DNA and Weight Determinations on 12 to 14 Day Embryonic Muscle Tissue of Fast and Slow Growing Crossbreds

Abstract

SELECTION for rapid growth rate or large size could be made more efficient by the use of supplemental measurements to predict growth of individuals. Larger body size has been found to be positively correlated with increased numbers of muscle cells (Smith, 1962; Lepore et al., 1965) and higher levels of glutathione (Charkey et al., 1965).A critical age for obtaining efficient indicators of potential growth may be embryos that are about two-thirds developed. At this stage, the numbers of muscle fibers are established during a gradual cessation of proliferation of the embryonic myoblast cells in mammalian (Bardeen, 1900; Joubert, 1956) and in chick embryos (Kitiyakara, 1959). The growth curve of chick embryos described by Lerner (1939) from 7 to 20 days showed a “sharp acceleration” in growth at 13 days, reaching a maximum rate at 14 days. Genetic effects for rate of embryonic growth have been reported as maximal at …