Fertility in Yearling Bulls – A Real Dilemma

I just got back from a Bull conference held at the Great Plans Veterinary Educational Center in Nebraska. The section on Breeding Soundness Examination of Yearling Bulls was interesting. This was one of the main reasons for me attending this meeting. My take home message was that this particular population of bulls is unique when it comes to fertility. Meaning, these bulls are just coming into sexual maturity. At 12 months of age some are mature and will have the ability to pass the breeding soundness exam, others are not. Yet, a large percent of the bulls that cannot pass at 12 months of age can pass a few months down the road. According to “Bull Breeding Soundness” by Albert D. Barth a manual produced by the Western Canadian Association of Bovine Practitioners, about 45, 60 and 75% of bulls are expected to pass at 12, 13, and 14 mo. of age, respectively. Testing bulls under 12 months of age is not recommended. This is interesting because of the real perspective of cattlemen and veterinarians does not seem to follow this mind set.

There are some very real dilemmas when it comes to yearling bulls. The bull buyer really wants to know if they are getting a fertile bull. Bull producers want to feel confident they are selling bulls that will not come back and bite them. Then the reality of nature comes in and smacks us across the head. We want to ignore this reality, we want to all feel good. So we have been producing feel good pieces of paper that really have little value. Bulls at this young age usually do produce semen, a cursory look under the microscope and at first look you would think that they could pass. When we take a deeper look at the morphological structure of the cells we find a different world. More abnormalities than most examiners would ever expect. Due to the desire to perform many tests in a short amount of time and the economic strains placed on veterinarians, we find ourselves not taking sufficient time to truly count and grade 100+ cells on a high enough power, using a well stained slide or correct microscope to find the abnormalities. If this bull was used at this time the bull could settle some cows when bred, however you would also expect a lower conception rate.

A large percent of bulls are not mature enough to pass the fertility exam at 12 months of age. The breeding soundness exam is not intended to be any kind of predictor for future fertility. It does identify subfertile bulls at the time the test is performed. Breeding soundness exams may also be good at finding early maturing bulls. This does have potential value when selecting for replacements and concentrating on the most important trait for cow-calf producers – fertility. When heifer replacements mature early we can breed them far in advanced of the rest of the herd and will therefore have the best probability of keeping our herd’s calving time bunched at the very beginning of the calving season. This is big bucks for producers.

Breeding soundness exams can also identify other types of physical problems that may affect fertility, the ability for a bull to breed, or other possible health concerns. Scrotal circumference, pelvic measurements, venereal disease testing, persistently infected BVD, and other tests may also be performed at this time. When a bull is not yet able to pass the breeding soundness exam it should simply be tested by the bull buyer just prior to breeding. It is not a reason to not purchase the bull, a large percent will still be able to pass at the later date. It is also important to understand that some may not pass later, there is no way to predict which ones this will be. So good communication between the bull producer and buyer is important, and prior arrangements made to handle these situations when they occur, and they will occur.  As long as bulls are sold at 12 – 13 months of age there will be bulls that cannot pass at this early time, and some that never will pass.

In conclusion: we have a lot of work to do in changing our current paradigm. This meeting was hopefully the beginning of an end of our current situation and a new day for yearling breeding soundness exams will soon happen. We have a long way to go. I will have the opportunity to be very involved in this process. I am excited for this opportunity and look forward to sharing our progress.


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