Assessing the Peripheral Levels of the Neurotransmitters Noradrenaline, Dopamine and Serotonin and the Oxidant/Antioxidant Equilibrium in Circus Horses

It has been suggested that a circus has a limited ability to make improvements in animal welfare. Though the horse is a domesticated species, the activities as well as the management that horses are subjected to could perturb homeostasis, alerting the organism and resulting in stress conditions. In the current study, the plasma concentrations of noradrenaline, dopamine and serotonin, as well as the reactive oxygen metabolites (d-Roms) and the biological antioxidant potential (BAP), were assessed in horses managed in different circuses. According to the results herein found, it appears that the welfare of horses under circus management was not compromised; nevertheless, better attention to the management of old horses is advocated, as they could be more susceptible to oxidative stress. Due to the paucity of information on circus management effects on the welfare of horses, this study investigated the plasma concentrations of noradrenaline, dopamine and serotonin, known to be indices of mental status, as well as the reactive oxygen metabolites (d-Roms) and the biological antioxidant potential (BAP), likely to denote the oxidant/antioxidant equilibrium of organisms, in horses managed in different Italian circuses. For the study, 56 circus horses of different breeds and ages were enrolled and divided into six groups according to the horses' management (circus management, groups G1-G5; classic riding management representing the control group, CG). From each horse, blood samples were collected in order to assess the concentration of selected parameters. One-way ANOVA showed no differences (p > 0.05) in serotonin, dopamine, noradrenaline, d-Roms and BAP values between circus and control horses. No differences related to the breed of the horses enrolled in the study were found in the values of all investigated parameters (p > 0.05). Furthermore, neurotransmitters showed overlapping levels between the different age classes of investigated horses (p > 0.05); contrariwise, the age of the horse displayed a significant effect on BAP values, with the oldest horses (16-21 age class) exhibiting lower BAP values compared to 4-5, 6-10 and 11-15 age classes (p < 0.05), whereas the d-Roms showed similar values in horses of different age classes (p > 0.05). The results gathered in the present study suggest that the mental status of horses under circus management was not compromised; however, better attention and care in the management of older horses is advocated, as they showed a lower biological antioxidant potential than younger horses; thus, they could be more susceptible to oxidative stress.