Blood Profile, Hormones, and Telomere Responses: Potential Biomarkers in Horses Exhibiting Abnormal Oral Behavior

The high prevalence of abnormal oral behavior (AOB) in working horses has been linked to management issues and the pathophysiology of this behavior remains unclear. Therefore, this study aims to elucidate the blood profile, hormones, and telomere length responses between low and high levels of AOB among different horse working groups. A total of 207 healthy horses from various breeds were initially selected from four working groups (leisure riding, equestrian, endurance, and patrolling) and observed for the time spent on AOB. Then, six horses each with higher and lower AOB than the population means were randomly selected from each of the working groups and categorized as high and low AOB horses, respectively. Blood samples were collected for hematology, biochemistry, cortisol, ghrelin, leptin, and relative telomere length analyzes. High AOB horses notably had higher values of glucose, alanine aminotransferase (ALT), alkaline phosphatase (ALP), and creatine kinase (CK) compared to low AOB horses. High AOB horses also recorded higher plasma cortisol and ghrelin, but lower leptin concentrations. Among working groups, both endurance and patrolling horses presented the highest values in sodium, potassium, chloride, phosphate, ALT, and CK. While patrolling horses had the lowest levels of urea, ALP, and albumin levels, equestrian and leisure horses recorded the highest and lowest plasma cortisol and leptin concentrations, respectively. Finally, the telomere length of endurance and patrolling horses were significantly greater than leisure and equestrian horses. The present findings suggest that AOB horses had distinctive physiological characteristics that could be linked to improper diet and a demanding workload, while ghrelin and leptin hormones could be potential biomarkers for this behavior.