Effects of the Calls and Presence of Roosters on Egg Incubation Behavior of Nagoya Laying Hens.

The incubation behavior of the Japanese Nagoya chicken breed is a commercial issue because it often causes a sudden and sharp drop in egg production. In this study, whether the incidence of incubation behavior in Nagoya laying hens was associated with calls and the presence of roosters in the same laying house was investigated. Four experiments were conducted using commercial layer-type Nagoya hens where the hatching time of the experimental birds and the treatment order in the presence of males were changed . In Experiment 1, the proportion of incubation behavior in the presence of roosters kept in another pen located between pen-rearing hens (51.3%) was higher than that in their absence (15.9%) or with only rooster calls (23.8%). In Experiments 2, 3, and 4, the proportion of incubation behavior in the presence of roosters (47.3%, 33.3%, and 37.9%, respectively) was higher than that in their absence (33.3%, 17.4%, and 25.6%, respectively). In all experiments, approximately 70% of the incubating hens observed in the absence of roosters exhibited incubation behavior, even in the presence of roosters. Therefore, the presence of roosters may enhance egg incubation behavior in Nagoya laying hens.