Estimation of genetic parameters for daily milk yield of primiparous Ayrshire cows by random regression test-day models

摘要: Abstract Test-day data comprising of 63,331 test-day milk records 6310 primiparous Finnish Ayrshire cows were used to estimate genetic parameters for daily production. Two alternative random regression (RR) sub-models describe breeding values the shape lactation curves individual cows: a five parameter logarithmic polynomial (ASM) or normalised third order orthogonal polynomial. Permanent environment (PE) cow was described by either common PE effect (ASM and OPMPE1) (OPMPE4). Variance components estimated with an animal model using EM-REML. A multitrait (MT) approach together continuous covariance function (CF) derive reference RR estimates. Heritability estimates obtained ASM (0.41–0.60) OPMPE1 (0.28–0.53) higher than those derived from CF analysis (0.20–0.28). Fitting sub-model effects strongly influenced magnitude heritability (0.23–0.36). Estimates found be highest during early late when models, while converse true CF. OPMPE4 at beginning between 183 256 days in milk. Genetic correlations high consecutive test days, but decreased intervals increased. Where models indicated negative correlation distant consistent Due statistical complexity use MT is more feasible estimation (co)variance coefficients.