GUIDE TO AGE OF CATTLE
 

At birth to 1 month Two or more of the temporary incisor teeth present.  Within first month, entire 8 temporary incisors appear.
 
2 years As a long-yearling, the central pair of temporary incisor teeth or pinchers is replaced by the permanent pinchers.  At 2 years, the central permanent incisors attain full development.
2 years Permanent first intermediates, one on each side of the pinchers, are cut.  Usually these are fully developed at 3 years.
3 years The second intermediates or laterals are cut.  They are on a level with the first intermediates and begin to wear at 4 years.
4 years The corner teeth are replaced.  At 5 years the animal usually has the full complement of incisors with the corners fully developed.
5-6 years The permanent pinchers are leveled, both pairs of intermediates are partially leveled, and the corner incisors show wear.
7-10 years At 7 or 8 years the pinchers show noticeable wear; at 8 or 9 years the middle pairs show noticeable wear; and at 10 years, the corner teeth show noticeable wear.
12 years After the animal passed the 6th year, the arch gradually loses its rounded contour and becomes nearly straight by the 12th year.  In the meantime, the teeth gradually become triangular in shape, distinctly separated, and show progressive wearing to stubs.  These conditions become more marked with increasing age.
Illustrations for this table were prepared by R.F. Johnson and published in The Stockman's Handbook by Ensminger Second Edition page 539.