Not all bulls are created equal. So how do you maximize your chances of putting a powerhouse rather than just a pretty boy to work in the breeding pasture?

Many factors play a role in a bull’s fertility and breeding ability, including semen quality, reproductive tract soundness, limb structure and libido (desire to breed cows). Most of these can be determined with a breeding soundness examination (BSE), says Ram Kasimanickam, a DVM in Washington State University’s Department of Veterinary Clinical Sciences.

But, interestingly, Kasimanickam adds that a reader survey reported in BEEF magazine (February 2010) showed that only 37.2% of bull buyers considered a BSE important when selecting a bull. He advises producers to make sure every bull is BSE-certified before putting him out with cows.

A basic BSE evaluates five factors:

• Physical soundness – feet, legs, eyes, etc.,
• Reproductive tract soundness,
• A minimum requirement in scrotal circumference,
• A minimum percentage of normal sperm cells,
• Acceptable motility in the sperm.

Passing the physical

Mike Sanderson, Kansas State University professor of epidemiology and beef production, explains that testicles are palpated during a BSE exam to make sure they feel normal and can move freely in the scrotum.

“We palpate internal reproductive organs and make sure the penis extends and there’s nothing wrong with it. We also palpate to make sure there are no hematomas, which can cause adhesions that prevent the bull from extending the penis. If the injury has completely healed, the penis is able to extend and everything seems fine, we don’t worry about an old injury. But we make sure it can extend far enough that we know the bull can breed,” he says.

Scrotal circumference is measured because it’s an important indication of sperm production capacity, and may determine how many cows he can potentially settle, Sanderson says.

“If it’s a bull we’ve tested multiple years, we’ll check to see if his scrotal size has changed. If it declines, it may be a sign he’s declining in fertility. Of course, scrotal size can be influenced by how fat the bull is, but if we’ve kept records we can look back to see if there’s a change in his condition. If he’s a little smaller this year with a lower body condition score (BCS) and if his semen still looks good, he’s probably okay. We need to weigh all the factors,” Sanderson says.

Semen motility, or how well the sperm swim, as well as the percentage of normal sperm cells are monitored in a BSE. Abnormalities are recorded. While these can be difficult to interpret, these tests sometimes provide clues in the event of a problem, about whether it’s a new condition, what might have happened in the past, and how likely he is to recover, Sanderson says.

“We also check feet, legs and eyes. Vision is important for a bull to identify sexually active groupings of cattle. A valuable bull with a vision problem could be used in a small pasture with a few cows, but would not do well in a large pasture,” he says.

Dee Whittier, Virginia Tech professor of large animal clinical sciences, recommends a bull undergo a BSE every year. He points to research conducted at the Western College of Veterinary Medicine in Saskatchewan, Canada, where researchers examined all the facility’s BSE data and found a similar failure rate among bulls in all groups. That flies against the popular perception that it’s more important to BSE test young and old bulls because middle-aged bulls don’t typically have problems.

And, Whittier adds, even though a bull might pass the test today, he may not be okay a month down the road. “Bulls can get sick, or become injured or lame. The breeding season is a stressful time,” he says.