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Selection for weaning weight in Targhee sheep in two environments. I. Direct response
Journal of Animal Science
|August 1, 1985
Summary
Selection for sheep weight showed greater gains in well-fed conditions than on rangelands. Genetic improvement in growth rate under better nutrition translated effectively to range environments.
Area of Science:
- Animal Science
- Genetics
- Animal Breeding
Background:
- Selection for 120-day weight in Targhee sheep initiated in 1961.
- Two distinct nutritional environments: high plane at Davis and range conditions at Hopland.
Purpose of the Study:
- To compare the effectiveness of selection for 120-day weight under different nutritional planes.
- To assess the expression of genetic gains in growth rate across varying environments.
Main Methods:
- Established selected (DW, HW, DH) and control (DC, HC) lines.
- Adjusted 120-day weights for age of dam, sex, and birth/rearing type.
- Estimated response to selection using linear regression of adjusted means on year.
Main Results:
- Greater direct response to selection for 120-day weight at Davis (.524 kg/yr) compared to Hopland (.151 kg/yr).
- Realized heritabilities were .17 (Davis) and .06 (Hopland).
- The DH line (selected at Davis, tested at Hopland) showed greater response (.226 kg/yr) than the Hopland selected line (HW).
Conclusions:
- Genetic improvement for growth rate under high nutrition is expressed, albeit to a lesser degree, in range conditions.
- Selection under better feed conditions achieved comparable or greater growth rate improvement in a range environment than selection solely under range conditions.