A breeding soundness exam has never been about finding the best bull in the pasture.
Instead, its purpose is much simpler: identify the bulls that are unlikely to breed cows successfully before they ever enter the breeding pasture.
That distinction is one Dr. John Kastelic, professor emeritus at the University of Calgary and most recent guest on “The Bovine Vet Podcast”, has come to appreciate over decades of research and clinical work.
“The breeding soundness evaluation is a relatively quick tool to identify the studs and eliminate the duds,” says Kastelic. “Even though we can take a group of bulls and say all of these bulls are considered acceptable, within that there could be something of a range of fertility.”
For today’s cattle industry, where natural-service bulls represent a significant investment and AI sires can influence hundreds of thousands of offspring, these exams are critical. A poor breeding season can cost producers an entire calf crop.
“If we don’t do any kind of breeding soundness evaluation whatsoever, in essence we’re doing a breeding trial,” Kastelic explains. “If we do have poor bull fertility, that can be very expensive for the producer.”
Every Breeding Soundness Exam Starts With the Fundamentals
Although semen evaluation often receives the most attention, Kastelic believes a successful breeding soundness exam begins much earlier. Before collecting semen, he carefully watches every bull move.
Lameness, poor feet and leg structure, or difficulty mounting cows may ultimately have just as much influence on reproductive success as sperm quality. From there, the examination progresses through a systematic evaluation of the reproductive tract, including palpation of both testes, measurement of scrotal circumference and assessment of the accessory sex glands.
That systematic approach reflects another important principle.
“A bull needs to do three things,” Kastelic says. “He needs to produce good sperm in large numbers. In a natural mating situation he needs to identify cows in estrus, he needs to be able to mount those cows and breed them and deposit that semen.”
The traditional BSE excels at evaluating the first requirement.
“The bull breeding soundness evaluation really is designed to identify the ability to produce quality sperm,” he says. “It really does nothing in terms of assessing bull libido and has limited ability with regard to his ability to actually breed those cows.”
That limitation explains why Kastelic encourages producers to continue watching bulls after turnout. Passing a breeding soundness exam does not guarantee a bull will actively seek cows in estrus or successfully complete matings.
Ultrasonography Should Answer a Question
As reproductive imaging has advanced, ultrasonography has become increasingly accessible to veterinarians. Kastelic welcomes the technology, but he cautions against using it simply because it is available.
“In a bull without palpable abnormalities of the scrotum or testes or of the accessory sex glands, ultrasound is likely not going to give you a lot more information,” he says.
Instead, he views ultrasonography as a problem-solving tool.
“If we detect something unusual, ultrasound is another tool to help us look at that in a non-invasive way and get a better understanding,” Kastelic says. “I think using it routinely for breeding soundness is probably not justifiable.”
The same philosophy applies to evaluating accessory sex glands.
If enlarged or painful seminal vesicles are detected during transrectal palpation, ultrasonography can help confirm those findings. However, if the glands feel completely normal, Kastelic says ultrasound is unlikely to provide meaningful additional information.
One of his favorite teaching examples involves testicular ultrasonography in young beef bulls.
“The first few times you do an ultrasound, you’ll often just be horrified,” he says.
Bright echogenic areas within the testes can resemble severe pathology. Many veterinarians initially assume those bulls will have poor semen quality. Instead, Kastelic says the opposite is often true.
“They’re super common, especially in young beef bulls. They’re not particularly diagnostic, and they’re not cause for massive concern.”
While these calcified areas likely represent previous testicular injury, they generally function as incidental findings rather than automatic reasons to fail a breeding soundness exam. They should always be interpreted alongside semen quality, physical examination findings and the remainder of the reproductive evaluation.
Thermography Reveals What Palpation Cannot
While ultrasonography helps characterize structural abnormalities, infrared thermography answers a different question. Instead of looking at anatomy, it evaluates function.
Using a handheld infrared camera, veterinarians can assess scrotal surface temperature patterns and gain insight into testicular thermoregulation, one of the key factors affecting sperm production.
“It’s an additional tool. It does not replace collection and evaluation of semen, but it gives us some sense of the scrotal thermal regulation,” Kastelic says.
He recommends several practical considerations when using thermography.
The scrotum should be clean and dry before imaging, and bulls should be examined out of direct sunlight to avoid misleading temperature patterns.
Like ultrasonography, thermography provides another piece of information rather than a standalone diagnosis.
The Smallest Details Make the Biggest Difference
Ask Kastelic what improves breeding soundness exams the most, and he doesn’t point to artificial intelligence or advanced laboratory testing. He points to the details.
A thorough palpation means evaluating both testes individually while tracing each epididymis from head to tail.
“I make sure that there’s a tail of the epididymis on both sides,” he says. “Lack of development of the tail of the epididymis is not rare and it’s incredibly embarrassing to have missed that.”
He recommends cleaning the rectum before transrectal examination to improve probe contact and gently massaging the seminal vesicles to facilitate semen collection.
Even management immediately before semen collection deserves attention.
“If it’s practical, hold bulls off water for a few hours,” Kastelic says, explaining that he suspects doing so reduces urine contamination of semen samples.
Equipment maintenance also matters, including routine maintenance of your electroejaculator.
“Periodically take some sandpaper, emery cloth or steel wool and clean up the electrodes,” he says.
He also stresses keeping semen warm during evaluation, preparing high-quality morphology slides, using a quality microscope and obtaining accurate scrotal circumference measurements. Even there, experience shapes his advice.
Although minimum scrotal circumference standards remain important, Kastelic cautions against assuming bigger is always better.
“Be very wary if the bull has excessive, massive testes,” he says. “We don’t want them way over at the right-hand side of the curve either.”
The Next Generation of Fertility Evaluation
Although Kastelic believes the fundamentals of a breeding soundness exam will remain unchanged, he expects veterinarians will gain access to increasingly sophisticated tools.
Messenger RNA, non-coding RNA, fertility biomarkers and genomics are already showing promise, particularly within AI centers and seedstock operations where additional testing can be economically justified.
Longer term, he believes artificial intelligence may become an important tool.
“As we move into artificial intelligence and bringing all this information together, we’re likely going to have new diagnostics and better interpretations,” Kastelic predicts.
Even then, he doesn’t expect technology to replace clinical judgment. Instead, it will help veterinarians interpret an increasingly complex picture of bull fertility.
That philosophy is reflected in the way Kastelic approaches every breeding soundness exam.
“There’s no one single thing,” he reminds. “When it comes to breeding soundness in bulls, we need to look at a whole bunch of things.”
Or, as he summarizes:
“Good veterinary medicine is doing a whole bunch of little things well and collectively that’s what gives you the best outcome.”
To hear more from Dr. Kastelic about the and science and practice of bull fertility, tune in to the latest episode of “The Bovine Vet Podcast”.
