The temperature and relative humidity of storage, as well as the gaseous environment, interact with the fertile egg over time during storage in such a way as to affect the success of incubation either negatively or positively. This interaction occurs both above and below the "physiological zero", at which embryonic metabolism is minimal. This interaction below physiological zero implies that certain physical aspects of the egg must be affected by the environmental conditions. As the eggshell is a relatively fixed component, changes in albumen, shell membranes, cuticle, yolk, or embryo proper must account for these time- and environment-related effects. It is concluded that the major contributor is the albumen, as it is obviously the most dynamic component below physiological zero and is strategically positioned.

The objective of these two experiments was to determine the temporal changes in albumen during storage and early incubation as a means of understanding some of the effects of egg storage on early embryonic development. Eggs from 30- or 50-wk-old broiler breeder hens were incubated (37.5 C dry bulb, 30 C wet bulb) after storage for 0 (fresh) or 5 d (18 C, 75% RH) in Experiment 1. Albumen height, albumen pH, and egg weight loss were recorded at 2, 24, 48, and 66 h of incubation. The same measurements were taken on another group of eggs from 43-wk-old hens stored for 0 (fresh), 4, 8, or 12 d in Experiment 2. All hens were of the same strain. Egg weight loss during incubation was significantly greater in fresh eggs than in stored eggs in Experiment 1. Fresh eggs had significantly greater albumen height and significantly lower albumen pH than stored eggs in both experiments. These differences diminished with length of incubation. Because the blastoderm is located adjacent to the albumen, changes in the viscosity or pH of the albumen may play an integral role in determining the viability of the embryo during the very early stages of development. Incubation of fresh eggs without storage appears to expose the developing embryo to an inappropriate trans-vitelline membrane pH gradient and a thick albumen that may slow vital gas diffusion and limit nutrient availability. These conditions may cause an increased incidence of embryonic death.

The relationship of albumen height (AH) to the compositions of yolks and embryos in hatching eggs from a young (30 wk of age) broiler breeder flock was evaluated during incubation. On Day 2 of incubation, egg weight, yolk weight, and yolk moisture, lipid, and fatty acid contents were determined in eggs from broiler breeders previously identified as laying eggs of either low or high AH. In addition, egg weight, wet and dry embryo weight, and embryo moisture and protein contents were determined on Days 10, 12, and 16, and embryo lipid content was determined on Days 12 and 16. Yolk and embryo weights were expressed as percentages of sampled egg weight. Egg, yolk, and wet embryo weights, yolk moisture and lipid contents, and embryo moisture, protein, and lipid contents were not affected by AH; however, yolk myristic acid concentration was higher, and yolk linoleic acid concentration was lower, in low AH eggs on Day 2 of incubation. Furthermore, on Day 16, dry embryo weight was significantly higher in low AH eggs. Young breeder hens laying eggs of different AH may also produce egg yolks with different fatty acid compositions. Differences in yolk fatty acid profiles between AH groups during early incubation may impact subsequent embryo DM weight without associated effects on embryo moisture, protein, or lipid contents.

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