Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 4, 1997
Publication Date: N/A
Interpretive Summary: All dairy breed associations and many artificial-insemination organizations in the United States have implemented linear type (conformation) trait programs. The American Jersey Cattle Association (AJCA) currently scores 15 type traits and assigns a final score. Genetic evaluations for linear type traits and for final score of Jerseys currently use a single-trait sire model, but use of a multitrait animal model would improve accuracy of evaluations. In this study, (co)variance components were estimated for final score and 15 linear type traits of Jersey cows from a model similar to the one proposed for the evaluation. These estimates will be the basis for a multitrait, animal model genetic evaluation system for U.S. Jerseys. The updated evaluation methodology will result in a more accurate ranking of animals, which will allow dairy cattle breeders to make greater genetic progress for conformation traits.
Technical Abstract: (Co)variance components for final score and 15 linear type traits of Jersey cows were estimated by multitrait restricted maximum likelihood using multiple diagonalization and a repeatability model with 34,999 records of 22,354 cows. Multiple diagonalization gave relative off- diagonals of <.01%. Heritabilities (and repeatabilities) were estimated as .29 (.48) for final score, .40 (.57) for stature, .26 (.39) for strength, .28 (.43) for dairy form, .13 (.25) for foot angle, .13 (.25) for rear legs (side view), .27 (.41) for body depth, .31 (.52) for rump angle, .22 (.33) for thurl width, .22 (.36) for fore udder attachment, .28 (.46) for rear udder height, .26 (.42) for rear udder width, .32 (.48) for udder depth, .20 (.36) for udder cleft, .29 (.46) for front teat placement, and .31 (.48) for teat length. Estimates of heritability generally were higher and estimates of repeatability were lower than values used previously for USDA genetic evaluations, which were based on data from the 1970's and early 1980's. Final score was highly correlated with dairy form and rear udder traits. These estimates of heritabilities and (co)variance components are necessary for multitrait genetic evaluation of linear type traits of U.S. Jerseys.