Genetic and environmental factors affecting staple length in Navajo and Navajo crossbred weanling lambs.

Abstract

The effects of breeding groups, sex, age of dam, year of birth, and type of birth and rearing on staple length were studied on 1618 lambs, representing all lambs weaned in 1947 and 1948 at the Southwestern Range and Sheep Breeding Laboratory, Fort Wingate, New Mexico. The effect of age at weaning on staple length was held constant by clipping an area close to the skin when the average age of the lambs was one month. In 1947 this growth period represented 111 days on all lambs, and in 1948 a period of 84 days' growth on all lambs. Variations in staple length due to age of dam and type of birth and rearing were not significantly different, indicating adjustment need not be made for these factors. Ewe lambs averaged 0.59 centimeter longer staple than did the ram lambs. Breeding groups varied from an average of 7.77 centimeters in Cotswold sired crossbred lambs to 4.11 centimeters in the Navajo lambs. The factors studied accounted for approximately 36 percent of the total variation in staple length. If the more important differences due to environmental factors are considered in culling lambs, more, improvement from selection can be expected.