Selection for economic characters in Austrialian Merino sheep. VII. Interactions between genotype and plane of nutrition

A number of groups of half-sibs were divided into two lots, one being exposed to a high plane of nutrition, the other to a low plane, from 3 to 17 months of age. Heritability, as indicated by the within sire correlation, did not vary with plane of nutrition. Genotype-treatment interactions were not present for any fleece characters or for 6-month body weight. Such interactions were large and highly significant for weight at 12 or 17 months. These findings indicate that the opinions of Hammond (1947) are not generally valid.