The aim of this study was to compare alternative measures of genetic persistency of lactation based on random regression models with Legendre polynomials. Three measures of persistency were analysed the difference between breeding values at days 280 and 60 of lactation, linear regression coefficient for animal genetic effects, and the second principal component of the additive genetic covariance matrix. Moderate heritabilities (0.07-0.18) of all three persistency measures were estimated for the first three lactations of Polish Holstein cows. The lowest correlation between persistency and the total yield in lactation was provided by the definition of lactation persistency based on the second principal component.

T. Strabel, J. Jamrozik

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume , , 01.33, 2006
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