Alterations in metacarpal characteristics in steers and heifers sequentially implanted with Synovex from 45 days of birth.

Forty-two heifers and 38 steers sired by either Charolais (n = 47) or Salers (n = 33) from Bos indicus x Hereford dams were used to determine the effects of an anabolic agent on metacarpal characteristics and accompanying weight gain and carcass characteristics. Calves were blocked by sex and sire breed and either not implanted or implanted with Synovex-C within 45 d of birth, and with Synovex-S or -H at weaning and 84 and 169 d postweaning. Calves grazed oat pastures immediately after weaning for 169 d, after which calves received a feedlot diet for 124 d and were slaughtered. Live weight and hip height were recorded at initial implanting, weaning, d 84 and d 169 postweaning, and at approximately 28-d intervals during the feedlot period. Metacarpal and carcass characteristics were determined after slaughter. Metacarpals from implanted calves had greater medio-lateral axis (P < .01), cortical areas (P < .05), and cross-sectional areas (P < .05) and tended to have a greater breaking load (P < .08) than bones from nonimplanted calves. Implanted steers had shorter (P < .05) metacarpals than nonimplanted steers. Implanted calves had a greater (P < .05) ADG to weaning and over the postweaning grazing and feedlot periods than control calves. The implant did not alter backfat thickness but decreased (P < .05) percentage of kidney, pelvic, and heart fat and quality grade and tended (P < .07) to improve yield grade in heifers, but not in steers. Implanted calves tended (P < .08) to have a lower marbling score.(ABSTRACT TRUNCATED AT 250 WORDS)