Seasonal variation of ‘cresty neck’ in horses

guest blog by Sarah Giles

‘Cresty neck’ in horses is an abnormally large amount of nuchal neck crest fat, fat along the top of the neck. It can be seen as akin to abdominal adiposity in humans, this region specific adiposity can cause a range of metabolic disorders in both species. In horses, this metabolic changes have been associated with laminitis, a debilitating condition affecting the hoof which can cause debilitating and sometimes fatal lameness. Our paper, recently published in BMC Veterinary Research explores seasonal differences in neck crest adiposity in groups of domestic horses and ponies.

http://www.biomedcentral.com/1746-6148/11/13/figure/F1

It is not yet known why neck crest fat specifically is more strongly associated with metabolic abnormalities, but our study has presented some unusual results which might warrant investigation. Our previous study highlighted the seasonal variation in body condition and obesity present in outdoor living domestic horses and ponies (see previous blog post). This second study was conducted on the same population of animals, yet crucially, showed the exact opposite pattern of seasonal variation!

Unusually, the prevalence of ‘cresty neck’ was highest at the end of winter. This is surprising, firstly because, quite obviously, there is less grass available at the end of winter for outdoor living animals. Then secondly, because it had previously been speculated, arguably quite rightly, that the role of fat stores is to aid survival during winter months when food is scarce. Why then, does cresty neck seem to be more prominent in outdoor living horses at the end of winter?

Supplementary feeding was recorded, and this did not explain the results observed. The paper therefore discusses several other possible explanations. Broadly this includes a physiological explanation, where cresty neck fat is physiologically different to fat stored elsewhere and due to a potentially different physiological role. Or alternatively, we consider whether these results are simply an anomaly with the cresty neck score itself. The score may be difficult to replicate under different conditions, or there may be something about winter conditions, such as a fluffier winter coat on the animals, or less fat elsewhere, which makes the neck crest seem more prominent.

Whatever the explanation, these results were certainly unexpected and are therefore very interesting! This paper was fun to write as it was explorative and allowed for a balanced, speculative and thought provoking discussion. Disproving a hypothesis in this case, was much more interesting than proving one.

Most of all this paper is a reminder that we really don’t know all of the answers with regards to obesity and metabolic pathways in horses. We truly hope that this paper inspires further research into these potentially unusual physiological mechanisms

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