Association between Temperament and Stress-related Gene Expression in Day-old Chickens.

Stress in day-old chickens from commercial hatcheries is associated with problematic behavior in adult animals. Recently, we developed a new behavioral handling test for day-old chickens and demonstrated that it assessed temperament differences between seven breeds of native Japanese and Western chickens. In this study, we used 2-day-old male chicks from five of the above breeds to investigate the relationship between temperament and mRNA levels of three stress-related genes (nuclear receptor subfamily 3 group C member 1 (NR3C1), cytochrome P450 family 11 subfamily A member 1, and hydroxy-delta-5-steroid dehydrogenase, 3 beta- and steroid delta-isomerase 1) involved in the hypothalamic-pituitary-adrenal axis. Principal component analysis of 10 behavioral traits for the handling test revealed that the Fayoumi breed and Hiroshima line of the Chabo breed, both of which exhibited boisterous temperament, clustered separately from the other breeds. Only NR3C1 expression showed a significant positive correlation with two behavioral traits (general vocalization and approaching the wall), and a negative correlation with movement. These results suggest that the complex temperament of day-old chickens is regulated, in part, by stress-related genes along the hypothalamic-pituitary-adrenal axis.