Using weaning weight to improve fleece weight evaluation in young Merino sheep

Adjusting fleece weights for environmental effects such as birth date, dam age and birth/rearing status had only a marginal influence on the accuracy of genetic evaluation given the cost of collecting this information. Using weaning weight as a covariate accounted for most of these environmental eff ects and also reduced direct and maternal environmental variances on yearli ng and hogget fleece weights, resulting in a higher heritability for the tr aits. The implications of using weaning weight as a covariate are discussed for Merino genetic evaluation.