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Extension by Scott Lake

by Wyoming Livestock Roundup

Do Calves Born Earlier in the Breeding Season Have an Advantage?   
By Scott Lake, UW Extension Livestock Specialist

For many years, university extension specialists and allied industry companies have promoted the benefits of a tighter calving window. These benefits have traditionally been suggested to be heavier calves at weaning and increased marketing premiums due to increases in calf crop uniformity. While these principles are still true, research indicates there are many benefits to calves born early in the calving season beyond weaning weight and calf uniformity.
    Certified Angus Beef CAB)  published a report evaluating five years’ worth of data on over 1,300 calves supplied from a single producer on the impact of birth sequence within the spring calving season on carcass characteristics. These data suggest that feedlot delivery weight, final harvest weight and marbling score were all greater in calves born within the first 21 days of the calving season, compared to calves born after day 43 of the calving season. Additionally, there was over a 10 percent increase in percentage of calves grading Choice and an increase of over 13 percent of calves qualifying for CAB for the older calves.  
    In a similar study at the University of Nebraska, data were analyzed from university steers over a 10-year period. The results were strikingly similar to those of the CAB study. Calves born within the first 21 days of the calving season had heavier weaning weights, heavier carcass weights and greater marbling scores compared to calves born after day 21. Although there was no difference in the percentage of calves grading Choice, there was almost a two-fold increase in the percentage of calves qualifying for CAB (upper two-thirds Choice).  
    These studies suggest that, whether steer calves are sold at weaning or ownership is retained throughout the finishing phase, there is a tremendous economic advantage to having a tighter calving window.
    However, the advantage goes far beyond just steer calves. While getting premiums on calves is a tremendous incentive to alter management strategies, it is extremely important to never look past the foundation of a cow-calf producer’s herd, which is the breeding female. It has been said that reproduction is the most economically important trait to a cow-calf producer, simply because more calves sold at weaning is advantageous to open cows. Therefore, a good practical approach is that all selection criteria for bulls and heifers should be made with cognizance to the potential impacts on maternal traits.  
    Similarly to the benefits of early calving season on steer progeny, there are tremendous advantages for heifer calves born early in the calving season. Research from Rick Funston, University of Nebraska, demonstrates on 10 years’ worth of data that heifer calves born during the first 21 days of the calving season are heavier at weaning than their contemporaries born later in the calving season.
    One of the greatest determining factors that will dictate how early and well heifers will breed is pubertal status entering the breeding season. In Funston’s evaluation, 70 percent of the early born heifers (born first 21 days of calving season) were cycling, or had reached puberty, prior to the breeding season, compared with heifers born after day 21 (58 percent cycling) or after days 43 (39 percent cycling) in the calving season, which resulted in a significantly greater overall pregnancy rate for early born heifers compared with heifers born after day 43 (90 percent versus 78 percent, respectively).
    Collectively, these re- sults demonstrate the benefits of calves being born earlier in the breeding season, not only on a yearly basis due to heavier calves that have higher quality carcasses, but also the beneficial impacts that older heifers have in terms of reaching puberty and conceiving during a shortened breeding season.

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