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

Records collected between 1997 and 2010 were used to determine the effect of calving period on heifer (n = 1,019) and steer (n = 771) progeny from the Gudmundsen Sandhills Laboratory, Whitman, NE. Progeny were classified as being born in the first, second, or third 21-d period of the spring calving season within year. Heifer birth BW was lightest (P < 0.01) for heifers born in the first period. Birth to weaning ADG tended (P = 0.10) to be least for heifers born in the first calving period; however, weaning BW decreased (P = 0.03) with advancing calving period. Weaning to prebreeding ADG tended (P = 0.07) to be least for heifers born in the first period; however, prebreeding BW was greatest (P < 0.01) for calves born in the first period. Heifer ADG from the beginning of the breeding season to pregnancy diagnosis was greater (P = 0.03) for heifers born in the third vs. first calving period. Heifers cycling at the beginning of the breeding season decreased (P < 0.01) with advancing calving date (70, 58, and 39%, respectively) and 45 d pregnancy rates were lowest (P = 0.02) for heifers born in the third calving period (90, 86, and 78%, respectively). Birth date of the first calf of the heifer and birth BW decreased (P < 0.01) if the heifer was born in the first calving period. First calf progeny had the greatest (P ≤ 0.10) weaning BW if born to a heifer born in the first calving period. As steer calving period advanced, weaning BW decreased (P < 0.01). Calving period did not affect (P = 0.81) feedlot ADG. As calving period advanced, HCW, marbling score, and yield grade decreased (P < 0.01). The percentage of steers grading USDA small marbling was not affected (P = 0.13) by calving period; however, the percentage of steers grading USDA modest marbling or greater and the total carcass value declined (P ≤ 0.01) as calving period advanced. Heifer calves born during the first 21 d of the spring calving season had greater weaning, prebreeding, and precalving BW; greater percent cycling before breeding; and greater pregnancy rates compared with heifers born in the third period. First calf progeny also had an earlier birth date and greater weaning BW. Steer calves born during the first 21 d of the calving season had greater weaning, final, and carcass weights; greater marbling scores; a greater percentage grading USDA modest or greater; and greater carcass value. Calving period of progeny significantly impacts performance.

Poor udder and teat confirmation decreases profitability due to decreased calf weaning weight, increased incidence of mastitis and labor, and decreased cow lifetime productivity. Therefore, the objective of this retrospective study was to evaluate the effect of beef cow udder score on cow performance and pre- and postweaning progeny performance. In a 5-yr study, crossbred cows at the Gudmundsen Sandhills Laboratory, Whitman, NE, were assigned an udder score each year at calving, from 1 to 5, using an udder and teat combination score. Cows were grouped by udder scores and classified as either low udder score (LUS, udder score 1 or 2; n = 223) or high udder score (HUS, udder score 3 or 4; n = 1,742). The udder score combines udder conformation and a teat scoring system. Low udder scores consisted of pendulous udders and large teats, whereas HUS consisted of tight udders and small, symmetrical teats. Mixed models were used to evaluate udder score on cow performance and calf pre- and postweaning performance. Cow body weight (BW) at prebreeding and weaning was greater (P &lt; 0.01) in LUS cows compared with HUS counterparts. Pregnancy rate was not different (P = 0.35) between udder classification groups. Calf BW at birth (P = 0.95), weaning (P = 0.40), and adjusted 205-d BW (P = 0.28) were not different between udder groups. Cow udder score did not influence feedlot entry (P = 0.41) and final BW (P = 0.30), dry matter intake (P = 0.53), average daily gain (P = 0.60), and gain:feed ratio (P = 0.85) of steer progeny. However, steers from HUS dams had greater hot carcass weight (HCW; P = 0.04) and backfat thickness (P = 0.02) compared with LUS counterparts. Results from this study suggest cows with less desirable udder structure may not have a negative impact on calf preweaning growth and performance; however, backfat thickness and HCW in the finishing phase were lower in steers from cows with a lower udder score.

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ABSTRACT:Three experiments were conducted to evaluate the response of supplementing primiparous heifers based on the metabolizable protein (MP) system during pregnancy and lactation. In Exp.