The importance of low-intensity exercise for overweight horses on a diet has been shown in fresh research.
The University of Melbourne study involved 24 horses and ponies, all of whom were assessed as overweight, with body condition scores of 7 or greater on a nine-point scale.
All were placed on a diet for 12 weeks, comprising a ration of grass hay given at 1.25% of their body weight on a dry matter basis. All the horses also received a single daily meal containing soybean meal, lucerne chaff, and a vitamin/mineral powder to ensure they received enough protein.
This total ration was estimated to provide 82.5% of their daily energy requirements.
Half of the horses on the diet received low-intensity exercise five days a week on an automated horse walker. Each session comprised five minutes of walking, 15 minutes of brisk trotting, and a further five minutes of walking.
Before and after being placed on the diet, the horses and ponies were weighed, their total body-fat mass was determined, their insulin sensitivity was measured using a glucose tolerance test, and tests were undertaken to measure inflammatory biomarkers as well as adipokines, which are cytokines released by fat.
Nicholas Bamford and his colleagues, writing in the Journal of Veterinary Internal Medicine, reported that decreases in body condition score, body weight, and total body-fat mass were similar between the groups.
After weight loss, both groups had decreased basal insulin and leptin concentrations, and increased concentrations of adiponectin, a protein hormone involved in regulating glucose levels and fatty acid breakdown.
However, when compared to the diet-only group, the animals who had been exercised had significantly improved insulin sensitivity and decreased concentrations of serum amyloid A, which is a protein secreted during the acute phase of inflammation.
“Regular low‐intensity exercise provided additional health benefits compared with dietary restriction alone in this population of obese equids,” the researchers said.
They said the central finding of their study was the greater improvement in insulin sensitivity seen in the exercise group.
“Previous studies have yielded conflicting results regarding the effect of exercise on glucose and insulin dynamics in equids,” they said.
“Low‐intensity exercise without dietary modification appears insufficient to improve insulin sensitivity despite decreases in total body-fat mass.
“The reason for a lack of improvement in insulin sensitivity for the diet group is unclear.
“This finding does not agree with several previous studies that achieved weight loss and improvements in insulin sensitivity or glucose tolerance by dietary restriction without prescriptive exercise,” they noted.
Direct comparisons among studies can be difficult because of the different approaches used, they said.
The decrease in serum amyloid A concentrations in the group that received exercise was supportive of a beneficial effect of exercise in decreasing this biomarker of systemic inflammation, they said, noting that levels were unchanged in the diet-only group.
“Further evaluation of the weight-loss program described here is warranted to determine whether our findings are broadly applicable.
“The animals enrolled had been obese for only a short period of time after a prior study of diet‐induced weight gain, and exhibited a range of starting insulin sensitivity values.
“Whether the weight-loss protocol described would have yielded different results using animals with chronic obesity or more severe insulin dysregulation is not known.”
They continued: “Although animals in our study were not selected with the prerequisite of severe insulin dysregulation, our findings were consistent across several breeds and a wide range of insulin sensitivities, supporting recommendations that exercise should be included, whenever possible, as part of a holistic management program for animals with obesity or equine metabolic syndrome.”
The full study team comprised Nicholas Bamford, Samantha Potter, Courtnay Baskerville and Simon Bailey, all with the University of Melbourne; and Patricia Harris, with the Equine Studies Group within the Waltham Centre for Pet Nutrition in Britain.
Influence of dietary restriction and low‐intensity exercise on weight loss and insulin sensitivity in obese equids
Nicholas J. Bamford, Samantha J. Potter, Courtnay L. Baskerville, Patricia A. Harris, Simon R. Bailey