February 26, 2024

Extension Notebook: Scrotal frostbite in bulls a risk to fertility

Scrotal frostbite is shown on a Hereford bull in this photo by George Perry, Ph.D., professor, Beef Cattle Reproductive Physiology, Texas A&M AgriLife Research and Extension Center.

The polar vortex last month sent humans and all animals scampering, seeking shelter to avoid the winds and brutally cold temperatures. During this period of cold, windbreaks for livestock were critical, especially since many cattle had wet hair due to the rains prior to the cold. Fortunately, temperatures are gradually returning to normal.

The first priority for many cattle producers would have been the bred cows calving this spring. Bulls, and definitely bucks and rams, this time of year are separated from the breeding females and particularly for bulls, are separated in a pasture with maybe a couple of other bulls.

During normal winters, running bulls on pasture or small pen areas is not a bad plan provided there is bedding of stalks or even leftover hay to protect them from the frozen ground. However, this is not a normal winter. Lack of wind protection and bedding, even during normal winters, will increase the chance of frost damage to the scrotum and testicles and affect the future reproductive success of the herd. The polar vortex experienced in January can strain even the most seasoned livestock producer to provide sufficient nutrition, bedding and wind protection.

Keep in mind that the scrotum (which envelopes the testes) has little protection compared with the rest of the bull’s body. It is basically bare skin with a fine hair covering. If bulls lie on frozen ground or snow, the testes are basically on ice. Bedding can serve as insulation when bulls lie down.

During normal winter conditions, frostbite is not a common problem with breeding bulls. Any injury to the testicles that damages stored sperm may put a bull out of business until the injury heals. It will take about 60 days before new sperm is available, thus If frostbite damage occurs, it will be at least two months before the bull will have viable sperm and may be longer depending on severity.

Evidence of frostbite to the scrotum is usually apparent a few days after freezing in the form of noticeable inflammation and swelling and later you may see scabs appear on the lower portion of the scrotum as healing occurs. The inflammation, which produces heat and swelling, interferes with the cooling and warming mechanism of the testicles. This heat 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.

Severe frost damage to the testicle and epididymis may cause tissue adhesions, affecting mobility and circulation within the scrotum. If the inflammation and its subsequent repair is severe enough, the testicles are no longer able to move freely in the scrotum; the bull then cannot raise or lower the testicles to maintain the proper temperature for sperm production.

Some bulls get frostbite even with good care and bedding and usually these bulls have large, pendulous scrotums that hang down lower and are more exposed to the wind. In cold weather, a bull normally pulls its testicles closer to the body for warmth, but older bulls with pendulous scrotums may be unable to do that.

Keep in mind that scrotal frostbite commonly occurs in bulls after a severe winter, particularly when they don’t have adequate bedding or shelter from wind. Even then, they may have to graze or eat hay in the open, exposed to wind. However, the absence of a scab does not indicate that frostbite injury has not occurred. Early after frostbite, semen quality is adversely affected due to inflammation. But we can check those bulls later, as they heal.

It may be prudent this year to have all bulls, rams, and bucks evaluated well before the breeding season. This will give you an opportunity to find an alternate breeding animal well before turnout time.

Teresa L. Steckler is a University of Illinois Extension specialist, commercial agriculture.