Determination of corticosterone concentrations in egg albumen: a non-invasive indicator of stress in laying hens.

Measurement of plasma corticosterone is difficult because the handling associated with blood sampling from birds is stressful. The use of non-invasive means of measuring stress could help to alleviate this problem. It was considered that the accumulation of plasma corticosterone into the egg albumen could provide a non-invasive indicator of stress in laying hens. The present study examined the relationship between plasma and egg albumen corticosterone concentrations and then determined what affect exposing hens to known stressors had on egg albumen corticosterone concentrations. Laying hens were given subcutaneous injections of either 0, 5, or 10 mg of corticosterone suspended in peanut oil and then the concentrations of corticosterone in the plasma and egg albumen determined. Also, groups of hens were handled, exposed to high ambient temperature and moved to new cages, all events known to be stress provoking, and then the concentrations of corticosterone in albumen determined. The injections increased plasma corticosterone concentrations substantially and these were directly related to the concentrations measured in the egg albumen. When hens were exposed to the various stressors, the level of corticosterone in the egg albumen increased. The corticosterone concentrations found in the egg albumen can provide a convenient non-invasive means of measuring stress in laying hens and other birds.