The effects of recombinant bovine somatotropin (rBST) on production and reproductive parameters of Holstein dairy cows, from 60 to 150 days of lactation were evaluated. Forty-one cows were assigned to treatments: 1- no rBST application (control), 2- rBST application 60 days post calving (rBST-60), and 3- rBST application 100 days after calving (rBST-100), in a completely randomized design. The rBST application 60 days post calving significantly increased milk production (14%) and corrected milk production (13%). No effects of rBST administration on milk fat production (% and kg/day), days open, number of services/conception and pregnancy rate and on cow weight gain were observed. The rBST application 60 days after calving increased milk production peak and lactation persistence but did not change the reproductive performance. The rBST application at 100 days after calving did not increase milk production or the reproductive performance of cows.
dairy cow; lactation curve; milk and fat yield; reproduction; somatotropin
