A review of environmental enrichment for laying hens during rearing in relation to their behavioural and physiological development

The environment in which a laying hen is reared can have long-term impacts on their behaviour, health and welfare later in life (Janczak and Riber, 2015). Alternative housing systems for layers provide access to larger areas and allow greater expression of behavioural repertoires, leading to positive acceptance by consumers. But the complexities of alternative systems can also place greater physical and behavioural demands on the birds, leading to increases in skeletal injuries or inter-bird aggression. For optimal welfare and production of hens, it is best to match the rearing environment with the layer environment (Janczak and Riber, 2015), but this is not always possible. Environmental enrichment – defined as a modification in the environment that increases behavioural possibilities leading to improvement in biological function (Newberry, 1995) is a potential method of modifying rearing conditions for improvements during lay. Enrichment can include additional objects, sensory stimuli or structural modifications, including alternative rearing systems themselves (e.g. furnished or aviary systems). The effectiveness of enrichments can be determined by quantifying impacts on the physiology and behaviour of the birds. The literature was reviewed to compile the impacts of different types of enrichments during rearing on skeletal development, immune system development, neurophysiological development, visual and auditory development and behavioural development, including fear and foraging/pecking.

Briefly, the literature identified that environmental enrichment has variable impacts on pullets depending on the type of enrichment provided. Alternative rearing systems that encourage jumping and flying or rearing systems that include perches can improve bone strength, skeletal symmetry, and reduce the incidence of keel fractures during lay. Furnishings within cages can enhance immune responses, and increased environmental complexity can reduce fear responses. Access to litter reduces the development of abnormal feather pecking behaviour. Modifications made within the first few weeks of life can have long-lasting effects.

The majority of research on enrichment during rearing has been conducted overseas, with a lack of understanding of impacts on commercial farms within Australia. In particular, birds destined for free-range systems may benefit from enrichment during rearing to better prepare them for outdoor access. New suggestions for enrichments, timelines for provision of enrichments and knowledge gaps are identified.

ACKNOWLEDGEMENTS: This research was supported by PoultryHub Australia.