Relationship of the Eggshell Conductance Constant to Neonatal Cardiac Physiology

Abstract

The hypothesis was proposed that changes in functional qualities of eggs, or the eggshell conductance constant (k), may affect cardiac weight and physiology and predispose poults to a weakened condition. Improved knowledge of this relationship may allow selection of k to optimize hatchling cardiac health. Egg weights (EW), eggshell conductance (G) and lengths of the incubation period (IP) (the three components of k) were manipulated to determine their effect on the heart. Eggs were selected based on EW and G in Experiment 1. In Experiment 2, eggs from the same strain were obtained from flocks of different ages so they differed in EW. Half of the eggs were exposed to increased temperature treatments resulting in shorter incubation periods (IP). Interactions of EW and G affected heart weight and metabolism in Experiment 1. In Experiment 2, imposing short IP on different EW reduced cardiac weights as well as elevated glycogen to lactate ratios in the heart. Post-hatching growth was also depressed by k due to interactions of EW and IP. Thus, k affects cardiac weight and function and may contribute to weak poults.