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.

Heifer calving date positively influences calf weaning weights through six parturitions1

“…In the present study, the advantage in Julian day of calving decreased to only ~2 to 3 d in the second calving season. When Funston et al (2012) grouped heifers based on their own birth period, the advantage for Julian day of calving for the calves born in the first calving period was only 5 to 7 d. Thus, it appears that more than an advanced age at first calving is contributing to the improved fertility associated with calving early as a heifer and selecting a replacement heifer based on the date she becomes pregnant is better than selecting her based on age.…”

“…Although this is not enough to recoup her development costs, it is better than a replacement heifer that does not produce a calf, a risk that still exists if heifers are chosen on age or BW alone. Although there appears to be inherent fertility based on calving early in the first calving season, not all of this is captured simply by selecting the oldest heifers as replacements, as suggested by Funston et al (2012). Minick Bormann and Wilson (2010) reported that age at first calving had a greater heritability than calving day (0.28 vs. 0.07), but that it was not a good indicator of inherent fertility.…”

“…Selection at first pregnancy diagnosis has advantages over selection on the basis of age of the heifer (Funston et al, 2012). The first advantage is that the majority of replacement heifers would produce at least 1 calf, given a 2% pregnancy loss between pregnancy diagnosis and calving.…”

“…Funston et al (2012) reported that these heifers were at greater risk to conceive later in their first breeding season or fail to be pregnant at pregnancy diagnosis. Perhaps, these are the heifers to target for ovulation induction protocols at the start of their first breeding season to attempt to induce them to conceive earlier.…”

“…Weaning weight was also positively influenced by early calving, because calves had a longer period of growth before the common weaning date (Lesmeister et al, 1973). Funston et al (2012) reported that heifers born earlier gave birth to lighter calves in their first calving season, but due to the increased age at weaning, these calves had a heavier weaning weight. To our knowledge, no report has ever investigated the influence of calving early as a heifer on calf performance in subsequent years.…”