title: Across-country test-day model evaluations for Holstein, Nordic Red Cattle, and Jersey.
abstract: Three random regression models were developed for routine genetic evaluation of Danish, Finnish, and Swedish dairy cattle. Data included over 169 million test-day records with milk, protein, and fat yield observations from over 8.7 million dairy cows of all breeds. Variance component analyses showed significant differences in estimates between Holstein, Nordic Red Cattle, and Jersey, but only small to moderate differences within a breed across countries. The obtained variance component estimates were used to build, for each breed, their own set of covariance functions. The covariance functions describe the animal effects on milk, protein, and fat yields of the first 3 lactations as 9 different traits, assuming the same heritabilities and a genetic correlation of unity across countries. Only 15, 27, and 7 eigenfunctions with the largest eigenvalues were used to describe additive genetic animal effects and nonhereditary animal effects across lactations and within later lactations, respectively. These reduced-rank covariance functions explained 99.0 to 99.9% of the original variances but reduced the number of animal equations to be solved by 44%. Moderate rank reduction for nonhereditary animal effects and use of one-third-smaller measurement error correlations than obtained from variance component estimation made the models more robust against extreme observations. Estimation of the genetic levels of the countries' subpopulations within a breed was found sensitive to the way the breed effects were modeled, especially for the genetically heterogeneous Nordic Red Cattle. Means to ensure that only additive genetic effects entered the estimated breeding values were to describe the crossbreeding effects by fixed and random cofactors and the calving age effect by an age × breed proportion interaction, and to model phantom parent groups as random effects. To ensure that genetic variances were the same across the 3 countries in breeding value estimation, as suggested by the variance component estimates, the applied multiplicative heterogeneous variance adjustment method had to be tailored using country-specific reference measurement error variances. Results showed the feasibility of across-country genetic evaluation of cows and sires based on original test-day phenotypes. Nevertheless, applying a thorough model validation procedure is essential throughout the model building process to obtain reliable breeding values.
authors.affiliation: Natural Resources Institute Finland, Green Technology, FI-31600 Jokioinen, Finland. Electronic address: martin.lidauer@luke.fi.
authors.forename: Martin H
authors.initials: MH
authors.lastname: Lidauer
authors.affiliation: Faba, FI-15871 Hollola, Finland.
authors.forename: Jukka
authors.initials: J
authors.lastname: Pösö
authors.affiliation: Knowledge Centre of Agriculture, DK-8200 Aarhus, Denmark.
authors.forename: Jørn
authors.initials: J
authors.lastname: Pedersen
authors.affiliation: Department of Genetics and Biotechnology, Faculty of Agricultural Sciences, Aarhus University, DK-8830 Tjele, Denmark.
authors.forename: Jan
authors.initials: J
authors.lastname: Lassen
authors.affiliation: Department of Genetics and Biotechnology, Faculty of Agricultural Sciences, Aarhus University, DK-8830 Tjele, Denmark.
authors.forename: Per
authors.initials: P
authors.lastname: Madsen
authors.affiliation: Natural Resources Institute Finland, Green Technology, FI-31600 Jokioinen, Finland.
authors.forename: Esa A
authors.initials: EA
authors.lastname: Mäntysaari
authors.affiliation: Knowledge Centre of Agriculture, DK-8200 Aarhus, Denmark.
authors.forename: Ulrik S
authors.initials: US
authors.lastname: Nielsen
authors.affiliation: Växa Sverige, SE-36220 Eskilstuna, Sweden.
authors.forename: Jan-Åke
authors.initials: JÅ
authors.lastname: Eriksson
authors.affiliation: Växa Sverige, SE-36220 Eskilstuna, Sweden.
authors.forename: Kjell
authors.initials: K
authors.lastname: Johansson
authors.affiliation: Natural Resources Institute Finland, Green Technology, FI-31600 Jokioinen, Finland.
authors.forename: Timo
authors.initials: T
authors.lastname: Pitkänen
authors.affiliation: Natural Resources Institute Finland, Green Technology, FI-31600 Jokioinen, Finland.
authors.forename: Ismo
authors.initials: I
authors.lastname: Strandén
authors.affiliation: Nordic Cattle Genetic Evaluation, DK-8200 Aarhus, Denmark.
authors.forename: Gert P
authors.initials: GP
authors.lastname: Aamand
mesh_terms: D000465:Algorithms; D000704:Analysis of Variance; D000818:Animals; D001947:Breeding; D002417:Cattle / Q000235:genetics*; D005223:Fats / Q000032:analysis; D005260:Female; D018740:Genetic Heterogeneity; D014644:Genetic Variation; D006823:Hybrid Vigor; D006824:Hybridization, Genetic; D007774:Lactation / Q000235:genetics*; D008892:Milk / Q000737:chemistry*; D008894:Milk Proteins / Q000032:analysis / Q000235:genetics; D015233:Models, Statistical; D010641:Phenotype; D012044:Regression Analysis; D012106:Research; D013045:Species Specificity
chemical_list: D005223:Fats; D008894:Milk Proteins
keywords: across-country genetic evaluation; covariance function; crossbreeding effect; heterogeneous variance