Assessing the seasonal prevalence and risk factors for nuchal crest adiposity in domestic horses and ponies using the Cresty Neck Score.

Background: Nuchal crest adiposity in horses and ponies has been associated with an enhanced risk of metabolic health problems. However, there is no current information on the prevalence of, and risk factors specific to, nuchal crest adiposity in horses and ponies. In addition, the cresty neck score has not previously been utilised across different seasons within a UK leisure population, it is not know whether nuchal crest adiposity shows the same seasonal trends as general obesity.

Results: A Cresty Neck Score (CNS, 0-5) was given to 96 horses with access to pasture (>6 h per day) at the end of winter and at the end of summer in order to obtain two prevalence estimates. Risk factors were assessed using the single outcome cresty neck/no cresty neck in either season (binary), from owner questionnaires and analysed using a mixed effects logistic regression model (outcome variable CNS <3 or CNS ≥3/5). Agreement between winter and summer scores was assessed using weighted Kappa methods. Winter CNS values were significantly higher than summer CNS values (p = 0.002) indicating a systematic bias. The prevalence of a CNS ≥ 3/5 was 45.83% at the end of winter, falling to 33.33% at the end of summer and was higher in ponies (<14.2 hh) than horses (≥14.2 hh) in both seasons. This may reflect a real winter increase in regional fat deposition, or an increased difficulty in obtaining an accurate estimate of regional adiposity in winter months. Breed was the strongest risk factor for CNS ≥3/5 in both seasons, with native UK breeds appearing to be most at risk (p < 0.001). In a separate, small validation study, the CNS showed good inter-observer reliability.

Conclusions: The prevalence of a CNS ≥3/5 was higher at the end of winter than at the end of summer, which was the opposite pattern seasonal variation to that observed for general obesity. Further studies are required to investigate the potential influence of time of year upon CNS interpretation and studies utilising the CNS should consider potential seasonal variability in nuchal crest adiposity.