Ask the Vet

By Dr. Ken McMillan
DTN/The Progressive Farmer Contributing Editor

QUESTION: We bought a really good bull last year. He bred all but one of our cows in a 60-day breeding season, and his calves are due to start coming in January. He passed a semen test when I bought him a year ago and is now less than 3 years of age. My county Extension agent says I need to have him checked before the next breeding season. What do you think?

ANSWER: Congratulations for making a good decision and a great investment in a quality bull. Most veterinarians, animal scientists and top producers will tell you all bulls should be checked before every breeding season. I agree completely. The risk of not doing a Breeding Soundness Evaluation (BSE) is too big a gamble. A BSE does not measure libido, so you must be sure the bull is interested in breeding cows. Certain problems with a bull's penis do not show up during a BSE so you must be sure he can breed cows.

It's important to watch for disease or injury that can render even the most fertile bull infertile overnight. Keep a sharp eye on bulls during the breeding season. Write down when a bull breeds a cow, and then watch that cow to see if she returns to heat in 18 to 24 days. Too many cows coming back into heat are a sign of a problem and must be dealt with immediately.

You used the term "semen test," but I used the term Breeding Soundness Evaluation. We may be talking about the same thing, but understand that a real BSE should always be conducted by a qualified veterinarian. It involves a physical examination of the bull and his reproductive tract. The testicles are measured, a semen sample is collected, and that sample is examined under a microscope for motility, morphology or normal or abnormal shape.

To pass a BSE, the bull must be physically sound so he can breed cows. The scrotal circumference must meet minimum standards based on age. The semen must not only move, but most of the sperm must have what we call progressive or forward motility, and at least 70% of the cells must have normal morphology.

Every year I find a few bulls that fail their BSE. No one can look at a bull and tell if he is fertile. A sterile bull can cost you thousands of dollars, but a subfertile bull can cost you a lot of money too. In a 25-cow herd, the difference in an 80% calf crop and a 95% calf crop would be 3.75 calves. Even if subfertile bulls get your cows bred later in the season, it can cost you. Cows bred on the first heat cycle wean heavier calves than those that don't settle until their third heat cycle.

The way I see it, a BSE is an important investment in your cattle operation.

(VM/CZ)

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