STRESS-RESPONSE TO CHRONIC INFLAMMATION IN THE HORSE

Five clinically healthy Thoroughbred geldings were injected with Freun d's adjuvant 3 times to induce a chronic inflammatory response, Blood was collected at various times before and after adjuvant administratio n. Clinical responses (rectal temperature and general demeanour) were also monitored, Adjuvant injection induced increases in rectal tempera ture and plasma fibrinogen concentration (maximum levels measured were mean +/- s.d. 39.7 +/- 0.5 degrees C and 8.2 +/- 0.3 g/l, respectivel y), indicative of an inflammatory response. A mild clinical depression was also observed in the horses for 24 h after the first injection of adjuvant only, Plasma cortisol levels decreased significantly from co ntrol levels of mean +/- s.d. 187.7 +/- 24.3 nmol/l to a minimum of 80 .2 +/- 221 nmol/l (P<0.01) 9 days after the first injection of adjuvan t. Conversely, plasma insulin levels increased after the first injecti on of adjuvant to a maximum (96.7 +/- 15.2 iu/ml; P<0.01) 12 days late r, while plasma glucose concentrations tended to decline. A control gr oup of horses to rule out contemporary environmental influences on the physiological and biochemical indices measured was not included in th is study, The results show that chronic inflammation in the horse depr essed resting plasma cortisol concentrations.