I just posted this on another thread, but it applies to this one too!
If your horse is in good health, has good feet, his coat is shiney, his mane/tails grows well, and his attitude is the way you want it, then there's no real reason to switch his feed. However, many people (myself included) have switched their horses to a more "natural" diet and have seen some great results. Horses are designed to eat and digest high quantities of low protein, low sugar/starch, low fat food. Sweet feed and most commercial horse feeds do NOT fall in to that category. Most are very high in sugar and/or starch and many are high in fat, or have low-quality fat.
Good health starts with hay! Make sure you're buying the best quality hay you can find for your horse. A grass type hay is best, or Timothy hay. I feeda local mix that is about 70% Bermuda with local grasses and clover mixed in. My horses do very well on it.
I prefer to feed my own "feed", rather than something storebought. Most of of the feeds on the market today are full of high starch, high sugar fillers and byproducts, without a lot of quality nutrition. It's like feeding your kids or yourself cereal and frozen dinners. They're okay, but not as healthy as homemade and fresh foods
With the grass hay, I feed Alfalfa pellets (1/2 to 1 scoop, 2-3.5 lbs), a vit/min mix, and flax meal. I have horsetech.com custom blend me a vitamind mix along with high levels of amino acids, 10 mg of biotin per serving, high Vit E, and some pro-biotics in their flax base. Each serving has 2 oz of flax (about 1/2 cup). All ingrediants are humane-food-grade and very fresh! It costs me $0.87 per-day per-horse to feed (about 1 measuring cup a day).
I use apple cider vinegar to mix the powdered supplement in with the alfalfa pellets. However, you can use water or oil if your horse needs extra fat.
Since switching to this "all natural" type diet my horses's coats have improved, their feet come in strong (vet and farrier RAVE about their feet!!), their attitudes have improved (calmer, more willing, better work ethic, etc.), and my mare's heats aren't so "mare-y" lol. We have very little rain rot (and it's been a BAD year here in Arkansas for it) and almost no thrush anymore. I will never go back to commercial horse feed again...
If you want an off-the-shelf vit/min, I can recommend a few. All worked well for me, I just wanted to have one bucket, instead of the flax & vitamins separate. Plus I wanted more Amino Acids (only the first one has the high levels in it that I like). Equine Products Inc - Top quality equine supplements
- the 1oz serving Uckele Equine Nutrition Platinum Performance Equine Wellness
- also has "joint goodies" in it SmartVite Maintenance Grass Pellets from SmartPak Equine Grand Vite from SmartPak Equine Select II from SmartPak Equine Daily Omegas Plus - Multi-Purpose Supplements from SmartPak Equine LinPro from SmartPak Equine
For the flax I recommend Horsetech.com's NutraFlax or Omega Horseshine.