title: Effect of calving distribution on beef cattle progeny performance.
abstract: 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.
authors.affiliation: University of Nebraska, West Central Research and Extension Center, North Platte, NE 69101, USA. rfunston2@unl.edu
authors.forename: R N
authors.initials: RN
authors.lastname: Funston
authors.forename: J A
authors.initials: JA
authors.lastname: Musgrave
authors.forename: T L
authors.initials: TL
authors.lastname: Meyer
authors.forename: D M
authors.initials: DM
authors.lastname: Larson
mesh_terms: D000822:Animal Husbandry; D000818:Animals; D002417:Cattle / Q000254:growth & development* / Q000502:physiology; D005260:Female; D008297:Male; D009329:Nebraska; D036801:Parturition; D011247:Pregnancy; D018873:Pregnancy Rate; D012621:Seasons; D013997:Time Factors; D014886:Weaning; D015430:Weight Gain