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Protect the investment – Vet encourages testing bulls before breeding season

by Wyoming Livestock Roundup

With calf prices at record highs, now is not the time to skimp on preparing the bull for breeding season. 

“A critical component of reproductive success is having sound, highly fertile bulls,” according to David Hardin, veterinarian at the University of Nebraska-Lincoln School of Veterinary Medicine and Biomedical Sciences. 

Breeding cows

To experience those record highs and maintain profitability, first, the cows need to get bred and preferably early in the breeding season. 

“This requires bulls that can detect cows in estrus and successfully mount and deliver viable, normal sperm into the reproductive tract of the cow,” Hardin says. 

He recommends a breeding soundness exam (BSE) for all bulls within 60 days of the start of the breeding season. Bulls can become infertile permanently or temporarily at any time. Scrotal damage can occur during the winter, and frostbite can impact the sperm produced and capacity. 

Testing for soundness

A BSE is a quick, simple test performed by a veterinarian to determine if the bull is capable of breeding cows. During this test, a veterinarian will perform a general physical exam evaluating the bull’s body condition, nutritional status, eyesight and teeth. 

The bull will also be observed for structural defects and disease conditions that could affect the feet and legs and hinder the bull’s breeding performance.

Orchitis, epididymitis, vesiculitis, testicular degeneration, traumatic injuries to the penis or prepuce and limb injuries or arthritis can all impact sperm production. 

“Some of these conditions are visible to the producer and are treated or the bull is culled when detected,” according to M. Wayne Ayers, veterinarian with Caine Veterinary Teaching Center at the University of Idaho. “However, most of the inflammatory conditions would only be detected if a thorough BSE were performed.”

“During this exam, the internal structures of the reproductive system are examined, such as the prostrate, seminal vesicles, ampulla and inguinal rings to ensure normalcy,” Hardin said. “The external structures of the reproductive system such as the penis, prepuce, sheath, testicles, scrotum and epididymis are also examined for normalcy.”

Sperm morphology

The veterinarian will also look for sperm mobility greater than 30 percent, sperm morphology greater than 70 percent and a scrotal circumference that is age dependent. 

“Semen evaluation is a critical component of the BSE and includes a microscopic evaluation of the semen to determine sperm mobility and the percent of morphologically normal sperm.” 

Scrotal circumference is also important.  

According to the Beef Improvement Federation, a 15- to 18-month-old bull should have a scrotal circumference of at least 31 centimeters. 

“It is a threshold trait,” according to UNL Beef Extension Specialist Rick Rasby. “As a producer, I like to see that a little higher. I select bulls with at least 33 to 34 centimeters.”

“The scrotal circumference impacts sperm production, and the relationship between scrotal circumference to the daughter’s puberty has been well-documented. As scrotal circumference increases, days to puberty decreases in the daughters,” he explained. 


For bulls from 15 to 18 months of age to maturity, Rasby also suggested working with a veterinarian to make sure vaccinations are up to date. 

“If the bulls are purchased from a seedstock producer, they should have current vaccinations and have passed a BSE,” he said. 

Producers may also want to consider having bulls tested for infectious diseases, like trichomoniasis, which could be devastating to a cow producer if it goes undetected during the breeding season. 

Testing for disease is not typically part of a BSE, but producers should consult with their veterinarian to determine if testing is recommended.


If a bull can service an average of 25 cows each season, that bull represents at least $35,000 in gross income each year. 

“It is the goal of most producers to get their cows bred and to get them bred early in the breeding season,” Rasby stated. 

The impact of the bull on the genetic makeup of a herd is important. 

“He provides half of the genetic material of each calf. He services between 15 and 50 females annually, and 80 to 90 percent of the genetic change in a herd is the result of the bulls selected,” Rasby noted. 

“This is why it is important to make astute and well-planned selection of bulls,” he added. 

Producers should have their bulls examined early in the breeding season and make the necessary preparations for a successful year. 

Gayle Smith is a correspondent for the Wyoming Livestock Roundup. Send comments on this article to

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