It’s often said that the herd bull contributes half the production in a calf crop. “That may be true for the average bull, but it likely exaggerates the contribution from a poor quality bull and dramatically under-estimates the contribution of a good bull,” says Bruce Carpenter, Texas AgriLife Extension beef cattle specialist in Fort Stockton.
Under natural service conditions, in order for a sire to be a genetic asset, he must first be able to find, travel to and successfully breed estrus females, Carpenter says. Fertile bulls are of greater economic value than poor bulls, not only because of the number of calves they can sire, but because they tend to settle cows earlier in the breeding season, resulting in older and heavier calves at weaning.
There are many factors to consider when managing the fertility in your herd bulls, Carpenter explains. Particularly, he stresses the importance of disease prevention.
“Diseases affecting both young and mature bulls are essentially the same as those of breeding females,” he says. However, he cautions, do not assume that vaccinating one will also protect the other.
“Vaccinate both males and females for common reproductive diseases such as leptospirosis and campylobacter (vibrio) and possibly bovine viral diarrhea (BVD), depending on your location and your veterinarian’s recommendations,” he says. “Lepto and BVD can develop in the fetus in utero, resulting in offspring that may be carriers of the disease. To prevent carriers, it’s best to vaccinate females at pre-breeding and again at preg checking.”
Trichomoniasis, on the other hand, is somewhat unique in the way it spreads, and its management and prevention strategies, he says. Trich is a venereal disease that passes both ways – male to female and female to male. It doesn’t produce signs of the disease in bulls, but if they pick up the disease organism they can become life-long carriers. There is no treatment for infected bulls – they must be sent to slaughter.
Trich manifests itself in cows by causing abortions, Carpenter explains, and that’s the only indication that trich is a problem in a herd. Unlike bulls, however, some cows can clear the organism after a period of time.
Prevention, he says, is the first step in managing trich. Here are some general guidelines:
- Maintain good perimeter fences to segregate cattle of unknown status. Fences are the first line of defense in preventing a trich infection in your herd.
- Keep the bull battery as young as possible. Buy only virgin bulls and heifers, and unless the virginity of bulls can be positively confirmed, test all bulls before adding them to the herd.
- Consider keeping bulls in the same breeding group for several seasons.
- Consider small sire groups vs. large sire groups to avoid infecting many bulls in a single season. Monitor pregnancy closely and implement an annual bull testing program to detect introduction of trich.
- Avoid buying open or short-bred (less than 120 days) cows. Open or short-bred cows from unknown sources are particularly risky and must be quarantined and examined before they are added to the herd.
- If you buy replacement cows, isolate them from the existing herd during the first breeding season.
“A vaccine is available for use in females,” Carpenter says, “but realize that it is not a preventative vaccine in the classical sense. That is, one shot once a year will not protect your herd from infection. The vaccine is efficacious only for a period of months, necessitating a booster and revaccination program.”
Vaccination is more effective in situations where you’re trying to clear a herd of a trich outbreak or in other high-risk situations, he says. “Working with your veterinarian will be the best way to ensure that a vaccine program is appropriate and if so, that the vaccine is being used correctly.”
For more on trich, go to https://agrilifebookstore.org/publications_details.cfm?whichpublication=2751