Before the fall breeding season begins, a few simple management procedures involving the bulls can increase the likelihood of a high pregnancy percentage among the cows:
In multi-sire breeding pastures, ensure that bulls to be pastured together have been in a common trap or pasture prior to the breeding season. Bulls WILL establish a social hierarchy. They will fight to find out who is “king of the mountain.” It is better to get this done before the breeding season begins, rather than wait until they are first placed with the cows.
Put young bulls with young bulls, and mature bulls with mature bulls. Mixing the ages will result in the mature bull dominating the younger bull completely, and in some instances causing a serious injury. If the plan is to rotate bulls during the breeding season, then use the mature bulls first, and follow with the yearling bulls in the last third of the breeding season. In this way, the young bulls will have fewer cows to breed, and will be 1-2 months older when they start breeding.
Breeding soundness exams will be a cost-effective way to help weed out those bulls that may be dominant in the bull pasture, but due to poor semen quality, could cause a lowered pregnancy rate or elongated calving season next fall. Visit with your local veterinarian about testing the bulls soon, so that if replacements are necessary, there is enough time and opportunity before the fall breeding season is to begin.
-- Glenn Selk, “Oklahoma State University Cow/Calf Corner”