Open Collections

Abstract

A comparison was made of rates of growth and body weights between pre- and post-hatching stages of development of the chicken as affected by strains or strain crosses, egg storage, egg weights, time of hatch, sex and post-hatching nutritional environment. The interrelationships of these factors were also investigated. The results of the investigation indicate that practically all of the variation of six-week body weight in this data was successfully accounted for by the combined effects of six-week growth rate, hatching weight and embryonic growth rate between eight and twelve days. The data also indicate that gains in six-week body weight may be made by selecting for early growth rate without concomitant change in other traits. Hatching time, hatching weight and post-hatching growth appear to be affected by egg storage only if some form of stress is present during incubation. In the absence of stress it appears that a compensatory increase in rate of embryonic growth overcomes the effect of a delayed initiation of growth caused by egg storage. A significant influence of sex on embryo weight in favour of the male embryos was observed.