Short Road Transport and Slaughter Stress Affects the Expression Profile of Serotonin Receptors, Adrenocortical, and Hematochemical Responses in Horses

Abstract

Horse transport is considered a cause of stress in animals and is known to affect the 5-HT concentrations in both the brain and other tissues. The aim of this research was to investigate the effect of horse transportation and slaughter stress on plasma serotonin’s concentration and the expression levels of the related 5-HT1B and 5-HT2A receptors in PBMCs. Furthermore, the IL-12 levels and a variety of blood parameters, including triglycerides, total cholesterol, glucose, aspartate aminotransferase, creatine phosphokinase, lactate dehydrogenase, were also considered. This research was carried out on 32 horses submitted to short road transport of 40 km to slaughter. Blood samples were collected in baseline conditions (T0) and 24 h later, after they were slaughtered (T1). The results showed a significantly increased expression of 5-HT1B and 5-HT2A receptors and a significantly decreased expression of IL-12 in PBMCs at T1 vs. T0. Furthermore, a significant increase in cortisol and glucose concentrations, and LDH activity was observed at T1. In contrast, a significantly lower circulating 5-HT concentration was observed at T1 vs. T0. These results indicate that the stress induced by transport and slaughter stimuli led to the serotoninergic system’s activation, suggesting that the expression of serotonin receptors could be used as a pivotal marker of stress, with potential applications for the improvement of elective protocols to observe the guidelines relating to transported horses.

Eye Temperature Measured with Infrared Thermography to Assess Stress Responses to Road Transport in Horses

“…In this regard, HPA activation is one of the most important neuroendocrine responses that occurs, promoting the restoration of the body's homeostasis. Many studies showed cortisol rising following transport [5,42,[54][55][56]. These results depend on the habit of the horses, their age and experience, the duration of transport, the environmental conditions and transport management itself.…”

“…In fact, high cortisol values after transport have been shown in foals during their first experiences over both short and long distances [54,57], in stallions [2] and in racehorses during both long and short journeys [42]. The lack of previous transport experience in subjects used for meat production as opposed to athletic horses used to being transported for competitions presumably contributed to the significant increase in blood cortisol levels detected after transport and slaughter [56]. This may explain the present findings, indicating that cortisol concentration was maintained during the various transport phases.…”

Oxidative stress in relation to serotonin under general anaesthesia in dogs undergoing ovariectomy

“… 2016 ; Bruschetta et al. 2024 ). The use of a balanced anesthetic protocol could reduce the anesthetics dose with an effective reduction in the side effects induced by surgical stress (Beloeil and Nouette-Gaulain 2012 ).…”

“…However, acute stress can induce increases or decreases in serotonin concentrations (Bruschetta et al. 2024 ).…”