FACTORS AFFECTING FORAGE QUALITYpp. 232 - 246

FORAGES OR ROUGHAGES

• General characteristics– Higher fiber concentration than energy and protein

supplements– Lower energy concentration than energy or protein

supplements– Lower protein concentration than protein supplements

• May have higher or lower protein concentration than energy supplements

• A high proportion of the protein in most forages is highly degraded in the rumen

– Calcium concentration greater than energy and plant protein supplements

– Concentrations of phosphorus and other minerals is highly variable

– Concentrations of fat soluble vitamins high in fresh forages, but low after storage

WHAT DEFINES FORAGE QUALITY?

FACTORS DETERMINING FORAGE QUALITY

• Forage species• Maturity• Soil fertility• Harvest method and quality of storage

– Leaf-to-stem ratio– Nutrient preservation

MAJOR CLASSES OF FORAGE SPECIES

MonthsJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Tota

l for

age

mas

s, lb

/acr

e

0

1000

2000

3000

Cool season grassLegumesWarm season grassStockpiled gr-leg (Hay equiv.)Corn stalks (Hay equiv.)

NUTRITIONAL VALUE OF LEGUMES, COOL SEASON GRASSES, AND WARM SEASON GRASSES AT

COMPARABLE MATURITIESDM basis

CP, %

NDF, %

ADF, %

ADL, %

TDN, %

NEmMcal/

kg

NEgMcal/

kg

Ca, %

P, %

Cool season grasses

Immature 18 50 31 4 63 1.48 0.89 .72 .34 Mid-maturity 13 58 37 4 60 1.33 0.75 .66 .29 Mature 11 69 42 6 56 1.18 0.62 .47 .26Legumes Immature 23 36 29 6 62 1.49 0.90 1.56 .31 Mid-maturity 21 43 33 6 59 1.38 0.80 1.37 .30 Mature 18 51 40 7 55 1.21 0.65 1.22 .28Warm season grasses Immature 14 - - - 64 1.45 0.87 .63 .20 Mature 6 - - - 51 1.08 0.58 .40 .12

COOL SEASON GRASSES• Most common grasses in the Midwest

– Kentucky bluegrass - Tall fescue -Smooth bromegrass– Orchardgrass - Reed canarygrass - Timothy– Perennial ryegrass

• Growth– 66% of production occurs before early-June– Very low productivity in mid-summer– Some late season growth

• Yields– Species effects Tall fescueReed >Smooth bromegrass>Timothy>>Kentuckycanarygrass Orchardgrass bluegrass– Very sensitive to soil fertility

• N, P, and K• When is it needed???????

USES OF COOL SEASON GRASSESGrazing Harvest Comments

Kentucky bluegrass

Excellent Poor

Smooth bromegrass

Excellent Excellent

Orchardgrass Excellent Excellent Better mid-summer growth than other CSG

Tall fescue Good Good Better fall growth than other CSG

Reed canarygrass

Good Good Grows well in wet environments

Timothy Fair Excellent Preferred for horse hayPerennial ryegrass

Good Excellent Higher quality, but poorer persistence than other CSG

NUTRITIONAL QUALITIES OF COOL SEASON GRASSES

• GeneralCompared to:

Legume forages @ comparable

maturity

Grains Plant protein supplements

CP Lower Greater/Lower LowerNDF Greater Greater GreaterADF Greater Greater GreaterTDN/NE Lower Lower LowerCa Lower Greater ComparableP Comparable Comparable Lower

• Effects of fertility• N, P, K, Mg, and many trace minerals will affect their

concentration in cool season grasses

ANTI-QUALITY COMPONENTS IN COOL SEASON GRASSES

• Endophyte fungus– Found in

• Tall fescue• Perennial ryegrass

– Produces toxic alkaloids• Classes

– Lysergic acid amides– Ergopeptines

» Ergovaline• Location

– Primarily in the seed– Also in stem and leaf

• Transfer to a pasture– Via the seed

– Effects of fescue toxicosis• Physiological effects

– Vasoconstriction– High core body temperatures– Low heart rate– Low prolactin– Suppression of immune system

• Results on animal– Hoof loss – Low forage intake and weight gains during summer– Retention of winter hair coat– Standing in water sources– Low milk production– Reproductive problems

» Low pregnancy rate» Dystocia» Retained placenta

– Management to prevent fescue toxicosis• Prevent excessive maturity of forage• Limit application of N-fertilizer• Plant or interseed legume forages in tall fescue pastures• Rotate animals to non-fescue pastures• Plant endophyte-free varieties of tall fescue

– Poor persistence• Plant tall fescue varieties containing beneficial

endophyte• Treatment of cattle with Ivermectin???

– A dewormer• Treatment of pregnant mares with Domperidone

– Blocks receptors for dopamine

• Tryptamine alkaloids– Common in native reed canarygrass varieties– Physiology

• Serotonin receptor agonists• Can cause staggers or sudden death

– Common effects on animal• Reduced feed intake and growth

– Management• Plant low alkaloid varieties of reed canarygrass• Rotate animals for paddocks that do not contain reed

canarygrass• Cobalt supplementation

LEGUMES

• Species– Alfalfa Red clover White clover Birdsfoot trefoil Sweet

clover Berseem clover Sweet clover• Growth

– Greatest in spring, but more uniform over the season than grasses

• YieldsAlfalfa > Red clover > Birdsfoot trefoil >> White clover Sweet clover

• Fertility needs– N fertilization is not required

• May reduce legume persistence in grass-legume pasture– Sensitive to pH, P, and K

• Persistence– Very sensitive to management

• Most species require some type of rest period to allow nutrient storage in roots and crown and/or reseeding

• Competition with cool season grasses• Sensitive to most herbicides

USES OF LEGUMES

Species Grazing Harvest CommentsAlfalfa Good Excellent Perennial, sensitive to wet

conditions

Red clover Excellent Good Biennial, sensitive to drought, easy to interseed

Birdsfoot trefoil Excellent Good Perennial, but responds to management that allows

reseedingLadino & White clover

Good Poor Perennial, less sensitive to close grazing than other

legumesSweet clover Poor Fair Biennial, less sensitive to

soil conditions than other legumes

Kura clover Excellent Good Perennial, very persistentBerseem clover Fair Good Annual

NUTRITIONAL QUALITIES OF LEGUMES• General

Compared to:Cool season grasses @

comparable maturity

Grains Plant protein supplements

CP Greater Greater Lower

NDF Lower Greater GreaterADF Lower Greater GreaterTDN/NE Greater Lower LowerCa Greater Greater Greater

P Comparable Comparable Lower

• Effects of fertility• K fertility will affect its concentration in legumes

NUTRITIONAL CONCERNS WITH LEGUME FORAGES

• Bloat– Inability of ruminants to release fermentation

gases– Occurs in ruminants consuming fresh, immature

legumes like alfalfa, white clover, red clover, and kura clover

– Caused by a high concentration of soluble protein in these legumes

• Results in the formation of foam in the rumen• Inhibits eructation• Can result in death

– Bloat prevention• Plant mixtures of grasses and legumes• Utilize non-bloating legumes• Allow legumes to mature before grazing• Feed animals some dry hay before placing animal on

pastures• Avoid moving animals into a pasture or paddock

containing a high concentrations of legumes early in the morning

• Limit the daily forage allowance to the cattle• Have water available in each paddock of a rotationally

grazed pasture• Make poloxalene available to animals grazing legumes

– Sold as ‘Bloatguard’– Available in blocks or supplements– Intake can be variable

• Phytoestrogens– Present in alfalfa, red clover, and ladino clover– Have affected reproduction and mammary

development in sheep• Coumarin

– Present in sweet clover– Converted to dicoumarol in moldy sweet clover

• Results in hemorrhaging in animals consuming the hay

• Tannins– Present in birdsfoot trefoil– Reduce protein degradation in the rumen and feed

intake

WARM SEASON GRASSES

• Warm season grasses– Perennial

• Switchgrass Big bluestem Eastern gamagrass – Annual

• Sudangrass Sorghum x Sudangrass Corn• Growth

– 70% of production occurs in June and July• Yields

– Very productive– Very sensitive to soil fertility

• N, P, and K• Persistence

– Require rest– Competition with cool season grasses– Very sensitive to early harvest or grazing

USES OF WARM SEASON GRASSES

Species Grazing Harvest CommentsSwitchgrass Fair Fair Perennial

Big bluestem Good Fair Perennial

Eastern gamagrass

Good Fair Perennial

Sorghum x Sudangrass

Good Poor (Hay)Fair (Silage)

Annual

Sudangrass Good Poor (Hay) Fair (Silage)

Annual

Whole plant corn Excellent Excellent (Silage) AnnualCorn stalks Excellent Fair (Baled)

Good SilageAnnual

NUTRITIONAL QUALITIES OF WARM SEASON GRASSES

Compared to:Cool season grasses @

comparable maturityGrains Plant protein

supplements

CP Lower Lower Lower

NDF Greater(Lower for whole plant

corn)

Greater Greater

ADF Greater(Lower for whole plant

corn)

Greater Greater

TDN/NE Lower (Greater for whole plant

corn)

Lower Lower

Ca Comparable Lower LowerP Lower Lower Lower

NUTRITIONAL CONCERNS WITH WARM SEASON GRASSES

• Nitrates– Most common in drought-stricken corn and sorghum

• Highest concentrations in stalks• Also present in some weeds

– Converted to nitrite in the rumen• Inhibits oxygen transport by hemoglobin

– Levels (DM basis)• < 3000 ppm Safe• 3000 - 6000 ppm Limit to 50% of diet for stress animals• 6000 – 9000 ppm Potentially toxic to cattle; Do not feedas only component of diet• >9000 ppm Dangerous to cattle

– Management• Ensile crops

– Take measures to avoid exposure to nitrogen dioxide• Dilute high nitrate feeds with other feeds

– Particularly grains

• Cyanogenic glycosides– Present in new growth of sorghum x sudangrass

and sudangrass forages• May be in spring growth or regrowth after harvest,

drought or frost – Converted hydrocyanic acid (prussic acid)

• Inhibits oxygen uptake by the hemoglobin– Management

• Avoid grazing until forage is a minimum of 18 inches tall

• Excessive corn intake– May occur in cattle grazing standing corn or

grazing corn stalks fields with a large amount of fallen ears

– May result in lactic acidosis or founder of the grazing animals

– Management:• Limit grain intake by controlling access

AnnualPasture Options

Species Digestible OM, %

Crude protein, %

Grasses (Grazed, hay or silage): Annual ryegrass 70 20 Cereal rye 68 22 Brown midrib sorghum or sorghum x sudan

68 12

Wheat 66 9 Triticale 65 9 Oat 65 9 Legumes (Grazed, hay or silage): Berseem clover 60 17 Brassicas (Grazed): Turnips 71 21

ANNUAL FORAGESSpecies

LIMITATIONS OF ANNUAL FORAGES• May have limited production

– Drought– Length of growing season before frost– Shading in standing row crop

• Weather losses of nutrients– Problem with brassicas and berseem clover

• Winter varieties must be killed before planting in the subsequent year– Unless reseeding is desired (Annual rye)

• Limited spring use– Soil compaction– Late growth

• Health problems– Bloat with brassicas and wheat– Goitrogens in brassicas

Chicory

• A perennial broadleaf from sunflower family• Drought resistant• Persistent for three to four years• Uses

– Good for grazing– Poor for harvest

• Good nutritional value:– 60 – 70% TDN– 13 – 16% CP

MATURITY EFFECTS ON FORAGE QUALITY

• Increasing forage maturity– Increases NDF

• Reduces feed intake– Increases ADF and lignin

• Reduces digestibility– Reduces CP and soluble carbohydrates

• Reduces digestiblity

EFFECTS OF MATURITY ON THE COMPOSITION OF FORAGES

I MMaturity

I MMaturity

I MMaturity

I MMaturity

ND

F, %

DM

35

40

45

50

55

60

65

SB

Alf

AD

L, %

DM

5

10

15

CP,

%D

M5

1

0

15

2

0

SB

AlfD

iges

tible

DM

, %D

M45

50

55

60

65

70

SB

Alf

SB

Alf

CHANGES IN PLANT STRUCTURE WITH MATURITY

Immature Mature

CellContents

Primary cell wall(Hemicellulose)

L L L L L L

LL

LL

Secondary cell wall(Cellulose)

CC

Middle lamella(Lignin)

LIGNIN• A complex polymer of phenylpropane units• Binds to hemicellulose in cell wall

– Needed to provide strength to plant• Increases with maturity• Reduces the digestibility of plant cell walls• Bonds to carbohydrates differ between forage

species– Legumes

• Ether linkages• Tough

– Grasses • Ester linkages• Degraded by alkali treatment

STRATEGIES TO MANAGE LIGNIN BEYOND CONTROLLING MATURITY

• Alkali treatments– Mature grass, straw, corn stalks– Treatments

• 3% anhydrous ammonia• 4% sodium hydroxide• 5% calcium oxide

– Effects• Increase digestibility 10%• Increase intake 20%• Only effective on grass lignins

– Economics• Profitable at high feed prices

• Brown mid-rib varieties– Corn and Sorghum– Genetically engineered to have lower lignin

content– Increases digestibility and intake of forage– Reduce stem strength