Comparative exploration of the β-endorphin, adrenocorticotrophic hormone, and cortisol patterns' response to simulated and conventional transportations of stallions (Equus caballus)

The present investigation was focalized to explore the circulating β-endorphin, adrenocorticotrophic hormone, and cortisol patterns as tool to compare the effects of simulated transportation (ST) and conventional transportation (CT) of 18 healthy Sanfratellano stallions accustomed to this procedure. Three different time points of duration (1, 2, and 3 hours) during STs were compared to three different time points of distance (50, 150, and 250 km) during CTs. Blood samples were taken 1 week before the experimental treatment, at rest in baseline conditions; at the first, the second, and the third week during STs, before loading, and after 1, 2, and 3 hours of duration, immediately after unloading; at the fourth, the fifth, and the sixth week during CTs, before loading, and after 50, 150, and 250 km, immediately after unloading. Compared to three different time points of distance (50, 150, and 250 km) of CTs, results showed lower β-endorphin concentrations after 1 hour (P < .001), 2 hours (P < .01), and 3 hours (P < .05) and lower cortisol concentrations after 1 hour, 2 hours, and 3 hours (P < .0001) after STs. Compared to before values, β-endorphin concentrations showed higher values after 2 hours (P < .001) of ST. The present research suggests that arousal levels of the two experimental treatments were different and that the highest circulating β-endorphin and cortisol values represented different moments of the active coping process in promoting the arousal levels and stress response.