PON1 and systemic inflammatory response syndrome: No differences were found in PON‐1 activity between SIRS‐negative (mean ± SD, 49.1 ± 8.2 U/mL; median, 46.5 U/mL; I‐III interquartile range, 43.6‐54.3 U/mL) versus SIRS‐positive horses (45.3 ± 11.9 U/mL; 45.8 U/mL; 35.4‐54.6 U/mL; P = .21) and between survivors (47.9 ± 9.1 U/mL; 46.5 U/mL; 39.9‐54.8 U/mL) versus non‐survivors (44.4 ± 13.5 U/mL; 44.1 U/mL; 33.3‐53.4 U/mL; P = .27).