Stress and feather pecking in laying hens in relation to housing conditions.

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.