Endotoxin stress responses in chickens from different genetic lines. 1. Sickness, behavioral, and physical responses

Genetic variation in response to lipopolysaccharide (LPS) challenge was studied in chicken lines divergently selected for high (HGPS) and low (LGPS) group productivity and survivability resulting from cannibalism and flightiness in colony cages and in a Dekalb XL (DXL) commercial line. Six-week-old chicks were randomly assigned to control or experimental groups and were injected intravenously with Escherichia coli LPS (5 mg/kg of BW) or distilled saline (control). Sickness responses were measured at 6, 12, 24, 48, and 72 h following injection (n = 10 at each point in time for each line). Although LPS induced widespread sickness symptoms in all of the treated chicks, the reactions were in a genotypic- and phenotypic-specific manner. Compared with LGPS and DXL chicks, HGPS chicks had acute, transient behavioral and physical changes with less effect on BW gain, organ development, and core temperature, which were in the order HGPS < DXL < LGPS. The effects of heritable factors and LPS challenge on the differential responses among the present lines may reflect each line's unique adaptability to stress and resistance to infection and inflammation. The results suggested that the present chicken lines may provide a valuable animal model for investigating the effects of genetic-environmental interactions on the behavioral and physiological homeostasis in response to stress and disease.