Pre- and post-weaning injections of bovine somatotropin to optimize puberty achievement of beef heifers.

The present study evaluated the growth and puberty attainment of heifers administered recombinant bovine somatotropin (bST) or saline injections during preweaning and/or postweaning. On day 0, 177 suckling Nellore heifers were stratified by initial age and body weight (BW) (80 ± 10 d; 97 ± 16 kg), and randomly assigned, in a 2 × 2 factorial design ( = 44 to 45 heifers/treatment), to receive s.c.