Weight gain and obesity in horses should be avoided to prevent insulin resistance, increased insulin and leptin blood levels, and laminitis, and to maintain a healthy metabolic state.
To date, "it is unknown whether obesity is the primary cause of or contributes to metabolic abnormalities or whether these abnormalities are inherent characteristics of the animal," wrote a group of researchers from the Virginia-Maryland Regional College of Veterinary Medicine. The research team, which included authorities in the fields of equine nutrition and metabolic disorders, hypothesized that diet-induced weight gain in horses would decrease insulin sensitivity and increase blood levels of various hormones and fatty acids.
To test this hypothesis, they fed 13 Arabian or Arabian-cross geldings, ranging in age from 8 to 20 years, 200% of their maintenance energy requirements for 16 weeks. Horses gained an average of 86 kg and body condition scores increased from 6 to 8 (out of 9).
Key alterations in blood parameters included:
- A threefold increase in both leptin and insulin blood concentrations;
- A 71% decrease in insulin sensitivity;
- A 40% increase in insulin response to glucose; and,
- No change in blood glucose or circulating fatty acids.
According to the authors, weight-gain had "profound" effects on plasma hormone concentrations and insulin sensitivity, prompting them to suggest that preventing weight gain and obesity could minimize these changes and ultimately reduce the risk for laminitis.
The study, "Effects of diet-induced weight gain on insulin sensitivity and plasma hormone and lipid concentrations in horses," was published in the October 2009 edition of the American Journal of Veterinary Research. The abstract is available on PubMed.
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