1. Possible association between high rates of feather pecking and increased stress were investigated in laying hens. 2. From week 19 to week 30 after hatching, 16 groups of 11 hens (white Lohman Selected Leghorn hybrids) were kept in pens with or without long-cut straw as foraging material and provided with food in the form of pellets or mash. 3. Stress was assessed by egg production, weight gain, tonic immobility (TI), heterophil/lymphocyte (H/L) ratio and antibody titres to sheep red blood cells (SRBC), tetanus toxoid (TT) and human serum albumin (HSA). 4. Provision of foraging material and food form influenced feather pecking. Rates of feather pecking were highest in groups housed without straw and fed on pellets. 5. Egg production was reduced in pens without straw but not affected by food form. Both the duration of TI and H/L ratios were influenced by provision of foraging material and food form. TI was longer and H/L ratios were increased in hens housed without straw and in those fed on pellets. Antibody titers to SRBC and TT were lower in pens without straw than with straw but not influenced by food form. 6. In conclusion, foraging material and food form affected both feather pecking and indicators of stress, suggesting that feather pecking in laying hens is associated with stress.

1. The aim was to test whether provision of foraging material and food form influence feather pecking and feather damage in laying hens. 2. From week 19 of age, 16 groups of 11 hens (white Lohman Selected Leghorn hybrids) were kept in pens with or without access to long-cut straw as foraging material and fed on either mash or pellets. 3. Foraging behaviour was increased in hens with access to straw and time spent feeding was increased in hens fed on mash. In addition, hens fed on mash had longer feeding bouts and higher rates of pecking at the food during feeding than hens fed on pellets. 4. There were interaction effects of foraging material and food form on both feather pecking and feather damage. High rates of feather pecking and pronounced feather damage were only found in hens housed without access to straw and fed on pellets. In groups characterised by high rates of feather pecking the hens also showed more severe forms of this behaviour. 5. Differences in the time budgets of hens kept in different housing conditions suggested that birds fed on mash used the food not only for feeding but also as a substrate for foraging behaviour. 6. In order to avoid problems with feather pecking it is recommended that laying hens are provided with foraging material and fed on mash.

A systematic review of investigations on productivity, mortality and cannibalism of laying hens housed in aviaries is presented. In Part One we reviewed the studies that compared these parameters between laying hens housed in aviaries and in conventional cages. In Part Two we investigated the relative impact of strain, beak trimming and rearing condition on productivity and mortality in aviaries. The comparative analysis revealed that aviary hens consumed 3.0 % more food than caged hens, and food conversion was 6.7 % higher in aviaries than in cages. On the other hand, the mortality rate and cannibalism rate did not differ significantly between the two housing systems. The analysis of causes of variation in productivity, mortality rate and cannibalism rate in aviaries revealed a strong effect of strain. Beak trimming was associated with a reduced prevalence of cannibalism rates but had no effect on overall mortality. It also reduced egg weight and food consumption. Early access to litter during the rearing period had a positive effect on egg weight; egg mass, food conversion and mortality rate. In conclusion, we found a slightly reduced productivity of aviaries in relation to cages although the mortality rates and the prevalence of cannibalism did not differ between these housing systems. To further improve productivity and reduce mortality of hens housed in aviaries we recommend the choice of suitable strains and the implementation of improved rearing conditions including early access to litter. Keywords: systematic review; laying hens; aviary; housing system; productivity; mortality; strain; beak trimming; rearing IntroductionThe aviary housing system for laying hens was developed as an alternative to conventional battery cages. In various countries, this new housing system has been assessed with regard to animal welfare health and economic aspects, and these investigations often compared various parameters between hens housed in aviaries and conventional cages. To draw general conclusions, however, each of these studies was neither large enough nor covered a sufficiently wide range of conditions. We therefore made a systematic and quantitative review in which we combined the independent results of these studies. The aim of a systematic review is to produce an up-to-date and reproducible account of the present state of research. Moreover, according to Gates (2002), a quantitative review provides a considerable advance in scientific rigour over traditional narrative or "vote-counting" reviews.An early type of aviary was already operating in 1979 (Fölsch et al., 1983) and since then, the system was further developed. One of the aviary's best features is the construction of tiers and perches above the littered area, which allows the hens to move and get out of the way both horizontally and vertically. Furthermore, the spatial separation of the areas for eating, drinking, resting, foraging and dust bathing is considered as advantageous (Fröhlich, 1995). The use of the third dimension allows for housing additional...