The effect of fear on catching-crating stress before slaughter in commercial turkeys

The study aimed to investigate growth and pre-slaughter stress responses of male turkeys differing in their fear responses to human at 7th wk which measured by voluntary approach (VA) test under commercial conditions using two flocks of the same company. Turkeys were grouped according to their responses to observer as approached-low fear (LF) or aversive-high fear (HF) at 8 observation-areas/flock. At each observation area, first 5 (Flock1) and 3 (Flock2) birds/area that approached to the observer were marked as LF (n=64) using leg bands. The same number of aversive birds were marked as HF (n=64). Fear groups were kept together in their own flock but in an experimental pen. Tonic immobility (TI) was tested on 15 birds/group/flock. At 7 and 17 wk of ages, bloods were collected from 7 birds/group/flock to measure H/L ratio, leucocyte differentiation and corticosterone hormone as stress measures. At 17th wk, additionally, blood samples were collected after a 30 minutes crating stress in transport cages. Body weights were measured at 7 and 17th weeks, individually. Slaughter weights of turkeys significantly differed between fear groups being higher in LF (16.65±0.22 kg) than HF (14.75±0.22 kg) group. Significantly lower H/L ratio (0.54±0.04) but higher lymphocyte (% 53.67±2.00) was observed in LF group (P≤0.05) than HF (0.67±0.04, H/L; 46.80% ±1.84, lymphocyte) which were associated with the lower stress response in LF. Tonic immobility responses of turkeys and plasma CORT levels did not significantly differ between the fear groups. Although it could not be associated with TI responses in this study; VA test could be used to define less fearful and less susceptible individuals to stress in male turkeys. Higher slaughter weight together with lower stress response associated with lower H/L ratios and higher lymphocyte percentage measured in LF group seemed to be promising to improve our understanding regarding to the relations among the behaviour, performance and welfare in commercial turkeys. Keywords: commercial turkey, fearfulness, voluntary approach test, tonic immobility, H/L, corticosterone.