I received this call a couple of weeks ago. I seem to receive calls similar to this one 6-8 times each year. This particular rancher had just finished getting his cows diagnosed for pregnancy. He had 43 falling calving cows. Last fall, these cows were synchronized for artificial insemination and were exposed to one bull for about 5 weeks and a second bull for 7 weeks. Only 22 cows conceived and all of them conceived to the AI. The first question I asked this rancher was the obvious one; did you get a breeding soundness exam (BSE) performed on your bulls? His response; the bulls had one when he bought them but he had not had one done since (2-3 years). The bulls were checked and, sure enough, both were infertile.
What is a BSE? A BSE is a fertility exam performed on bulls by a veterinarian. A BSE has three components; scrotal circumference, a physical exam, and a semen evaluation. Scrotal circumference is highly correlated with semen output and serving capacity. It is recommended that a 12-13 month old bull have a scrotal circumference of at least 30 cm. The physical exam is performed to simply ensure that a bull is physically up to the challenge of the breeding season.
Are his feet and legs structurally correct? Is he free from injury and/or infection? The veterinarian then examines the bull’s semen to determine if the sperm cells are normal. The bull is then graded as satisfactory, unsatisfactory, or deferred. Bulls classified as unsatisfactory are considered infertile and it is not recommended that they be used for breeding. Bulls that receive the deferred classification had some irregularities in their ejaculate and a second collection is required to determine his fertility. A BSE is a highly reliable tool to use to identify bulls that are infertile.
The extreme cold temperatures we experienced this winter may impact a bull’s fertility. Low temperatures and windy conditions can easily increase feed requirements 25 to 30 percent above normal maintenance requirements even in bulls that are not working. Also, lack of wind protection and lack of bedding will increase the chance of frost damage to the scrotum and testicles. During normal winter conditions frostbite is not a common problem with breeding bulls, but prolonged exposure to extreme cold and wind increases the incidence of frostbite and is a problem that must be considered when planning for the breeding season.
Evidence of frostbite to the scrotum is usually apparent a few days after freezing in the form of noticeable inflammation and swelling. The heat generated from the inflammation directly affects the sperm that are maturing and stored in the epididymis, which surrounds the testicle at the lower end of the scrotum. The resulting damage may cause temporary or, in more severe cases, permanent sterility in the bull. A scab may appear on the lower portion of the scrotum as healing occurs. However, the absence of a scab does not indicate that frostbite injury has not occurred. Severe frost damage to the testicle and epididymis may cause tissue adhesions, affecting mobility and circulation within the scrotum.