effects of feeding monensin sodium to lactating goats: milk composition and ruminal volatile fatty...

Effects of Feeding Monensin Sodium to Lactating Goats: Milk Composition and Ruminal Volatile Fatty Acids

D. L. BROWN ~ and O. E. HOGUE Corneil University Ithaca, NY 14853

A B S T R A C T

When diets containing 33 and 18 ppm monensin sodium were fed for ad l ibitum intake to dairy goats, milk fat content was reduced by 15 and 5%. Milk protein content was increased 10% when 33 ppm sodium monensin was fed with diet at restricted intake. Milk yield was not af- fected. Both ad libitum and restricted consumption of diet containing 33 ppm monensin sodium reduced ratios of rumi- hal acetate:propionate. These resulted from increased propionate concentration with ad l ibitum consumption and from reduced acetate with restricted feeding. Diets containing 18 ppm monensin sodium resulted in slightly higher concentrations of both propionate and acetate. Monensin sodium did not reduce feed intake significantly.

I N T R O D U C T I O N

Monensin is a carboxylic ionophore pro- duced by Streptomyces cinnarnonensis. In both in vitro and in vivo environments, mixed populations of monensin-fed ruminal organisms produce more propionic acid with respect to acetic and butyric acids than populations of organisms not challenged by monensin (13). Armstrong and Blaxter (2) reported that ruminal infusions of propionic acid at 10% of the intake of metabolizable energy of lactating does resulted in an average reduction of 15% milk fat content and an average increase of 12% milk nitrogen content. These two observations together with observations of monensin-induced milk fat depression in cattle (10, 11) and reports of amino acid sparing in male goats fed monensin

Received July 16, 1984. a Depar tment of Animal Science, University of

California, Davis 95616.

(4) resulted in the formation of the following hypothesis: if lactating goats are fed monensin sodium, then they will produce milk with lower fat content and higher protein content than similar does fed a control diet.

The hypothesized changes of milk composition were expected to be accompanied by increased ruminal propionic acid.

M A T E R I A L S A N D METHODS

Methods Specific to Trial 1

Fourteen mult iparous French Alpine does were fed complete mixed diets (Table 1) during the 4th mo of lactation. Seven of those does received 33 ppm monensin as part of their diet, and the other seven received a diet free of monensin. During the first 10 days, does were fed according to previous production and estimated energy requirements (5) to maintain body weight. The goats were fed for ad libitum consumption during the second 10 days. All animals were hand-milked and fed in the same order each day at 0600 and 1800 h. Fresh water was available at all times. Milk was weighed daily and double-sampled at both morning and evening milkings on the last 2 days of each 10-day feeding period. One duplicate was preserved with potassium dichromate and the other was frozen. Ruminal fluid was drawn at 0900 h on the last day of each 10-day feeding period. The sample was drawn with a syringe through a 1-cm diameter polypropylene tube that was passed down the esophagus of each doe.

Methods Specific to Trial 2

Ten mature does and 14 yearlings were assigned randomly (within age groups) to one of two monensin concentrations (18 or 0 ppm). Does were offered fresh feed (Table 1) free choice once each day at about 0800 h for 1 calendar month. Fresh water was replenished

1985 J Dairy Sci 68:1141--1147 1141

1142 BROWN AND HOGUE

TABLE 1. Ingredient and nutrient composition of experimental diets.

Trial 1 Trial 2 Ingredients Control Monensin Control Monensin

Alfalfa-grass hay, % 58.5 58.5 59.9 59.9 Shelled corn, % 35.0 35.0 34.9 34.9 Soybean meal, % 5.0 5.0 3.0 3.0 Dicalcium phosphate, % 1.0 1.0 1.0 1.0 Trace mineral salt, % .5 .5 .5 .5 Corn oil, % 0 0 .7 .7 Monensin sodium, ppm 0 33.0 0 18.0

Nutrient composition ~ NE I estimated, mcal/kg 2 1.69 1.68 1.56 1.59 Crude protein, % 16.7 16.8 16.7 16.9 Calcium, % 1.1 1.2 1.04 .89 Phosphorus, % .5 .5 .45 .45

Percentage of dry matter. 2 Net energy for lactation estimated from acid detergent fiber (ADF) content by: NE 1 = .886 - (.007 ×

%ADF).

after each milking. The herd was machine- milked in the same order each day beginning at 0600 and again at 1800 h. Milk was weighed daily and sampled at both milkings on days 1, 7, 15, 23, 28, 29, and 30 of the experimental period and preserved with potassium dichromate. In addition, duplicate samples were quick-frozen during the last two milkings of the experimental period.

Ruminal fluid was drawn at 1000 h at the end of the month experimental period. Daily feeding was delayed until after sampling to allow an unweighted stomach tube to penetrate the ruminal pack. Consequences of taking Trial 2 samples 26 h after the previous feed offering are discussed later.

Analyses

Acid detergent fiber (ADF), crude protein, and calcium analyses were by methods of Goering and Van Soest (7), Kjeldahl (modified) (14), and atomic absorption (1), respectively. Phosphorus was determined by spectropho- tometry (1). An estimate of net energy for lactation (NEt) was from ADF content of the equation: NE 1 = .886 - (.007 × %ADF). Milk fat and milk protein content were measured by a Foss Milko-Scan device.

Lactose was measured in thawed, homoge- nized milk samples by the method of Feitosa Teles et al. (6). Ruminal volatile fatty acid con-

centrations were measured by gas chromatog- raphy from metaphosphoric acid deproteinized samples. One-microliter samples were injected onto a 1.8 m × 32-mm metal column containing 10% SP 1000 and 1% phosphoric acid (H3PO4) 100/120 on Chromasorb WAW in a Varian 3000 gas chromatograph at 125°C.

Student t tests (15) were applied to Trial 1 data. Comparisons were between treated animals and controls of restricted and ad libitum regimens.

Two-way classified analysis of variance of equal numbers within rows (15) were applied to Trial 2 data for potential differences from monensin, age, and interaction of monensin × age.

RESULTS AND DISCUSSION

Milk Composition

Means for milk, ruminal, feed, and body variables are in Tables 2 and 3. The summary of Trial 1 compares monensin and controls for two feeding styles. The summary for Trial 2 compares treatment effects for monensin and for age.

Monensin reduced milk fat content in both trials for does fed ad libitum. Only when feed intake was restricted did monensin substantially increase milk protein content. No treatment effect on milk lactose was detected, although

Journal of Dairy Science Vol. 68, No. 5, 1985

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TABLE 3. Means for milk composition, ruminal fluid analyses, feed intake, and body weight (Trial 2).

Monensin Age Item 18 ppm 0 ppm >2 yr <2 yr

No. 12 12 10 14

Milk Yield, kg/day 2.37 2.41 2.34 2.44 Fat, g/lO0 ml 3.31 3.49 a 3.35 3.45 Fat, g/day 79 84 79 84 Protein, g/lO0 ml 2.98 b 2.90 2.92 2.96 Protein, g/day 71 70 69 72 Lactose, g/100 ml 5.19 5.51 5.50 5.23 Lactose, g/day 123 133 129 128

Rumen fluid pH 6.63 6.71 6.84 a 6.50 Acetate (A), mad 25 b 21 19 27 a Propionate (P), mad 8 c 6 5 8 a Butyrate (B), mM 6 6 4 7 a A + P + B, mad 40 b 32 27 42 a Ratio A:P x 3.6 3.5 3.5 3.6

Feed intake Feed, kg/day 2.3 2.5 2.7 a 2.1 Feed, kg/100 kg body weight 5.07 5.15 4.81 5.57 b

Body weight Body weight, kg 48.8 47.3 56.4 a 39.0 Body weight change, kg/mo 1.3 1.9 0 2.7 a

aLarger than the other member of pair (P<.01). bLarger than the other member of pair (P<.IO). CLarger than the other member of pair (P<.05). 1 Ratio of ruminal acetate concentration to ruminal propionate concentration.

means for Trial 2 were h igher and more var iable t han those for Trial 1.

Milk yields were no t a f fec ted b y monens in . Fa t and p ro t e in yields t e n d e d to vary w i t h fa t and p ro te in percentages .

In the i n t e r ac t i on b e t w e e n m o n e n s i n and age (Table 4), y o u n g does were more suscept ib le to m o n e n s i n - i n d u c e d milk fat depress ion t h a n were o lder does, and mos t of t h e con t r a s t in mi lk fa t pe rcen t b e t w e e n m o n e n s i n c o n t e n t s was f rom y o u n g subclasses. Feed in take (kg/ 100 kg b o d y we igh t ) also d i sp layed i n t e r ac t i on (P< .01) in w h i c h y o u n g an imals a te m o r e w h e n fed monens in , b u t old an imals a te less (Table 5). The grea te r r e d u c t i o n of mi lk fat pe r cen t was associa ted w i th grea te r in t ake (kg /100 kg) of monens in - l aden feed.

Effects on milk sec re t ion were as hypo- thes ized, b u t m o n e n s i n effects were no t as large

as t hose o f t en associa ted w i th t he p r o f o u n d fa t depress ion wi th grain-fed dairy catt le. Resul ts f rom these goa t trials were c o m p a r a b l e w i th m o n e n s i n effects observed b y P a n k h u r s t and coworker s in ca t t le (10, 11).

The 33 p p m m o n e n s i n was a s soc i a t ed w i th 15% r e d u c t i o n of mi lk fat c o n t e n t , and the 18 ppm caused a 5% overall r educ t ion . These ex- p e r i m e n t s were no t des igned to tes t dosage (in fact , o t h e r fac tors are c o n f o u n d e d w i th m o n e n - sin concen t r a t i on ) , bu t fu tu re inves t igators are advised to use doses of at least 33 p p m if t h e y expec t to s tudy subs t an t i a l mi lk c o n s t i t u e n t changes caused b y feeding m o n e n s i n to goats.

Rumen Volatile Fatty Acids

Table 3 displays rumina l f lu id volat i le f a t t y acids ( V F A ) for Trial 1. As expec ted , m o n e n s i n caused a r educ t i on o f the ra t io of ace ta t e :


MONENSIN AND LACTATING GOATS 1145

TABLE 4. Milk fat content, interaction of monensin X age (Trial 2).

Monensin Item >2 yr <2 yr means

Control 3.37 3.60 3.49 Monensin 3.33 3.29 3.31 Age means 3.35 3.45 3.40

F Factor ratio P

Monensin (M) 9.54 <.01 Age (A) 2.13 >. 10 M × A 4,28 <.05

propionate. When intake was restricted, the altered ratio was due to reduced acetate of the control diet. When does were fed ad libitum, the reduced ratio was driven primarily by greater propionic acid concentrations.

The ad libitum feeding of monensin both reduced milk fat and increased ruminal propionic acid concentrations but did not increase protein content of milk. Beede (4) demonstrated that feeding 27 ppm monensin or abomasal infusions of glucose or propionate reduced glucose and threonine turnover in goats (suggesting a sparing of amino acids from gluconeogenesis). The restricted feeding of monensin resulted in the predicted enhancement of milk protein content, but at the same time it not only failed to increase propionate concentrations but appar- ently reduced concentrations of acetate and total VFA. Although entry rates were not measured, something other than propionate alone is

responsible if amino acids are spared by monensin treatment. In experiments with wether goats, Beede (3) concluded that monensin increased nitrogen absorption by reducing micro- bial degradation of feed protein.

The ruminal fluid sampling methods during the second trial probably resulted in the low VFA of Table 6. Does ate most of their daily feed within a few hours after it was offered, although there was always some feed in front of them. The main postprandial pulse of VFA production probably had passed by the time the does were sampled, a day after the previous feed offering (8, 9). Young animals maintained higher VFA concentrations than aged does. This is consistent with the casual observation that the young does seem to eat longer than older does.

Monensin did not affect the ruminal ratio of acetate:propionate in the second trial, although

TABLE 5. Feed intake, interaction of monensin × age (Trial 2) (kg/lO0 kg body weight).

Monensin Item >2 yr <2 yr means

Control 5.25 5.08 5.15 Monensin 4.37 5.57 5,07 Age means 4.81 5.32 5,11

F Factor ratio P

Monensin (M) .10 >.1 Age (A) 3.95 <.1 M X A 7.11 <.05



TABLE 6. Mean squares for milk, luminal fluid, feed intake, and body weight (Trial 3).

Monensin Item (M) Age (A) M × A Residual

df 1 1 1 2O

Milk Yield, kg/day 0 .06 .38 .41 Fat, g/100 ml .24** .05 .11" .03 Protein, g/100 ml .03 t .01 0 .01 Lactose, g/100 ml .63 .44 .68 1.35 Fat, g/day 126 182 188 499 Protein, g/day 24 84 363 342

Rumen fluid analyses pH .05 .69** .04 .03 Acetate (A), mM 150 t 424** 91 52 Propionate (P), mM 27* 50"* 4 .87 Butyrate (B), mM 0 38** 1 4 A + P + B, rnM 398 t 1314"* 100 108 Ratio A:P .01 .04 .02 .42

Feed intake Intake, kg/day .1 2.1"* .6 .2 Intake, kg/lO0 kg body weight .04 1.52 t 2.74** .39

Body weight Avg body weight, kg 12 1638"* 0 40 Body weight gain, kg/mo 2 42* * 8 4

tp<.10.

*P<.O5. **P<.01.

the re m a y have b e e n a sl ight increase o f V F A concen t r a t i on .

A l t h o u g h R a u n et al. (12) r epo r t ed t h a t feeding m o n e n s i n caused m a r k e d depress ion of in take of c o n c e n t r a t e die ts b y f a t t en ing steers, no s ignif icant r e d u c t i o n o f feed in t ake was observed in l ac ta t ing does fed m o n e n s i n .

Young does were smaller and a te less t h a n o lder does, b u t dur ing the e x p e r i m e n t a l per iods yearl ings ate m o r e per 100 kg b o d y weight .

F u t u r e e x p e r i m e n t s shou ld focus on rela- t ionsh ips a m o n g m o n e n s i n effects on pro- p iona te me tabo l i sm, feed intake, and mi lk compos i t i on . Doses of 3 3 p p m or more m o n e n - sin in t he d ie t m a y be needed to ensure m o n e n - sin has an ef fec t suf f ic ien t for s tudy .

ACKNOWLEDGMENT

The au tho r s t h a n k D. Sacke t t and M. T h o m p s o n for t he i r exper t care and mi lk ing o f expe r imen t a l does.

REFERENCES

1 Association of Official Analytical Chemists. 1980. Pages 136, 139 in Methods of analysis. 13th ed. Assoc. Offic. Anal. Chem., Washington, DC.

2 Armstrong, D. G., and K. L. Blaxter. 1965. Effects of acetic acid propionic acids on energy retention and milk secretion in goats. Proc. 3rd Syrup. Energy Metab. Eur. Assoc. Anim. Prod. Publ. No. 11:67.

3 Beede, D. K., G. T. Schelling, G. E. Mitchell, Jr., and R. E. Tucker. 1978. Dietary protein utilization in growing goats fed monensin. Univ. Kentucky, College Agric. Exp. Stn. Progr. Rep. 241:11.

4 Beede, D. K., G. T. Schelling, G. E. Mitchell, Jr., and R. E. Tucker. 1980. Gluconeogenesis from threonine in growing goats abomasally adminis- tered glucose, propionate, oleate or fed monensin. J. Anim. Sci. 51(Suppl. 1):345. (Abstr.)

5 Brown, D. L. 1980. Nutrition of lactating dairy goats. Pages 7 1 - 7 7 in Proc. Cornell Nutr. Conf.

6 Feitosa Teles, F. F., C. K. Young, and J. W. Stull. 1978. A method for rapid determination of lactose. J. Dairy Sci. 61:506.

7 Goering, H. K., and P. J. Van Soest. 1970. Forage fiber analysis. Pages 8--9 in USDA Agric. Hand-


MONENSIN AND LACTATING GOATS 1147

book 379. 8 McClymont, G. L. 1949. Acetic acid in bovine peri-

pheral blood and its utilization by the mammary gland. Biochem. J. 45:i.

9 McClymont, G. L. 1950. Volatile fatty acid metabolism of ruminants with particular reference to the lactating bovine mammary gland and the composit ion of milk fat. Aust. J. Agric. Res. 2: 158.

10 Pankhurst, I., and A. McGowan. 1978. Monensin administration to cows in early lactation. Pages 50--51 in Res. Rep. 1978, Dairy Res. Inst., Ellin- bank Kyabram, Victorian Dep. Agric.

11 Pankhurst, I., I. Robinson, and A. McGowan. 1977. Effect of monensin, cobalt and hien on milk composit ion and yield. Pages 3 3 - 3 4 in Res. Rep.

1977, Dairy Res. Inst., Ellinbank Kyabram, Vic- torian Dep. Agric.

12 Raun, A. P., C. O. Cooley, E. L. Potter, R. R. Rathmacher, and L. F. Richardson. 1976. Effect o f monensin on feed efficiency of feedlot cattle. J. Anita. Sci. 43:670.

13 Richardson, L. F., A. P. Raun, E. L. Potter, C. O. Cooley, and R. R. Rathmacher. 1976. Effect of monensin on ruminal fermentat ion in vitro and in vivo. J. Anita. Sci. 43:657.

14 Scales, F. M., and A. P. Harrison. ].920. Boric acid modification of the Kjeldabl me thod for crop and soil analysis. J. Ind. Eng. Chem. 12:35.

15 Snedecor, G. W., and W. G. Cochran. 1980. Pages 92, 416 in Statistical methods. Iowa State Coll. Press, Ames.

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effects of feeding monensin sodium to lactating goats: milk composition and ruminal volatile fatty...

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