A rancher runs a closed herd of breedin cattle.He keeps and breeds the top 3%of bull calves based on individual performance for yearling weight. His sires avg 3 years of age when their offspring are born. He is studying two female replacement strategies:
1. Saving the top 20% of heifers based on YW (Lf=6.2 years)
2. Saving the top 60% based on YW (Lf=3.2years)
If h sq YW=.05, and variability pyw=60 lb, calculate the expected rate of genetic change in yearling weight for each strategy. What elements of the key equation is the rancher experimenting with? What element appears to be more important?