Obesity, despite its significant health implications, may not be a reliable indicator of poor metabolic health and associated laminitis risk, a new study has found. The research, Relationships between total adiponectin concentrations and obesity in native-breed ponies in England,was conducted in association with the Spillers brand, via the Waltham Equine Studies Group.

It supports earlier research, including Predictors of laminitis development in a cohort of non-laminitic ponies, which won the Peter Rossdale Equine Veterinary Journal (EVJ) Open Award at BEVA Congress this year and showed that severe insulin dysregulation can also be found in lean ponies. Collectively, the work confirms that lean ponies can also be at higher risk of metabolic disease and associated laminitis.

“This study together with our previous work has provided us with the important take-home message that you cannot presume that just because your horse or pony is lean or of ideal bodyweight it is automatically at reduced risk,” said Sarah Nelson, Product Manager at Mars Horsecare, home of the Spillers brand. “They may still have insulin dysregulation and/or low adiponectin concentrations and so be at an increased risk of laminitis. If you are concerned it is important to speak to your vet and have your horse or pony tested. It’s also advisable to contact your nutrition advisor to ensure you provide the best diet to manage your individual.”

Hormone levels

Adiponectin, a hormone coming from fat deposits, which can be measured in the blood, is thought to improve sensitivity to insulin. Previous work by the Spillers and its associates has shown that low blood concentrations of adiponectin reflect an increased risk of laminitis. Decreased concentrations of the hormone have been found in association with obesity, but this new work has shown that decreased levels of adiponectin can also be found quite commonly in lean, native-breed ponies.

In the new research, total adiponectin [TA] was compared between 734 ponies of different body condition score (BCS) classification (ideal-weight, overweight, and obese), breed, and body shape, with and without a history of laminitis. Age, breed, sex, weight, height, and weight:height ratios were recorded. BCS was assessed on a scale of 1 to 9 and was determined by a single assessor. Blood samples were collected from non-grain fed but not forage fasted animals to determine basal insulin and total adiponectin.

The results showed that total adiponectin was weakly positively correlated with BCS, height, weight, and weight:height ratio. There were significant differences in adiponectin concentrations in ponies with different BCS group classification, body shape, and breed. More of the obese (54.6%) than ideal-weight ponies had normal total adiponectin concentrations and a greater percentage of ideal-weight (38.6%) than obese ponies showed low adiponectin concentrations.

Body shape factors

Another valuable initial observation from the study was the significant difference in total adiponectin concentrations between ponies of different body shapes. The middle-heavy body shape was associated with higher total adiponectin concentrations than both other shapes. This is similar to research in humans that has shown increased thigh fat or a ‘pear’ shape may be protective against insulin resistance compared to increased visceral fat or ‘apple’ shape. However, more work is needed to investigate these initial findings.

“Understanding the modifiable factors that are associated with total adiponectin concentrations may help to identify targets for preventive or therapeutic intervention, with the goal of reducing the development of endocrinopathic laminitis in at-risk horses and ponies,” said Marine Barnabé, who led the study.

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