Predicting cattle age from eye lens weight and nitrogen content, dentition, and United States Department of Agriculture maturity score.
This research explores the relationship between generally accepted and alternative cattle age-prediction methods and chronological age. Cattle (n = 386) of documented ages ranging from 370 to 1,115 d of age were used. Dentition (DEN), USDA maturity score (MS), lens weight (LW), and lens total N (LN) content were used as possible predictors of age. Correlations with age were determined: LW (r = 0.77); DEN (r = 0.74); LN (r = 0.71); and MS (r = 0.64). Stepwise backward regression was used to generate an age prediction equation: Age (mo) = -21.79 + 17.23(LW, g) + 0.038(DEN). By this equation, 38% of cattle </= 20 mo of age were verified as </= 20 mo of age. Independent measures verified the following percentages of cattle as </= 20 mo of age: LW (20.2%), MS (11.0%), DEN (9.6%), and LN (8.7%). The DEN verified that 87.6% were verified as <30 mo old, and LW verified 81.6% of cattle as <30 mo old. A separate group of cattle (n = 18) ranging in age from 1 to 12 yr were evaluated for lens properties, for which LW (R(2) = 0.91) and LN (R(2) = 0.92) were highly correlated with age. The LW and DEN were the best predictors of age for cattle 13- to 37-mo-old and yielded the most accurate age prediction when used in combination (R(2) = 0.67).