Correlation of body weight with hatchling blood glucose concentration and its relationship to embryonic survival.

The negative correlation between selection for rapid growth and embryonic survival was investigated. Embryonic growth was assessed with hatchling weights of a closed population of commercial turkey breeders. Hatchling weights were highly significantly (P < 0.0001) and positively correlated with blood glucose concentrations at hatching. This relationship existed for both tom and hen poults. Significant differences among dams for hatchling blood glucose were observed. Further experiments examined dams selected for producing poults hatching with high (High) or low (Low) blood glucose concentrations. The High embryos were in larger-sized eggs with the same eggshell conductance but with significantly lower conductance constants than the Low embryos, suggesting that Low had longer incubation periods. High embryos grew faster than Low embryos with elevated organ glycogen concentrations. Organic acid analysis indicated elevated plasma alpha-ketoglutarate, urate, and beta-hydroxy butyrate concentrations, suggesting a greater reliance on gluconeogenesis for the High group. Posthatch growth was significantly positively correlated with hatchling blood glucose concentrations in toms but not in hens. Tom poults hatching with elevated glucose were heavier than low glucose hatch mates until 22 wk of age, but hen poults displayed no differences until 16 wk when High hens weighed less than Low hens. These data suggest that the negative correlation between rapid growth and embryonic survival is related to egg-shell conductance constants and embryonic energy metabolism.