Obesity is a growing problem and whilst it is relatively easy to monitor your horse’s body condition score in most cases, the amount of internal fat he is storing remains a mystery. New research published in collaboration with SPILLERS developed and tested a novel method for scoring internal fat storage sites or ‘depots’ in horses and examined if internal fat correlates to body condition score.
Is being fat on the inside a problem?
Fat tissue is now recognised as being the body’s largest endocrine (hormonal) organ and secretes numerous chemical messages which communicate with other organs in the body. However little is known about the specific functional role of different regional fat depots in horses.
In people, CT imaging has been used to identify regional fat storage as a risk factor for cardiovascular disease. Although obesity has been identified as a risk factor for several equine clinical conditions including laminitis, the mechanism for this is still not clear. Due to their size, assessment of regional adiposity in horses and ponies by MRI or CT is not possible. Although body condition scoring is commonly used to assess ‘body fatness’, little is known about the link between body condition score (BCS) and internal fat depots.
- Four internal fat depots were photographed in 38 horses and ponies at post mortem*. Photographs from each depot were ranked in order of least to most visual fat. These photographs were then used to develop a 5 point scoring system (EQUIFAT) which included representative photographs and score descriptors for each fat depot.
- To test reliability of the EQUIFAT system, 33 photographs were shown to 24 observers in a random slideshow. Observers were asked to grade each photograph using the EQUIFAT system. To test repeatability, 8 observers (4 from each group) were asked to score the photographs a second time no less than 2 weeks later.
- To determine whether there is a link between BCS and internal fat depots, a further 207 horses were body condition scored. The same horses were then scored using EQUIFAT immediately after euthanasia.
*all horses were euthanased for reasons unrelated to this study and not for research purposes.
- Reliability of EQUIFAT was ‘moderate’ or ‘substantial’.
- Repeatability was ‘almost perfect’ or ‘substantial’.
- Of the 3 abdominal fat depots assessed (retroperitoneal, omental and mesenteric), only one was strongly associated with BCS (retroperitoneal). Omental fat was less strongly associated with BCS and there was no association between mesenteric fat and BCS.
- There was also no association between fat around the heart (epicardial) and BCS.
What does this mean?
EQUIFAT was found to be a robust method of scoring internal fat and could be used in future studies to help improve our understanding of the role that internal fat depots plays in the development of conditions such as laminitis, insulin dysregulation and colic. Results of this study also suggest that retroperitoneal fat has an important role in long term energy storage.
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