Question

4. A rancher runs a closed herd of breeding cattle. He normally keeps and breeds the top 2% of his bull calves based on individual performance for yearling weight (YW). His sires average three years of age when their offspring are born. He is trying to decide between two female replacement strategies:

 Saving the top 20% of his heifers based on YW (L_f = 6 years)

 Saving the top 50% of his heifers based on YW (L_f = 3 years)

a. If h² = 0.4 and σP_(yw) = 50 lb, calculate the expected rate of genetic change in YW for each strategy. (Assume infinite population size.)

b. What are two trade-offs between the factors that affect rates of genetic change?

Answer 1

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