Equine Obesity Research: Breeds Respond Differently to Changes in Diet and Exercise

Does it take a university research study to prove that horses need exercise and diets?

If spring weight gain isn't on horse owners' minds right now, it will be soon. Many horses now come through the winter in robust condition, thanks to modern feeds, warm barns, snuggly blankets and owners who don't ride often in winter...if ever.


Once horses are turned out on spring grass, those owners might find themselves shopping for a bigger girth before they can ride. Sadly, they may also be calling the vet because yet another obese horse has laminitis.

Equine obesity isn't just a tack problem, it's a health problem. Links between overweight horses and laminitis are clearly documented. Spring grass intake lights a match to a smoldering insulin-resistance problem in many overweight horses and ponies, and laminitis--sometimes in a very subtle low-grade, chronic form--is the result.

Left unresolved, insulin resistance can persistently affect a horse's metabolism and flare-ups of painful chronic laminitis, or more severe attacks, may become a problem.

Once a horse has shown signs of laminitis, exercise may be difficult, or impossible. So, laminitis experts advise, when the blankets come off, the tack should go on, even if it is just a cavesson to lunge a horse, or a leadline to pony from the back of another horse. "Get them moving!" is the best advice for horses in the spring.

Why do so many horses--whether they have insulin resistance or not--gain weight, while others do not? And just as importantly, why is so hard to get certain horses to lose weight?

Research in Australia has looked at whether the breed of a horse affects its resistance to weight loss efforts.

As it turns out, some breeds are much less willing than others to part with their surplus pounds. The new study has confirmed that Standardbred horses lose weight much more readily than Andalusians or ponies. The findings will help to improve the effectiveness and safety of weight loss programs in the future.

Denial of grass turnout is necessary for some horses and ponies to stay healthy.

The study, Comparison of weight loss, with or without dietary restriction and exercise, in Standardbreds, Andalusians and mixed breed ponies, was conducted by the University of Melbourne’s Faculty of Veterinary Science in Australia, in collaboration with the WALTHAM® Equine Studies Group. It will be presented at the Equine Science Symposium in Mescalero, New Mexico next month.

In the study, twelve obese animals (four Standardbreds, four ponies and four Andalusians, all with body condition scores of 7-9 out of 9) were initially kept on free-choice hay for 20 weeks and then fed individually on a restricted diet of 1.25% bodyweight of hay for up to 12 weeks.

Two from each breed group were exercised daily on a horse walker. Dietary restriction was stopped when each horse reached a body condition score (BCS) of 5, which occurred between 4-6 weeks in the Standardbred group.

However, even after the full 12 weeks of dietary restriction, the ponies only dropped from a BCS of 7.1 to 5.9 and the Andalusians from 6 to 5.2.

In the study, ponies lost weight at a much slower rate than Standardbreds, even though the diet restrictions and exercise were the same. (Beamish Museum photo)

Clare Barfoot RNutr, the research and development manager at the British feed company Spillers® said: “The ponies and Andalusians retained condition on ad-libitum hay and were relatively resistant to body fat loss even when hay was reduced to 1.25% body weight.

"Daily exercise also didn’t have much impact on these two groups. However, the Standardbreds lost significant amounts of weight and body condition when maintained just on ad-lib hay and subsequently lost weight much more rapidly on the restricted diet.

"Further work is planned to find out whether these breed variations are related to insulin sensitivity or other hormonal differences.”

Advice to humans who want to lose weight is "break a sweat every day" and this study suggests that the same may be true for horses. Exercise may need to be more vigorous than taking a turn on the horse walker...but that's a start.

Did your horse break a sweat today?

To learn more:
Comparison of weight loss, with or without dietary restriction and exercise, in Standardbreds, Andalusians and mixed breed ponies: S.J. Potter, N.J. Bamford, and S.R. Bailey, (Faculty of Veterinary Science, The University of Melbourne, Victoria, Australia), and P.A. Harris, Equine Studies Group, WALTHAM Centre for Pet Nutrition, Leicestershire, UK

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