Pre-breeding evaluations assess semen quality, the bull’s desire to breed and include an overall physical exam
REGINA — There aren’t as many bulls on an operation as there are cows, but that doesn’t mean they need less management.
After all, they account for half of a calf crop’s genetics.
According to the Beef Cattle Research Council (BCRC), there are three phases of bull management: pre-breeding or conditioning for about two months, the two- to three-month breeding season and then post-breeding.
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Bulls should have at least a four- to eight-month rest after the breeding season.
A pre-breeding soundness evaluation, done by a veterinarian, is the place to start.
The exam can rule out any disease or condition that causes infertility.
It includes a scrotal exam to measure circumference, check resilience and tone of the testicles and look for any injuries. It should include an inspection of where the epididymides attaches to the bottom of the testicle. This is where sperm are developed, stored and then transported.
The BCRC said field studies in Western Canada show a positive correlation between scrotal circumference and pregnancy rates, but there is an upper limit.
“Increasing scrotal circumference is correlated with an increase in seminal quality up to 38 centimetres, with no further observed differences in bulls with larger testes,” says its bull management web page.
During a 2023 BCRC webinar, Dr. Roy Lewis said bulls with larger circumferences aren’t necessarily better because they’re too big.
“Those ones do not last. They break down,” he said.
“Where we’re at now is a pretty good place.”
Semen quality, including sperm count and motility, should be examined, along with the bull’s desire to breed, although the latter can be hard to assess.
The bull should also have an overall physical exam.
Body condition score should be three to 3.5 out of five when the bull goes out on pasture.
Lewis said soundness exams can be done quite easily. Bulls may look healthy but have problems with fertility, and the semen test will show that.
“We can really help steer the direction of the reproductive fertility of the herd,” he said.
Purebred breeders can cull out any problem bulls and won’t have to deal with consequences after, Lewis said, while commercial buyers know what they’re getting.
Many commercial buyers will re-test their bulls after they get them home.
Lewis said the minimum scrotal circumference that each breed has adopted is “bang on.”
Caveats would be the age at which the measurements are done. Also, measurements are done differently in the United States, so buyers should be aware of that.
Lewis said vaccinations and parasite treatment can also be given while the bull is in the chute for scrotal measurement.
Herd vaccinations should be up to date and bulls should, if possible, be vaccinated three to four weeks before breeding begins.
Lewis also said annual testing and maintaining records for each of those can help detect when a bull is aging and not performing as well.
Other tips include managing bull nutrition to avoid over- or under-conditioning, quarantining new bulls and buying from reputable sources.
The appropriate bull to cow ratio is 1:20 or 1:30, depending on other factors such as terrain, total number of animals and social behaviour/dominance.
Producers should monitor all cattle for signs of trouble.
“Bull lameness or injury, or a less subtle issue such as fever, can be hard to detect but left unmanaged may devastate reproductive rates,” said BCRC.
Foot rot is the most common cause of lameness, and while vaccine is available, it isn’t always effective. Producers should consult their veterinarians.
Venereal disease is another concern that, if unchecked, can lead to significant fertility issues in a herd. Trichomoniasis, vibrio and leptospirosis are rare and bulls show no clinical signs of disease.
Animals that test positive for any of these should be culled for slaughter.
