THE EFFECTS OF MODIFYING THE AMOUNT OF HUMAN CONTACT ON BEHAVIORAL, PHYSIOLOGICAL AND PRODUCTION RESPONSES OF LAYING HENS

The effects of modifying the amount of human contact on the behavioural (withdrawal responses to humans), physiological (corticosterone and immunological) and production (hen-day egg production) responses of laying hens were examined in a total of 144 hens (White Leghorn X Australorp) housed in two-bird conventional cages in two treatments: (1) 'Minimal' - in which birds received regular but limited human contact during egg collection (daily), inspections (daily) and feeding (twice weekly); the birds' vision of humans was limited to what they could see through a 5 cm gap between the bottom of a blind and the egg tray. (2) 'Additional' - in which birds received a total of 15 min additional (to routine husbandry) human contact per day for 5 days per week. The treatments were imposed for 17 weeks from 19 weeks of age and then all birds received routine husbandry. Measurements were taken on 12 cages per treatment at three periods over the following 3 weeks. At each sampling period there were two behaviour tests (3 days apart) to measure withdrawal responses of birds to an approaching human using birds remaining in their cages (approaching human test - AHT) and birds removed from their cages and placed on a table at the end of an enclosed corridor (shute test - ST). At the end of the ST, a blood sample was taken for corticosterone analysis and 3 days after the AHT, a measure of cell-mediated immunity (CMI) was made. Hen-day egg production was measured from 23 to 36 weeks of age. In both behaviour tests there were fewer withdrawal responses in the 'Additional' treatment and they were maintained over time. A lower proportion of birds moved away from the human in the ST (0.41 vs. 0.64; P < 0.06) and the number of times (max. = 3) that birds were in the front 10 cm of the cage and oriented forwards in the AHT were greater (2.12 vs. 1.22 and 2.54 vs. 1.80, respectively; P < 0.01). The corticosterone response at the end of the ST was greater in the 'Minimal' treatment (P < 0.05) and there were no changes with time. CMI was greater in the 'Additional' treatment only at the first sampling period (2.1 vs. 1.4 mm; P < 0.01) and hen-day egg production was higher in the 'Additional' treatment over the experiment (89.4 vs. 83.1%; P < 0.05). Compared with the 'Minimal' treatment, increasing the amount of human contact reduced the level of fear of humans shown by birds, on the basis of their withdrawal responses in the two behavioural tests and decreased corticosterone response to handling, with consequent effects on production. The mechanism may involve a chronic stress response since adverse changes in cell-mediated immunological responsiveness were found in the 'Minimal' treatment. The results indicate that human contact may be an important determinant of bird behaviour, production and possibly welfare.