To evaluate effects of 2-hydroxy-4-( methylthio) butanoic acid isopropyl ester ( HMBi) on milk yield and composition and serum biochemical indicators of dairy cow, 24 Holstein cows were randomized into 2 groups, with the control fed with basal diet only and the treatment group fed with diet containing 20 g?d-1 HMBi ( 21 days before parturition ) and 30 g?d-1 HMBi ( 80 days after parturition) . The trial lasted from 21 days before parturition to 80 days after parturition. Results showed that milk yield from the treatment group increased by 6.83 kg?d-1( P>0.05) compared with the control. Milk protein content increased by 0.14% ( P0.05),牛奶中的乳蛋白率升高了0.14个百分点(P<0.05),体细胞数下降了26.80万个?mL-1(P<0.01).产前14 d时,试验组奶牛血清中的球蛋白含量和尿素氮浓度升高,免疫球蛋白G(IgG)含量降低(P<0.05);产后14 d时,试验组血清中的总胆固醇浓度降低(P<0.01);产后70 d时,试验组奶牛血清中的总胆固醇浓度也降低(P<0.05).结论:在日粮中添加HMBi可以提高奶牛的产奶量,改善血清生化指标,促进机体的脂代谢;同时提高牛奶的乳蛋白含量,有效降低体细胞数.
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