Submitted to: Journal of Dairy Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/29/2004
Publication Date: 2/1/2005
Citation: Norman, H.D., Van Raden, P.M., Powell, R.L., Wright, J.R., Verboort, W.R. 2005. Effectiveness of national and regional sire evaluations in predicting future daughter milk yield. Journal of Dairy Science. 88(2):812-826. Interpretive Summary: Computation of regional evaluations of dairy bulls is based on the premise that such evaluations would rank bulls for dairy producers in that region more accurately than would national evaluations because of the advanced methodology possible with smaller data sets and the existence of an interaction between genotype and region. Regional evaluations for the Northeast United States were compared with USDA national evaluations to determine evaluation accuracy in predicting future yield of bull daughters. National evaluations were found to predict first-, second-, and third-lactation milk yields better than did Northeast regional evaluations; no evidence was found of any interaction between genotype and environment. When other regions (California and North Central and Southeast United States) were examined in addition to the Northeast, the results were the same: national evaluations were better predictors of future daughter yield than were regional evaluations, especially for California and the Southeast. Because regional evaluations included fewer bulls, the top 100 bulls for milk yield regionally were inferior to the top 100 bulls nationally by 55 to 380 pounds of genetic merit. Therefore, increased reliance on regional evaluations likely would reduce genetic improvement from that currently being achieved in the United States.
Technical Abstract: Bull evaluations published from national and regional sire reports over a 15 year period were compared with standardized milk yield of daughters born at a later date. Correlations between evaluations and first, second, and third lactation yields of daughters added were calculated within herd-year-season. Mean correlations (across years) with first lactation yield were higher for national evaluations (0.11) than for Northeast evaluations (0.10) for Holsteins. Mean correlations with second and third lactation yields were higher also for national evaluations (0.09 to 0.11) than for Northeast evaluations (0.06 to 0.08). Correlations with yield of daughters added in the Northeast were similar to those with yield of all US daughters, which indicated no genotype by environment interaction between national and Northeast data. In a second study, bull evaluations derived separately using lactations from daughters first calving through 1991 from California, the North central, Northeastern, Southeastern United States, and from all 50 states were compared with standardized milk, fat, and protein yield of daughters arriving later. Again, correlations between first, second, and third lactation yield were higher for national evaluations than for regional evaluations (usually by 0.01). ADD GXE DISCUSSION National evaluations consistently were better predictors than were regional evaluations of lactation milk yield of future daughters, regardless of where the daughters were located. Regional evaluation reports have fewer bulls due to limited numbers of daughters in each region so the top bulls on the regional lists are usually not the highest on the national report. For this reason, it is likely that increased reliance on regional lists would reduce genetic improvement from the current rate achieved in the United States.