Don’t forget morphology
Some great little swimmers can indicate good sperm, but Barclay advises not being satisfied with just that. “I’ve found that there are a lot of practitioners out there who don’t routinely perform morphology exams,” he states. “I’ve had to do quite a bit of explaining to some producers who think that just because the motility is good, then the bull is fertile, but that may not be true.”
Laurin also looks at morphology. In young bulls, a common issue is primary droplets that as the animal matures become secondary droplets, then finally disappear. Misshapen heads, or heads that have fallen off are also common defects that can fail a BSE, especially on a young bull. “Another thing that changes with maturity is that tails get longer with age. It is not a problem, just an indicator of maturity,” she says.
One thing that has helped Barclay educate owners is a phase-contrast microscope with a video monitor that he uses at his clinic. “When we do a BSE in the clinic, the owner can watch me examine both motility and morphology and I can explain what I’m seeing.” Barclay always follows the Society for Theriogenology guidelines, which call for motility and morphology evaluation. “Some sperm can be morphologically abnormal and incapable of fertilizing an oocyte, but still motile,” he says. “I charge for my time and I believe that the producer is getting more value from a complete exam.”
Failing the BSE
Historically, young bulls failing a BSE most commonly failed to meet the minimum requirements for satisfactory potential breeding in the areas of insufficient scrotal circumference, conformational defects of the feet and legs, or an inadequate percentage of morphologically normal sperm in the ejaculate. “However, by using sires with positive EPD values for scrotal circumference and eliminating bulls that were structurally unsound, a greater percentage of young bulls are now found to be satisfactory potential breeders according to the standards of the Society for Theriogenology,” Wolfe says.
Laurin notes that seminal vesiculitis is becoming a bigger reason for culling young bulls. “We start to see it in 18-month to 2-year old bulls, and it can become a persistent problem with some bulls that will pull them from production at 3–4 years of age.”
The most common reason for Barclay to fail a young (i.e. 1 to 2-year old) bull is sperm morphology, but, “I always recommend a re-evaluation because a lot of those will improve after they’ve matured a bit,” he says.