Lipopolysaccharide exposure modifies salivary and circulating level of cortisol in goats

The aim of this study was to investigate response of salivary and blood cortisol level and cardinal physiological variables in presence of endotoxaemia in goats. For this, eight healthy adult male Jakhrana goats (3-4 years of age; 41.9 ± 1.9 kg BW) were adapted to experimental conditions for 10 days, after which, they were randomly assigned equally into two groups i.e. control (CON; 20 μL/kg BW i.v. physiological saline) or lipopolysaccharide (LPS; 1 μg/kg BW i.v.; Escherichia coli 0111:B4). Recording of cardinal physiological variables [rectal temperature (RT), respiratory rate (RR) and heart rate (HR)] was done at about 10 min before (baseline) and at different time intervals (2, 4, 6, 8, 26, 32 and 48 h) after saline or LPS infusion. Immediately thereafter, matched saliva and blood samples were collected at similar time points to investigate time dependent changes in cortisol concentration after LPS administration. The results showed that cortisol concentration in both saliva and blood plasma were increased significantly (P < 0.05) at 2 h and remains elevated in both the biological fluids up to 8 h after LPS infusion. Correlation analysis showed a significant positive relationship of salivary cortisol with plasma cortisol concentration (r = 0.556, P < 0.001). After systemic LPS exposure, increased HR and RR were observed earlier (at 2 h after LPS infusion) compared to the increase in RT (at 4 h after LPS infusion) (P < 0.05). The results of the present study demonstrated that the measurement of salivary and blood cortisol level could be a practical tool for monitoring time dependent effects of LPS and for evaluating early inflammatory response to acute bacterial infection in goats.