You're going to have a hard time competing pricewise with oats if you buy them right out of the field. With a big name senior feed, you are paying for a lot of slick ads and extensive research. You should get a price break on anything you buy by the pallet (typically one ton). I'd pursue a locally milled product first. It will save on transportation and all the other nonsense. How many tons of each product are you using? That will give you an idea of how many Mcals you need for the season and when you need it. How much product can you transport at any given time? Oats are going to be the most bulky feed but is it a set weight, volume or a combination of the 2? You might be able to feed a cheaper product (oats) when it's the only thing being fed but when you need to start adding serious calories, than you need to swap them out for a pelleted feed that is less bulky and more calorie dense. I don't think oats by themselves are ideal as the horses are lacking salt, vitamins, minerals and protein (I would add it here to get back on topic). If you are buying bagged oats from a feed store, with enough product purchased at once, you can get them to add these to the oats (pellet form or it will settle on the bottom of the bag) so you are only dealing with one product.