Body trait profiles in Holstein-Friesians modeled using random regression.
Legendre polynomial and cubic spline functions were used in random regression models to model the change in body traits over the course of the first lactation for daughters of 954 sires. Both functions estimated similar genetic variances for d 50 to 250 across lactation for the majority of traits. The heritability of the traits was similar to other studies using univariate models as well as random regression models. There was little difference between the 2 functions in their predictive power for each of the body type traits, as measured by the absolute difference between the predicted and actual type traits and the proportion of the total phenotypic variance explained by the model. Overall, the Legendre polynomial appeared to model these traits slightly better. Plots of the fixed curves and daily sire solutions obtained from the random regression models showed that there were differences in how the traits and sires changed across lactation. The daily sire solutions were then used to predict differences in liveweight of sires' daughters across first lactation and showed that the daughters of some sires grew faster during first lactation than others. The spatial differences in the body traits that are displayed by this study could be an important indicator of the physical and biological changes that cows are undergoing in their first lactation. Information from these sire profiles could be harnessed to indicate production and functional traits later in life.
Wall
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Sustainable Livestock Systems Group, Scottish Agricultural College, Bush Estate, Penicuik, Midlothian, EH26 0PH, UK. Eileen.Wall@sac.ac.uk .
Coffey
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Brotherstone
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D000704:Analysis of Variance; D000818:Animals; D001823:Body Composition; D001824:Body Constitution; D001835:Body Weight / Q000235:genetics; D001837:Body Weights and Measures / Q000662:veterinary; D001947:Breeding; D002417:Cattle / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D005260:Female; D007774:Lactation / Q000235:genetics; D008297:Male; D010641:Phenotype; D019655:Quantitative Trait, Heritable; D012044:Regression Analysis