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Some Genetic and Phenotypic Parameters in Navajo and Navajo Crossbred Yearling Ewes

Agricultural Research Service, U. S. Department of Agriculture and New Mexico Agricultural Experiment Station, University Park

Abstract

Data on 1075 yearling ewes at the Southwestern Range and Sheep Breeding Laboratory, Fort Wingate, New Mexico, were analyzed to obtain heritability estimates, genetic and phenotypic correlations among the following seven traits: body weight, body type, body condition, staple length, fiber diameter, grease fleece weight, and clean fleece weight. The ewes were from three separate breeding groups and were born over the 14-year period 1947 through 1960.

The three body traits (body weight, body type, and body condition) were found to have moderate to high genetic and phenotypic relationships. Highly significant positive phenotypic correlations were obtained among the fleece traits (staple length, fiber diameter, grease fleece weight, and clean fleece weight). The most important genetic correlations among the fleece traits were 0.93 between grease fleece weight and clean fleece weight and 0.44 between staple length and clean fleece weight. The genetic correlation of –.24 between staple length and body weight appeared to be the only one which would handicap selection. The genetic relationship between clean fleece weight and fiber diameter was found to be negligible. Heritability estimates fell in the moderate range (0.20 to 0.40) for all traits except body type (0.17) and clean fleece weight (0.19).

¹ Sheep and Fur Animal Research Branch, Animal Husbandry Research Division, Agricultural Research Service, Southwestern Range and Sheep Breeding Laboratory, Fort Wingate, New Mexico, in cooperation with the New Mexico Agricultural Experiment Station, University Park, New Mexico.

² Present address: New Mexico State University, University Park, New Mexico.

³ Sheep and Fur Animal Research Branch, Animal Husbandry Research Division, Agricultural Research Service, Beltsville, Maryland.

⁴ The authors wish to acknowledge the assistance of W. R. Harvey in analyzing the data. All computations for this study were made by the Biometrical Services, A. R. S.