Summer-long study finds lots of fat horses

Over the course of 60 days in summer 2006, the Virginia Tech equine research team studied 300 horses from 114 farms, chosen randomly from more than 1,000 animals in the Virginia-Maryland Regional College of Veterinary Medicine’s field service horse population.

The horses were studied between 6 a.m. and noon, prior to any grain or concentrate consumption, which can alter glucose and insulin levels.

Each horse was checked for signs of laminitis and blood was drawn to assess glucose and insulin levels as well as other hormones, cytokines, and oxidative biomarkers. Each horse’s owner completed a questionnaire to gather background information on breed, gender, health history, feed, and exercise. The horses ranged in age from 4 to 20 years old. Ponies, miniatures, donkeys, draft breeds, and their crosses were excluded from the study, as were pregnant and lactating mares and horses undergoing treatment for medical problems.

Two independent body-conditioning scores (BCS), which assess the amount of fat on the horses, were assigned to each animal. The scores range from 1 to 9 and a score of 8 or 9 signifies obesity. Morphometric measurements were also taken to allow the research team to calculate body weight and body mass index (BMI). These measurements include girth circumference, neck circumference, body length, and height.

Even before laboratory testing and data analysis were complete, the research team made some alarming discoveries:

• 51 percent of the horses in the study were found to have a BCS greater than 6.

• 32 percent of the horses in the study were found to have a BCS of 6 to 7, and 10 percent of these were insulin resistant.

• 19 percent of the horses were found to have a BCS of 8 to 9, and 32 percent of these were insulin resistant.

These findings support the researchers’ hypothesis that the rate of overweight and obese horses is greater than the 5 percent figure reported in the 1998 National Animal Health Monitoring System study. The insulin resistance in obese horses was expected, consistent with the findings of a large study conducted by the Middleburg Agricultural Research and Extension Center of horses in Northern Virginia.

Photo by Kim Peterson.

Photo by John McCormick.