Development of cage-free systems for laying hens

In the recent years, consumers are more aware about the production systems of eggs and draw their attention towards laying hens welfare and sustainability. Therefore, nowadays one of the most important changes in the egg production is the shifting from cage systems to cage-free systems because of societal demands. Under cage-free systems, such as free-range or aviary, animals have more space and a greater chance to exhibit their species-typical behaviour, such as dust bathing, foraging and nesting. However, the great interaction between many individuals inside the cage-free housing systems can lead to some problems like aggressive behaviours between animals, overcrowding, bone fractures and an increase of eggs laid out of the nests or on the floor. Despite many studies have been made, more knowledge of cage-free housing systems regarding welfare and behaviour of laying hens is still needed. Moreover, cage-free systems are not so standardized in management practice and equipment as cage systems, so these variables during the rearing period can be very different from one system to another. Therefore, the main objective of the present PhD thesis was the development and improvement of cage-free rearing systems for laying hens, to ensure animal welfare and to provide standard management practice and equipment for the rearing of laying hens in cage free-systems. This main goal was pursued through four specific objectives aimed at evaluating the effects of: i) early training of pullets during the first fifteen days after housing; ii) nest lighting during the first period and colour of nest curtains; iii) enrichment with additional perches in different genotypes at housing; besides the evaluation of the possibility of iv) using machine leaning tools to measure comfort behaviours of laying hens. A multidisciplinary approach was used which included animal welfare indicators (both health and behavioural ones), egg production, external egg quality and egg physical trait, and use of farming livestock precision tools. Considering the contributions of this thesis it can be concluded that the use of some management practices and equipment can led to a better use of the cage-free systems by the laying hens. Moreover, this thesis showed that the different behaviour between genotypes must lead to consider genotype-specific management for the rearing of laying hens, to optimize animal welfare and productive results. Finally, some PLF tools, could be useful for the control of the hens during rearing, thus providing to the farmer an additional instrument for the management of hens and for improvement of animal welfare, but further research is requested in this regard.