The neurophysiology of cognitive development in laying hens
Conventional battery cages (CC) for laying hens will be banned in 2012. The new regulations will allow several alternative possibilities. However, nearly all Norwegian egg laying hens will be reared in aviaries and then housed in aviaries or furnished cages (FC) during the laying period. Producers using aviaries report that hens have problems with fearfulness and associated clumping, stress, feather loss, and sub-optimal utilization of resources (i.e. feed, water, perches, and nest boxes). These problems have a larger impact in aviaries than in CC because of the large number of animals involved. The costs to animal welfare and the producers’ economy can be large. It is therefore essential to develop practical methods of improving the welfare and productivity of laying hens by optimizing rearing methods. This is the main goal of the present project. The basic research in this project aims at producing new knowledge to help understand how rearing conditions influence cognitive, emotional and physiological development in laying hens.
a) Test practical methods for reducing fearfulness and sensitivity to stress by exposure to fear-reducing stimuli during rearing. This study will compare a fear-reducing treatment to the ordinary control condition (standard aviary environment according to regulations, only necessary contact with humans). In addition to on-farm studies experimental studies will be run at The Norwegian School of Veterinary Science (Oslo, Norway). Treatments we will use may include 1) different clothing colours on normal stockpersons, 2) model humans, 3) recorded sounds associated with humans, 4) animated model objects, and/or 5) recorded non-human noises. For the farm studies we will use 4 blocks of N=30000 pullets per block, over a two year period. Each aviary row will be divided into two, using solid partitions, and birds in each half of each aviary row will be subjected either to one standard or one fear-reducing treatment. At 17 weeks of age each treatment group of n=15000 birds will be redistributed to two aviaries, each containing a single treatment, and housed at 7500 birds/aviary. This will produce eight flocks per treatment over a two year period for which pooled average values will be used. In the aviaries, effects of rearing on selected measures related to fearfulness and welfare (fearfulness, anxiety, feather loss) will be monitored in adult laying hens.
b) Test how practical methods of enrichment affect the ability to function well in aviaries. This study compares hens reared under environmentally enriched aviary conditions with hens reared under conventional control conditions as specified by the regulations. In addition to on-farm studies experimental studies will be run at The Norwegian School of Veterinary Science (Oslo, Norway). In practice the standard aviary rearing environment provides chicks with access to litter and perches only from the time that they are released from the aviary row at three to five weeks of age. Preliminary suggestions for the enrichments are access to 1) perches within the aviary row from hatching, 2) perches within the aviary row from one week of age, 3) dust bathing and pecking substrates such as whole grain, sand, straw and string pecking devices available from hatching, instead of only the normal flat paper substrate, 4) substrates available from one week of age, and 5) a larger vertical distance between feed and water after the first week of life. The experimental design will be the same as in 2a, but measures will have a greater focus on cognitive ability related to use of available resources (use of perches and nest boxes).
Pending documentation of treatment effects on behaviour we plan to use histology to look at effects on brain morphology, LCMS/MS to assess effects on brain glucocorticoids and their metabolites, HPLC to assess effects on brain monoamine concentrations and turnover, and xMAP technology to assess effects on cytokines and other neuroactive peptides. Tests of emotionality and spatial cognition will also be relevant.