Dominance rank and cage density effects on performance traits, feeding activity and plasma corticosterone levels of laying hens ( Gallus domesticus)

Abstract

The effects of dominance rank and cage density on egg production rate, feeding activity, body weight gain, egg weight, shell strength and plasma corticosterone levels were determined for adult laying chickens in battery cages. White Leghorn layers were housed 5, 6 and 7 per cage, which provided 430, 358 and 307 cm 2 of floor area per bird (low-, moderate- and high-density cage environments, respectively). The chickens were maintained on a controlled lighting program of 8L:10D:2L:4D during the production cycle with the 8-h light segment beginning at 08.00 h. Dominance rank and cage density had significant effects on egg production rate and feeding activity. Moderate- and high-density treatments generally resulted in reduced egg production performances and feeding activities. Low dominance rank was associated with reduced egg production rates and feeding activities for the moderate- and high-density environments. However, the relationship of dominance rank with egg production and feeding activity varied with the density. Effects of dominance rank on body weight gain, egg weight, shell strength and plasma corticosterone level were not significant. Blood samples for corticosterone determination were obtained at 49 and 51 weeks of age from 06.00 to 07.00 h and from 19.00 to 20.00 h. Plasma corticosterone levels tended to increase with increasing density, but were not correlated with individual dominance status. Plasma corticosterone analysis failed to indicate a physiological stress response even though individual egg production rates demonstrated reduced well-being for low-ranking individuals. The results show that individual egg production rates may be used as an indicator of well-being for chickens in different cage environments.