Hornedness and polledness in sheep. 5. Some effects of the horn alleles on characters in the Merino

Abstract

The influence on certain characters of the three alleles which affect horn growth has been investigated in three flocks of medium Peppin Merinos. These alleles have been named P, P', and p. The characters investigated were: greasy and clean wool weight per head, body weight, wrinkle score, fibre number per sq. millimetre of' skin, fibre diameter, staple length, clean scoured yield, crimps per inch, face cover, and, on some sheep, spinning count, character, colour, and handle. Comparisons between Pp and pp rams and ewes revealed that Pp rams had a significantly lower fibre number and a higher fibre diameter than their pp halfb-rothers, but there was no other evidence of any relationship between horn genotype and the phenotype of the above characters in either sex. In comparisons between Pp and P'p sheep, rams showed no significant differences, although they had the same hornedness phenotypes as Pp and pp rams. Pp ewes cut more clean wool and greasy wool than P'p ewes at 12 months of age, but not at 22 or 30 months. Pp ewes also had a higher fibre number at 12 months and a lower fibre diameter at 22 months than P'p ewes. In the third flock, comparison \\-as made between P'P' plus P'p ewes, which have female horns, and pp ewes, which have either scurs or knobs. In none of the above characters was there any significant difference between ewes with and without, horns. The presence of P had no demonstrable effect on spinning count, character, colonr, or handle in either the Pp v. pp or the Pp v. P'p comparison. Sire x hornedness genotype interactions were found in the Pp v. P'p comparisons of body weight at 22 months for rams and spinning count for ewes.