Effect of prebreeding body weight or progestin exposure before breeding on beef heifer performance through the second breeding season.
作者： J. L. Martin , K. W. Creighton , J. A. Musgrave , T. J. Klopfenstein , R. T. Clark
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摘要: Two experiments evaluated prebreeding target BW or progestin exposure for heifers developed lighter than traditional recommendations. Experiment 1 the effects of system on heifer performance through subsequent calving and rebreeding over 3 yr. Heifers (229 kg) were assigned randomly to be 55% mature (299 before a 45-d breeding season (intensive, INT; n = 119) 50% (272 60-d (relaxed, RLX; 142). Prebreeding pregnancy diagnosis greater (P 0.15) between systems. Cost per pregnant 2-yr-old cow was less RLX INT development system. Of that failed become pregnant, proportion 0.07) in prepubertal when began. Therefore, second 2-yr experiment melengestrol acetate (MGA, 0.5 mg/d) as means hastening puberty BW. control (n 103) MGA 81) treatment 14 d placed with bulls 13 later 45 d. similar (280 380 kg, respectively; P > 0.10) treatments. The pubertal (74%), rate (90%), date, calf weaning weight, (92%) Developing 50 resulted overall rates, supplementing diets did not improve reproductive performance.
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