|Dimov G, - UNIV OF NEBRASKA|
|Keown Jeff F, - UNIV OF NEBRASKA|
|Van Vleck L Dale,|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 14, 1994
Publication Date: N/A
Interpretive Summary: At a symposium in 1976, USDA reported that sire by herd interaction accounted for 14% of variation in milk yield based on unpublished ARS research. That research was never published but the 14% value has been incorporated into national genetic evaluations for dairy cattle since 1968, including the most recently introduced method based on an animal model. The effect of such a large interaction component is to penalize severely bulls that have daughters in only one herd. The current research shows that the interaction is only 1 to 2% of variation based on records of Holsteins from California, New York and Pennsylvania. Research on effects of ranking both bulls and cows caused by using a value of 14% rather than 1 to 2% seems necessary.
Technical Abstract: An animal model with a derivative free REML algorithm was used to estimate variances due to additive genetic and sire by herd interaction effects. Milk and fat 305-d ME yields for first and all up to third lactation of Holsteins from California (CA), and New York and Pennsylvania (NY) were used. For twenty samples the average number of lactations was 36,820 from 18,189 cows in 156 herds. The milk and fat means in CA were 9,225 kg and 332 kg for first and 9,478 kg and 339 kg for all lactations and corresponding means for NY were 7,936 kg, 289 kg, 8,060 kg and 294 kg. The models contained fixed effects of herd-year. Average number of sire by herd classes was 6,499 and number of mixed model equations varied from 19,248 to 46,988 for first and from 32,212 to 74,919 for all lactations. The average fractions of sire by herd variance for milk and fat were .015 and .019 for first and .019 and .021 for all lactations. Average heritability estimates for milk and fat yields were .26 and .24 for first and .21 and .21 for all lactations in CA and .34, .35, .28 and .29 for NY.