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The response of adrenal glands of Single Comb White Leghorn laying hens housed under different population densities was studied. The birds were reared in floor pens until they were 19 weeks of age, after which they were housed in cages. Cage size was 30.5 X 50.8 cm. Three, four, or five birds were housed per cage. Corticosterone concentrations were measured in all birds 48 and 96 hr following housing in cages and weekly thereafter for 6 weeks. Corticosterone concentrations were consistently higher in the serum of birds housed five per cage than in birds housed three or four per cage. It was concluded that in order to minimize physiological stress in cage layers, more than 387 cm2 per bird should be considered.

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Quantitative relationships between the cage area allotted per hen and parameters associated with egg production were examined by regression analysis. Hens were placed 3, 4, and 5 birds per cage (30.5 x 50.8 cm) with 516, 387, and 310 cm2 of floor area per hen, respectively. Egg production declined as the area per hen was reduced. There was no numerical difference for feed consumption per dozen eggs between 516 or 387 cm2 per hen. Feed conversion was less efficient when the area was reduced to 310 cm2 per hen. Feed conversion when adjusted to 20 dozen eggs accentuated the decline in efficiency as previously noted. Mortality was significantly related to a reduction in cage area per hen. Egg weight tended to increase as the allotted area per bird decreased. Eggs produced and feed consumed per cage were highly correlated to bird numbers per cage area. An economic analysis based on dozens of eggs produced, feed consumption, egg and feed prices, grower payment, and pullet cost showed that profitability associated with increased bird numbers in a fixed cage area is sensitive to changes in egg and feed prices.

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