Selection for Body Weight at Eight Weeks of Age

HAYS AND NICOLAIDES (1934) observed variation in stages of embryonic development at oviposition. Kosin (1956) and Becker and Bearse (1958) found that certain preincubation warming treatments had a beneficial effect on the hatchability of avian eggs. This provided evidence that eggs are not necessarily laid in a stage optimum for preincubation storage. Siegel (1962) reported a two-way selection experiment in chickens for body weight at eight weeks of age. A correlated response in embryonic development was observed in these lines by Coleman et al. (1963). They found that embryos from the low weight line had approximately four more somites at 42 hours of incubation than embryos from the high line. Arora and Kosin (1964) observed that 43.6 percent of the embryos in a line of turkeys selected for large mature body size were early gastrula at oviposition. In a line selected for small mature body size the percentage of early …