Effect of biostimulation, monensin and recombinant bovine somatotropin on the daily weight gain and onset of puberty of Girolando heifers raised in pastures

Abstract

To evaluate the effect of three management strategies on ovarian function of Girolando heifers raised in a pasture-based system, 80 females with 10 months of age and weight 169,3 ± 26,4 kg were divided in eight groups and submitted by 180 days to the treatments: Control (T1); Biostimulation (T2); Monensin (T3); Recombinant bovine somatotropin (BST) (T4); Biostimulation and Monensin (T5); Biostimulation and BST (T6); Monensin and BST (T7); Biostimulation, Monensin and BST (T8). Oestrus activity was evaluated daily and heifers were weighted every 15 days. Starting from the 15th month of age animals were submitted to ovarian evaluation by ultrasound to verify follicles and corpus luteum. Daily weight gain (kg) was 0,52 ± 0,02 (T1); 0,42 ± 0,03 (T2); 0,68 ± 0,04 (T3); 0,43 ± 0,03 (T4); 0,42 ± 0,04 (T5); 0,42 ± 0,02 (T6); 0,70 ± 0,04 (T7) and 0,53 ± 0,01 (T8), with differences (P<0,05). Weight on the 16th month of age varied from 270 kg (T2) to 323 kg (T3), with differences (P<0,05). The signals of oestrus where observed in females starting from the 13th month of age and the higher concentration of these signals being observed at the 14th (T8) and 15th (T3), compatible with the ovarian activity to the 15 months when the animals of these groups had antral follicles or corpus luteum. The present results allow to conclude that the offer of monensin to pre-pubertal Girolando heifers, alone or in association with bioestimulation and BST allows homogenizing the age at puberty in pasture-based systems, reducing the age of the first service and calving.