Long term use of bovine somatotropic (bST) on reproduction and health of Nili-Ravi buffaloes

The study was conducted to determine the effect of long term use of bovine somatotropic hormone (bST) on days to first oestrus post-partum, number of services per conception, pregnancy rate, lactation length, dry period and calving interval for a period of three years, from 2004 to 2007. Thirty Nili-Ravi lactating buffaloes with approximately similar milk yields and stage of lactation were selected and randomly allocated to two treatments, A and B, with 15 animals in each group. Group A served as control while animals in group B were given injections of bovine somatotropic hormone (250 mg intramuscular per animal) at intervals of 14 days over a period of three years. The calving interval, dry period and lactation length were shorter by 71, 63.9 and 7 days, respectively, in the treated compared with the control group. The days to first oestrus post-partum, service period and services per conception were 160 +/- 56.9 vs. 98.2 +/- 76.4 days, 207.0 +/- 85.0 vs. 115.1 +/- 107.0 days and 1.47 +/- 1.1 vs. 1.31 +/- 0.5 in group A vs. B, respectively. Statistically, differences were significant for post-partum oestrous and service period but for services per conception the difference was non-significant. Prevalence of mastitis was significantly higher in the treated animals while differences in body weights of the animals in the groups were not significant.