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Genetic study of weight, height and body condition score in beef cows
Weight (W), weight adjusted for condition score ( WA), height (H) and condition score (CS) of 2 to 8 yr-old cows from the first four cycles of the Germplasm Evaluation project at the U.S. Meat Animal Research Center were analyzed to estimate phenotypic and genetic parameters, and breed differences between 22 breeds of sires. Variance components were estimated by REML using finite-dimensional (FD) models for all traits, and infinite-dimensional models ( ID, Covariance Functions-Random Regression) for W. Additive genetic and permanent environmental effects were included in all models. Estimates of genetic correlations among W at different ages using FD (>.9) agreed with those using ID (>.7) except at extreme ages, indicating that a repeatability model might be an acceptable approximation to model variability of weight trajectories in this population. Estimates of heritabilities for W from FD were .55 to .66 and agreed well with those from ID, except for extreme ages (after 88 mo), indicating that weight at maturity can be efficiently changed by selection. Estimates of heritability for WA, H and CS were .51 to .66; .67 to .75 and .18 to .25 (except for one value of .51), respectively. In general, results indicate no antagonistic relationship between the traits. Selection would be effective for either weight or height, and would produce important correlated responses for both traits. The CS might be included as correlated trait in a multiple-trait model or selection index or used as an adjustment factor to evaluate cow weight at constant fatness. Large differences were found among breed groups for all traits. Breed differences were maintained throughout, with few interchanges in ranking at different ages. Adjustment of W for CS caused some differences in estimates of differences among breeds; however, ranking of breed groups was generally the same for W and WA. On average, proportion of among breed to within breed variability was similar for W and WA, greater for H and less for CS. Such results indicate that breed substitution might offer similar, greater and less opportunity than within breed selection to affect muscular growth (W), skeletal growth (H) and fatness (CS), respectively, in this population. ^
Biology, Biostatistics|Biology, Genetics|Agriculture, Animal Culture and Nutrition
Arango, Jesus A, "Genetic study of weight, height and body condition score in beef cows" (2000). ETD collection for University of Nebraska - Lincoln. AAI9991974.