I am having great luck with this diet with my "hot" horses that are worked hard.
I like this type of set-up because you can change the calorie intake, but still keep the nutritional aspect stable. The StaySTRONG pellets have 100% of the vit/min needs of the horse concentrated into a tasty pellet. All of my horses love them.
The Alfalfa pellets provide extra protein, calories, amino acids (important for muscle development), and good nutritional value as well. If you notice your horse becoming "hot" on the Alfalfa (only a small percentage of horses have a feed allergy to Alfalfa), then you can switch to Timothy pellets or beet pulp. I prefer Alfalfa though as it has better nutrition and protein than the alternatives.
If you don't have an ADM dealer near you, you can order their products
online.
If you want an all-in-one feed that you don't have to mix, I'd look in to the following products. Check the web sites to see if you have a dealer in your area. I would recommend staying AWAY from Purina feeds. They do not have a fixed formula and they have more recalls and violations than any other feed dealer...
http://www.admani.com/AllianceEquine...UltraFiber.htm Triple Crown Lite Formula | www.triplecrownfeed.com Triple Crown Low Starch Formula | www.triplecrownfeed.com Premium - Lo-Carb Formula Pleasure/Leisure - BUCKEYE® Nutrition
I know some of the above say "lite" or "easy keeper", but you want a feed that is low in starch and sugar, with no corn and very little to no molasses. High sugar/starch feeds can make hard keepers even harder to keep weight on, and it can make your horse more hyper.