The popularity of marker bulls has dropped since the advent of timed breeding synchronization programs, but they are still valuable in visual heat detection.
When looking for a marker bull, also known as a gomer bull, it is best to select one from your own operation to minimize disease transmission. Stay away from a young bull brought in from an unknown source.
Generally, a poorer quality bull or one that fails its semen evaluation is chosen for the procedure. Smaller testicles are a plus because there will be less bleeding during surgery.
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It is a good idea for veterinarians to palpate the bull’s internal reproductive organs to avoid using one with seminal vesiculitis. This is undesirable because pus will be discharged into the cow during breeding, which could disrupt the breeding program.
Various surgical procedures are available to inhibit bulls from inseminating without stopping their sexual activity.
I use the epididymectomy technique, which still allows bulls to enter cows naturally. Studies have shown that if the marker bull enters the female, there is a higher conception rate than with non-entry techniques.
The procedure can be done on the standing bull in a chute with a local anesthetic. Sometimes a tranquilizer may be necessary.
The epididymis at the bottom of each testicle is removed. This stops sperm flow, much like a vasectomy, with the only difference being that the sperm flow is blocked at a different location. Bulls can be used 10 days after the surgery or sooner if they are “cleaned out” on an in-heat cull cow.
It is an economical procedure, taking no more than half an hour. Producers ship the bull after the breeding season because it is more costly to keep it over the winter than to repeat the procedure on a new bull the next year. Smaller, younger bulls make better markers because they have to work harder to mount cows.
The chin ball marker is a necessary piece of equipment when using gomer bulls. It releases paint from a ball valve when the bull rubs its chin over the backs of in-heat females. Colours can be alternated to make these females easier to identify.
The bull will mark cows that have a silent heat and those cycling at night when observation is difficult. They save producers labour when it comes to heat detection. It is wise to choose a marker bull with a good disposition because it will need to have the chin ball marker filled frequently.
I strongly recommend putting an empty chin ball marker on the bull early. Until it gets used to it, a bull will rub it on fences and trees in an attempt to remove it, painting the whole pen and wasting a lot of ink.
If producers want a non-entry bull, a sidewinder is the best method. This is where the exit for the penis is moved laterally and comes out sideways when it attempts to breed.
There have been instances of bulls mounting a cow sideways and having successful intromission. Most veterinarians will also perform an epididymectomy to be safe. The procedure is costly and surgically complicated, so these bulls are usually kept for several years.
Vasectomy is another common technique, producing results similar to an epididymectomy.
The negatives are that the bull has to be cast, the surgery is tougher and because the vas deferens is a tiny duct, both must be nipped out, identified and sent away to a lab to confirm the veterinarian has removed the right structure.
If you are thinking of having a marker bull procedure done, plan it out and speak to your veterinarian about the preferred procedure.
Occasionally, a cystic cow will be dominant and act like a bull. They can have a chin ball attached and do a fine job marking.
I have also tried multiple ear implants of testosterone or testosterone injections, but find neither gave consistent results.
Roy Lewis is a veterinarian practising in Westlock, Alta.
