Influence of Obesity on Histological Tissue Structure of the Cardiovascular System in Horses

SIMPLE SUMMARY: Obesity is a global problem, not only in humans but also in companion animals, including horses. It is well known that obesity in horses is associated with an increased risk of laminitis, other orthopedic problems, reproductive disorders, and decreased exercise capacity. In humans, however, obesity is known to be of great importance in increasing the risk of cardiovascular disease and thereby increasing the death rate. The aim of the study was to demonstrate the microscopic changes in heart and vessels structure in obese horses. Heart and vessels specimens (aorta, pulmonary, coronary and palmar arteries) from 19 draft slaughter horses (12 extremely obese and 7 with normal body condition) were used in the study. The results showed significant architecture changes in heart muscle and vessels in obese horses. Obese animals had increased amount of pericardial and cardiac fat. Vessels had increased thickening and diameter in this group. Visible structural changes were similar to these observed in people and may be an indicator of subclinical dysfunction, which could lead to severe disease. To the authors’ knowledge, this is the first study to analyze cardiovascular tissue in obese horses. ABSTRACT: It has been well established that obesity in horses can have a negative impact on their health, including endocrine disturbances. In humans, it is well known that obesity leads to structural and functional changes of the cardiovascular system. The aim of the study was to assess the impact of obesity on the histological structure of the myocardial tissue, as well as great and peripheral arteries in horses. The heart, arteries (aorta, pulmonary artery and palmar arteries) specimens from 7 horses with normal BCS (4–5/9) and 12 extremely obese (BCS 9/9) draft slaughter horses were obtained for histopathological evaluation. The heart tissue and great arteries showed more intense disturbances in the architecture and vacuolization in the aorta in obese horses as compared to the healthy group. The intima in the pulmonary artery, coronary arteries and palmar arteries was thicker in the obese, rather than healthy horses. The palmar arteries in obese horses had a larger lumen diameter and the lumen-to-total diameter ratio as compared to the control group. The presented study showed a significant effect of obesity on the heart as well as the central and peripheral vessels in horses. This forms the basis for a deeper reflection on the impact of obesity on the equine body.