Equine metabolic syndrome: Size of neck crest an important sign, research suggests

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A cresty neck is an enlarged fat deposit along the nuchal ligament, identified by the black bar. This pony was assigned a cresty neck score of 3. Photo: Fitzgerald et al. https://doi.org/10.1371/journal.pone.0220203.g001

Significant fat deposits on the neck crest are a better predictor of insulin dysregulation in ponies than general obesity, the findings of fresh research suggest.

Researchers from Queensland, Australia, reporting in the open-access journal PLOS ONE, have described an experiment involving 26 ponies of mixed breeds, comprising 14 males and 12 females.

They wanted to learn more about links between body condition score, cresty neck score and insulin dysregulation.

The cresty neck scoring system was first described in the Veterinary Journal in 2009. It is on a scale of 0 to 5 where 0 equals no visual appearance of a crest and 5 equals a crest so large it permanently droops to one side.

The Henneke scoring system is commonly used to assess overall body condition in horses. It ranges from 1 to 9, with 1 being poor and 9 being extremely fat. The ideal range for most horses is from 4 to 6.

Insulin dysregulation is a metabolic problem that falls among a cluster of derangements found in equine metabolic syndrome.

The early identification of insulin dysregulation might enable horse owners to reduce the risk of laminitis, which is identified as a primary weight-related disorder.

However, not all cases of horses and ponies with equine metabolic syndrome are overweight. As such, levels of regional fat deposits may prove to be a stronger identifier of equine metabolic syndrome – and therefore the risk of developing laminitis – than generalised obesity.

Queensland University of Technology researcher Danielle Fitzgerald and her colleagues noted that no studies had compared obese animals with animals displaying regional fat deposits but an otherwise normal body condition.

The ponies used in the study were evaluated by an experienced individual for body condition score and cresty neck score.

Half of the ponies were assessed by a second experienced individual to validate the scoring of the first assessor, but these were not used in any other analyses.

Of the 26 ponies, 10 were grouped as “normal”, five were “obese”, and 11 were classified as having a high cresty neck score.

The body weight, height at the withers, girth circumference and neck circumference were also measured.

After assessment, the animals underwent an oral glucose test, with blood samples collected before and two hours after dosing for analysis.

Responses to the oral glucose test indicated that both normal and insulin-dysregulated ponies were included in the cohort.

Of the entire group, 13 ponies were found to have insulin dysregulation. Of these 13 ponies, two had an ideal body condition, three were obese and eight had a high cresty neck score.

“Thus, a cresty neck on an otherwise normal body conditioned pony appears to be a strong predictor of insulin dysregulation,” they reported.

“Further, of the 13 ponies without insulin dysregulation eight were in ideal body condition, two were obese and three had a high cresty neck score.”

Their analysis found that the ponies with a cresty neck score of three or higher had five times greater odds of being insulin-dysregulated – a finding which they said may be relevant to the diagnosis of equine metabolic syndrome.

Those with higher cresty neck scores had a greater insulin response to the oral glucose test than those assessed as being in the normal or fleshy group.

Cresty neck score, they concluded, was more predictive of insulin dysregulation than body condition score.

“This finding agrees with current thinking that measures of regional adiposity have strong associations with insulin dysregulation, but the role of obesity per se in identifying equine metabolic syndrome is less important.”

They noted that the cresty neck score limit of 3 of higher suggested in the current study as being a threshold for increased risk of insulin dysregulation was supported in another study, in which it was found that ponies with a score of three or greater had an increased laminitis risk.

Although the findings in the Australian research suggest that fat on the neck crest may be of greater interest in relation to insulin dysregulation than generalised obesity, obese ponies may still be insulin-dysregulated, the authors stressed.

In the study, two obese ponies were found to be insulin-dysregulated, while two were not. Therefore, a greater sample size of obese ponies with a range of cresty neck scores would be required to learn more about the role of generalised obesity in equine metabolic syndrome.

“While generalised obesity should always be managed,” they said, “it was not a particularly strong predictor of insulin dysregulation in this population.”

The study team comprised Fitzgerald, Martin Sillence and Melody de Laat, all with the Queensland University of Technology; and Stephen Anderson, with the University of Queensland

Fitzgerald DM, Anderson ST, Sillence MN, de Laat MA (2019) The cresty neck score is an independent predictor of insulin dysregulation in ponies. PLoS ONE 14(7): e0220203. https://doi.org/10.1371/journal.pone.0220203

The study, published under a Creative Commons License, can be read here

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