By Mark Andrews

Obesity has a significant impact on the structural changes in cardiovascular tissue in horses, a recent study has found.

Obesity is known to have significant adverse effects on horse health with laminitis an obvious example, but it can also contribute to other problems such as those affecting soundness or fertility.

In humans, obesity is recognised as a risk factor for cardiovascular problems. However, until now there has been little research into the effect of obesity on the wider cardiovascular tissues of horses. 

A recent study by Natalia Siwinska and colleagues at the Faculty of Veterinary Medicine, Wroclaw University of Environmental and Life Sciences in Poland assessed the impact of obesity on the microscopic structure of the heart muscle and selected arteries in horses.

Related: The Dangers of Equine Obesity

Microscopic image of the heart muscle from an extremely obese horse. Left ventricular wall: myocardial cell degeneration, severe stenosis. Photo: Animals Journal

They conducted post-mortem examinations on nineteen draft slaughter horses, comparing specimens from twelve extremely obese (body condition score 9/9, and seven with normal body condition score 4-5/9. They examined specimens of heart muscle and major blood vessels (aorta, pulmonary, coronary and palmar arteries). A report of the work is published in the journal Animals.

The researchers found significant changes in the heart muscle and vessels in obese horses compared with those in normal condition. 

Microscopic image of the heart muscle specimen from a lean horse. Left ventricular wall: normal structure. Photo: Animals Journal

Obese animals had increased amounts of pericardial and cardiac fat, and the intima (the inner layer) of the pulmonary artery, coronary arteries and palmar arteries was thicker, compared with the healthy animals. They also found changes in palmar arteries in obese horses, which had a larger lumen diameter and the lumen-to-total diameter ratio compared to the control group.

The structural changes that they found are like those observed in people. The researchers suggest that these changes “may be an indicator of subclinical dysfunction, which could lead to severe disease.”

Macroscopic image of the whole isolated heart from an extremely obese horse. (A) Heart surrounded by pericardial fat. (B) Cross-section of the heart wall with increased amount of pericardial fat infiltrating the heart wall. Photo: Animals Journal

They suggest that the direct effects of obesity on cardiovascular health and function in horses require further exploration.

For more details, see: Influence of Obesity on Histological Tissue Structure of the Cardiovascular System in Horses. 

Related: Feeding to the Horse's Body Condition

Published with the kind permission of Mark Andrews, Equine Science Update.

Main Photo: Shutterstock/Vprotastchik