, but that he would expect this level to extend over a period of at least 90 days before any symptoms of deficiency would be observed.

The blood plasma analyses on the experimental range were conducted with 12- to 18-head lots of yearling steers at monthly or bimonthly intervals from the fall of 1942 through 1945. The results of these studies showed that the blood plasma contained rather high quantities of inorganic calcium and inorganic phosphorus at all times in the year (table 7). There was no significant difference in the mineral content of the blood between the steers receiving bonemeal and those receiving salt alone. This indicated that the range forage and protein concentrates used as supplements provided all the phosphorus needed. This observation is substantiated by the report of Beeson and others {S) that, when fed at the same level, the organic phosphorus of cottonseed meal was as effective in preventing a phosphorus deficiency as the inorganic phosphorus in bonemeal.

Expressed in terms of milligrams per 100 cc. of plasma, the calcium content ranged from 9.9 mg. in November to 11.3 in April, with an

" Senior animal husbandman, in charge, Beef and Dual-Purpose Cattle Investi- gations, Bureau of Animal Industry.


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average of 10.7 for the entire year. Similarly expressed, the phosphorus content varied from 4.3 mg. in November to 7.5 in March, with an average of 5.8 for the year. Thesç three phosphorus figures for blood plasma, when converted to the basis of milligrams per 100 cc. of whole blood for comparison with the data cited for the other investigators mentioned above, would be 3.3, 5.8, and 4.5 mg., respectively. These data, under the conditions prevailing in this locality, are indicative of a satisfactory phosphorus supply for yearling steers. The fact that no sudden or pronounced decrease in phosphorus content of the blood occurred during the year is further evidence of adequate phosphorus in the feed, since W. E. Watkins ^^ of New Mexico reported that the inorganic blood plasma phosphorus drops within a week or so when livestock is changed to low phosphorus forage.

The phosphorus content of the range forage declined successively from April to the following January and March. In contrast to these results, the phosphorus content of the blood was maintained at monthly levels mostly in excess of 5 mg. per 100 cc. of plasma throughout the year. The superiority of conditions for range production in this locality is indicated by comparing these results with those obtained by the junior author from cattle grazing on phosphorus-deficient range in eastern Oklahoma. There the content of inorganic phosphorus in the blood often falls as low as 2.5 mg. per 100 cc. of plasma during winter months and UwSually averages much less than 4 mg. at that time. Further evidence of the adequacy of phosphorus without mineral feeding under local conditions is indicated by comparing the 5-mg. level maintained in the blood plasma of both the salt- and mineral-fed cattle with the analyses reported by Knox, Brenner, and Watkins (^6), The blood plasma from their mineral-fed cattle possessed an inorganic phosphorus content of 2 to 3 mg. per 100 cc. in the winter and spring and 3 to 4.5 mg. in the summer. They reported these figures as being indicative of adequate phosphorus, since the cattle were maintained in excellent health and superior condition.

EFFECT OF COTTONSEED CAKE ON CATTLE GAINS

The composition data previously discussed show clearly that a protein feed of some kind is required to supplement the dry winter range in this region. Stockmen fully recognize the deficiency at that time and usually attempt to correct it with the use of cottonseed cake, wheat pasture, or similar feeds. It is not commonly known, however, that a deficiency in protein content also occurs frequently in native forage during the latter part of the summer. It has been shown in this report that the protein content of most range grasses in July, August, and September often falls below the minimum required tor rapid growth and fattening of beef cattle. The gain data support this conclusion by showing that yearling steers make an average daily gain of only 1.4 pounds per head during these 3 months, as compared with an average of 2.3 pounds for the first 3 months of the summer when the protein content of the forage satisfies requirements for rapid growth and fattening.

In view of these results, a comparative feeding test was conducted during the summer of 1945 to obtain more definite information on the

"^ See footnote 10, p. 42.


effect of feeding protein supplements to yearling steers late in summer. Five lots of extremely uniform cattle were used. All lots averaged the same in initial weight and feeder grade on April 22, and were allotted the same acreage, kind, and quantity of grass for the season. All lots averaged the same in weight at the end of June and had gained the same on grass and salt alone before the supplemental feeding period was started on July 1. One lot was fed a daily ration of 2 pounds per head of cottonseed pellets (43 percent protein) from July 1 to the end of the season (October 5), and another lot was fed 1 pound of the same supplement per day during this period. The range forage was fairly green and fairly high in protein content through most of July but thereafter was partially to wholly dry much of the time.

The gain data, as summarized in table 8, show that the feeding of cottonseed pellets during the latter part of the summer of 1945 resulted in maintaining the rate of gain at nearly the same high level recorded on richer grass alone earlier in the season. The gains were approximately in proportion to the quantity of pellets fed. The cattle that received a daily ration of 2 pounds of cottonseed cake per head after June 30 gained 361.4 pounds per head for the entire season, as compared with 341.5 pounds for the 1-pound lot and 290.7 pounds for the three lots that had received no protein supplement. The average season-long gain advantage was 70.7 pounds per head for the 2-pound rate of feeding and 50.8 for the 1-pound.

TABLE 8.—E-ffect of two rates of feeding cottonseed cake on the average gains of yearling steers during the last half of the 166-dœy summer gracing season of 191^5^ April 22 to Octoher 6

Head Acres

per head

Initial weight (Apr.

22)

Final weight (Oct. 5)

Total gain per head

Average daily gain

Protein supplement fed daily

To June 30

(69 days)

After Julyl

(97 days)

Season total

Gain per acre

Two pounds One pound None -

Num- ber

20 20 32

7. 1 7. 1 7. 1

Pounds 543.2 542.8 542.3

Pounds 904. 6 884.3 833.0

Pounds 144. 0 145.0 144. 9

Pounds 217.4 195.8 145.8

Pounds 361. 4 341.5 290.7

Pounds 2. 18 2.06 1.75

Pounds 50. 9 48. 1 4L 3

Gain in favor of caking:

At 2 Dounds 71.6 50.0

70.7 50.8

.43

.31 9.6

At 1 pound 6.8

The cottonseed pellets not only provide the additional protein required for rapid growth and fattening, but, according to a recent report by Hobbs, Gallup, and Taylor (20), this concentrate also increases the apparent digestibility of all nutrients contained in the dry grass. Fur- thermore, the feeding of the protein supplement stimulates the appe- tite and increases the consumption of dry roughage, according to Brouse (6) in a recent report of tests conducted in the Nebraska sand hills. The increase in energy intake afforded by the extra forage con-


sumed is probably responsible for part of the additional gam obtained from feeding protein on the experimental range late in summer.

The cake-fed cattle had more "bloom," graded higher, and were ap- praised at higher prices in the fall than the cattle that received no protein supplements. In making an economic appraisal of the results by converting them to the basis of a section of land (640 acres), the 2-pound rate of feeding showed a net return of $491.40 more than the nonsupplemented lot. On the same basis the 1-pound rate of feeding the pellets showed a return of $303.30 more than the checks. The additional weight gains and the higher prices received per pound were more than sufficient in 1945 to defray the cost of buying and feeding the cottonseed pellets. These results corroborate in part the report by Ellis and Hodgson {12) that the "fattening of cattle on grass with cottonseed cake during the spring and summer months has been found during more recent years to be an economical practice."

CAROTENE IN CATTLE BLOOD AND RANGE FORAGE

The carotene content of the blood plasma of yearling steers grazed on the experimental range, in comparison with the quantity of this material in the principal classes of range forage at monthly or bimonthly intervals for the 2-year period 1944-45 is shown m table 9. The trend in the content of carotene in the blood showed a direct but delayed relation to that contained in the forage. An increase in the carotene of the forage, caused by the revival of growth m March, was reflected in an increase in this constituent in the cattle in April. The high April content of forage carotene caused a large increase m the blood carotene for May. Likewise, successive decreases in carotene m the forage were responsible for successive but delayed decreases m the carotene content of the blood.

TABLE ^,—Carotene content of the Uood plasma of yearling steers^ in relation to the quantity of this constituent in the range forage during the 2-year period WJ^Jr-íB

Cattle blood and forage analyzed

Carotene, or provitamin A, content of blood plasma and range forage

Blood plasma (in gammas per 100 ml.) :

For steers fed bonemeal and salt

For steers fed salt alone Average, all steers

Range forage (in micrograms per gram (p. p. m.)):

Warm-weather grasses Cool-weather grasses All grasses

Apr.

379 359 369

449 474 462

May

685 602 644

236 151 228

July

633 606 620

HI 89

106

Sept.

459 506 483

71 106

Nov.

373 378 376

17 87 26

Jan.

125 209 167

3 128

16

Mar.

94 280 187

13 1,050

118

Aver- age

393 420 407

129 298 149


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MATURITY. N. Mex. Agr. Expt. Sta. [Tech.] Bui. 311, 43 pp., illus.

(48) WENGER, L. E.

1943. BUFFALO GRASS. Kaus. Agr. Expt. Sta. Bui. 321, 78 pp., illus. (49) YouNGBURG, G. E., and YOUNGBURG, M. V.

1930. PHOSPHORUS METABOLISM. A SYSTEM OF BLOOD ANALYSES. JOUF Lab. and Clin. Med. 16: 158.


52 TECHNICAL BULLETIN 943, U.. S. DEPT. OF AGRICULTURE

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Documents

Nutritional Qualities of Range Forage Plants in Relation