Age-Dependent Change of Tonic Immobility Response in Chicks of a Native Japanese Chicken breed, Tosa-Jidori

Abstract

The objective of the present study was to evaluate the temperament of a native Japanese chicken breed (Tosa-Jidori) using the tonic immobility test for the detection of fearfulness. Each chick (2, 5, 10 or 15-day old) was placed on its back on a table and restrained by hand. Thereafter, if the chick lay still, it was then released and observed. The number of inductions and tonic immobility duration was recorded. The duration in the male was shorter than that in the female at 2-day old, whereas higher than that in the female at 15-day old. The duration of tonic immobility was affected by age in the male (P<0.05). There was a positive correlation between them in the male, and a negative correlation in the female. As for the number of induction, no significant differences and tendencies were found between sex and age. These findings demonstrate that Tosa-Jidori chicks show sexual differences in the fear response and further suggest that the temperamental differences may correspond to genetic characteristics of breeds.