Bull Management Considerations
by Troy Smith for Angus Productions Inc.
NASHVILLE, TENN. (Aug. 6, 2010) — When maintaining one herd sire or a large battery of bulls for natural service, a manager’s goals are much the same as the producer making extensive use of artificial insemination (AI). The herd manager wants females bred early in the breeding season and high pregnancy rates. He or she wants the highest possible number of offspring from bulls with the greatest genetic value. And the manager wants to achieve all of that as economically as possible.
“We can evaluate bull fertility, but we don’t have the ability to adequately predict breeding performance or libido,” said University of Georgia Veterinarian Roger Ellis. “That has to be observed.”
But University of Georgia veterinarian Roger Ellis fears many managers do not capture the full potential and breeding power of their bulls. During the Applied Reproductive Strategies in Beef Cattle (ARSBC) Conference in Nashville, Tenn., Ellis discussed management considerations that could help producers optimize return on their investments in breeding bulls.
“All bulls do not perform equally,” warned Ellis. “There can be significant variability in fertility and reproductive performance among bulls. And the same bull’s performance can vary year to year or even between one breeding cycle and the next.”
According to Ellis, 25% to 40% of bulls do not perform optimally, either because of subfertility or because they are inefficient breeders. There are many reasons, with the leading causes being physical faults or injury. Other reasons range from disease, nutritional and environmental effects to hindering social or sexual behavior. Bulls won’t perform up to expectations, added Ellis, unless they possess essential attributes, including the capacity to produce functionally normal sperm, the physical capability and a willingness to breed cows.
“Additionally, bulls must be adaptable to survive environmental challenges and social hierarchy. They also need some luck, to remain injury free,” said Ellis.
Offering tips for prebreeding management, Ellis advised producers to acquire new bulls at least 60 days prior to breeding season to allow adequate time for them to adapt to the new environment. He recommended testing for persistent infection with bovine viral diarrhea virus (BVDV), trichomoniasis and Johne's disease. All bulls, he added, should be subjected to a complete breeding soundness examination prior to turn-out. With regard to body condition, Ellis recommended having yearling bulls in body condition score (BCS) 6, while mature bulls can be in BCS 5 or 6.
Calling proper bull-to-cow ratio very important, Ellis said the recommendation for yearling bulls is no more than 20 cows, and 40 cows for mature bulls. For multi-sire breeding pastures, he advised producers to group bulls together by similarity in size and age. Ellis warned against running yearlings together with older bulls.
“Watch what’s going on in the pasture after putting bulls with cows,” urged Ellis. “We can evaluate bull fertility, but we don’t have the ability to adequately predict breeding performance or libido. That has to be observed.”
Ellis noted that estrous synchronization can also be used successfully with natural service, to get more cows bred early in the breeding season. However, producers should make sure they have adequate bull power. He also recommended that bulls be turned with cows prior to the onset of maximum estrous activity. Nor is it wise to have synchrony overly tight, or a bulls performance may wane before he gets his job done.
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