During the bull selection process, growth traits receive a lot of attention.
Performance data (adjusted weaning and yearling weights, average daily gain, ratios, etc.) can only be used to compare animals in the same contemporary group because these measurements are affected by feeding strategies and environmental conditions. Because of how they are calculated, expected progeny differences (EPDs) can and should be used to compare bulls from different breeders or even bulls from the same breeder. In most situations, genomic-enhanced EPDs are the best tool to evaluate growth differences.
Weaning Weight (WW), Yearling Weight (YW) and Carcass Weight (CW) EPDs all are indicators of growth. For most producers, YW is a better indicator of growth than WW, especially those that precondition or hold their calves after weaning. Additionally, YW is more heritable than WW (0.42 vs. 0.28). Consider looking at both CW and YW, if ownership is retained through the feedlot.
When evaluating increases in growth, it is valuable to see how changes in growth affect mature weight. Was YW increased while maintaining mature weight or did increases in YW result in increases in mature weight? In most situations, the goal should be to increase growth while maintaining or even decreasing mature weight.
Over the last 20 years, many seedstock producers have substantially increased growth traits in their bulls. For example, the breed average YW EPD for Angus has increased by 61 pounds from 2001 to 2021. Interestingly, mature weight has increased by 54 pounds during this same time. So most of the increase in growth is just due to an increase in mature size. If replacement heifers are being kept, look for bulls that have good YW EPDs with below average mature weight EPDs. As an example, one popular A.I. sire ranks in the top 10th percentile for YW and the 70th percentile for mature weight.
Is it a good investment to pay more for bulls with higher YW EPDs? That is something each producer must decide based on their forage resources, management and marketing strategies, and the expected value of additional weight gain. Value of gain will likely range from about $0.80 to $1.20 per pound depending on the price of corn. At these values, 30 pounds of additional gain is worth $24 to $36 per head.
While growth is important, it is definitely not the only factor that should be evaluated when buying bulls. Also, remember that growth can be limited by nutrition or genetic potential.
