Fats and oils have more than twice the energy of carbohydrates (been doing the Coursera Equine Nutrition course - absolutely brilliant, can well recommend!) and are tolerated well by the horse. Corn oil is the most palatable. You can use the oil to increase the energy content of the feed, up to 2% of the ration (up to 2 cups (cookery type measures) a day depending on bodyweight). Other benefits of feeding oil are improved energetic efficiency, improved athletic performance, enhanced body condition, less excitable behaviour and improved health, according to my course. Why don't you contact Coursera.org to see if you can join the course? It's free and online, and the lectures are on video - I've learned a lot from it. It's a 5 week course and we're on week 3 now, so you could easily catch up!
