Ask the Vet

Udder Heritability

Udder quality is mostly a genetic issue, making bull selection especially important. Check the dam's udder scores when choosing a bull. (Photo by istockphoto/thinkstock)

Question: We have a herd of cows that for some reason all have huge bags and udders. Are they lacking some mineral? Any ideas what causes this and what we can do?

Answer: Udder quality, especially when it is a herd problem, is, in my mind, a genetic issue until proven otherwise.

Cows' udders are evaluated based on udder suspension and teat size. Each is scored on a scale of 1 to 9 at calving. The scoring is based on the largest teat. An udder with a score of 9 is very tightly attached to the body wall, while a 1 would be very loose. A teat score of 9 is very small, while a 1 would be very large.

While a score of 9 in either case may not be ideal, a score of 1 is always highly undesirable since floppy udders and very large teats are more prone to mastitis, tend to produce less milk and often keep the newborn calf from getting adequate colostrum.

Udder and teat conformation is moderately heritable, so bull selection is critical in improving this aspect of your herd. Look for bulls whose dams have excellent udder quality. When selecting a bull, ask for the udder score of the dam. When possible, try to see the dam. Also, a trip through the cow herd can be enlightening. A herd of good-uddered cows is always a good sign the breeder puts a priority on this important trait.