EXPERT ADVICE
ECONOMICS OF BEEF BULLS: Selection & Fertility
By Lee Jones DVM, M.S., Associate Professor, UGA College of Veterinary Medicine
P
regnancies matter. Reproductive efficiency is a priority in beef herds. If producers depend on natural service, then bulls contribute to at least half of reproduction and at least as much to the future of the cow herd through the bull’s daughters. Selecting the right kind of bull (from the right program) and a fertile bull is an important investment – not just in the calves sold each year. The bull leaves his influence in the kind of daughters and cows kept in the herd for 2-3 decades. While a good, fertile bull might be half the reproduction equation of a herd, a bad one could be 100-percent responsible for reproductive failure. While we can never guarantee that all bulls will be successful breeders, there are steps we can take to pick bulls that are up to the task of achieving an effective, efficient reproductive program. Bulls affect the economics of cow/calf systems by getting cows pregnant and by breeding them early. The best bulls don’t have to rebreed many cows. Even under the best herd conditions, not every breeding results in a sustained pregnancy. Some matings don’t result in conception, while some do but don’t result in pregnancy. Research has shown that only 70-80 percent of natural services actually result in a pregnancy under the best management conditions. If the bull has any fertility issue, then cows may not get bred early or may not get bred at all. The most productive cows calve early 12 BRAFORD NEWS l WINTER 2020
in the calving season, resulting in older, heavier calves. In a study done on the King Ranch in Texas in 1986, researchers compared the pregnancy rate (PR) of a random group of bulls to ones that had passed a complete Breeding Soundness Evaluation (BSE). What they found was that in the herds that used bulls that passed the BSE, there were 5-6 percent more pregnant cows than in the herds that used the randomly selected bulls. In another 2011 study done in Brazil in Nelore cattle, researchers found that using bulls that passed a BSE not only improved calf production by 31 percent, but calf weaning weights increased by 50 pounds because more cows got bred earlier and calves were older at weaning. Every mating that doesn’t result in a pregnancy means the cow has to recycle (21 days +/- 3 days) for another chance to get pregnant. Every cycle means the calf is 45-50 pounds lighter at weaning. Therefore, sub-fertile bulls not only have more open cows; the cows that finally do get bred have lighter calves. They cost producers money in two ways. Table 1 is an example of the cost of infertility in a herd of 35 cows, which would be typical for many Southeast herds. The example assumes that 25/35 cows are cycling at the beginning of the breeding season and the fertile bull has a 60-percent conception risk compared to 30 percent for the sub-fertile bull.
