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Research Examines Impact of Stocking Density in Enriched Colony Cages

20 June 2014

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Researchers at Michigan State University found minimal differences in measures of production and well-being at the various stocking densities, from 464 to 929 square centimetres per bird during the period of 17 to 69 weeks of age, and suggest that future research should focus to determine at which point stocking density provides a significant impact on feathering.

Consumers are expressing a greater interest in knowing that laying hens have good well-being, and the consumers' perception is that the issue can be easily resolved with alternative housing systems for laying hens, according to Dr Darrin M. Karcher and Dr Maja M. Makagon of Michigan State University.

One potential housing system becoming more popular, they say, is the enriched colony cage. As the commercial laying hen industry begins to phase out the conventional cage and move 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 of the East Lansing work 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, sponsored by the US Poultry & Egg Association, 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 behaviour.

W-36 laying hens were housed in the enriched colony cage at 464, 580, 651, 748, 799 and 929 square centimetres 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 square centimetres of space per hen had slightly higher production than hens with less space allowance. Egg production declined over time with all treatments ending around 79 per cent, with the exception of the 929 square centimetres treatment, which ended around 82 per cent. Egg weight, feed consumption and bodyweights were similar across all treatments.

The other aspect of the trial was to evaluate the health, stress and behaviour of the birds using the European Union Welfare Quality® (WQ) Assessment Protocol for Poultry (Welfare Quality Consortium, 2009), continued Drs Karcher and Makagon.

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 colourful rod, were not different by density.

According to the WQ protocol, hen health can be assessed through observation of hens with laboured breathing/sneezing and visual examination of faeces 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.

The welfare quality measures of comb abnormality, comb wound, keel deformation or fracture, skin lesions, toe damage, foot condition and plumage damage were assessed bi-monthly in 10 per cent of each enriched colony population.

Keel deformation or fracture increased over time and was similar amongst all treatments over time (20 to 30 per cent).

Plumage damage was assessed on seven different areas of the hen. All areas became worse with time (increased feather loss or feather breakage), and the areas of the head, abdomen and back were impacted by density with the proportion of hens having worse plumage quality in 464 square centimetres.

Drs Karcher and Makagon added that further research should additionally focus on finding the density between 651 and 748 square centimetres at which improvements to feathering occur.

June 2014

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