Rearing enrichment affects perching behaviour and bone strength in pullets and in free-range hens varying in range use patterns

The high laying rates of domestic hens places significant strain on the calcium metabolism in their bones and shell glands. Behavioural and physical impacts of housing systems begin during pullet development, but exercise is still important throughout lay for maintaining bone strength. Free-range systems may improve bone strength for those hens that range more. This study assessed the effects of rearing enrichment for pullets housed in experimental floor pens. Perching and wing-flapping behaviour, and bone breaking load at the end of rearing were measured. Perching behaviour was observed throughout the flock cycle and bone breaking load assessed at the end of lay in hens that differed in range use. As predicted, pullets perched more when they were given perching structure enrichments compared with pullets exposed to varying novel objects or control pullets. However, this did not affect the breaking load of the pullets' tibias. The novelty treatment pullets had the lowest humeral breaking load, but wing-flapping behaviour was observed equally across treatments. During lay, the novelty treatment hens perched the most and showed the highest tibial breaking load at the end of lay. Differing range use patterns were not correlated with the breaking load of the tibias or humeri. This study indicates that enriched rearing environments can have long-term impacts on hen behaviour and subsequent skeletal health, but that more time spent outside on the range does not impact bone strength. Further research should continue to explore the behavioural and physical effects of enrichments provided in floor-based laying hen rearing systems.