Ask the Vet

Think Generations Ahead When Picking a Bull

Be a picky "buyer" when choosing a bull, even if that bull is coming from your own herd.(DTN/Progressive Farmer photo by Clair Vath)

Question: I have a group of young bulls out of which I'm selecting replacements for my line-breeding program. The heaviest bull has a high testicle. I assume this condition is genetic. If I use him, what can it cause in his offspring? The second-best bull is also a concern to me because he came backwards at birth and was a hard pull. Is that a genetic condition, as well?

Answer: Let me start by saying I believe that just about everything has some heritability to it.

We know that cryptorchidism, or testicles retained in the abdomen, is a heritable condition—and a very bad thing for a lot of reasons.

Testicles are outside the body cavity for a reason. Sperm need to develop at 4 to 6°F below normal body temperature. A temperature-sensitive muscle, the cremaster, adjusts the distance from the body wall so that this lower temperature can be maintained. Cryptorchids and "high flankers" where the testicle is next to the body will have decreased viable sperm production.

My country logic says that the condition you are describing is probably a continuum from anything from an unbalanced scrotum to a high flanker and finally a true cryptorchid.

When I do a breeding-soundness evaluation (BSE), I carefully palpate the testicles and note any abnormalities. This is a key part of a BSE.

If the testicles are not uniform in size, shape, texture and position, I will write that on my BSE form. Bull customers will also want to see a nice, uniform, bottle-shaped scrotum with a well-defined neck.

In this case, you may be your own customer, but you should still be a picky buyer. You are, after all, making a choice that will impact not just conception in the herd but future generations of your business.

Regarding your reference to your second-best bull's posterior presentation at birth, you can take some comfort from the fact that this is not considered to be a highly heritable trait.

In fact, most breeds discount an abnormal presentation when calculating calving ease EPDs.

Now, what I cannot say is whether this particular incidence had much heritability to it. The fact that you note it was a hard pull is my main concern. Most of my true posterior presentations, when two back feet are in the birth canal, have been fairly easy pulls.

There are many factors that enter into dystocias, or difficult births: calf size, gender and calf shape, gestation length, female pelvic area, body condition, nutrition, season and calf presentation. All of these things can have an influence. So even if presentation is not highly heritable, other factors in this case, especially those that lead to the calf being a "hard pull," as you describe it, may be concerning.

The bottom line for me is this: I would look for other bulls to use on my herd than the two you described to me. I often say a good bull will make a great steer. I try to only select what I think will be great bulls.