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Semen Evaluations

After all this time there are still some producers who are sceptical about the merits of having a semen evaluation done on their breeding bulls before turnout. This article will attempt to highlight the positive points and hopefully lay to rest the misconceptions surrounding it.

Veterinarians are really doing much more than just checking the semen, which is why it is really called a Breeding Soundness Evaluation. The abbreviation is a BSE exam but that is seldom used anymore, not since BSE became linked to mad cow disease.

During a semen evaluation under a high-powered microscope, we check both live sperm for motility, how active they are, and killed sperm for their morphology, which gives us the percentage that are defective. Certain defects are caused by faulty formation due to improper maturation of the sperm. Others crop up when the bulls are not very active and the sperm becomes stagnant.

When the bull is restrained for collection is the easiest time to assess his body condition as well as his feet, legs and sheath for any noticeable defects. The veterinarians will also be watching the bull as he walks away from the restraint to see if any structural defects are evident.

A big part of any evaluation is the measurement of the scrotum, which indicates semen production. Generally the larger the scrotum the more semen will be produced up to a maximum of 39 centimetres. Beyond that semen production does not go up very much.

The testicles, spermatic cords and epididymis (area where the sperm mature) are palpated for signs of abnormality. The testicles are compared for size and shape and any differences in terms of firmness or softness. Abnormalities in any of these areas may indicate a problem, which will show up in the sperm. One defective testicle will markedly diminish the serving capacity of the bull.

To collect the sperm a probe is inserted into the rectum, and a very low electrical current gently increased, causing the bull to become erect and ejaculate.

It’s important that the penis protrudes beyond the sheath so it can be inspected for cuts, warts or a frenulum, which is a ligament tie-down between the penis and sheath. Most of these conditions are detected in yearling bulls, albeit at a fairly low percentage. But all of them can render a bull infertile or sub-fertile. Blood, which is often present because of these conditions, is very detrimental to semen quality.

Just before inserting the probe all the internal sexual organs are palpated for differences is size, infection or scarring. The seminal vesicles are the dominant organs much as the prostate gland is in humans. Inflammation of the seminal vesicles either from blood borne infections or ascending from an infected navel are detrimental to lively sperm. It can show up as pus in the semen. In some cases these infections can be treated but most often the bull will need to be culled.

Eyes are examined closely. Ideally you want a bull with two fully functioning eyes and adequate depth perception so he can identify cows in heat. Of course, a one-eyed bull can breed cows. The question is can he find them when they come into heat at the other side of a large pasture?

If you can eliminate infertile or sub fertile bulls with a breeding soundness evaluation conception rates should definitely improve. As a general guide, around 20 per cent of bulls have fertility issues. The problem is exaggerated in large herds using multiple bulls if the dominant bull is the infertile one. In a single bull pasture it would be a wreck. I have seen instances of a 100 per cent open rate. That’s a situation you want to avoid.

If we rank the importance of checking bull groups the list would look something like this. Ideally it’s best to test all breeding bulls every year. If not, the new young bulls should definitely be tested. Normally, as a condition of sale, purebred breeders test all their yearlings to eliminate selling problems to their customers. Older bulls past their prime (beyond four years) are prime candidates for testicular degeneration and other conditions affecting their reproductive ability. Any bulls that have been sick, injured, frostbitten, or show swelling on the testicles should definitely be examined, as well. The last group would be bulls of prime breeding age with no previous problems. Infertile bulls can still be found in this group, but the chances of that happening are much less.

The only breeding prerequisite that is not tested for is the libido or sex drive. Veterinarians often leave that up to the producer. Watching bulls breed the first one or two times in the season is always a good idea. Yearlings especially can be awkward at the start. Be sure they are capable of entering the cow and ejaculating before turning them out into the herd.

Always be on the lookout for other signs of trouble during the breeding season — such as swelling on the sheath or scrotum. This could indicate a broken or cut penis. Problems can and often will happen, making it necessary to replacing a bull in order to get the cows bred on time.

Breeding soundness exams are an integral part of any beef herd health program. Other chores such as vaccinating for footrot or pinkeye and tagging might as well be done at the same time as the bulls are being processed to eliminate that headache in the future.

Hopefully your breeding season this spring will be uneventful as far as the bulls are concerned. — Dr. Roy Lewis

Roy Lewis is a private practitioner based in Westlock, Alta.



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