HO, D.H.*; WANG, J.; BURGGREN, W.W.; Univ. of North Texas; Univ. of North Texas; Univ. of North Texas: Cardiac Performance and Embryo Mass in Early Avian Embryos Depends Upon Egg-Borne Maternal Cues Specific to Species and Breed

Avian species exhibit marked inter- and intra-specific differences in egg mass (EM) and yolk/albumen quality, all of which are thought to affect offspring morphology and physiology. We investigated the role of maternal factors initially present in yolk/albumen on embryonic wet and dry mass and cardiovascular performance. First, HH stage 9-14 chicken embryos were transplanted from their native eggs onto yolk from the eggs of quail (~13g), chicken (~60g), goose (~180g) and emu (~500g), where they were subsequently cultured for 48h. Heart rate (f_H) of the transplanted embryos (~HH stage 17) measured at 24h post-transplant (PT) was positively correlated with donor egg weight across species (f_H = 125 + 26 * log₁₀ EM, r² = 0.48, n = 31, p < 0.001). To look at intra-specific maternal effects involving different chicken breeds, White Leghorn layer (n = 79) and Cornish Rock broiler (n = 26) chicken embryos (HH stage 9-14) were transplanted and cultured for 48h on donor yolk/albumen medium from either layer or broiler eggs of equivalent mass (~60g). f_H of broilers cultured on layer yolk/albumen (167 beats·min^-1) was 10% lower compared to broiler controls (broiler embryos on broiler yolk/albumen) at 24h PT (p < 0.05), while f_H of layers cultured on broiler yolk/albumen were not different from layer controls (layer embryos on layer yolk/albumen) at 24h PT. At 48h PT, wet and dry mass of layer embryos cultured on broiler yolk/albumen were elevated over controls by 20% and 21%, respectively (p < 0.05). We conclude that breed-, species- and/or egg mass-dependent maternal factors, deposited in the yolk and albumen at the time of avian egg formation, influence the regulation of the developing cardiovascular system and early embryonic growth.