Bull breeding soundness exam (BSE): what it checks and the minimums
By the RanchOS Global editorial team · Updated
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The breeding soundness exam. A bull can look great and still not settle cows; a BSE checks what you can't see. The vet checks four things: a physical exam (eyes, feet, legs, body condition), scrotal circumference, sperm motility (at least 30% progressive) and morphology (at least 70% normal sperm). Bulls over 2 years need at least 34 cm scrotal circumference; younger bulls have lower, age-based minimums (Society for Theriogenology). Pass them all and he's a satisfactory potential breeder. Test every bull, every year, before the breeding season.
In short: a bull can look perfect and still fail to settle cows. A breeding soundness exam (BSE) checks the things you cannot see, takes little time, and should be done on every bull before every breeding season.
What the vet checks
- Physical exam: eyes, feet and legs, body condition and the reproductive tract. A lame bull will not cover cows.
- Scrotal circumference: measured in centimeters. Under Society for Theriogenology (SfT) standards, bulls older than 24 months need at least 34 cm; younger bulls have lower, age-based minimums.
- Motility: at least 30% of sperm moving forward (progressive motility).
- Morphology: at least 70% of sperm normal in shape.
A bull that meets every minimum is classed as a satisfactory potential breeder. A bull that misses one may be deferred and retested, or classed unsatisfactory.
When to book it
Book the exam 30 to 60 days before turnout, so there is time to retest or replace a bull. Test every bull every year: a bull that passed last season can fail this one.
What the exam does not tell you
A BSE does not measure libido or serving ability, and it does not predict the genetic merit of the calves. Watch new bulls work in the first days of the season, and use EPDs for genetics. See How to read an EPD.
Buying a bull?
Look for "passed BSE" in the sale catalog footnotes, with the date. See What to put in a bull sale catalog.
General guidance. Your veterinarian performs and interprets the exam.
Common questions
What does a breeding soundness exam check?
A physical exam (eyes, feet, legs, body condition and reproductive organs), scrotal circumference, sperm motility and sperm morphology. A bull must meet the minimums for all of them to be classed as a satisfactory potential breeder.
What scrotal circumference does a bull need to pass?
Under the Society for Theriogenology standards, bulls older than 24 months need at least 34 cm. Younger bulls have lower, age-based minimums; your veterinarian will apply the right one for the bull's age.
What motility and morphology does a bull need?
At least 30% of sperm with progressive motility and at least 70% morphologically normal sperm.
How often should bulls be tested?
Every bull, every year, before the breeding season, including bulls that passed last year. Injury, illness, weather and age can all change a bull's fertility between seasons.