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Cold weather can affect first semen evaluation

It may take retesting before sperm counts improve

This frostbite scarring on a bull’s scrotum indicates the bull should be semen tested.

With an extended period of cold weather across the prairies this winter, semen results on young bulls and herd sires may not be all that desirable. We may see more bulls deferred because of semen defects. Don’t panic. Work with your veterinarian. They can provide the best advice on the outcome and even give a rough idea of when the semen scores could rise.

Extreme cold can cause inactivity in bulls, resulting in stagnant semen and even cold shock to the sperm. Both can cause abnormalities and a failing semen score. Semen defects can appear as bent tails, detached heads and other defects. The bull may be tested a second time to see if there’s any improvement.

Some vets know cold-weather tests may be iffy at best. They are measuring the bulls and palpating the testicles as well as the internal sex glands for any signs of enlargement or scarring.

They then lightly ejaculate the bulls to get protrusion of the penis so they can be proactive checking for warts, cuts, hair rings or a persistent frenulum. This is a ligamentous attachment between the sheath and penis that causes the penis to bend on full erection, making it very difficult to enter the vagina.

Persistent frenulums are an interesting phenomenon. They are heritable and there is no female counterpart. Commercial cattlemen will have no issue to buy a bull that has had a frenulum as all male offspring become steers. But purebred breeders want to avoid using an affected bull as a herd sire as incidence of the condition in his purebred bull calf offspring will increase.

An evaluation before breeding season can help detect this condition known as persistent frenulum, which can affect breeding ability. photo: Roy Lewis

The best example I can use is a small Angus purebred breeder who had three out of eight bulls with persistent frenulums. That’s an extremely high number whereas on average I might see one in every 100 bulls or so.

If any pus (white blood cells) is found in the semen the bull is potentially treated with antimicrobials. Checking all these things goes a long way to ensure breeding soundness and that it’s unlikely they will pass on unexpected problems. The beauty of this system is the actual test day then becomes a recheck day as well on other problems.

We can test bulls in pretty cold weather, but a heat source is needed to look after the microscope, the veterinarian, and the semen sample. We need to be careful not to cold-shock the sample as this may lead to bent tails in sperm — a problem due to temperature and not the fault of the bull. Many of these so-called ‘rusty loads’ are just that. The bulls simply need to be retested. If the bulls can be naturally stimulated by having cycling cows, heifers or even cull ones nearby, that will go along ways to ensuring they have fresh semen to examine. It will be a truer test of their real fertility.

Assessing frostbite

Frostbite is always hard to assess as the bulls can pull up their testicles and even though the scrotal skin may be scarred and sloughing off you won’t know the degree of damage to the formation and maturation of the sperm without a semen test. Also, damage may be reversible and of course there is lots of inflammation with the scab sloughing off.

Other bulls have lots of tag on them and if it freezes onto the testicles that can also lead to frostbite. Some bulls, even though they have lots of bedding, will stand backed into the wind and experience strong wind chill. Again, each case needs to be assessed on its merits.

All purebred breeders should also test their main herd bulls as they are often assumed to be OK, but one never knows. Also, purebred breeders at least initially run with single sire mating’s so if the one bull is infertile that can have disastrous consequences to their breeding program. Commercial breeders often test every bull every year. If a bull has two breeding seasons yearly it is wise to test just before each season as you never know what may have happened over the winter or between the two breeding seasons.

We can also find bulls with one testicle severely damaged but still be fertile from undamaged testicle and still get cows bred. They may be good to perhaps keep as a spare. The breeding capacity may be reduced somewhat as only one testicle is functioning but it can still be a functional bull. Your vet would be best to advise on the future use for your bulls.

Again, most vets will advise about giving necessary vaccines to the bulls as well as the value of possibly treating for internal and external parasites. Let’s hope semen evaluating goes well for you this spring and there are no unexpected surprises.

About the author


Roy Lewis is an Alberta-based veterinarian specializing in large-animal practice. He is also a part-time technical services vet for Merck Animal Health.



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