Establishing Age-Correction Factors Related to the Level of Herd Production

Abstract

Age-correction factors have been developed based on the level of herd production. They are additive factors, expressed as regressions on the age-corrected herd average and, as such, might be termed within-herd additive gross comparison factors. They indicate that age corrections should be larger in herds of high production than in herds of low production, independent of the actual production of the young cow. One comparison with the multiplicative factors indicates that the latter do take account of between-herd differences in age effects. Work is in progress on comparing different sets of age-correction factors.