Effects of vision-restricting "polypeepers" on the behaviour of laying hens during adaptation, feeding, on general activity, agonistic behaviour and pecking damage.

Vision-restricting "polypeepers" have been reported to result in higher egg production with improved food utilisation in hens. In the present experiments behavioural explanations of these effects were sought. For detailed observations 128 White Leghorn X Black Australorp hens were used and for pecking damage comparisons a further 192 hens.

Stress by immobilization, with food and water deprivation, causes changes in plasma concentration of triiodothyronine, thyroxine and corticosterone in poultry.

Measurements were sought for assessment of stress during investigations of welfare in intensively housed poultry. Immobilization was used as a stressor in experiments involving 64 cockerels of various ages. Two parameters were found to be related to acute stress: plasma triiodothyronine (T3) concentration, which fell markedly, and plasma corticosterone concentration, which rose considerably, in all birds during severe stress.