Effect of rbST on weight gain and fat cover of heifers in semiconfinement

The objective of this study was to evaluate the effect of recombinant bovine somatotropin (rbST) on average total weight gain, average daily gain, muscularity and finishing. 24 Nellore heifers were used, up to two years of age and weighing 307.4 kg. The animals were semi-confined in Brachiaria ruziziensis and were supplemented per day, with 1.5% kg live weight per animal feed. Heifers were divided into 2 groups, T1: with the use of rbST and T2: unused rbST (control). The rbST was applied every 14 days at a dose of 500 mg per animal. For the statistical analysis, the results were submitted to analysis of variance (ANOVA) at 5% significance level. There was no significant difference (p> 0.05) for average initial body weight, average final body weight, total average gain and average daily gain, and ribeye area (REA) adipose tissue thickness. Therefore the use of rbST did not promote change in performance characteristics in Nellore heifers 2 years old.