Iām not sure about the advice to stay away from Ultium feed (for example, Purina Ultium). My horse (a Westfalen) used be be a very hard keeper as a youngster. I consulted the Purina nutritionist (Ph.D., he comes to town for things), the Cargill PhD nutritionist, plus my vet and separately her husband, and another vet. Basically all advice was similar - increase fat, watch the sugar, and the recās came down to Purina Ultium and Nutrena Pro Force Fiber or Fuel. The Coolstance did nothing for my horse. I picked Nutrena PF Fuel and my horse eventually gained wait very nicely. Another horse in training was on Ultium and his owner swore by it. Feed by the label and weigh your feed.
The company nutritionists are very helpful and do not push their product (in my experience). You can easily call them.
Oil is a fine additive, but not too much. If it makes the grain too oily, oil will get on everything your horse puts his nose on in the stall (ask me how I know!!). Beet pulp is great for adding calories. It is the basis of Nutrena Pro Force Fiber.
Ration balancer is for horses NOT getting mush/any grain and is mainly a vitamin/mineral supplement. NOT what you need. My horse has now gained weight (over years) to the point that he gets just a little grain but mostly balancer.
Thereās nothing wrong with alfalfa hay supplementing regular hay. It adds calories. BTW, when I lived in NM, some horses (mine-another horse) on sand were given straight alfalfa and did just fine. Currently, I supplement alfalfa hay in the winter when it is cold, he LOVES it but would be obese if I wasnāt careful about his diet now. BTW, he lives outside on almost an acre of excellent, very well-maintained pasture which is supplemented with local hay in the winter.
Good luck!