Ask the Vet

Bull Fertility Drops

A significant change in conception rates in the herd has one cattleman asking what's wrong with his bull. (Progressive Farmer image by Victoria G. Myers)

Question: We used a young bull on a small group of cows last year and had 19 calves from 21 cows. This year, we had only five calves born. We think his testicles are smaller than they were last year. Is this possible? What could

have happened to him?

Answer: I will begin my answer with the assumption that this bull did not have a complete Breeding Soundness Exam (BSE) done before he was put in with the cows. If that is true, his testicles may well have been too small from the start. It is easy to become more critical after a crisis, and, with no records on which to base a possible change in testicle size, it's hard to say if that is really the case. This is why a complete BSE before every breeding season is so important.

Unless you know for certain this bull's testicles are smaller than they were the previous year, we could be looking in all the wrong places for an answer.

Let's assume they are smaller, and they are hard. He could have had orchitis or inflammation of the testicles. This is uncommon in bulls, but it does happen. It usually is caused by bacteria that get into the testicles from the bloodstream from other parts of the reproductive tract or some kind of penetrating wound. Testicular tissue can even be damaged by high temperatures either from a fever or, in some cases, the environment.

Frostbite can lead to inflammation and increased temperatures within testicular tissue. Even obesity can be an issue. Bulls that are overweight, for example, often have excess fat in the scrotum, and that can disrupt normal temperature regulation within the bull's body. Trauma from being stepped on or butted could be involved.

As you've probably guessed by now, I am doing a lot of guessing. The only guaranteed answer is that this bull absolutely has to be examined by your veterinarian before you even think about using him again. He may well be a cull if the testicles are smaller, in which case, your problem will disappear in the back of a truck. If that's not the case, you have some detective work ahead of you to find out what happened to conception rates.