We often get asked what is warmer for a horse as an under rug wool or Doona. So just to clarify things
1. Natural fibre with the best breathability. Wool can absorb its own weight in water (either sweat or water) before it actually feels wet. Holds warmth but not moisture against your horse’s skin
2. Doona, often made with a synthetic outer (nylon or polyester) so loss of breathability and build-up of static, so always choose a doona with a cotton outer. Doona’s get their warmth from the pocket of air that it held within the fibres of the fill, the higher the fill grams, the greater the area to hold this air and so the warmer the rug……UNTIL you put something over the top with any sort of weight, ie canvas or synthetic top rug. This additional weight will flatten the fill of the doona and therefore decrease the warming ability of the rug, the more rugs you put on, the worse it gets.
So, Wool will win as a warmer under rug with better breathability every time. Doona rugs are excellent in stables etc. where nothing is placed over them.