Studies of the effects of the gene N on body growth and fleece development of the New Zealand Romney. I. The body growth of the N type lamb

Abstract

A study has been made of the pleiotropic effects of the gene N on the body growth and the carcass of the Sew Zealand Romney lamb. Measurements of body weight and height at withers were taken from birth to about 5 months of age for lambs born in 1952 and 1953 from matings of N/+ x +/+, N/N x N/N, N/N x N/+, and N/+ x N/+ parents. In 1952, +/+ lambs grew faster than N/+ or N/N lambs and this was shown in the greater body weight of the +/+ lambs at 30 days of age. The differences in weight gains corrected for initial weight were greater for single lambs than for twin lambs. The differences in the height at withers were proportional to those in body weight except for the N/N lambs. The N/N lambs had a greater height at withers for their body weight but this could have been the result of factors other than the gene N which were associated with the N–type flock. N–type ewe lambs kept up to 18 months of age maintained lower body weights than +/+ lambs. In 1953 no differences between N/+ and +/+ lambs were found in body growth. It is suggested that a genetic-environment interaction exists for body growth and that the environmental factor is possibly one of climate. No differences were found between the carcass measurements of N/+ and +/+ ram lambs which could not be attributed to the previous differences in body growth.