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Male Fertility: A New Emphasis
on Breeding Soundness

DES MOINES, Iowa (Sept. 7, 2016) — “There are some changes afoot,” announced veterinarian Patrick Phillips. The Iowa State University College of Veterinary Medicine faculty member believes it is time to update standards for evaluating breeding soundness in bulls. He spoke during the Applied Reproductive Strategies in Beef Cattle symposium, Sept. 7-8 in Des Moines, Iowa, explaining that the Society for Theriogenology is currently considering what he believes are needed changes.

Iowa State University College of Veterinary Medicine faculty member Patrick Phillips.

According to Phillips, standards for the bull breeding soundness evaluation (sometimes referred to as a BSE) were first recommended by the Society in 1954. As research evolved and more data was accumulated, revamping of standard procedures has occurred twice since then, at intervals of roughly 20 years. Phillips said the BSE standards employed today were adopted in the early 1990s and consist of a general physical exam, including examination of internal and external genitalia, scrotal circumference measurement, and evaluation of sperm motility and morphology.

However, Phillips said a thorough BSE also includes evaluation of body condition score to gauge service capability, plus scrutiny of vision and teeth. Information regarding the health history of bulls is also useful to veterinarians charged with evaluating breeding soundness.

“Producers need to realize that a BSE does not predict future fertility and it does not test libido,” stated Phillips. “It does not detect STDs (sexually transmitted diseases).”

Phillips explained how, in some countries, libido is tested by placing a bull with a female that has been treated with estrogen. This kind of libido test is required in Australia. He suggested that producers consider conducting this kind of test to evaluate a bull’s willingness to breed. Phillips lamented the fact that too many managers of small breeding herds do not spend any time observing bulls to evaluate libido and nearly as many do not subject bulls to an annual BSE prior to the breeding season.

“I worry about the small operators who run one bull with 30 or 40 cows. If he’s no good, the producer stands to lose a calf crop,” said Phillips. “Generally, those are the producers least likely to get a BSE.”

Regarding the ongoing review of BSE standards, Phillips said the 20-year-old U.S. requirements lag behind those implemented by Canada and Australia. Calling it “time for a change,” he voiced his expectations for updating U.S. standards.

“I look for an increase in the minimum requirement for scrotal circumference, an increase in the minimum requirement for sperm motility and certain morphological abnormalities could be changed to normal,” predicted Phillips.

According to Phillips, these potential changes will be considered if evidence-based science points in that direction and it is agreed to by producers, breed associations and veterinarians.

Phillips spoke during Wednesday’s ARSBC session focusing on male fertility. Visit the Newsroom at, which features comprehensive coverage of the symposium, to view his PowerPoint, read the proceedings or listen to the presentation. Compiled by the Angus Media editorial team, the site is made possible through sponsorship by the Beef Reproduction Task Force.

Editor's Note: This article was written under contract or by staff of Angus Media. To request reprint permission and guidelines, contact Shauna Rose Hermel, editor, at 816-383-5270.