Effect of recombinant bovine somatotropin on sheep milk production, composition and some hemato-biochemical components

Effect of recombinant bovine somatotropin (rbST) on milk production, composition and some hemato-biochemical characteristics were studied in Rahmani sheep. Fifteen Rahmani ewes in their third to fourth lactation season and at 30-40 days postpartum were divided into three groups, five animals each. The first group was served as control, while the second and third groups were injected, once every other week for 60 days, with low (50 mg per ewe) and high (100 mg per ewe) doses of rbST, respectively. Injection with rbST significantly (P < 0.01) increased total milk yield by 19.0 and 27.0% for low and high doses, respectively compared with control ewes. Body weight and dry matter intake of ewes were not affected by rbST treatment. While, average daily gain (ADG) of lambs that were suckling rbST-treated ewes was higher (7.7 and 11.0% for low and high dose of rbST, respectively) than for lambs of control ewes during the treatment period. Milk protein was significantly (P < 0.05) increased, while total solids, fat, lactose and ash were not affected by the treatment. Also, hematological parameters, plasma proteins and the activities of plasma aspartate aminotransferase (AST), alanine aminotransferase (ALT), glutathione S-transferase (GST), alkaline phosphatase (AlP), acid phosphatase (AcP), and the levels of thiobarbituric acid-reactive substances (TBARS) did not change. Administration of rbST reduced urea, creatinine, total bilirubin and cholesterol concentration in plasma. The results of the present study suggest that rbST is efficacious in increasing milk yield and kid growth up to 100 mg/14 day without adverse effects on lactating ewes.