Sunday, September 26, 2010

Veterinary fact of the day: measuring the scrotal circumference of a bull

Two weeks ago we started a new class, Theriogenology, about the medicine of reproduction. (What do you do if she has trouble getting pregnant? What do you do if she has trouble during her pregnancy? Etc.) So far it has all been about cattle, though we will get into other species soon. Much of the veterinary work for the dairy industry specifically is about timing pregnancies, making sure cows get pregnant promptly, and managing herd health reproductive problems.

We had six hours of lecture on cows, and finished up with two hours on bulls. The Society for Theriogenology has guidelines on how to perform a breeding soundness exam on the bull. Is he physically healthy enough to mount a cow? Is the circumference of his scrotum large enough to suggest that he has plenty of sperm (more important for his ability to service multiple cows sequentially than for his ability to get lots of sperm into a single cow)? Are his sperm well-formed and mobile, and mobile in the right direction (forward, not backward)?

Bull scrotums contain vertically oriented testicles, so it is actually useful to wrap a measuring tape around them. (The circumference should be a minimum of 30 cm in a bull of breeding age.) This sort of measurement is not useful in horses, dogs, pigs, or humans, whose testicles are oriented in a different direction.

Most amusingly, the product used to measure the scrotal circumference, with a feature that lets you see if you’ve wrapped the tape too tight, is called ReliaBull. That made me giggle.


  1. Little known fact: if you can milk a bull you'll have a friend for life.

  2. Give them the facts! It is a reality of life. It really makes you look at life from different eyes when in an agricultural environment. It is a bit like doing dissections. After you are finished with anatomy class it gives a lifelong change in philosophy.

    Love your blog- I am very happy to see a veterinary blog!

  3. Thanks, b! And I agree, things look different the more you learn. In vet school stuff gets crammed down your throat so fast, sometimes your brain changes at scary rates.