Comparison of Five Methods of Adjusting for Environmental Differences in Evaluation of Dairy Sires

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Abstract
Five methods of adjusting the sire''s daughter average, namely: (I) the actual herd average and herd-mate averages for (II) annual lactation, (III) 6-mo. season, (IV) 7-mo. rolling season, and (V) annual actual age group, were compared with the simple daughter average (VI). Measures II, III, and IV were the ME averages of all non-paternal herd-mates freshening in the designated periods. The highest 6 mo. period based on month of freshening was November through April. Intrasire regressions of the daughter record for milk and fat on the contemporary averages were computed and the daughter records adjusted by these regressions. A variance component analysis of the adjusted records showed that Measure IV was most effective in removing the herd variance, with Measures III and II next. Eleven sets of correlation comparisons of sire progeny adjusted averages for the various measures with later daughters of the same sires showed Measure IV ranked 1st the most times, with Measure III a very close 2nd. Measures V and VI gave very low correlation estimates from 0.00 to 0.24. From this study, Measures IV and III are the preferred ones. In view of the slightly higher rating of Measure IV and season differences around the country, Measure IV would have the most merit of those tested for countrywide usage.