Cortisol response to road transport stress in calm and nervous stallions

Cortisol may be useful as marker in predicting how an animal will respond to stressful stimuli, thus providing information on animal’s temperament. To quantify the level of transport stress and the effect of temperament on the adrenocortical response, the changes of circulating cortisol levels were evaluated in eighty-four healthy experienced Thoroughbred and Crossbred stallions, 4-20 years old, after road transport in a commercial trailer (6 horses per load, stocking density: 2 m2/horse) on a distance of 200 km for about 2.30 hours. Several experienced caretakers were asked to also answer a questionnaire, that used a 5-point scale and a 3-point scale to assess impression on each horse’s temperament, on the basis of the norm and tendencies in ordinary care and daily management. Each response was given based on a scale of 1-5. They were also asked about ordinary behavioral responses. The scores were defined as follows: a score of 1 indicated that the horse had never or rarely troubled the caretaker during management, 2 occasionally, and 3 usually. On this basis the subjects were distinguished between calm (No. 64) and nervous (No. 20) stallions. Blood samples were taken at 08.00, in single box, immediately before loading, then after transport and unloading. Serum cortisol concentrations were analysed in duplicate by immunoenzymatic assay. Compared to basal, cortisol increases were observed both in calm (p < .001) and in nervous (p < .05) stallions after transport. RM-ANOVA showed significant effects of transport on cortisol changes (p < .001). Nervous subjects showed lower (p < .01) cortisol levels than calm subjects after transport; basal cortisol levels did not differ between calm and nervous subjects. No significant differences (p > .05) between different age, breed and orientation were detected. The results showed that temperament could influence the adrenocortical responses of stallions after short-term transportation. The presence of the same staff for handling, loading, confinement and unloading, the same vet taking all blood samples, and the presence of co-specifics did not reduce the response to short transport stress both in calm and nervous stallions already accustomed to transport. Moreover, signs of transport stress were less pronounced in nervous stallions. LP Increases of cortisol levels after road journey of 200 km confirm that cortisol is a marker of stress in horses and show that horse’s temperament seems to greatly modify the susceptibility to stress, although age, breed, previous experience did not appear to have an influence.