EFFECT OF PRENATAL ANDROGENIZATION ON PERFORMANCE, LACTATION, CARCASS, AND SENSORY TRAITS OF HEIFERS IN A SINGLE-CALF HEIFER SYSTEM

Twenty-four prenatally androgenized (PA) heifers, born to testosterone propionate-implanted cows, and 27 control (C) heifers, born to nonimp lanted cows, were bred, calved, and placed in drylot pens, with calf a t side, to assess the effects of PA on feedlot growth and lactational performance of heifers used in a single-calf heifer (SCH) system. Lact ating heifers were fed an 85% concentrate diet, calves weaned at 117 d postpartum, and heifers slaughtered at a constant compositional end p oint of 1.1 cm of s.c. fat. Preweaning, PA heifers gained 22.5% faster (P < .01) and were 17.3% more efficient (P < .01) than controls. Pren atal androgenization of the heifer, however, did not affect calf growt h performance. All calves gained more than 1.4 kg/d and had an average weaning weight of 159 kg at 117 d of age. Combining heifer-calf weigh ts, PA and C pairs gained 2.88 and 2.53 kg/d, respectively. Correcting for DMI of calves, PA improved (P < .01) efficiency of beef productio n 10.8%. Four percent fat-corrected milk yield of PA and C heifers ave raged 7.96 and 7.60 kg/d, respectively, and the percentage of milk pro tein and fat did not differ. Accounting for average BW, milk productio n, and DMI, PA and C lactating heifers should have gained 1.27 kg/d; h owever, gains were 137 and 127% of those predicted, respectively. Over all, pre- and postweaning, PA heifers required 10 fewer (P < .04) days on feed, gained 23% faster (P < .01), and were 16% more efficient (P < .02) than C heifers. At slaughter, PA and C heifers averaged 853 and 865 d of age, respectively. Bone and lean maturity scores averaged B- 0 and A(60), respectively, although one carcass was classified as matu re (C-maturity). Marbling scores exceeded Small(50), and sensory trait s did not differ. Thus, PA enhanced growth and efficiency of beef prod uction from heifers used in a SCH system but did not affect lactationa l or carcass traits.