Research Note: A sip of stress. Effects of corticosterone supplementation in drinking water on feather corticosterone concentrations in layer pullets

The measurement of feather corticoste-rone concentrations (fCORT) is a comparatively new method for the evaluation of stress in wild and captive birds and may be a useful indicator in animal welfare research. The aim of this study was to assess the suitabil-ity of fCORT as an indicator of stress, and for this pur -pose a prolonged stress period was experimentally simulated by oral intake of corticosterone via drinking water and corticosterone concentrations were analyzed in feathers grown during this period. Layer pullets of both a control group (n = 20) and a CORT group (n = 20) were offered drinking water ad libitum through-out the entire experimental phase. The drinking water of the CORT group was supplemented with corticosterone at a concentration of 20 mg/l from the 64th to the 114th day of life. The vaned parts of the primaries 5 (P5s) were clipped on d 114 and fCORT was analyzed by ELISA after extraction. Body weights increased from day 64 until d 114 in both groups, however, at the end of the experiment, mean body mass in the CORT group was significantly lower than in the control group (P < 0.001). Pullets of the CORT group also showed shorter and lighter P5s as well as a retarded molt of the primar-ies. The supplementation of drinking water with cortico-sterone increased the average fCORT in the P5s of the CORT pullets compared with the control group (median: 110.3 pg/mm [interquartile range (IQR): 47.2] vs. 10.0 pg/mm [IQR: 2.5], P < 0.001). The results show that experimentally increased systemic corticosterone concentrations over a period of seven weeks in layer pul-lets are reflected in corticosterone concentrations of feathers grown during that time. This indicates that the measurement of fCORT may be a useful and minimally invasive tool for the evaluation of long-term stress in chicken and provides the basis for further investigations on its use in animal welfare research.

Automated summary

The study analyzed the effects of corticosterone supplementation on feather corticosterone concentrations (fCORT) in layer pullets, finding that increased corticosterone levels led to decreased body weight, shorter and lighter feathers, and a delayed molt. The results suggest that fCORT measurement can be a useful tool for evaluating long-term stress in chickens and may have implications for animal welfare research.