Home / Guides / Breeding, Genetics & Reproduction
Breeding, Genetics & ReproductionBull Fertility Testing
A bull that looks healthy can still be a poor breeder. A breeding soundness exam done by a veterinarian before the season starts is the most reliable way to avoid empty cows and lost months.
Key points
- A bull that looks sound can still be infertile.
- Schedule a breeding soundness exam before every season.
- Retest after illness, injury or heat stress.
- Watch bulls work and check pregnancy rates early.
- Treat every bull as dangerous and follow safety guidance.
Why test a bull at all
Natural service bulls are often used on heifers or as clean-up sires after AI. If a bull is not fertile, you may not find out until cows or heifers come back open weeks later. By then the breeding season is half over.
Testing before each season catches problems early. It also protects you from buying a bull that cannot do the job, which is why many farms ask for an exam before purchase.
A bull is also half the genetic input into every calf he sires. Putting an untested animal with your best heifers risks both the calendar and the genetic plan. A small exam fee is easy to justify against the cost of a season of open animals and extra days to rebreed.
What a breeding soundness exam includes
The veterinarian looks at the whole animal, then the reproductive organs, and then a semen sample. Each part gives different information, and the final result is a combined judgment.
Ask your vet to explain the results in plain terms and to put the classification in writing. Standards are set by the veterinary profession, so ask what the pass mark is and how it was applied to your bull.
- General health, feet and legs, eyes
- Physical exam of the reproductive tract
- Scrotal measurement
- Semen collection and evaluation under the microscope
Timing the exam
Schedule the exam well ahead of when the bull is needed. If he fails or is questionable, you need time to retest or find a replacement. Fertility can change with illness, injury, weather stress and age, so a bull that passed last year still needs a new exam.
Retest after any fever, injury or heavy illness. Heat stress can affect semen quality for some time afterward, so talk to your vet about when a retest makes sense.
Write the exam date on the farm calendar the same way you would a vaccination day. Ask the vet to examine all bulls on one visit so the farm pays one trip charge and no bull is forgotten.
Interpreting the result
A satisfactory result means the bull met the minimum standard on the day of the exam. It does not guarantee fertility with every cow, and it says nothing about his willingness to breed or his libido. Watch him work.
A questionable or unsatisfactory result is not always permanent. Some bulls recover and pass a later exam. Your veterinarian can advise on whether to retest, rest the bull or retire him.
Keep the written report in the bull's file. If you sell the bull, the result and date are useful to the buyer, and honest records protect your reputation.
Watching performance in the pen
Even a bull that passes needs to be observed. Does he find cows in heat, mount correctly and breed? Is he keeping up with the number of cows he has been given? Keep notes on how many cows were bred and how many return.
If a bull is working with a group, check pregnancy rates early. A poor result in the first weeks should lead to a call to the vet, not waiting until the end of the season.
Bull safety
Bulls are dangerous, including dairy breed bulls that seem docile. Never turn your back on a bull, never work alone with one and always have an escape route. Use sturdy pens, proper restraint and handling facilities built for the job.
Follow guidance from OSHA, your extension office and the equipment manufacturer. Train every person who may handle a bull, including family members and part-time workers.
- Strong pens and gates
- Never work alone
- Escape route always in mind
- Handlers trained and aware of bull behavior
Common mistakes and record keeping
Skipping the exam because the bull is young, trusting looks alone and not rechecking after illness are common errors. So is leaving a single bull with too many cows.
Keep a file for each bull: purchase date, exam results, vaccinations, health problems, groups bred and pregnancy results. Review it each year with your vet to decide who stays and who goes. Disease testing and biosecurity rules for bulls come from your vet and state animal health officials.
Sources and further reading
Organization homepages are linked so you can search them for current guidance on this topic.