April is here, and many cattle producers are likely thinking about the spring breeding season. One key factor is making sure the herd sire or sires are up to the task. Nora Schrag, veterinarian in Kansas State University’s College of Veterinary Medicine, said a bull breeding soundness exam conducted by a veterinarian can be a valuable tool for producers.
A breeding soundness exam sorts out bulls that are not capable of getting cows pregnant, Schrag explained, and also helps identify bulls that are going to be more efficient at breeding cows in the first 45 days of the season, rather than stringing the season out for a longer period of time.
On average, in pastures with more than one bull, there will be five more calves born in the breeding season if the bulls pass their breeding soundness exam prior to turn out, she said.
“It’s important that we’re certain these bulls are capable of producing high-quality semen and being efficient breeders,” Schrag said. “But, keep in mind it’s not a perfect system. Even if he tested well on the day he was tested, you still need to watch for heifers or cows to come back in heat.”
She said breeding soundness exams provide a breeding wellness benchmark. To be an efficient breeder, there are three main aspects to consider: service capacity, functional anatomy and semen quality.
Testing a bull’s service capacity means testing his libido, or willingness and desire to breed a cow in heat. Schrag said testing service capacity on adult bulls is performed in some countries, but it requires a great deal of time and equipment. This testing is not common in the United States, where producers mainly rely on their observations to evaluate this aspect of fertility.
Schrag said assessing service capacity is especially difficult in a yearling bull, because he doesn’t have any experience yet: “With yearling bulls, it’s especially important to keep in mind you still have to watch him breed cows.”
The breeding soundness exam will help identify any anatomic defect that might keep a bull from breeding. That means checking the eyes, including watching for old pinkeye scars, because it’s suggested that bulls need to have good eyesight to detect a group of cows in heat, she said. An anatomical exam also means palpating the testicles and other reproductive glands to make sure there are no signs of infection or injury.
“These bulls are generally coming off winter, so there is the potential for frostbite (effects),” Schrag said. “A lot of times it can be mild, and it doesn’t do much. If it’s severe, we might pick that up on palpation. We can also palpate them rectally, palpate their inner glands, and make sure there are no knots, signs of damage or any signs of a genetic defect.”
Testing semen quality, she said, has two parts: one is motility, or watching how fast and vigorously sperm swim under the microscope; and the second is morphology, which considers the size and shape of the sperm and is probably the least understood both by producers and veterinarians. However, morphology is an extremely important part of a bull’s fertility.
“Morphology in a yearling bull is especially complicated, because they’ve just barely reached maturity at the time of the test,” Schrag said. “Some of these bulls are going to be fully mature and ready to breed cows at 12 months; some might be there at 11, but many probably won’t be there until month 13 or 14 and fully able to show what kind of semen quality they have.”
“Yearlings are still developing, so if he’s poor on this test day, there’s a likelihood that just because of age, he’s going to be quite a bit better later,” she added.
Schrag said this poses the main disadvantage of a breeding soundness exam. While veterinarians would like to have a test that would indicate or guarantee a bull will be good for the breeding season, other factors can affect the results.
“We can do a pretty good job predicting (bull soundness) most of the time, but we’re left with what that bull gave us for a sample on that day,” she said. “Really, bulls are quite fragile, and it doesn’t take much to knock them off balance. They can get sick. They can get injured. Maybe they get a fever one day. Maybe they have foot rot, and their foot hurts for a week. Then their semen quality is going to go down during that time.”
Despite its imperfections, Schrag said a breeding soundness exam is a useful tool. Bulls that meet the semen quality requirements at 12 months are bulls that should be tagged and identified as early maturing. A producer needs to decide how much value he or she places on early maturation to determine if buying a bull that passes the breeding soundness exam at 12 months should be a priority.
“If you’re keeping your own heifers, that value needs to be significant,” she said. “Early maturing genetics will help (replacement) heifers mature early.”
Bulls that do not pass at 12 months could pass in another month of two. They could have great genetic value – desired carcass or growth traits, for example – but are just not early maturing. That would be one reason to re-test those bulls, Schrag said.
For adult bulls that do not pass their breeding soundness exam, the decision about what to do with them depends on the situation, she said. Because semen quality is somewhat variable, if a bull fails on semen quality alone it is rare that he should be culled based on one test. However, if he tests poorly multiple times, and no injury or sickness or other stress can be identified, it is safe to assume he will not be an efficient breeder.
“I think there is no question that a bull should pass his breeding soundness exam before you turn him out with cows,” Schrag said. “The accuracy of the breeding soundness exam and its relation to how that bull will perform is the highest when he’s examined right before you turn him out.”
Recommendations for exactly when to test are specific to different types of production systems. Producers should direct any questions related to breeding soundness to their regular veterinarian.