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Effects of Some Environmental Factors on Traits of Yearling and Mature Rambouillet Rams

United States Department of Agriculture

Abstract

The effects of age of dam, type of birth, year of birth, age at shearing and percent inbreeding on grease fleece weight, clean fleece weight, staple length, body weight, type, condition, face covering and neck folds were studied on 499 yearling Rambouillet rams born from 1941 to 1945. Differences between yearling rams and ewes were determined by comparing part of the ram data with data studied previously on comparable yearling ewes. The effect of years and inbreeding on grease fleece weight, clean fleece weight, body weight, type and condition were studied on 165 a-year-old rams and 69 3-year-old rams.

Differences between years had the most important environmental effect upon yearling Rambouillet ram traits of any factor studied followed by inbreeding. Type of birth, age of dam and age at shearing did not have important effects on yearling Rambouillet ram traits with the possible exception of age at shearing on grease and clean fleece weights and type of birth on clean fleece weights.

Differences among years were greatest for neck folds, body weight and grease fleece weight. Inbreeding had important effects on body weight, grease fleece weight, clean fleece weight, type score and-condition score. Each of these traits became poorer with inbreeding. Staple length and face covering were least effected by environmental factors of the traits studied.

Yearling rams excelled ewes for every trait studied except type and neck folds, and in these traits the differences were slight. The greatest differences were found for body weight and grease fleece weight.

Yearly differences continued to be important for traits studied on 2- and 3-year old rams. The effect of inbreeding on these groups was similar to its effect on yearling rams. The accuracy of selecting rams can be increased by adjusting their records for differences in years and inbreeding.

¹ Western Sheep Breeding Laboratory, Dubois, Idaho.

² Present address, Southwestern Range & Sheep Breeding Laboratory, Ft. Wingate, New Mexico.

³ Present address, Animal Husbandry Department, Iowa State College, Ames, Iowa.