LPS-Induced Immune System Stimulation Alters Urinary Volatiles and Behaviour in Growing Pigs

Abstract

Volatile compounds from body fluids and secretions may indicate the health status of individuals to other conspecifics. We sought to identify urinary volatiles that might act as biomarkers indicative of the health status of growing pigs. Immune system stimulation (ISS) was induced in pigs (N = 5) by intramuscular (IM) injection of bacterial lipopolysaccharide (LPS; 25 µg/kg BW). Urine samples were collected before (baseline) and after LPS treatment. The urinary headspace volatile compounds were identified using Solid-phase microextraction (SPME) coupled with GC-MS. Pig eye temperatures  was measured using an infrared imaging technique, and behaviours (i.e. standing, feeding, drinking, moving, lying, sitting and active) were video-recorded and quantified 24 h before and after ISS. Data were analysed using mixed model ANOVA examining periods before and after LPS administration with pigs serving as their own control. Pig eye/body temperature increased post-ISS (at 6 h, P = 0.03) and correlated negatively with active behaviours (r = −0.64, P = 0.048). Relative to pre-ISS, pigs spent less time standing (P = 0.018), moving (P = 0.061) and active (P < 0.0001) during the post-ISS period. SPME-GC-MS revealed 7.2- and 4.3-fold increases in 3-Methylphenol (P < 0.0001) and 4-Ethylphenol (P = 0.005), respectively, in post-ISS urine compared with urine collected during the pre-ISS period. In conclusion, ISS reduced pig activity, and elevated (P < 0.01) urinary levels of 3-Methylphenol and 4-Ethylphenol. Behavioural changes and volatile molecules may be used as a non-invasive method for detection of fever, illness and health in farm and possibly other animals. Furthermore, the effects of 3-Methylphenol and 4-Ethylphenol on the behaviour of other pigs remain to be determined.