J. Anim Sci.
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Published online first on July 18, 2008
J. Anim Sci. 1910. doi:10.2527/jas.2007-0445
© 2008 American Society of Animal Science
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Predicting cattle age from eye lens weight and nitrogen content, dentition, and USDA maturity score

C. R. Raines*, M. E. Dikeman*, J. A. Unruh*, M.C. Hunt* and R. C. Knock{dagger}

* Department of Animal Sciences and Industry, Kansas State University, Manhattan, 66506 {dagger} Department of Animal Science, Iowa State University, Ames, 50011

mdikeman{at}ksu.edu

Abstract

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 nitrogen (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%). 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 (R2 = 0.91) and LN (R2 = 0.92) were highly correlated with age. 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 (R2 = 0.67).

Key Words: Age Verification • Lens • Dentition • Cattle Maturity






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