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United States Department of Agriculture
Abstract
Selection of breeding ewes involves the culling of the least desirable ewes up to the point where a more or less constant number is retained in the breeding flock. To be most effective, culling should be done at an age when reliable measures of merit are available, but before many offspring are produced. The proportion of ewes which may be culled depends not only upon age and death losses but also upon the ages and reproductive rates of the ewes retained in the flock. A knowledge of the interrelationships among selection, age and reproduction is essential to the effective planning of a breeding program.
The purpose of this study is to present information on the Selection actually practiced, in order to maintain a constant number, in a range flock of Rambouillet ewes over a period of 15 years at the U. S. Sheep Experiment Station, Dubois, Idaho. Data are also presented on the value of some early measures of mutton and wool characters for predicting lifetime merit and how such factors as age and reproduction have influenced the selection of ewes.
* Acknowledgement is made to D. A. Spencer, W. A. Denecke, John M. Cooper, John A. Stoehr and Stanley L. Smith for assistance in collection of the data used.
Spencer, D .A., J. I. Hardy and Mary J. Brandon, 1928. Factors that influence wool production with range Rambouillet Sheep. U. S. D. A. Technical Bulletin No. 85.
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