Genetic parameters for type and functional traits in the French Holstein breed

In France, EBVs are routinely estimated for lactation somatic cell counts, female fertility, and functional longevity. These functional traits have rather low heritabilities, leading to limited reliabilities for young sires. To include these traits in a total merit index, it is desirable to improve their genetic evaluations taking advantage of indirect information. Type traits are potential early predictors of functional traits, because they are early scored and because their heritability is moderate to high. To combine the direct information on functional traits with the indirect information on type traits, it is necessary to know the genetic correlations between all traits. But it is difficult to estimate the genetic relationship between all these traits directly from the data. This is especially true when one of the traits is functional longevity evaluated by survival analysis. Here we present an approximate estimation of these genetic correlations in the French Holstein breed based on MACE methodology applied to A.I. bulls evaluations. These estimates are compared to correlations between proofs and, for some traits, to REML estimates obtained from smaller data samples. According to these estimates, prediction of functional longevity could be improved by udder depth and temperament, somatic cell counts by milking speed and udder depth, and (to a smaller extend) female fertility by temperament and rump angle.

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