that every bull passes a breeding soundness examination before putting him out with cows. This evaluation basically looks at five things: physical soundness (feet and legs, eyes, etc.), reproductive tract soundness, scrotal circumference that meets the minimum requirement, minimum percentage of sperm cells that are normal, and acceptable motility. There are some things that cannot be evaluated, however, until the bull actually tries to breed a cow.
I
Duane Mickelsen, DVM, a cattle breeder at Pullman, Washington (now retired from Washington State University), has spent his lifetime specializing in reproductive problems in cattle - either in private practice or as a professor teaching bovine theriogenology and obstetrics to veterinary students. He has evaluated thousands of bulls and stresses the importance of breeding soundness examinations - not only for virgin bulls but also for the older bulls. Even if they were fertile last year, they may not be fertile this year, if they suffered an injury, infection, or damage from scrotal frostbite during the preceding winter. You may not know if these bulls are fertile and functional, unless you check them again before their next breeding season.
“Some abnormalities can be discovered when doing a semen evaluation, using an electro- ejaculator, which stimulates the bull to extend the penis. It does not make the bull extend far enough, however to determine some of the problems. For example, one year I went through a herd in the fall preg-checking and found quite a few open cows. They still had the bulls in with the cows, and I told them to split off the bulls because they should not still be with the herd or they will be getting heifer calves pregnant. They put their open cows in a pen, and there was also a bull there. One of the open cows was in heat and this bull tried to breed her but could not; his penis went downward in a big corkscrew. To discover some of these problems, you have to watch the bull try to breed a cow,” explains Mickelsen.
“I always tell my clients to monitor the bulls when they turn them out with cows, to make sure they are doing their job, and are able
t is always a good idea to make sure
to breed the cows. All too often, especially around here, the ranchers haul semi-loads of cows up into the mountains for summer pasture, and turn the bulls out with them. Away they go, and they never do know if the bulls are doing their job,” he says. Even if the bull passes a breeding soundness exam, it is the rancher’s responsibility to see whether the bull has good libido and serving capacity. Even if the bull is fertile, with good sperm quality, he may not settle any cows if he does not actually breed them.
“Some ranchers keep some of their own calves as bulls, and only about 20 percent of the ones I worked with did any form of breeding soundness examination. I always told my clients that any new bull - even the ones they raise themselves - should be semen tested.” And, the next important step is to make sure the bull is able to breed. He may pass his semen test just fine, but if he cannot breed a cow he will not sire any calves.
Another example Mickelsen tells about is a herd he was checking.
“There were 19
females and two bulls in with them. For two years, they did not have very many calves. The young bull was a yearling the first year, and then a 2-year-old the second breeding season. The older bull was 9 or 10 years old. We checked him after the second year of poor pregnancy rate and found that he had a hematoma just ahead of the scrotum. He could not extend the penis properly (and was therefore unable to breed cows) and even if he could have, his semen was not good. He was incapable of settling the cows, but he kept the young bull from breeding them,” says Mickelsen.
Dr. Ram Kasimanickam, Department of Veterinary Clinical Sciences, Washington State University, says it is always important to look at behavior of the bull in a multi-sire group. Social factors can play a major role in a multi- sire breeding program; a dominant bull may keep the others from breeding cows. “Most importantly, if a dominant bull starts having a problem (like lameness, or a fertility problem), he will not settle cows, plus he will not let the other bulls breed cows.” This can be a serious situation unless that bull is removed from the
“Some ranchers keep some of their own calves as bulls, and only about 20 percent of the ones I worked with did any form of breeding soundness examination.”
2017 JULY i TEXAS LONGHORN JOURNAL 25
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