Comparative endocrinological responses to short transportation of Equidae (Equus asinus and Equus caballus)

In order to evaluate the effects of short transportation on β-endorphin, adrenocorticotropic hormone (ACTH) and cortisol changes, 12 healthy stallions of Equidae (Equus asinus and Equus caballus) were studied before and after transportation of 50 km. Blood samples were collected 1 week before transportation in basal conditions, immediately before loading and after transportation and unloading, on their arrival at the breeding station. Compared to basal and before values, donkeys showed an increase in circulating ACTH (P < 0.001) and cortisol (P < 0.0005) levels after transportation and higher ACTH (P < 0.01) levels than horses after transportation. A positive and significant correlation (r = 0.885; P < 0.01) between ACTH and cortisol levels after transportation was found. No significant differences were observed for β-endorphin levels. Compared to basal and before values, horses showed higher cortisol (P < 0.005) levels after transportation and no significant differences were observed for ACTH and β-endorphin levels in donkeys. Horses facing forward (direction of travel) showed higher (P < 0.01) β-endorphin levels after transportation than donkeys; horses facing backward (the opposite direction of travel) showed lower (P < 0.05) ACTH levels after transportation. The results indicate that short transportation induces a preferential activation of the hypothalamus-pituitary-axis (HPA), with significant release of ACTH and cortisol in donkeys and only of cortisol in horses, suggesting that transportation for donkeys may be more stressful than horses.