Abstract
Results obtained from 10 generations of simultaneous selection for gain from 12 to 21 days and 51-day weight in mice have been described. A technique for estimating realized genetic parameters from simultaneous selection for two traits is presented and used to compare such estimates when selection is for high or for low performance in each of the traits. Realized estimates of the genetic parameters were compared with estimates from offspring-sire regressions by lines and periods of selection. Combined estimates of the realized genetic parameters from all lines were consistent with offspring-sire regression estimates in the control. Changes which may have occurred in the genetic parameters from generation to generation could not be detected from the regressions of offspring on sire. There were essentially no differences between realized estimates of the genetic parameters for high or low selection through the first seven generations. In generations eight through 10, the realized response in 51-day weight to selection for high gain and high weight decreased appreciably. Copyright © 1975. American Society of Animal Science. Copyright 1975 by American Society of Animal Science.