Two 250 mg doses of bovine somatotropin increase conception rate, IGF-I plasma concentration and reduce the days to estrus in Holstein cows following estrus synchronization

Abstract

To determine whether the administration of two low doses of recombinant bovine somatotropin (bST, 250 mg each) improves conception rate in Holstein cows when using a. protocol of estrus synchronization 266 multiparous, postpartum first service Holstein cows were used. Control cows (CON; n=158) were injected with placebo and bST cows (TRT; n=108) received two doses of 250 mg of bST on d 56 and 67±2 d (at the time of AI). Insulin-like growth factor-I plasma concentration was higher in TRT cows (d 58; P<0.01 and d 62; P<0.05) and conception rate was also higher in TRT cows (P<0.05). Days to estrus in TRT cows were shorter (62.2±0.8 vs 74.1±0.9; P<0.01). Milk production was higher in TRT cows (58 to 63 d; P<0.05). The results indicated beneficial effect of bST given in two divided doses in respect of conception rate, insulinlike growth factor-I plasma concentration and days to estrus in postpartum lactating dairy cows. © GSP, India.