Myeloperoxidase expression in diencephalon is potentially associated with fear ‐related behavior in chicks of laying hen
In this study, in two representative laying breeds (White Leghorn [WL] and Rhode Island Red [RIR]) that have different FP frequencies, we identified a candidate gene associated with fear-related behavior in chicks and FP in adult hens. In the tonic immobility test and open-field test, the behavioral activity was lower in WL chicks than in RIR chicks (P < 0.01), suggesting that WL chicks were more fearful than RIR chicks. Based on previous studies, 51 genes that have been found to be differentially expressed in the brain between high- and low-FP populations were chosen, and their expression levels were screened in the chick diencephalon. This anal ysis revealed that myeloperoxidase (MPO) gene expression level was higher in WL chicks than that in RIR chicks (P < 0.05). Furthermore, STRING analysis predicted the gene network includingMPO andMPO-related genes and revealed the association of these genes with fear-related behavior. These results suggest thatMPO is potentially associated with fear-related behavior in growing female layer chicks and FP in adult hens.