Age of molar and central incisor tooth eruption in cattle

This study was conducted to determine the age at which certain permanent teeth begin to erupt in cattle and to follow the progress of that eruption. It was designed to reveal effects of breed and sex on teeth eruption. It was hoped that these data would be useful in estimating age of young cattle. The data for this study were taken from the available cattle of known birth dates at Blount and Alcoa Farms of the University of Tennessee, Knoxville. Included were seven readings taken at 30 day intervals beginning in July, 1971, and continuing through January, 1972. Data were obtained from 120 head of cattle for the following stages of tooth development: temporary or permanent teeth and degree of permanent tooth eruption (erupting, 1/8, 1/4, 1/2, 3/4 and all). In addition, the breed of cattle, sex, sire, location, identification numbers, and date of examination were recorded. The strongest single factor affecting the time of eruption or appearance of the molar and central incisor teeth was the age of the animal. The mean ages of cattle at eruption of L2M, U2M, L3M, and II is 13 months; 16 months, 2 weeks; 22 months, 1 week; and 21 months, 3 weeks, respectively. The range of tooth eruption for purposes of age estimation for L2M, U2M, L3M, and I1 were 11 to 16 months; 14 months, 3 weeks to 19 months; 19 months, 2 weeks to 24 months, 3 weeks; and 19 months, 1 week to 23 months, 2 weeks, respectively. Breed had a statistically significant effect (P<.01) upon the stage of tooth eruption and showed an interrelationship with age. The Angus had the earliest stage of tooth eruption followed by Angus-Hereford crosses and then by Herefords. In age estimation, the observer will have to allow for differences between breeds in rates of eruption. The rate of tooth eruption was not significantly influenced by sex of the animal. The L1M, L2M, U2M, L3M, and I1 teeth had similar mean eruption times in steers and heifers.