does anyone create their own feed?
Yes, sort of. My horses' main diet is grazing. I feed literally a handful daily of a pelleted supplement(because it's palatable & my horse is fussy) & add other supps to it, so they get what they need. I don't know if you'd class them as 'household products' but I add liquid seaweed emulsion for iodine & add magnesium chloride to their premixed 'ration balancer' powdered supp to 'top dress' that handful of pellets. They have a rock of salt near their trough too, to lick if/when needed.
I use to mix a 14% sweet feed with oats and something else, I can't remember. Prior to making my own, I was using strategy. My horses are just for pleasure, they are not worked hard, so the strategy was a bit over kill and very expensive. I had also heard of a lot of horses colicing on it, so I stopped using it.
Afraid sweetfeed is not a healthy choice - junk food for horses generally. Oats are a good choice IME *IF* a horse needs grain. But often there are also healthier alternatives if your horse needs more energy/phosphorus. It also depends on how many feeds a horse gets daily as to whether I'd consider grain or other high sugar/starch or hard to digest feeds. Though it sounds like your horses aren't likely to need any 'high octane' ingreds anyway like that if they're easy keepers.
Strategy is a sweetfeed 'product'(most ingredients 'products', not actual straights... Purina also don't have fixed ingredients or list them on their site, because they use different ingreds according to what's available & cost) that is meant more as a 'ration balancer' than feed - so you shouldn't have to feed much, so it may be more expensive per bag but may still be economical. But being relatively low-grade as far as they go, for a horse to get adequate levels of those supps, you do have to feed a relatively large amount compared to, say, Triple Crown. There are likely to be extra supps needed too (especially given high starch/sugar, I'd be giving extra Mg for eg.).
I have found, after analysis, that you do (often) tend to get what you pay for & choosing a cheaper product may be doing your horse no favours, so you're effectively wasting your money. BUT I have also learned, after analysis of many feeds & supps NOT TO TRUST blindly in the lables & company spiel about a product. I personally use a service called feedxl.com which is an invaluable program, to take the guesswork... & headaches out of working out specific horse's diets & nutrition.
My pony is an EASY keeper, my Arab is average and I have 4 miniatures. I have the miniatures on the new purina miniature/pony feed and the baby on equine junior/mare & foal mix. He gets purina 12:12 as well.
Are the mini's hard keepers?? If not I'm curious why you're feeding them high fat feed? I'd steer well away from any high fat/energy/starch rich prods such as that. If they are hard keepers, I'd actually want to get at the root of the problem first, but would still be inclined to avoid the Purina.
Looking for economical but nutritionally complete.
Something comes to mind about cakes & eating them!
As I said, you do tend to get what you pay for, so IMO if you want good products you'll generally pay a fair bit more, but that's not to say they're necessarily uneconomical either - for eg. I used to feed a KER pelleted 'ration balancer' that essentially was perfect for my guys with nothing extra. It was (sit down!) $170/20kg bag
, but I literally had to feed a single handful daily to the big guys(less for the ponies & after diet analysis, worked out they needed about 2/3 what the package recommended). So it was quite economical despite the outlay.... when I was feeding lots of horses - not worth it for the 2 I have now.
Oh & re diet analysis, so you can buy the prods that are genuinely best for your horse's situation, know how much to feed & therefore not be guessing & throwing supps at them willy nilly, I vote FeedXL Horse Nutrition: The D.I.Y. Equine diet planner
as great value from an economic perspective too. Know I sound like I'm on their payroll, but IME for the minimal signup fee, this service has paid for itself a number of times over, in savings on amounts(of course the feed co's recommend more than needed), good supps that actually have what's needed, don't just say that on the lable, and peace of mind that my horses are getting what they should.... oh & the qualified nutritionist on call on the forum for info, research & to ask specific questions of shouldn't be undervalued either!
So... after all that, I'd start with the basics of grass/hay(pref. Low NSC, especially for the easykeepers) & add appropriate supplements to provide good nutritional balance. Then if they need more, ingredients such as beet pulp, rice bran, etc are high energy but very low sugar/starch.