Corticosteroid Levels in White Leghorn Hens as Affected by Handling, Laying-House Environment, and Genetic Stock

Abstract

Correlation coefficients between handling time and plasma corticosteroid concentration of White Leghorn hens were minimal when times varied from 43 to 161 sec (r=.17; P<.05, df=244), and no association was found when blood collection times exceeding 90 sec were omitted (r=−.02, df=219). Handling times carried to specific endpoints of 30 and 60 sec indicated no difference, but times of 60, 120, 180, and 600 sec were associated with highly significant differences in corticosteroid levels that were inconsistent between genetic stocks. Strains selected for increased part-year egg mass responded less rapidly to handling than did unselected control strains. Confinement of hens for 4 to 6 hr in nests within their own pens caused increases of >30% in corticosteroids as compared to samples obtained from hens caught directly from the floor.Neither floor pen vs. colony cage nor genetic stock differences were found for plasma corticosteroid levels of hens at a mean age of 55 weeks. Adrenocorticotropic hormone stimulation of 63-week-old hens caused an 8.5-fold increase in corticosteroids above basal but failed to elicit differential effects associated with environments or genetic stocks. Nevertheless, hens kept in floor pens had 10.8% higher survival in the laying house and exceeded colony-cage hens by more than 40% in hen-day egg mass for the final 10 weeks of a 40-week laying period.