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Five selection indexes for early milk-fat spring lambs were developed and compared. These were based on the weanling traits, daily gain from birth to weaning or slaughter, 120-day weight, and live market grade. Selection on daily gain alone seems most practical because it is easiest to use and should give near maximum genetic returns in economic terms. Estimates of heritabilities, genetic and phenotypic correlations, and economic values were calculated.
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Givens et al. (1960) studied this question.
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