Genetic Parameters for Three Experimental Linear Type Traits

Abstract

Multiple-trait REML was used to calculate heritabilities and genetic and phenotypic correlations for three experimental linear type traits (thurl position, rear legs rear view, and teat length) and 14 primary linear type traits. Data were linear appraisal scores on 17 traits for 79,576 daughters of 722 Holstein sires. Heritabilities were .06, .09, and .26 for thurl position, rear legs rear view, and teat length, respectively. Genetic correlation between thurl position and rear legs rear view was .52. Thurl position was genetically most highly correlated with two other skeletal traits, rump angle (.66) and rear leg set (–.36). Rear legs rear view had its largest genetic correlations with foot angle (.64) and rear leg set (–.54). The highest genetic correlations between teat length and the other udder traits were with udder depth (–.21) and front teat placement (–.28). Teat length was also moderately genetically correlated with other traits indicating the size of the cow, i.e., stature (.27), strength (.34), and body depth (.34). Genetic parameters indicate that including thurl position as a primary trait is not justified. Definition of rear legs rear view should be refined before judging its potential as a primary trait. Teat length should be included as a primary type trait because it has moderate heritability, is genetically distinct from other type traits, and has economic importance. Addition of three experimental traits into multiple-trait analyses had little influence on reliabilities of most primary traits.