Ask the Vet

Mouth-Aging Cows Under Five

After a cow is 5 or 6 years old, the condition of her teeth will be dictated to by what she eats and her genetic makeup. Before that, "mouth-aging" can provide a fairly accurate estimate of her age. (DTN/Progressive Farmer photo by Karl Wolfshohl)


I bought a small herd of cows, all represented to be 3 to 5 years of age. I am not sure I wasn't sold some cows a lot older. How accurate is mouthing cows in determining their age?


Teeth can be very helpful in aging cattle. The incisors come in at about the same time in all cattle. Based on a table from the USDA and Mississippi State University Extension, I can tell you the first incisors show full development around 36 months, leveling at 5 to 6 years, with noticeable wear at 7 to 8 years.

After 4 to 5 years of age, however, guess replaces estimate. But we can at least make our guess an educated one. Aging a cow by her mouth is based on wear levels of the teeth. As you might think, this can vary greatly depending on what the cow eats.

For example, animals grazed on sandy land in Florida, those fed course or gritty grains or those grazing course native forages typical in the Western Plains will show more wear to their teeth than cattle on improved forages common in the Eastern United States. And crossbred cattle and Brahman-influenced cattle maintain incisors longer.

A good rule of thumb is to compare the teeth of cattle with known ages to those you are trying to estimate an age for. Doing this, you can actually develop a system that works for cattle in your area and operation.

While I learned the aging formula chart as a child, I also was taught the incisions "necked out", or showed a narrowing just above the gumline, beginning at about age 6 for the first incisor, age 7 for the second, age 8 for the third, and age 9 for the fourth or outside incisor.