Obesity or regional adiposity is one of the components of EMS. Regional adiposity is an accumulation of fat in certain areas, such as around the nuchal ligament in the neck (cresty neck), development of fat pads close to the tailhead, supra-orbitally (just above the eye) or fat accumulation behind the shoulder or in the prepuce (sheath) or mammary gland region. Obesity is common; however some horses have a leaner overall body condition with accumulation of fat in only certain areas.
Fat pads near the tailhead
"Cresty" neck
Location of nuchal ligament identified by marker.
The mechanisms underlying obesity and regional adiposity in EMS are unknown but chronic overfeeding along with insufficient exercise appears to be a contributing factor. It has been suggested that horses and ponies with EMS are evolutionary adapted to survive in harsh winter conditions and do well on sparse, poor quality grasses. This results in a genetic pre-disposition to obesity and insulin resistance (IR) under management conditions where feed is plentiful year round.
*This project was supported by Agriculture and Food Research Initiative competitive grant no. 2009-55205-05254 from the USDA National Institute of Food and Agriculture Animal Genome Program.