CSU Extension: Mouthing Cows for Culling

SEPTEMBER 28, 2020 – In years when forages are in short supply, a decision to thin the herd and cull out cows can be necessary. Mouthing cows for age and tooth wear can be helpful in making those decisions. Most producers keep good records and know the age of the cows in their herds, but for those females whose age is questionable, examining the teeth and using dentition to estimate age is a common practice. Cattle teeth can give a good estimation of the age of the individual by their appearance and amount of wear. Young calves develop 20 temporary teeth termed deciduous, milk or baby teeth.

Around the age of 14 to 18 months, these teeth begin to be replaced by the permanent teeth. By the time they are 5 years old cattle will have grown 32 permanent teeth.
The easiest teeth to examine to determine age are the incisors. Incisors are the bottom front teeth that close against the dental pad on the top of the mouth. The first two permanent middle incisor teeth to appear are called the pinchers. Pinchers erupt through the gums between age 18 and 24 months and are usually up in wear by 24 months. Then the rest of the incisors begin erupting to fill the lower jaw. At 24 to 30 months the next pair of incisors, first intermediate pair, erupt and come into wear by 36 months.

Followed by the second intermediate pair erupting around 36 months and in wear by 48 months. The final set of incisors, the corners, erupt at 42 to 48 months and are in wear by 60 months. Examining a cow who has all eight front incisors is a good indicator she is at least 5 years old and under 10 years old. Closer examination of the wear pattern on the incisors can give additional estimation to age. Incisors tend to “level off” and wear in the same order as they appeared. If the Pinchers are the only incisors that appear to have leveled off, the cow is estimated under 6 years of age.

Leveling and wear of the first and second intermediate pairs indicate estimated ages of 7 and 8 years old, respectively. When leveling and wear appears to have occurred on the corner incisors, the cow is closer to 10 years of age.

Aging might not be the only reason to inspect teeth. Broken and missing teeth are also indicators of possible future care issues. Many livestock sales use three terms to identify the teeth quality of cows: solid mouth, broken mouth and smooth mouth. Solid mouth cows have all their teeth and are usually the youngest. If teeth appear heavily worn, damaged or missing, a cow may be considered broken mouth.

The broken teeth may occur due to wear from diet, injury, health issues or just general aging. Smooth mouth cows are those whose incisors have become completely missing or worn down. Those cows are most likely over ten years old and may have some significant issues when foraging and therefore issues maintaining or gaining weight.
There are other factors that can be used when examining teeth to determine age. For further information, the Mississippi State University Extension Service has a great fact sheet Estimating Cattle Age Using Dentition reference available at:
https://extension.msstate.edu/sites/default/files/publications/publications/p2779.pdf or a short online
video available at: https://www.youtube.com/watch?v=0JdgnCDU0kI.

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By Tucker Allmer - The BARN

Tucker Allmer & the BARN are members of the National Association of Farm Broadcasting (NAFB), the Colorado FFA Foundation, the Colorado 4H Foundation, the Colorado Farm Show Marketing Committee, 1867 Club Board Member, Denver Ag & Livestock Club Member, the Weld County Fair Board, the Briggsdale FFA Advisory Council, Briggsdale 4H Club Beef Leader & Founder / Coordinator of the Briggsdale Classic Open Jackpot Show.

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