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Additive Versus Multiplicative Precorrections of Dairy Records for Some Environmental Effects in Sire Evaluation

Institute of Animal Sciences, Swiss Federal Institute of Technology, CH-8092 Zurich, Switzerland

ABSTRACT

Additive and multiplicative correction factors were compared for precorrection of milk production records for effects of age at calving, month of calving, and pasture, using the data on 168,480 progeny of 70 proven sires of the Simmental breed. Criteria used for the comparison were unremoved variation, interactions of the mentioned effects with herd-year, residual variance ignoring interactions, and the bias in sire predictions. For age at calving and month of calving both types of correction factors were equally efficient in removing the variation in yields of milk and fat. Pasture effects were removed more effectively with additive than with multiplicative factors. The variances due to herd-year x month of calving and herd-year x pasture interactions were larger with multiplicative factors. The herd-year x age at calving interaction variances were similar with both types of corrections. Different criteria of the comparison showed that the differences in the efficiency of both types of correction factors were unimportant. A model of sire evaluation was found equally accurate with additive or multiplicative factors.

¹ Present address: Animal Genetics Division, Indian Veterinary Research Institute, Izatnagar, UP 243122, India.