Hornedness and polledness in sheep. I. The inheritance of polledness in the Merino

Abstract

Twenty-five polled Merino rams were mated singly to either polled or horned Merino ewes, the horned ewes having either bone knobs or short scum on their horn sites. All parents and offspring were horn-scored with the aid of a detailed classification system suitable for defining all types of horn sites encountered in the Merino. Polledness is dominant to hornedness and results from the action of an autosomal dominant gene, P. The recessive allele, p, in homozygous form results in true horns in the male and bone knobs or short sours in the female. The inheritance of horns in the female is discussed in a later paper. Details are given of the phenotypic differences between PP and Pp rams, which are important in the selection of poll Merino rams. There is some overlap between the phenotypic ranges of these two genotypes.