Energy sensing in developing chicken embryos and posthatch chicks from different size eggs

We hypothesized that 5'-adenosine monophosphate-activated protein kinase (AMPK), a ubiquitous energy sensor, plays a key role in coordinating nutrient use in developing broiler breeder embryos. To test this hypothesis, we measured AMPK activity in the liver of embryos developing in small versus large (typical) eggs. Small (53.2 ± 1.0 g) eggs from 26-wk-old and large (69.0 ± 1.9 g) eggs from 42-wk-old broiler breeder hens were acquired and measurements were made on embryonic day (e) 11, 14, 17, and 20, and on posthatch d 1. The initial weight of dry yolk to albumen was higher (2.3 vs. 1.7) in large versus small eggs, and embryo weight differed from e17 onward. The AMPK activity was higher in livers of embryos from large versus small eggs across all sampling days, and activity was highest on e14 for both sizes of eggs. We speculate that higher AMPK activity in livers of embryos from large eggs may facilitate increased metabolism of their larger nutrient supplies to support faster growth rate in ovo. Taken together, our results are the first to investigate the relationship between liver AMPK activity and egg size and nutrient composition in developing chicken embryos.