Cortisol concentrations in sheep before, during and after sham foot trimming on a tilt table - the suitability of different matrices

Matrices that can be collected non-invasively for quantification of a stress response in sheep have received little attention in the veterinary literature. This study examines the suitability of blood, tears and saliva for determining a stress response in sheep undergoing sham foot trimming on a tilt table. The cortisol concentration of blood, tears and saliva and the concentration of cortisol metabolites in faeces were measured in 13 healthy Meat Merino ewes once a day for six days. Sham foot trimming on a tilt table was used as the stressor and was done during a one-hour period on day 4; cortisol concentrations of blood and tears were measured at 0, 10, 20, 30, 40 and 60 minutes. Cortisol concentrations of blood (maximum at 30 minutes) and tears (maximum at 40 minutes) increased during the procedure and then decreased. There were significant correlations between cortisol concentrations of blood and tears (p = 0,04) during sham foot trimming (area under the curve, 0 to 60 minutes). Over the entire 6-day study period, significant correlations were seen between the cortisol concentrations of blood and tears (r = 0,55; p < 0,001), blood and saliva (r = 0,53; p < 0,001) and tears and saliva (r = 0,78; p < 0,001). Faecal cortisol metabolite concentration was significantly increased on day 5 (p <= 0,05), but the cortisol concentration of the other matrices did not change significantly in the 6-day study period. Sham foot trimming on a tilt table was considered an acute stressor in sheep because of increased cortisol concentrations in blood, tears and increased corti- sol metabolite concentrations in faeces. The cortisol concentration of tears was similar to that of blood, and therefore collection of tears represents a viable non-in- vasive alternative to blood for cortisol testing. The delay in the peaks between the maximum concentration of cortisol in tears and blood must be considered when interpreting results.