Influence of first calving date on stayability and productivity in <i>Bos indicus-Bos taurus</i> crossbred cows

Lay Summary Reproductive longevity, or how long a cow remains reproductively capable, is one of the most important influences on herd profitability. Therefore, it would be advantageous to identify traits correlated to longevity that can be measured and used to select the next generation of herd sires and dams. Here, a herd of B. indicus–B. taurus crossbred cows (n = 293) were used to characterize 1) the effect of first calving season period on measures of future cow productivity, and 2) the influence of the cow’s own birth period on her potential for future productivity. Calving period was assigned by designating each of the calving seasons into four 21-d periods, and each cow was assigned a score of 1–4 for the relative period of her first calving date and her own birth. There was a clear advantage to heifers calving within the first 21 d of their first calving season. These females were more likely to meet reproductive longevity benchmarks, had significantly greater average lifetime calf crop weaned, and their first calves were significantly heavier at weaning. Earlier born cows had greater heifer pregnancy rates than later born cows. Due to the advantages to both maternal productivity and calf performance, calving within the first 21 d of an annual calving season is expected to increase the herd longevity of these females, and may be considered as an earlier-in-life evaluation criterion when selecting for longevity or lifetime productivity in B. indicus-B. taurus crossbred beef cows.