Further observations on the association between lipid metabolism and low embryo hatchability in eggs from young broiler birds

Comparisons have been made of the lipid compositions of the yolk contents, yolk sac membrane, plasma, and liver of chick embryos at days 14 and 19 of incubation from young (23 week) and mature (35 week) hens. A reduced yolk lipid absorption displayed by embryos from the young parents at day 19 of incubation was accompanied by lower plasma and liver lipid concentrations. As shown by electron microscopy, there was an obvious reduction in cystolic accumulation of lipid within the liver. The reduced yolk lipid concentration in embryos from the young hens was associated with lower levels of plasma low‐density lipoproteins and an alteration in the relative proportions of the major plasma lipid fractions. The altered yolk, plasma, and liver lipid concentrations are discussed with respect to values for embryos from mature hens.