Endotoxin Challenge

Lipopolysaccharides from Salmonella enterica serotype Typhimurium (Sigma-Aldrich, Milwaukee, WI) were used in the study. The endotoxin was suspended in saline by ∼20 inversions of the mixture. The suspension was injected intramuscularly into the breast muscle at a concentration of 8 mg per bird (1 mL; 0.4 mg kg⁻¹); similar doses were being used in turkeys (Ball et al., 1962, Emory et al., 1991), chickens (Cheng et al., 2004, Wideman et al., 2004, Baert et al., 2005), and ducks (1, 10, and 100 μg kg⁻¹; Gray and Maloney, 1998). The vehicle, saline, was similarly injected via the i.m. route. Blood samples were taken 30 min after the challenge.