Adrenocortical responses of Japanese quail to a routine weighing procedure and to tonic immobility induction.

Tonic immobility (TI) is induced by brief manual restraint, and it is a commonly used test of fearfulness, particularly in poultry. However, in view of increasing ethical concerns about experimentation on living animals, there is a need to ensure that the tests used do not elicit unacceptable distress. In the United Kingdom, there is some debate as to whether TI should be classified as a regulated experimental procedure that requires a Home Office license to experiment on living animals under the Animals (Scientific Procedures) Act of 1986. The present study compared plasma corticosterone (PC) concentrations in undisturbed Japanese quail (controls) with those exposed to the induction of TI or those exposed to a routine weighing procedure. Circulating PC concentrations were higher following TI induction or weighing than in the controls, but the 2 treatments elicited similar adrenocortical responses. Further, the PC levels found here were lower than those reported elsewhere when quail were exposed to crating, transport, or mechanical immobilization stressors. We therefore concluded that the induction of TI might be best regarded as a mild stressor. Furthermore, studies using this technique can identify ways of alleviating fear and thereby improving well-being. Collectively, we believe that the use of TI is justified, and it does not require classification as a regulated procedure in the United Kingdom or elsewhere.