Regulation of energy metabolism and carbohydrate utilization in developing chicken embryos

Broiler chicks hatched from small (<55 g) compared to typical size (65–70 g) eggs have greater embryonic and post‐hatch mortality, and this has been linked to low glucose status and tissue glycogen stores. We hypothesized that with even more limited resources, carbohydrate utilization and regulation of energy metabolism would differ between embryos from the two sizes of eggs. Small (53.2 ± 1.0 g, n=60) and typical size (69.0 ± 1.9 g, n=60) broiler breeder eggs from 26 wk and 42 wk‐old hens respectively, were acquired from Perdue Farms Inc., and measurements were made on embryonic (e) days 11, e14, e17, e20 and on post‐hatch day 1. The initial dry yolk:albumen ratio was higher (2.6 vs 1.6) in typical vs small size eggs. At set, glucose and mannose contents in albumen were 500‐fold higher than fucose, but by e11 glucose content decreased to negligible levels whereas mannose and fucose remained constant. 5′‐AMP‐activated protein kinase (AMPK) activity, determined by enzyme linked‐immuno‐sorbent assay, was higher in livers of embryos from typical vs small size eggs at each sampling time. In conclusion, preformed glucose is used preferentially by embryos until e11 whereas mannose use predominates after e11. Liver AMPK activity is higher in embryos from typical size eggs, and this may reflect increased metabolism of the larger lipid stores (yolk) available to these embryos to support their faster growth rate in ovo . Grant Funding Source : University of Maryland Agricultural Experiment Station