Horses that won't lose weight may need stricter diet

Some obese horses and ponies may need to have their diets restricted more severely than previously thought in order to help them lose weight according to new research.

The studies were conducted  at the University of Liverpool. They showed that although some obese animals will lose weight, in an appropriate way,  on a diet restricted to 1.25% of body weight (on a dry matter basis), others may need their diet restricted to as little as 1% of body weight in order to shift those surplus pounds. Such animals have been described as being ‘weight loss resistant’ in a  report  presented at the WALTHAM International Symposium in September.

The work has been published as an abstract in the proceedings of the 5th European Workshop on Equine Nutrition and will be written up and published as a full paper in due course. It was funded by the government-initiated Knowledge Transfer Partnership and the WALTHAM Equine Studies Group.

The study, which was conducted over 16 weeks, involved 12 overweight/obese horses and ponies of mixed ages and breeds, with body condition scores of between 7 and 9 (1 being emaciated and 9 being obese). They were individually housed on wood-shavings and provided with a balanced fibre-based diet at 1.25% of body weight. They were allowed daily access to a bare paddock but no structured exercise was given. Eight of the horses achieved a slow, gradual but consistent loss of body weight over the study period, but weight loss was much slower in the remaining four.

These four horses, deemed to be weight loss resistant, were monitored for a further four weeks during which their diet was reduced to 1% of body weight daily. This significantly increased their rate of weekly weight loss, to a level comparable to the weight loss seen in the other eight horses in the original study. It is thought that genetics may account for such individual differences in sensitivity to weight loss. In all cases the horses remained healthy and no stereotypic behaviours were seen.

Dr Caroline Argo explained: “It is important to understand that the appetite of obese ponies will drop to around 2% of body weight (dry matter) yet their body weight will be maintained or they may even continue to gain in weight. If weight loss is to be stimulated, food intake must be limited quite severely.”

Clare Barfoot BSc (Hons) RNutr, the research and development manager for SPILLERS® and a member of the research team added: “Controlled but balanced nutrition, under careful veterinary guidance, is essential to promote weight loss in overweight or obese horses and ponies, especially when exercise is not an option but we have had little evidence-based advice on how far the diet can be restricted safely to help shed weight in stubborn cases until now.”

“In practice where exercise can be used to increase energy expenditure, such severe restriction may not be required; in this situation access to grazing must be reduced, exercise increased and a low calorie high fibre forage fed in a monitored way alongside an appropriately formulated forage balancer.”

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