We are approaching the breeding season for many cow-calf herds, and most ranches have already booked or will soon book their local veterinarian for a bull breeding soundness examination.
Breeding soundness examinations, also known as “bull testing,” were initiated in the early 1950s in North America.
It appears that a fierce central Colorado blizzard in December 1949 was the major impetus for routine bull breeding soundness evaluations in the United States.
The blizzard resulted in severe scrotal frostbite in many bulls. The following March, Colorado A&M Breeding Service collected semen from 70 range bulls using an artificial vagina and discovered that 10 to 12 percent of them had poor semen quality.
Many of the standards that we currently use in Western Canada when evaluating the breeding soundness of bulls have been developed from the work of Dr. William Cates and Dr. Albert Barth at the Western College of Veterinary Medicine.
Their research and leadership, along with work done by other notable veterinarians across Western Canada, have led to the development of standards for bull testing that were updated as more research became available.
Barth finished writing the Bull Evaluation Manual in the spring of 1994, which is the ultimate reference document for most western Canadian veterinarians when it comes to bull testing.
Along with a committee of veterinarians from across Western Canada, he was also responsible for creating the standardized bull testing forms and system, which all veterinarians in Western Canada now use. These forms are distributed and managed by the Western Canadian Association of Bovine Practitioners (WCABP).
We have been fortunate to have such strong research and leadership from Barth and other members of the WCABP, which have standardized the approach to testing bulls in Western Canada.
In one of the most recent supplements of the Journal of Animal Science, researchers from North Dakota State University have reported on research into why bulls have failed their breeding soundness examination.
Data was collected from five veterinary clinics and included 14,698 bulls in 1,374 groups. The researchers collected information on the numbers of yearling and mature bulls tested and the reasons why bulls did not pass.
The failure rate was 22.1 percent for yearling bulls and 11.6 percent for mature bulls.
Bulls that were presented for re-testing failed at a higher rate: 39.5 percent for yearlings and 38.6 percent for mature bulls.
There was no difference in failure rates between bulls that were tested as part of a breeding herd and bulls that were tested for a production sale.
Yearling bulls were more likely to fail for semen morphology and penile warts than mature bulls, while mature bulls had a higher failure rate for penile injuries and defects and issues with feet and leg conformation.
Bulls are a substantial investment for cow-calf ranches, and optimal fertility of cows and bulls is a vital economic component.
Cates and Barth emphasized that the breeding soundness evaluation is more than just a semen check. It also helps ensure that a bull is physically sound, able to complete service and has satisfactory semen quality.
Scrotal circumference is directly linked to the age of puberty and lifetime fertility of female offspring and has become an important criteria of all breeding soundness examinations.
Research by Dr. Cheryl Waldner of the WCVM showed that cows exposed to bulls with smaller scrotal circumference were less likely to become pregnant and had a longer interval from calving to conception.
Data collected by Barth has shown that our selection for higher scrotal circumference over the years has created a steady trend toward bulls having larger scrotal circumferences in all of the major beef breeds.
Veterinarians who examine semen samples under a microscope find that some problems are permanent, while others are short lived.
The western Canadian cow-calf surveillance project found that 87.1 percent of all producers ask their veterinarians to perform breeding soundness exams on bulls. However, the western Canadian cow-calf survey conducted by the Western Beef Development Centre found that only 64 percent of producers did so.
The old adage that a bull is half your herd is still true today. Breeding soundness examinations are an important tool to provide information that will help evaluate the fertility of bulls before the breeding season begins.