VARIANCE OF INTERACTION EFFECTS OF SIRE AND HERD FOR YIELD TRAITS OF HOLSTEINS IN CALIFORNIA, NEW-YORK, AND PENNSYLVANIA WITH AN ANIMAL-MODEL

An animal model with a REML algorithm was used to estimate variances o f additive genetic effects and interaction effects of sire and herd. M ilk and fat yields were analyzed for first, second, and third lactatio ns of Holsteins from California, New York, and Pennsylvania. Twenty sa mples of data were used in the study: 10 from California, 4 from New Y ork, and 6 from Pennsylvania. Mean number of lactations per sample was 36,820 from 18,189 cows in 156 herds. Mean fractions of phenotypic va riance of interaction effects of sire and herd for milk and fat yields were .015 and .019 for first lactation and .019 and .021 for all (up to three) lactations rather than the .14 used for national genetic eva luations in the US. Mean heritability estimates for milk and far yield s were .26 and .24 for first lactation and .21 and .21 for all lactati ons in California and .34 and .35 for first lactations and .28 and .29 for all lactations in New York. Sums of variances of permanent enviro nmental and interaction effects of sire and herd were similar to those used for national genetic evaluations in the US. Analysis of another 10 samples from California and 10 samples from New York showed only sl ightly different fractions of phenotypic variance for milk yield for i nteraction effects of sire by herd, sire by herd by year, and sire by herd by year by season: .O23, .027, and .037 for California and .023, .017, and .023 for New York, respectively.