Obesity: Cause or Consequence of Metabolic Disease?

Obesity: Cause or Consequence of Metabolic Disease?

The team confirmed that horses don’t necessarily have to be obese to have EMS, but that obesity can point to an underlying metabolic condition.

Photo: iStock

We know that obesity and metabolic disease in horses often go hand-in-hand, but does obesity cause metabolic disease or is it the other way around? A group of researchers from the Swedish University of Agricultural Sciences recently set out to determine the answer.

Veterinarians know that high-starch and -sugar diets can decrease insulin sensitivity (IS) and lead to insulin resistance (IR), which is also an indicator of equine metabolic syndrome (EMS). The research team hypothesized that weight gain resulting from a low-starch and -sugar diet would not negatively impact IS, and that unlimited pasture access would further decrease IS and cause hyperinsulinemia (increased blood-insulin concentrations).

The team employed nine sedentary Standardbred mares with moderate IR in their 30-week, five-part study, which included:

  • Period 1: A three-week maintenance period;
  • Period 2: Continual increase of forage low in water-soluble carbohydrates and supplemented with fat “to speed up the weight gain process, without adding more sugar to the diet,” said lead researcher and PhD student Sanna Truelsen Lindåse, DVM;
  • Period 3: A diet consisting of 2.5 times daily maintenance requirement of metabolizable energy;
  • Period 4: Adaptation to small grass paddock for one week; and
  • Period 5: Four weeks of turnout in a 25-acre pasture during the growing season.

The researchers analyzed blood samples throughout the study period. They found that:

  • All horses gained weight throughout the course of the study and by Period 5 were obese;
  • Weight gain induced by low-glycemic diet did not further decrease IS in horses; and
  • Pasture turnout out after weight gain actually increased IS.

Lindåse said the fact that pasture turnout increased IS was an unexpected finding, but could be due to increased exercise, decreased nutrient intake, or even breed.

“The breed we used in this project is less prone to develop EMS and laminitis compared to many others,” she explained. “Results may have been different if a pony breed was used instead.”

The team concluded that “obesity is not the primary requisite for the equine metabolic syndrome phenotype but, rather, a marker of underlying metabolic dysfunction.” Essentially, the team confirmed that horses don’t necessarily have to be obese to have EMS, but that obesity can point to an underlying metabolic condition.

The study, “Effects of diet-induced weight gain and turnout to pasture on insulin sensitivity in moderately insulin-resistant horses,” will appear in an upcoming issue of the American Journal of Veterinary Research

About the Author

Casie Bazay, NBCAAM

Casie Bazay holds a bachelor of science degree in education from Oklahoma State University. She taught middle school for ten years, but now is a nationally certified equine acupressure practitioner and freelance writer. She has owned Quarter Horses nearly her entire life and has participated in a variety of horse events including Western and English pleasure, trail riding, and speed events. She was a competitive barrel racer for many years and hopes to pursue the sport again soon.

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