[Amino acid and lipid metabolism in embryos of flesh fowl with different yolk mass].

ABSTRACT

It has been proposed that variations in relative yolk mass in a population of flesh fowl be used as a model of development of nidicolous and nidifugous birds. During development of the eggs with a high proportion of yolk, an excess of lipids is cleaved at a higher rate and oxidized until day 17 of incubation, while in the embryos developing from the eggs with a low relative yolk mass, amino acids are intensely cleaved during the period preceding the hatching. Significant differences in the body content of cystine were found in 17-day embryos and upon hatching, thus suggesting a delayed activity of the genes encoding keratins in the group corresponding to the seminidicolous type according to the egg content of lipids. These biochemical differences question the widespread concept on the occurrence of dichotomy by the end of embryogenesis and beginning of neonatal growth of nidifugous and nidicolous birds.