Evaluation of Corrective Mating for Type Traits in Jersey Cattle

Abstract

First available appraisals of 14,721 Jersey cows having valid scores for 13 linear type traits, dams with cow indexes for linear traits, and sires and maternal grandsires with Predicted Differences for linear traits, were used to evaluate corrective mating for type traits. Predicted Differences of sires and four measures of merit of dams were used to predict offspring linear trait scores relative to herd average. Measures of dam's merit were phenotypic score relative to the overall mean, phenotypic score relative to herd mean, cow index, and half her sire's Predicted Difference.Regressions of offspring linear scores on a composite pedigree index (sire + dam measure) ranged near 1.0, whereas regressions on measures of sires and dams separately, yielded coefficients for sires that consistently were larger than those for dams. Mean squares and least squares means for measures of dam's merit suggested dam's cow index is superior to dam's phenotypic score for predicting mean score of offspring groups. Frequencies of predicted scores within ±4 points of actual scores ranged from 52% for stature to 80% for udder depth. Correlations between measures of sires and dams indicated little assortative mating has been practiced for linear type traits in Jersey cattle.