The Impact of Early-Life Cecal Microbiota Transplantation on Social Stress and Injurious Behaviors in Egg-Laying Chickens

Simple Summary A plethora of studies have evidenced that the gut microbiota profoundly influences host brain function and behavioral characteristics in humans and various animals. In laying hens, it has been reported that injurious behaviors (such as aggressive pecking, feather pecking, and cannibalism) are associated with dysregulation of the microbiota-gut-brain axis. This study further investigated the effects of the early-life transplantation of different cecal contents on aggressiveness and related behaviors in chickens. Cecal bacterial profiles of two divergently selected inbred genetic lines (donors) were analyzed and then orally transferred separately into newly hatched male chicks of a commercial layer strain (recipients). Effects of cecal microbiota transplantation on growth, physiology, and behavior were examined in the recipient chicks. This study first evidenced that social stress and stress-related injurious behaviors in chickens can be reduced by modification of the gut microbiota composition and brain serotonergic activities via the gut-brain axis. The results provide new insights into understanding the cellular mechanisms of the gut microbiota in regulating stress-induced abnormal behaviors and offer a novel strategy for improving health and welfare in laying hens.Abstract Injurious behaviors (i.e., aggressive pecking, feather pecking, and cannibalism) in laying hens are a critical issue facing the egg industry due to increased social stress and related health and welfare issues as well as economic losses. In humans, stress-induced dysbiosis increases gut permeability, releasing various neuroactive factors, causing neuroinflammation and related neuropsychiatric disorders via the microbiota-gut-brain axis, and consequently increasing the frequency and intensity of aggression and violent behaviors. Restoration of the imbalanced gut microbial composition has become a novel treatment strategy for mental illnesses, such as depression, anxiety, bipolar disorder, schizophrenia, impulsivity, and compulsivity. A similar function of modulating gut microbial composition following stress challenge may be present in egg-laying chickens. The avian cecum, as a multi-purpose organ, has the greatest bacterial biodiversity (bacterial diversity, richness, and species composition) along the gastrointestinal tract, with vitally important functions in maintaining physiological and behavioral homeostasis, especially during the periods of stress. To identify the effects of the gut microbiome on injurious behaviors in egg-laying chickens, we have designed and tested the effects of transferring cecal contents from two divergently selected inbred chicken lines on social stress and stress-related injurious behaviors in recipient chicks of a commercial layer strain. This article reports the outcomes from a multi-year study on the modification of gut microbiota composition to reduce injurious behaviors in egg-laying chickens. An important discovery of this corpus of experiments is that injurious behaviors in chickens can be reduced or inhibited through modifying the gut microbiota composition and brain serotonergic activities via the gut-brain axis, without donor-recipient genetic effects.