Authors: İSMAİL ABAŞ, HAYDAR ÖZPINAR
Abstract: The aim of this study was to investigate the influence of growth hormone (rbST)on milk yield, milk composition, animal health and sera concentration of glucose, GOT, GPT, insulin, free fat acids and blood urea of Holstein dairy cows. In this study,20 primiparous Holstein dairy cows were treated with rbST or placebo (control)in weeks 10-18 and 20-28 of lactation. In the first treatment period, the ten cows of the treatment Group A were administrated 500 mg methionyl bovine growth hormone, and the other ten cows (Group B)the same quantity of placebo.The treatment with growth hormone or placebo was switched over in the second period. Growth hormone was administered subcutaneously every 14 days during the treatment period. In the first treatment section during growth hormone administration, the amounts of milk yield and FCM (4 % Fat-corrected Milk) were higher in treated than in non-treated animals by 20.30% and 22.18% respectively (p<0.001). Milk fat and lactose levels were elevated significantly, 5.40% and 6.70% respectively (p<0.05). In the second treatment period during rbST administration,the amounts of milk yield and FCM were higher in treated than in non-treated animal by 11.30%and 14.30% respectively (p<0.01). Milk SNF, protein and lactose levels were not changed.Milk fat levels increased by 1.60%(p<0.05). The mean glucose, urea, GOT, GPT, insulin, and free fat acid levels between the two experimental groups were not significantly different. The results of this study show that milk yield, milk fat and lactose levels were significantly increased by exogenous administration of rbST. No differences in animal health and blood parameters were observed between control and rbST treated cows.
Keywords: Dairy cows, somatotropin hormone (rbST), milk yield, milk composition, animal health.
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