Recombinant Bovine Somatotropin (Rbst) on performance and body characteristics of creep-fed crossbred calves

Abstract

This study aimed to evaluate performance and body characteristics of crossbred calves submitted to recombinant bovine somatotropin (rbST) and creep-feeding. Sixty-four animals aging 60 days were divided in four groups: T1 (16 heifers rbST), T2 (17 heifers control), T3 (15 steers rbST), T4 (16 steers control). Randomized factorial 2 x 2 design used as “A” sex and “B” rbST. The animals were fed in pasture “ad libitun” and creep. Every 14 days animals received rbST doses (0,15 mg kg/BW/day) from 60 until 210 days. Body weight and bone development were evaluated by weighting and measurement of ankle perimeter every 14 days. For Longissimus dorsi muscle area and thickness fat, ultrasonography at 150 and 210 days was used. Results showed no significant difference (P > 0.05) among the steers for weight gain, but the heifers showed difference (p < 0.05). For Longissimus muscle area steers showed a higher mean than heifers at 150 and 210 days however there was no difference between rbST animals and control, but for fat thickness it was observed significant difference (p < 0.05) between heifers and steers. For bone growing there was no significant difference (p > 0.05) between rbST animals and control but there was difference between sexes. Thus the use of rbST (0.15 mg/BW/day) increased by 9% the body weight of heifers creep-fed.