Fact Sheet Written by:
Robert L. (Bob) Weaber, Ph.D. University of Missouri
And Provided by
University of Missouri
Why do we need indexes?
The complications of multiple-trait selection and animal breeding decisions may be best summarized by Dr. Lanoy N. Hazel in the opening paragraph of his landmark paper on the topic of selection indexes published in the journal Genetics in 1943:
The idea of a yardstick or selection index for measuring the net merit of breeding animals is probably almost as old as the art of animal breeding itself. In practice several or many traits influence an animal‟s practical value, although they do so in varying degrees. The information regarding different traits may vary widely, some coming from an animal‟s relatives and some from the animal‟s own performance for traits which are expressed once or repeatedly during its lifetime....These factors make wise selection a complicated and uncertain procedure; in addition fluctuating, vague, and sometimes erroneous ideals often cause the improvement resulting from selection to be much less than could be achieved if these obstacles were overcome.
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