Do Icelandics really require less food or is it hypometabolism

Icelandic horses on glacier from Cornell
Collection circa 1900

When you reduce the food to 30% of what they are normally fed, thrifty breeds like Shetlands (and I would imagine Icelandics) go into a state of hypometabolism in which the body metabolism slows down and other physiological changes occur so the pony can maintain its weight.    This is a primitive adaptation to enable wild animals to adapt and to survive seasonal variation in the amount of food available.  Most domestic horse breeds have lost this ability.  

So when you severely reduce the amount of food for Shetlands (and probably Icelandics since they are so closely related), you may be inducing hypometabolism, not putting them on a diet.  The study does not mention if the reduced core temperature, lowered activity level, and reduced heart rate has any impact on the comfort level or  long term heath of the horse. 



http://www.horsetalk.co.nz/2012/06/29/shetlands-retain-ancient-temperature-ability-control/#axzz459c2LgZK.