Bull selection is one of the most important long-term decisions in a cow-calf operation. Sires influence not only the next calf crop, but also the genetics of replacement females retained in the herd. For that reason, selection pressure should match the ranch’s forage resources, cowherd goals, and marketing endpoint.
Research funded by the USDA Agriculture and Food Research Initiative Grant 2022-67016-36201 at Oklahoma State University evaluated steer calves sired by Angus bulls selected for either high or moderate yearling weight EPD to produce calves with divergent post-weaning growth potential. Steers were raised in OSU spring- and fall-calving cowherds, weaned, preconditioned for 60 days, and then finished at the Willard Sparks Beef Research Center.
Weaning weights were not affected by the sire genetics, indicating that the extensive range environment was insufficient for full expression of the genetic potential for pre-weaning growth. As expected, calves from high-growth sires gained faster after weaning and were heavier at harvest, with fewer days on feed. This shows that when nutritional limitations are removed the high-growth steers could really show their true potential. The High-growth steers averaged 1,500 pounds at harvest compared with 1,428 for moderate-growth steers. Hot carcass weight averaged 911 pounds for high-growth steers compared with 884 pounds for moderate-growth steers.
With the increased performance came greater feed intake. High-growth steers consumed more feed per day, averaging 31.5 pounds DM/day compared with 27.5 pounds DM/day for moderate-growth steers, resulting in reduced feed efficiency for high-growth steers. Residual feed intake, an efficiency metric that measures the amount of feed consumed above or below expectations based on the level of performance, favored the moderate-growth steers, indicating they consumed less feed than expected for their body weight and gain. In contrast, residual average daily gain, an efficiency metric that measures the amount of gain above or below expectations based on the amount of feed intake, tended to favor high-growth steers. This illustrates that different feed efficiency measurements describe different biological outcomes. More growth does not always mean better efficiency, but it depends on how you measure it.
Carcass quality also differed. Even though backfat thickness and yield grade were similar, moderate-growth steers had greater percentages of carcasses grading Prime and High Choice. This may reflect differences in maturity pattern and nutrient partitioning, with moderate-growth cattle having more opportunity to deposit intramuscular fat when finished to a similar fat endpoint.
High-growth genetics can increase body weight, carcass weight, and reduce days on feed. But they may also increase feed intake and may not improve all measures of efficiency. Growth EPDs should be considered alongside mature size, feed intake, carcass merit, maternal traits, health, and marketing goals. Increased performance is valuable only when it fits the production system’s environment.
