How to use recombinant bovine somatotropin in crossbred Holstein x Gyr (¾ and 7/8) cows?

Abstract Our objective was to evaluate the effects of dose, start and application interval of recombinant bovine somatotropin (rbST) on performance, health, and reproduction parameters of 180 crossbred Holstein x Gyr dairy cows (¾ and 7/8). The statistical design in a 2 x 2 x 2 factorial design included: application dose (250 or 500 mg) x starts of application (40 or 63 days in milk – DIM) x application interval (12 or 14 d). The treatments with 500 mg – rbST (rbST 500) resulted in increased milk production, 3.5% fat-corrected milk (FCM), and energy-corrected milk (ECM). In the factorial design analysis, an increase in the production of FCM, ECM, and milk solids production (kg/d) were observed when the rbST 500 started at 63 DIM, while for the animals that received 250 mg – rbST was observed increase in milk production (kg/d), FCM, ECM, and milk solids production (kg/d) when it was performed every 12 d. In rbST 500 there was an increase in the number of open days and number of services per pregnancy (P = 0.01). The Holstein-Gyr cows (¾ and 7/8) showed better response to rbST when treated with 500 mg, started at 63 DIM, and performed every 14 d.