The term heating is often used to describe feeds that can make horses or ponies excitable. For instance feeds high in cereals are often attributed to having a heating effect. Such excitability could be due in part to an increase in dietary energy supply, a reduction in fibre supply, or a simple rush of rapidly available carbohydrate into the bloodstream. In all cases these effects are usually observed at feed intakes of several kilos per day.
Simplyirrestistible is typically fed at 50-100g per day, so at a much lower rate than feeds. The fruit and vegetable components do add some sugar to the diet but this is at such a very low level that is unlikely to have a heating effect.