Effect of different levels of monensin in diets containing whole cottonseed on milk production and composition of lactating dairy cows

Document Type: Full paper (Original article)

Authors

1 Department of Animal Sciences, College of Agriculture, Ilam University, Ilam, Iran

2 Department of Animal Sciences, College of Agriculture, Shiraz University, Shiraz, Iran

3 Graduated from College of Agriculture, Ilam University, Ilam, Iran

4 Department of Animal Sciences, College of Agriculture, Gilan University, Rasht, Iran

Abstract

The objective of this study was to determine the effects of feeding different levels of monensin on feed
intake, milk production and composition, and milk fattyacid profile in lactating Holstein cows. Four
multiparous cows averaging 517 ± 47 (SD) kg in body weight and 101 ± 19.8 (SD) days in milk were housed
individually in tie-stalls. The study was conducted as a 4 × 4 Latin square design for four periods (14-d for
adaptation and 7-d for sampling). Cows were offered four dietary treatments (0, 10, 20, or 30 mg of
monensin/kg of DM) as total mixed ration, twice daily. Dry matter (DM) intake was similar among
treatments. Monensin supplementation significantly increased (P<0.05) milk yield and 4% fat corrected milk
(FCM). Milk fat and protein percentages were not affected by monensin supplementation, but fat yield was
increased. Monensin reduced the percentage of the short-chain and saturated fatty acids in milk fat, but had
no effect on the percentages of medium- and long-chain fatty acids. Monensin supplementation increased
(P<0.05) unsaturated fatty acids concentrations in milk fat. Based on the results of this study, feeding
monensin was effective in inhibiting the biohydrogenation of unsaturated fatty acids in the rumen, and
consequently increased the percentageof unsaturated fatty acids in milk fat, which improves the health
characteristics of milk for human consumption.

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