The Effect of Recombinant Bovine Somatotropin Administration on Milk Production, Some Hemato-Biochemical Parameters and Reproductive Performance of Lactating Cows

An experiment was conducted to examine the effect of bovine somatotropin on the milk yield, hematology, some serum biochemicals values and some reproductive performance of primiparous and multiparous cows. Sixty Holstein-Friesian cows were divided into 2 groups; 30 primiparous and 30 multiparous, each group was further sub-divided into 3 subgroups each of 10 cows, the first group was served as control while the 2nd and 3rd groups were injected once every 2 weeks for 5 months with 250 and 500 mg of bovine somatotropin (rbST), respectively. For all groups, milk production/day was registered during the whole period of the experiment. Blood samples were collected for the hematological examination and some serum biochemical parameters. The reproductive performance as expressed by days-open and conception rate were recorded. Supplementation with rbST resulted in significant increase in the average milk production especially in multiparous cows given rbST. The hematological parameters revealed a non significant changes in the erythrogram while leucogram showed a non significant leucocytosis accompanied with neutrophilia and lymphocytosis, the activity of both AST and ALT and creatinine revealed non significant changes in both primiparous and multiparous cows given rbST. While the level of insulin, total protein, albumin and lipogrammes revealed non significant increase in both primiparous and multiparous cows given rbST, while, level of urea and calcium showed significant decrease and phosphorus level showed a reverse trend in cows received rbST. Regarding the days-open in months the study showed non-significant differences between subgroups for primiparous cows while there was apparent increase in multiparous cows receiving 250 and 500 mg bST. An improvement of conception rate (%) in all treated cows as compared with that of control was observed.