Effects of Feeding Aflatoxin-Contaminated Diets With and ...€¦ · tion, and mineral absorption and retention in wean- ling and growing pigs fed control and aflatoxin- contaminated

Effects of Feeding Aflatoxin-Contaminated Diets With and Without Clay to Weanling and Growing Pigs on Performance, Liver

Function, and Mineral Metabolism1

T. C. Schell, M. D. Lindemann, E. T. Kornegay, and D. J. Blodgett

Virginia Polytechnic Institute and State University, Blacksburg 24061-0306

ABSTRACT: Ninety-six crossbred weanling pigs (36 d of age, initial weight of 8.8 kg) were used in a three-phase study to determine the effects of feeding an aflatoxin-contaminated corn (AC) diet (922 ppb of aflatoxin B1) with and without sodium bentonite (clay) on performance, liver function, and mineral metabolism. In the nursery phase, control corn ( N C 1 or AC was fed in corn-soybean meal diets with and without 1% clay for 6 wk. Compared with NC, AC decreased ADFI and ADG ( P c .O 1) and increased serum activities of y-glutamyltransferase ( P < .O 1) and alkaline phosphatase ( P < .05). In the growing phase, 48 pigs from the nursery phase were fed NC but continued on their respective clay treatments for 5 wk. Pigs previously fed AC had higher ( P < .01) ADFI

and lower ( P < .05) gainifeed, serum Ca, K, and glucose; ADG, other serum values, and liver minerals were not affected by treatments. In the metabolism phase, 24 barrows from the nursery phase were continued on the same corn and clay treatments for two 4-d total collections of urine and feces. Feeding AC increased ( P < .05) P and Na absorption. The addition of clay lowered Mg and Na absorption ( P < .01) for both AC and NC. Significant interactions for many minerals indicated that the effects on mineral metabolism were more pronounced when AC was fed. Serum and liver mineral concentrations were generally unaffected by the treatments in all phases. Feeding clay with AC results in partial restoration of performance and liver function without greatly influencing mineral metabolism

Key Words: Pigs, Aflatoxins, Bentonite, Mineral Metabolism, Hepatotoxins, Serum

Introduction

Aflatoxin-contaminated feed is detrimental to the swine industry (CAST, 1989). Reduced feed intake, lowered daily gains, and in some cases reduced feed efficiency have been observed for swine fed contaminated feed (Harvey et al., 1988; Lindemann et al., 1988). The physiological effects of aflatoxin consumption include liver damage characterized by enlargement, release of enzymes into the blood (e.g., aspartate aminotransferase, y-glutamyltransferase, and alkaline phosphatase), and impaired protein synthesis (CAST, 1989). Recent studies have shown that the

lAppreciation is expressed to American Colloid Co., Arlington Heights, IL and the Virginia Pork Industry Board for partial financial support, to the Swine Center staff at the Tidewater Agric. Exp. Sta. for care of the animals; to Gary Apgar and Lisa Flory for laboratory assistance; and to Cindy Hixon for manuscript prepara- tion.

Received March 30, 1992. Accepted January 11, 1993.

J. Anim. Sci. 1993. 71:1209-1218

addition of clays to contaminated diets can greatly reduce the bioavailability of toxins in the gastrointestinal tract (Carson and Smith, 1983; Phillips et al., 1988) due to high adsorptive properties of certain clays. Up to 85% of performance losses due to aflatoxins have been recovered by the addition of .5% clay to the contaminated diets, and alterations in serum clinical chemistry profiles indicative of liver damage due to aflatoxins have also been prevented (Lindemann et al., 1990). However, little is known regarding the effects of inclusion of the clays on the availability of other nutrients.

This study was conducted to examine the effects of feeding sodium bentonite on performance, liver function, and mineral absorption and retention in weanling and growing pigs fed control and aflatoxin- contaminated diets. To exacerbate any potential effects on mineral metabolism, a level of 1% clay (twice the level routinely used in studies with aflatoxin-contaminated corn) was used.

1209

Published December 11, 2014

1210 SCHELL

Materials and Methods

Seven days after weaning, 96 crossbred pigs with an average initial weight of 8.75 kg and age of 36 d were used in a three-phase study (nursery, growing, and metabolism).

Nursery Phase

Weanling barrows and gilts were randomly assigned from outcome groups based on sex, litter, and BW to two concentrations of aflatoxin B1 (0 and 922 ppb) and two levels (0 and 1%) of sodium bentonite (Volclay-90, American Colloid, Arlington Heights, IL) in a 2 x 2 factorial arrangement of treatments. Corn- soybean meal-based diets were formulated to contain 18.9% CP and met or exceeded NRC (1988) requirements for vitamins and minerals (Table 1) . Pigs were given ad libitum access to feed and water. Aflatoxin diets were mixed to contain 922 ppb of aflatoxin B1 ( ABFJ using the appropriate blend of contaminated corn (2,305 ppb of AFB1) and uncontaminated corn (0 ppb of AFB1). Aflatoxin content of the corns used in the diets was determined by HPLC (Pons et al., 1980). All diets were sampled and later analyzed for mineral content.

Pigs were housed in a totally enclosed, environmen- tally controlled nursery in plastic-coated, welded-wire- floored pens (1.22 m x 1.83 m) with three replicate pens (eight pigs per pen) per treatment. Pigs were weighed and feed intake was determined weekly. Blood samples were taken by anterior vena cava venipuncture initially and on d 42 of the 6-wk trial for later serum analysis.

At the conclusion of the nursery phase, two barrows representative of the performance average for their respective treatments were selected from each nursery pen for use in the metabolism phase. From the remaining pigs, two pigs from each pen were randomly selected to be killed by electro-immobilization and exsanguination. After the pigs were killed, their livers and kidneys were removed, weighed, and frozen for later analysis. The remaining 48 pigs were assigned to growing phase treatments as outlined below.

Growing Phase

At the conclusion of the nursery phase, the assigned 48 pigs were moved and housed in 1.52-m x 3.05-m pens (four pigs per pen) with partially slotted concrete floors (60% slotted and 40% solid area). The Protein content of the diets was lowered from 18.9 to 15.9% CP. Although only uncontaminated corn was used (Growing Diets I and 111; Table l), pigs were continued on their respective clay treatments. A clay level of 1% was continued as in the nursery phase. Pigs were allowed ad libitum access to feed and water (nipple waterers). Diets were again sampled for later analysis of mineral content.

ET AL.

Pigs were weighed weekly and feed consumption by pen was determined at that time. After 34 d on test, blood samples were taken from all animals by anterior vena cava venipuncture for later serum analysis. At the conclusion of the trial (d 35), one male and one female pig randomly selected from each pen were killed by electro-immobilization and exsanguination. Livers and kidneys were removed, weighed, and frozen for later mineral determination.

Metabolism Phase

After the completion of the nursery phase, the two barrows (selected as outlined above) from each pen were randomly assigned to one of two groups, A or B.

Group A ( n = 12) barrows were placed in stainless- steel metabolism cages and the same treatments they received in the nursery phase were continued, except that the CP was lowered to 15.9% (Growing Diets I, 11, 111, and IV; Table 1). They were fed 8% of metabolic BW (BW.75) per day divided into two equal feedings (0700 and 1500). Barrows were given 1 h for eating, after which the orts were removed, weighed, and recorded. Deionized water was available for 1.5 h, beginning at the start of each feeding.

Barrows were given 4 d to adjust to the cages. On d 4, at the 0700 feeding, .05% Cr203 was added to all diets and fed. On d 8, barrows were again fed diets to which .05% Cr2O3 was added at the 0700 feeding. Total feces were collected during all feeding periods from the time the first marker was seen in the feces until the second marker was seen. Daily fecal collections were weighed and recorded, and the total fecal collection from each pig was stored at -10°C. Total urine was collected starting 2 h after the feeding of the first marker until 2 h after the feeding of the second marker. Urine was filtered through glass wool into 20-L plastic jugs containing 25 mL of 25% HzS04. The pH of the urine was kept less than 5 at all times to prevent loss of ammonia. Collection jugs were emptied into storage containers, and volumes were recorded daily.

At the end of the collection period, the total volume of urine per pig was measured and mixed, and a representative urine sample (500 mL) was taken for each pig and frozen for later mineral analysis. After thawing at room temperature, total fecal samples for each barrow were oven-dried at 60°C, ground to pass a 1-mm screen, and frozen for later mineral analysis.

Group B pigs ( n = 1 2 ) were fed the same dietary treatments (Growing Diets I, 11,111, and IV) and were placed in 1.22-m x 1.83-m plastic-coated, welded-wire- floored pens (three pigs per pen). The protein level was decreased to 15.9% CP, but aflatoxin and clay treatments were continued as in the nursery phase. Group B barrows were given ad libitum access to feed and water.

After the collection period, the Group A barrows were removed, weighed, and placed in pens (three

EFFECTS OF FEEDING CLAY AND AFLATOXIN TO PIGS 1211

Table 1. Percentage composition of diets

Nursery dieta Growing dietb

Item I I1 I11 IY I I1 I11 IV

Uncontaminated corn Contaminated cornC Soybean meal (48% CP) Soybean oil Dicalcium phosphate Limestone VPI vitamin premix' Trace mineral premixe Salt ASP-250f Aureo-5Og Sodium bentoniteh

68.95

26.90 1 .oo 1.20 1 .oo .25 .05 .40 .25

-

- -

28.95 40.00 26.90 1 .oo 1.20 1 .oo .25 .05 .40 .25 - -

67.95

26.90 1 .oo 1.20 1 .oo .25 .05 .40 .25

1.00

-

-

27.95 40.00 26.90

1.00 1.20 1 .oo .25 .05 .40 .25

1.00 -

76.90

19.00 1.00 1.40 .90 .25 .05 .40

.10

-

-

-

36.90 40.00 19.00

1.00 1.40 .90 .25 .05 .40

.10 -

-

75.90

19.00 1.00 1.40 .90 .25 .05 .40

.10 1.00

-

-

35.90 40.00 19.00 1 .oo 1.40 .90 .25 .05 .40

.10 1.00

-

aCalculated to supply 18.9% CP, .96% Ca, .74% P, and 1.01% lysine. bCalculated to supply 15.9% CP, .74% Ca, .59% P, and ,788 lysine. CCorn contained 2,305 ppb of aflatoxin Bl; diets calculated to contain 922 ppb of aflatoxin. dSupplied per kilogram of diet: 4,400 IU of vitamin A, 440 IU of vitamin D, 11 IU of vitamin E, 4.4 mg of riboflavin, 22 mg of d-pantothenic

eSupplied per kilogram of diet: 150 mg of Zn, 176 mg of Fe, 60 mg of Mn, 17 mg of Cu, 2 mg of I. fSupplied 110 mg of chlortetracycline, 110 mg of sulfamethazine, and 55 mg of penicillin per kilogram of diet. %upplied 55 mg of chlortetracycline per kilogram of diet. hVolclay-90, American Colloid Co., Arlington Heights, IL.

acid, 22 mg of niacin, 489.5 mg of choline, ,022 mg of vitamin BIZ, .5 mg of menadione, .44 mg of d-biotin, and .3 mg of Se.

pigs per pen from the same dietary treatment) similar to those occupied by the Group B pigs. Group A barrows were then given free access to feed and water; dietary treatments were continued. The metabolism cages were then cleaned and the Group B barrows were weighed and placed in the cages. Group B barrows were given 2 d to adjust to the cages, and then a 4-d collection was made using the same procedures as for Group A. At the conclusion of this collection period, Group B pigs were replaced by Group A pigs. After a 1-d adjustment, a 4-d collection was made. Following the collection, Group A pigs were weighed, blood samples were taken by venipuncture, and then the pigs were killed by electro-immobilization and exsanguination. Livers and kidneys were removed, weighed, and frozen for later mineral analysis. Group B pigs were then placed in the cages, and a 1-d adjustment and 4-d collection procedure followed. At the end of the collection, Group B barrows were weighed, killed, bled, and organs were collected using the same procedures as for Group A.

Tissue and Feed Analysis. All minerals except P were analyzed using flame atomic absorption spectrophotometry on a Perkin-Elmer 5100 instrument (Norwalk, CT). Feed, feces, and livers were prepared using nitric-perchloric acid digestion (Perkin-Elmer, 1982). Livers were thawed at 7°C for 24 h then homogenized using a Waring blender before nitric- perchloric acid digestion. When necessary, urine was diluted with deionized water before analysis. For all Ca and Mg analyses, samples were diluted in 1% lanthanum oxide. Phosphorus was analyzed using the Fiske and Sabbarow ( 19 2 5 ) procedure. Nitrogen analysis was performed using the Kjeldahl procedure (AOAC, 1980).

Blood Samples. Immediately after collection, all blood samples were placed on ice for 30 min before they were centrifuged for 15 min. Serum was removed and samples were frozen for later analysis. Serum concentrations of Zn, Cu, Fe, and Mn were determined using flame atomic absorption spectrophotometry. All other serum analyses were performed at the Virginia- Maryland Regional College of Veterinary Medicine using a Kodak Ektachem 700 instrument (Eastman Kodak, Rochester, NY).

Statistical Analysis. All data were analyzed by analysis of variance as a 2 x 2 factorial using the GLM procedure of SAS (SAS, 1988). In the nursery and growing phases, pens were considered the experimental unit for each analysis. In the metabolism phase, serum clinical analysis, liver minerals, and organ weights were analyzed with the individual pig as the experimental unit. Because there was no pig x collection period effect, the absorption and retention data were analyzed as 48 observations. Orthogonal comparisons were used in all phases to determine main effects of aflatoxin and clay and the aflatoxin x clay interaction.

Results

Nursery Phase

Final body weight, ADG, and ADFI were decreased ( P c .01) for pigs fed aflatoxin-contaminated corn (AC) diets compared with those fed control corn (NC) diets (Table 2). Pigs fed diets containing clay consumed more and grew faster ( P < .O 1) than pigs fed diets without clay. The aflatoxin x clay interaction

1212 SCHELL ET AL.

Table 2. Nursery phase performance and serum analysis of weanling pigs fed noncontaminated and aflatoxin-contaminated corn with and without clay

Treatment

Uncontaminated corn Contaminated corna

Items' 0% Clayc 1% Clay 0% Clay 1% Clay SEM

Body wt, kg Initial 8.78 8.78 8.80 8.72 .04 Finald& 29.99 31.19 25.27 28.49 .47

ADG, kgd& .505 ,534 .392 .471 .01 ADFI, kgda 1.10 1.15 .88 1.07 .03 Gainifeede .46 .46 .45 .44 .01 Serum anal sism

46.7 51.0 67.0 57.5 4.1 GGT, UIL 2 J

ALP, u/Leh 129.1 118.3 135.0 127.6 3.7 AST, U,kk 66.1 68.0 81.6 53.6 5.9

Urea N, mg/dLf 13.4 12.1 10.4 11.8 1.0

Albumin, g/dLik 3.5 3.4 3.0 3.7 .2 Total protein, gidd 6.1 5.8 5.6 6.2 .2

CU, mgiLd 1.58 1.67 1.41 1.44 .05 Fe, mg/Lf 1.75 2.06 2.31 2.12 .16

Glucose, rng/dL1 116.6 108.5 100.1 117.0 3.6

aContaminated with 922 ppb of aflatoxin B1 in the diet. bValues are means of three pens (eight pigsipen). Irolclay-90, American Colloid, Arlington Heights, IL. d,e,fEffed of aflatoxin ( P < .01, .05, and .lo, respectively). ghViEffect of clay ( P < .01, .05, and . lo, respectively). J,k%'Aflatoxin x clay interaction (P < .lo, .05, and .01, respectively). mGGT = gamma glutamyltransferase, AST = aspartate aminotransferase, and ALP = alkaline phospha-

tase.

indicated ( P < ,101 that the magnitude of the increase in ADG and ADFI tended to be greater for pigs fed AC diets than for pigs fed the NC diets. Pigs fed the NC diets had higher ( P < .05j gain:feed ratios than pigs fed the AC diets.

Serum y-glutamyltransferase ( GGT) and alkaline phosphatase (ALP) activities were higher ( P < .01 and .05, respectively) for pigs fed the AC than for pigs fed the NC diets (Table 2 j . Pigs fed the clay had lower ( P < .05) serum ALP activity than pigs not fed the clay. The aflatoxin x clay interaction indicated that the clay reduced ( P < .05) aspartate aminotransferase ( AST) activities and tended to reduce ( P < . l o ) GGT activities when fed with AC but not when fed with NC diets. Pigs fed AC diets had lower ( P c .01) serum Cu and tended to have higher ( P < . l o ) serum Fe than pigs fed the NC diets (Table 2). Serum Ca (9.6 mg/ dL), Mg (1.9 mg/dL), P (7.5 mgidL), Na (141.6 mmol/L), K (6.6 mmol/L), and Zn (.6 mgiL) were not affected by the treatments.

Serum urea N tended to be lower ( P < . l o ) in pigs fed the AC, whereas clay had no effect on serum urea N concentration. The aflatoxin x clay interaction for serum glucose showed that the clay lowered glucose concentrations when added to the NC diet but increased serum glucose when added to the AC diet ( P < .Ol j . Although serum albumin concentrations tended to be higher ( P < . l o ) for pigs fed the clay diets, the aflatoxin x clay interaction showed ( P < .05) that the addition of clay to the AC diet increased

albumin concentrations. The interaction of aflatoxin x clay showed a tendency ( P < . l o ) for the clay to increase total serum protein concentrations when added to the AC diet and decrease concentrations when added to the NC diet.

Relative weights of livers were numerically heavier from pigs fed AC than from pigs fed NC diets, and pigs fed AC with clay had liver weights closer to those of pigs fed the NC (Table 3). Weights of kidneys were not affected by aflatoxin or clay treatment. The mineral content of livers on a DM basis was unaffected by the aflatoxin or clay treatment. Mean values were Ca (276 pprn), P (5,614 ppm), Mg (699 ppm), Na (5,325 ppm), K (11,450 ppm), Cu (58 ppm), Fe (990 ppm), and Zn (276 ppm).

Growing Phase

Mineral content of the growing metabolism diets on an as-fed basis was as follows: Ca, .75%; P, .58%; Mg, .14%; Na, .16%; K, .79%; Zn, 120 ppm; Mn, 40 ppm; and Cu, 22 ppm. The Fe content of diets with clay was 446 ppm, whereas the Fe content of diets without clay was 292 ppm. Crude protein content was 15.9%.

As shown in Table 4, ADG was not affected by the previous feeding of AC diets in the nursery phase or by clay that was fed throughout the nursery and growing phases. However, pigs previously fed the AC diets had higher ( P < .O 1) ADFI in the growing phase than did pigs that received NC throughout both phases. The

EFFECTS OF FEEDING CLAY AND AFLATOXIN TO PIGS

Table 3. Weights of livers and kidneys of pigs fed noncontaminated and aflatoxin-contaminated corn with and without clay, expressed as

a percentage of live body weight

Treatment*

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Uncontaminated corn Contaminated corn

Items 0% c ~ a y b 1% Clay 0% Clay 1% Clay SEM

Nursery phase‘ Liver, % 3.16 2.99 3.44 3.05 .24 Kidneys, 8 5 5 .57 .54 5 4 .02

Kidneys, 8’ .35 .36 .39 .38 .01

Liver, o/,ef 1.76 1.66 1.90 1.80 .12

Growing phaseC Liver, %df 1.78 1.67 1.90 1.78 .05

Metabolism phaseg

Kidneys, %d .41 .44 .34 .44 .03

aThese treatments applied in the nursery and metabolism phases; in the growing phase pigs fed the contaminated corn diet in the nursery were fed uncontaminated corn while continuing on the clay treatment.

bVolclay-90, American Colloid, Arlington Heights, IL. Values are means of three pens (two pigs per pen). d’eEffect of aflatoxin ( P < .10 and .01, respectively). fEffect of clay ( P < .05) . Walues are means of six pigs per treatment.

ADFI of pigs fed clay tended to be lower ( P < ,101 than that of pigs not fed clay. Additionally, pigs fed AC in the nursery phase had lower ( P < .05) gain:feed ratios in the growing phase than pigs fed NC in both phases.

No effects were found on serum GGT and AST activities (Table 4). The aflatoxin x clay interaction ( P < .05) showed that when clay was fed with the NC in pigs continuously fed NC, ALP activities were lower than when NC was fed without clay, and when clay was fed to pigs that had previously been fed AC, ALP activities were not reduced.

Serum Ca concentrations were lower ( P < .05) in pigs previously fed AC than in pigs previously fed NC. The aflatoxin x clay interaction showed that pigs previously fed AC with clay tended ( P < . l o ) to have higher concentrations of Ca than pigs previously fed AC without clay. Similarly, the aflatoxin x clay interaction showed ( P < .O 1) higher Fe concentrations in pigs previously fed AC with clay than in pigs previously fed AC without clay. Furthermore, the aflatoxin x clay interaction showed that of the pigs fed the NC in both phases, the pigs that were fed clay had lower Ca and Fe concentrations than pigs that were not fed clay. The clay treatment tended to increase ( P < . l o ) serum Cu concentrations. Pigs previously fed AC had lower ( P < .05) serum K concentrations than pigs not previously fed AC, but the aflatoxin x clay interaction showed ( P < .05) that of the pigs previously fed AC the pigs that received clay had higher serum K than the pigs that did not receive clay. Serum concentrations of Na tended to be lower ( P < . l o ) in pigs previously fed AC than in pigs previously fed NC in both phases.

Serum glucose concentrations of pigs previously fed the AC diets were lower ( P < .05) than those of pigs

fed the NC diets continuously. Serum values for urea N (9.85 mg/dL), albumin (3.6 g/dL), bilirubin (.17 mg/dL), and total protein (6.2 g/dL) did not differ among treatments.

Pigs fed AC diets in the nursery phase tended to have heavier ( P < . l o ) livers and kidneys in the growing phase than those fed NC diets (Table 3). The livers of pigs fed clay were lighter ( P < .05) than those of pigs not fed clay. Liver DM concentrations of Ca (214 ppm), P (5,431 ppm), Mg (745 ppm), Na (3,433 ppm), K (6,681 ppm), Fe (1,089 ppm), Zn (385 ppm), and Cu (42 ppm) were not affected by previous aflatoxin or clay treatment.

Metabolism Phase

The mean gain was 2.5 kg per pig for each collection-adjustment period with no differences among treatments. Initial BW was lower ( P < .01) for pigs fed AC than for pigs fed NC (Table 5 ) . Also, pigs not fed clay had lower ( P < .01) initial BW than did pigs fed clay. Thus, feed intake was lower for pigs fed aflatoxin and no clay because feed intake was based on metabolic BW.

Total wet feces excreted was related to BW and feed intake, because pigs fed AC ( P < .05) and pigs fed no clay ( P < .Ol) had less total feces than pigs fed NC and clay, respectively. Dry matter as a percentage was similar among all treatments. Digestibility of DM was lower ( P < .O 1) for pigs fed diets with clay than for pigs fed diets without clay but was similar for the two types of corn. Crude protein digestibilities were not different among treatments.

Serum profiles at the end of the metabolism phase showed that pigs fed AC diets tended to have higher

1214 SCHELL ET AL.

Table 4. Growing phase performance and serum data of pigs previously fed uncontaminated or aflatoxin-contaminated corn with or without clay

Treatment

Uncontaminated corn Uncontaminated corna

Itemsb 0% Clayc 1% Clay 0% Clay 1% Clay SEM

Body wt, kg Initiald 29.82 30.38 26.06 28.58 1.01 Final 59.42 58.50 61.85 58.73 1.42

ADG, kg .903 .876 .975 .883 ,042 ADFI, kg"g 2.05 1.97 2.38 2.20 .07 Gaidfeedd .44 .44 .41 .40 .03 Serum analysish GGT, UL 57.0 50.6 45.5 51.0 4.8 AST, U/L 57.3 37.5 46.2 41.5 7.8 ALP, U P 169.3 136.4 137.5 142.9 7.8 Ca, mgidLa 10.7 9.7 8.3 9.5 .4 P, mg/dL 7.8 7.1 6.0 7.5 .4

K, mmol/ldi 5.6 5.2 4.1 5.2 .3

Fe, mg/Lk 3.21 2.75 2.68 3.18 .14 Cu, m a g 1.60 1.67 1.57 1.75 .06

Na, mmol/Lf 146.6 142.2 125.6 137.0 6.0 Glucose, rngidLd 105.3 98.1 78.9 90.8 4.8

aPigs were previously fed aflatoxin-contaminated diets (922 ppb of aflatoxin B1) in the nursery phase. bValues are means of three pens (four pigs per pen). Performance values were aausted using initial

Cvolclay-90, American Colloid, Arlington Heights, IL. d,epfEffect of previous aflatoxin feeding ( P < .05, .01, and .lo, respectively). gEffect of clay ( P < .IO). hGGT = gamma glutamyltransferase, AST = aspartate aminotransferase, and ALP = alkaline phospha-

'JPkAflatoxin x clay interaction ( P < .05, . lo, and .01, respectively).

weight as a covariate.

tase.,

( P < . l o ) concentrations of GGT than pigs fed NC diets (Table 5). Serum ALP concentrations were normal and unaffected by both treatments. Serum Zn concentrations tended to be higher ( P < ,101 in pigs fed clay than in pigs not fed clay, the magnitude of the difference being greater for pigs fed the AC diet. The serum Cu aflatoxin x clay interaction ( P < .05) showed that serum Cu concentrations were lower for pigs fed AC without clay than for those fed NC, and concentrations were similar to controls when clay was added to the AC diet. Serum Ca (10.5 mg/dL), P (8.8 mg/dL), Fe (2.6 pgiL), Mg ( 2 . 1 mg/dL), Na (151.0 mmol/L), and K (8.0 mmol/L) concentrations were unaffected by the treatments. Total protein (6.5 g/ dL), albumin (3.8 g/dL), glucose (116.8 mgidL), and urea N (9.85 mg/dL) in the serum were not affected by the treatments.

Pigs fed the AC diets had larger ( P < , O 1) relative liver weights than pigs fed the NC diets (Table 3 ) , and pigs fed clay had smaller ( P < .05) livers than pigs not fed clay. Relative weights of kidneys tended to be smaller ( P < . l o ) in pigs fed the AC diets than in pigs fed the NC diets, the difference being due to the AC diet without clay. Liver minerals (DM basis), including Ca (243 ppm), P (5,600 pprn), Mg (726 ppm), Na (4,333 ppm), K (8,818 ppm), Fe (852 ppm), Zn (400 pprn), and Cu (53 pprn), were also unaffected by clay or AC treatment.

Calcium absorption and retention were elevated when clay was fed with the NC diet and were lowered when clay was fed with the AC diet, as illustrated by the aflatoxin x clay interaction ( P < .01; Table 6). Aflatoxin increased ( P < .05) P absorption and tended to increase ( P < . l o ) P retention compared with pigs fed NC diets. Clay reduced P retention ( P < .05) and tended to reduce ( P < . l o ) P absorption compared with pigs fed no clay. Magnesium absorption and retention were lower ( P < ,011 in pigs fed diets with clay than in pigs fed diets without clay.

Pigs fed AC had higher ( P < .05) Na absorption than pigs fed NC (Table 7), and pigs fed diets with clay had lower ( P < .01) Na absorption than pigs fed diets without clay. Regarding Na retention, the aflatoxin x clay interaction ( P < .05) showed that AC increased N a retention when fed without clay but decreased retention when fed with clay. The addition of clay had no effect on Na retention when added to NC. The absorption and retention of Zn tended to be higher ( P < . l o ) in pigs fed AC than in pigs fed NC. Zinc absorption tended to be lower ( P < . l o ) and Zn retention was lower ( P < .05) for pigs fed diets with clay than for pigs fed diets without clay. The Fe intake was higher ( P < .01) for pigs fed clay diets because of the Fe content in these diets. The absorption and retention of Fe were lower ( P < .05) for pigs fed clay than for pigs not fed clay. Potassium absorption (82.4

EFFECTS OF FEEDING CLAY AND AFLATOXIN TO PIGS

Table 5. Intake, feces, and serum data for the metabolism phase

1215

Treatment


Itemsb 0% Clayc 1% Clay 0% Clay 1% Clay SEM

Feed intake, gdg 4,909 5,220 4,402 4,957 139 Feed DM, % 91.6 91.4 91.2 91.3 .2 Water intake, L 30 31 24 31 4 Feces wet wt, 1,491 1,807 1,286 1,617 95 Feces DM, % 37.5 36.4 36.5 37.7 1.5 Digestibilities

Initial wt, k@g 38.9 41.4 33.4 38.9 1.2

DM, %g 88.1 86.7 88.8 86.8 .5 CP, % , 83.3 82.9 84.3 82.3 .a

GGT, U/Lf 41.2 62.3 72.2 60.2 8.6 ALP, UIL 161.3 127.5 144.5 155.3 9.9 Zn, mgiLh .93 .98 .76 1.02 .07 CU, m a f i 1.90 1.96 1.67 2.03 .07

Serum datd

*Contaminated with 922 ppb of aflatoxin B1 in the diet. bAll values except feed DM values are means of six pigs per treatment. Yolclay-90, American Colloid, Arlington Heights, IL. d,e,fEffect of aflatoxin (P < .01, .05, and .lo, respectively). FhEffect of clay ( P < .01 and .lo, respectively). 'Atlatoxin x clay interaction ( P e .OS). JGGT = gamma glutamyltransferase, AST = aspartate aminotransferase, and ALP = alkaline phospha-

tase.

rfr 1.4%) and retention (26.5 k 4.9%), Cu absorption (20.9 k 8.5%) and retention (18.7 f 8.3%), and Mn absorption (21.9 ic 4.4%) and retention (18.6 k 4.3%) were not different among treatments.

Discussion

Performance. In agreement with the results of Lindemann et al. (1990) and Colvin et al. (19891, our results show that the performance of weanling and growing pigs fed AC diets was improved with the addition of clay to the diets. In the nursery phase, AC decreased ADG and ADFI, which was similar to responses reported by Lindemann et al. (1990). As reported by Panangala et al. (19861, gain:feed ratios were reduced by feeding aflatoxin compared with not feeding aflatoxin. Lindemann et al. ( 1990) reported that the restriction of gains was accomplished by alterations in ADFI because the addition of clay was ineffective in improving gain:feed ratios when fed with AC .

Although final BW were not different in the growing phase, which suggests no apparent long-term negative effects of feeding AC on ADG when it is replaced by NC, as in this study, gain:feed ratios were reduced for pigs previously fed AC. The tendency for lower ADFI for pigs fed clay did not affect growth rate. Similar results have been reported for chickens (Oliver, 1989). The fact that ADG was similar between pigs that continued on the AC in the metabolism phase and those fed NC suggests that

much of the differences in performance due to AC is related to effects of ADFI.

Liver Function. In agreement with findings reported by Harvey et al. (1989b, 1990), serum ALP and GGT were increased by feeding AC in the nursery phase, indicating apparent liver damage. After a 5-wk withdrawal period of AC during the growing phase, effects of AC were noted on serum ALP activities; however, all values were well within normal ranges and did not approach the activities observed by Lindemann et al. (1990), which were almost twofold higher than those observed in the present study. However, the pigs that continued on the AC in the metabolism phase showed sustained liver damage by having higher GGT activities than pigs that continued on the NC. The return of serum ALP activities to normal in the metabolism phase is in contrast to results obtained by Harvey et al. (1989a, 19901, who found serum ALP activities increased in growing pigs fed AC compared with pigs fed NC. However, the pigs in their study were fed AC for 3 wk, whereas pigs in the present study were fed AC for 10 wk and were limit-fed for the periods of collection in the metabolism phase. Our results may indicate a reduction in the production of ALP after prolonged exposure to aflatoxins, or that wide disparities in feed intake may be responsible for much of the difference.

The addition of clay to the AC diet in the nursery phase was effective in reducing the high activities of these enzymes, which is in agreement with results reported by Lindemann et al. (1990). However, in contrast to the results in the nursery phase and the

1216 SCHELL ET AL.

results of Beaver et al. (1990) and Lindemann et al. (1988, 19901, feeding the clay had no effect on serum enzymes of pigs fed the AC diet in the metabolism phase. The lack of a response is due to the lack of a significant increase in AST and ALP serum activities, possibly because the feed intake was restricted. In the nursery phase, when those concentrations were elevated by aflatoxins, the clay was effective in reducing enzyme activities. This suggests that the clay did not act directly, but rather prevented the serologi- cal aberrations normally observed with aflatoxin consumption. The data indicate that aflatoxin is indeed adsorbed in the gastrointestinal tract and the addition of clay limits aflatoxin absorption.

The aflatoxin-induced lower concentrations of serum urea N in the nursery pigs indicate a lower level of protein catabolism with a concurrent lowering of protein synthesis, as evidenced by lower serum albumin (Kaneko, 1989). These results are consistent with previous reports of decreased protein synthesis in pigs during aflatoxicosis (CAST, 1989). In the growing phase, the lack of difference in serum total protein, albumin, and urea N concentrations suggests the recovery of normal protein synthesis after withdrawal from AC. The lack of a response for these protein indicators in the pigs fed AC in the metabolism phase suggests again that feed intake plays a major role in the response. Armbrecht et al. (1971) found graded responses to different concentrations of aflatoxin when fed to grower pigs, indicating higher levels of response to higher concentrations of aflatoxin.

Serum glucose concentrations seem to be reduced by feeding AC in the nursery phase and in the growing phase when pigs were previously fed AC. Limit feeding may have neutralized this effect in the metabolism phase. Feeding clay increased the serum glucose concentrations of pigs fed AC in the nursery phase. This is again probably related to the ability of clay to bind aflatoxin in the gastrointestinal tract.

As reported by Armbrecht et al. ( 197 11, Murthy et al. (1975), and Harvey et al. (1990), the livers of pigs fed AC were heavier than those of pigs fed NC in the metabolism phase. At the end of the nursery phase, the effects due to consumption of AC were not significant, but the absolute increase (. 17 %) was as great as the increase after the metabolism phase (.14%). The enlargement of livers in the growing phase ( P c .05) suggests that the difference in weight in the nursery phase was real but not significant. Also, the liver damage was sustained even after withdrawal of aflatoxin. Feeding clay was effective in reducing the relative liver weights in the growing and metabolism phases, in which AC was found to increase liver size. This is in agreement with the findings of Harvey et al. (198913) and Kubena et al. (19901, who also reported prevention of increased liver weight when clays were fed with aflatoxin. Pigs that were fed AC in the nursery phase tended to have heavier kidneys in the

growing phase. Armbrecht et al. ( 19 7 1) also reproted increased kidney weights in pigs fed 400 ppb of AC for 7 wk.

Mineral Metabolism. The lack of a decrease in serum Ca concentrations in pigs fed the AC diet in the nursery phase probably reflects the slow growth rate of pigs with body stores that were able to keep concentrations normal (Lepine et al., 1985) In the growing phase, the lower serum Ca concentrations for pigs previously fed AC than for pigs previously fed NC might be attributed to the rapid increase in growth rate after removal of the AC. The NRC (1988) has reported an increased need of Ca for faster-growing pigs. In the metabolism phase, the decrease in Ca absorption and retention exhibited when AC was fed with clay is probably due to the relative increase in Ca absorption and retention of pigs fed AC rather than to inherent detrimental effects due to clay because pi.gs fed AC plus clay had absorption and retention similar to that of NC controls and, also, because the clay addition to the NC diet was not detrimental.

The tendency for increased P, Na, and Zn absorption and retention in pigs fed AC may be related to a possible increased need for these minerals. Why the demand for these minerals might be increased during aflatoxicosis was beyond the scope of this research.

Copper metabolism seemed to be related more to performance than to aflatoxin treatment. In the nursery phase, Cu serum concentrations were lower in pigs fed AC diets, which is consistent with their slower growth rate. However, in the growing and metabolism phases, when performance was not different, serum Cu concentrations were not affected by AC. Addition- ally, Cu absorption and retention were not affected by feeding AC.

In the growing phase, the lower serum K and Na in pigs previously fed AC suggests an increased demand for K, possibly because of their increased growth rate. The tendency for higher concentrations of Fe in the serum of nursery pigs fed AC than in that of nursery pigs fed NC is consistent with higher serum Fe concentrations during hemolytic anemia (Lanza et al., 19791, which has also been reported in chickens fed aflatoxins (CAST, 1989). If this relationship also exists in pigs, anemia would seem to persist in the rapidly growing pigs removed from AC in the growing phase, whereas it seems that the pigs that were restricted-fed recovered from the anemic condition of the nursery phase. The absorption of Fe was not increased in this study, as reported by Lanza et al. (1979) in chickens. However, pigs fed the AC did have a numerically higher absorption and retention rate than pigs fed the NC.

The addition of clay to NC and AC diets resulted in some effects on the absorption and retention of Ca, P, Mg, Na, Zn, and Fe with no effects of K, Cu, and Mn. A decrease in Mg absorption by sheep fed clay was also reported by Chestnut et al. (1992). Although Mg

EFFECTS OF FEEDING CLAY AND AFLATOXIN TO PIGS 1217

Table 6. Calcium, growing pigs

phosphorus, and magnesium absorption and retention by fed uncontaminated and aflatoxin-contaminated corn

with and without clay

Treatment


Items 0% Clayb 1% Clay 0% Clay 1% Clay SEM

CalciumCd Intake 596 604 598 600 7 Absorptione 64.1 67.0 71.3 63.3 1.9 Retentione 62.2 64.8 69.6 61.1 1.9

Intake 461 467 463 464 5.2 Absorption? 59.5 58.6 64.2 59.9 1.4 Retention@ 54.8 54.0 60.0 54.5 1.5

Intake , 111 113 112 112 1.3 Absorptio? 33.0 22.9 34.1 25.0 1.8 Retentiod 23.8 12.9 23.8 13.2 1.7

PhosphorusCd

MagnesiumCd

aContaminated with 922 ppb of aflatoxin B1 in the diet. bvolclay-90, American Colloid, Arlington Heights, IL. CIntake milligram~/(days~kiIogram.~~) . dValues are means of six pigs per treatment. Absorption and retention are a percentage of intake. eAflatoxin x clay interaction (P < .01). f,gEffect of aflatoxin ( P < .05 and .lo, respectively). h,iJEffect of clay ( P < . lo, .05, and .01, respectively).

is present in excess amounts in normal swine diets, lowered when clay was added to the NC diet. These the possibility that a long-term problem could arise results suggest the possibility that the clays bind with when high concentrations of clay are fed is open and these minerals in the gastrointestinal tract, making further assessments of the interaction of Mg with them unavailable for absorption, or that the minerals clays are warranted. Whereas the addition of clay to are required in the gastrointestinal tract for purposes the AC diet resulted in a lower absorption and of osmotic balance. A shift in the route of excretion of retention of Ca and Na, only Na absorption was Na has been demonstrated with fiber (Lindemann et

Table 7. Sodium, zinc, and iron absorption and retention by growing pigs fed uncontaminated and aflatoxin-contaminated corn with and without clay

Treatment


Items 0% Clayb 1% Clay 0% Clay 1% Clay SEM

SodiumCd Intake 127 129 128 129 1.5 Absorptioneg 86.9 80.1 88.9 84.7 1.4 RetentionhJ 31.7 32.0 41.9 27.0 3.7

zincd

Absorptionfh 40.3 39.7 47.2 40.6 2.0 Retention' 37.8 37.0 44.7 37.4 2.0

Iron'' Intakeg , 23.2 35.9 23.3 35.7 .3

Intake 9.54 9.67 9.58 9.61 .11

Absorption' 23.7 16.6 34.8 15.4 4.6 Retention' 22.0 15.7 33.2 14.3 4.5

aContaminated with 922 ppb of aflatoxin B1 in the diet. bvolclay-90, American Colloid, Arlington Heights, IL. 'Intake milligrams/(days~kilogra~n.~~). dValues are means of six pigs per treatment. Absorption and retention are a percentage of intake. e,fEffect of aflatoxin ( P < .05 and . lo, respectively). g,h,iEffect of clay (P c .01, .lo, and .05, respectively). JEffect of aflatoxin x clay interaction ( P c ,051.

1218 SCHELL

al., 1986). Although absorption was altered, absolute retention was not affected in NC-fed pigs. The lower percentage of Fe absorbed and retained when the clays were fed may reflect the higher concentration of Fe in the diets with the clays. When the mineral concentration in the diet exceeds the level of requirement by the animal the efficiency of absorption is reduced (Geor- gievskii et al., 1982).

The lack of a response of the mineral concentrations of the liver to the AC suggests that the alterations in mineral metabolism due to feeding AC are not mediated by the liver.

Implications

These experiments show that clay can effectively reduce some of the toxic effects associated with feeding aflatoxin to pigs. Performance and liver function were enhanced by the addition of clay to aflatoxin-contaminated diets, and mineral metabolism was only slightly affected by the clay. The inability of the clay to restore all functions indicates different degrees of sensitivity of the functions examined to aflatoxins. The binding of only part of the available aflatoxins in the gastrointestinal tract, leaving some aflatoxins available for absorption, would allow the more aflatoxin-sensitive traits to still be adversely affected.

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Effects of Feeding Aflatoxin-Contaminated Diets With and ...€¦ · tion, and mineral absorption and retention in wean- ling and growing pigs fed control and aflatoxin- contaminated