Phenotypic and Genetic Relationship Between Linear Functional Type Traits and Milk Yield for Five Breeds

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Abstract
Lactation records of cows first calving between 18 and 35 mo were combined with linear type ratings assigned during the same lactation if before 43 mo. Phenotypic relationships were examined between final score and 13 type appraisal traits and first lactation milk yield from 2935 Ayrshire, 3154 Brown Swiss, 13,110 Guernsey, 50,422 Jersey, and 924 Milking Shorthorn records. Most phenotypic correlations between type and milk yield were low. Linear correlations of final score with first lactation milk yield were 0.18 to 0.38. Of the linear functional type traits, correlations with first lactation yield had greatest absolute values for dairy character (0.19 to 0.53), udder depth (-0.26 to -0.30), and rear udder width (0.20 to 0.31). Multiple correlations of all type appraisal traits with first lactation milk yield ranged from 0.41 to 0.59. Herd-year-season components of variance averaged 25% for type traits. Herd-year-season with sire interaction averaged 4%. Heritability estimates for final score from paternal half-sib analysis were from 0.11 to 0.21. Heritability estimates for linear traits ranged from 0.01 to 0.37. Genetic correlation between milk and final score was positive for Guernseys (0.25) and Jerseys (0.21). Genetic correlations between yield and most linear type traits were low to moderate except for dairy character (0.53 to 0.77).