Enriched Colony Cages: Stocking Density On Laying Hen Well-being

By Dr. Darrin M. Karcher & Dr. Maja M. Makagon

Consumers are expressing a greater interest in knowing that laying hens have good well-being. The consumers' perception is that the issue can be easily resolved with alterative housing systems for laying hens. One potential housing system becoming more popular is the enriched colony cage. As the commercial laying hen industry begins to phase out the conventional cage moving toward alternative housing systems, research studies need to populate data that can provide guidance on management practices relative to the housing system. The overarching objective was to investigate laying hen space allocation in enriched colony systems.

The long-term goal was to provide a better understanding of how production and well-being are entwined to aid producers in making sound decisions and provide information to address issues raised by the consumer. The specific objectives for this grant were to 1) evaluate performance of a single strain of laying hens at different stocking densities in enriched colony cages and 2) assess impacts of different stocking densities on laying hen well-being using measures of health, stress, and behavior.

W-36 laying hens were housed in the enriched colony cage at 464 cm2, 580 cm2, 651 cm2, 748 cm2, 799 cm2, and 929 cm2 from 17 to 69 weeks of age. Production measures including egg production, body weight, egg weight and feed disappearance were collected. Hen-day production was similar across the various densities. Hens with greater than 748 cm2 of space per hen had slightly higher production compared to hens with less space allowance. Egg production declined over time with all treatments ending around 79 percent, with the exception of the 929 cm2 treatment which ended around 82 percent. Egg weight, feed consumption and body weights were similar across all treatments.

The other aspect of the trial was to evaluate the health, stress and behavior of the birds using the European Union Welfare Quality® (WQ) Assessment Protocol for Poultry (Welfare Quality® Consortium, 2009). The Avoidance Distance Test, which assesses the hen's response to humans, was not practical as the hens interacted with farm staff daily during egg collection and were habituated to human presence. The fear response of the hen was therefore only assessed using the Novel Object Test.

The hen's responses to the novel object, a colorful rod, were not different by density. According to the WQ protocol hen health can be assessed through observation of hens with labored breathing/sneezing and visual examination of feces to identify enteric infections. Based on these procedures, hen health was deemed not to be of issue. The lack of health concerns was confirmed by an avian pathologist who conducted necropsies of mortality. Due to lower than expected numbers of pullets at placement, the sacrificing of pullets was not possible, and the adrenal weights of the pullets, an indicator of stress, were not evaluated.