By Russ Daly
Special to the Farm Forum
Beef producers are frequently reminded to pay attention to their cows during our harsh northern plains winters. Because of the cold and the cow’s rapidly growing fetus, nutrition is especially important: feeding the cow the proper amount of energy and protein is essential to her calf getting off to a healthy, vigorous start.
Bulls, on the other hand, don’t garner as much attention during the winter. We often consider them to be in a holding pattern until they can become useful again. Harsh winter conditions however, can have profound effects on a bull’s ability to productively breed cows later on.
Cold stretches during winter affect bulls’ nutritional needs. They also need to get sufficient energy and protein to keep their weight and maintain body temperature throughout the winter. Cold weather can also have some more direct effects on bulls’ reproductive anatomy, though.
Of all the organs in the bull’s body, none are more persnickety about outside temperature as their scrotum and testicles. If those things get too hot, sperm production is decreased. That’s why a bull’s anatomy is uniquely designed to raise and lower the scrotum according to external conditions. When it’s cold, they get pulled up near the body for warmth; when it’s hot, they descend so they stay a bit below normal body temperature.
Frigid conditions can do more than just make the testicles cold – they can directly damage that tissue if frostbite sets in. A bull’s scrotum is built more for keeping things cool, rather than for warmth: the skin there is relatively thin and hairless. These factors make frostbite of the testicles and scrotum a real possibility during frigid temperatures, while it’s rare for frostbite to develop elsewhere on a bull.
Frostbite can occur when bulls lay on frozen ground for long periods of time, or when they’re outside in the cold and wind for prolonged periods of time. As with other parts of the body, freezing directly damages skin cells and in bulls, the underlying testicles. When the sperm-producing cells of the testicle are frozen, that damage is immediate and persistent. Healing can, and usually does occur, but as long as testicular cells are damaged they won’t produce viable sperm cells. Since the formation of a sperm cell takes about two months, sperm production will take a hit for at least that long after frostbite.
Besides hoping for a mild winter, there are two things we can do to minimize the harsh adverse effects of frostbite on our bulls: prevention and detection.
Cattle producers can help prevent frostbite in bulls by providing ample amounts of dry bedding during cold weather. This makes it more likely the scrotum will be insulated from the frozen ground when the bull lies down. Providing windbreaks will help decrease frostbite chances as well.
Sometimes frostbite damage is visible externally. Initially, skin and tissue damage shows up as swelling in the scrotum, but as damage progresses and eventually heals, sores and scabs will form on the bottom portion of the scrotum. If the testicles themselves are significantly damaged, they can shrink over time as scar tissue replaces the sperm-producing cells. This might not become apparent until weeks or months later.
It’s been my experience, however, that bulls can undergo some significant frostbite damage even without external evidence of a problem. This fact makes bull breeding soundness exams even more important. Another thing to consider is that the damage often heals. A bull that doesn’t pass the semen evaluation the first time should be reevaluated in 3-4 weeks, to give him the best evaluation. This is another reason not to wait until the last minute to test bulls for breeding soundness.
Additionally, just because a bull has some scabs and skin damage on the scrotum does not necessarily mean it will fail a semen test. Sometimes, sufficient underlying healing has already taken place by the time of testing, or the skin turned out to be more damaged than the underlying testicle.
Since bulls are so critically important to the reproductive success of a beef herd, it pays to pay close attention to them – and their body parts – during the cold of winter.
Russ Daly, DVM, is the Extension veterinarian at South Dakota State University. He can be reached via e-mail at [email protected] or at 605-688-5171.