Effects of Some Environmental Factors on Yearling Traits of Columbia and Targhee Rams

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 359 Columbia and 213 Targhee yearling rams. These rams were born during the years 1941 through 1945. The effect of environmental factors was greatest on grease fleece weight, body weight and clean fleece weight and least on face covering and staple length. Year of birth was the most important environmental source of variation and age of dam was least important. Age of dam was more important in Columbias while age at shearing was more important in Targhees. Single rams had heavier bodies and fleeces than twins. Fleece and body weights, staple length, type and condition improved with increasing age at shearing and became poorer with inbreeding. Inbreeding had a greater detrimental effect on body weight, type and condition than on other traits. Inbreeding had a noticeably greater effect on Targhees than on Columbias. Greater effectiveness of selection is the practical result of adjusting for environmental effects. Accuracy of selection of Columbia and Targhee rams may be increased by adjusting grease fleece weights, clean fleece weights body weight, type and condition for differences between years; grease fleece weight, clean fleece weight and body weight for age at shearing; body weight for type of birth; grease fleece weight and body weight for age of dam in Columbias; and body weight, type and condition for inbreeding in Targhees.