Feeding a horse can be a super easy task if need need for concentrates if minimal and you’re lucky enough to have unlimited, lovely pasture growing in high nutrient soil or have access to hay cut from such fields, as well as a horse not prone to metabolic issues or founder and has maintained teeth that allow him to chew well.
If the above perfect set up doesn’t apply to you, you may have a learning curve.
A lot of people feed in the way their grandparents fed, and I like to remind folks, “When you know better, you do better,” and the fact is, in hindsight, there are a lot of things that works okay 100 years ago that we know we’ve improved on (not to say all things, but certainly some things). For instance, how often do we see rickets or scurvy in developed countries these days? Or what about dysentery?
The average horse will need 2-3% of his body weight a day in hay, pasture and feed. Most of this needs to be in forage (hay, pasture, cubes, pelleted hay).
First, nature dictates that forage should be foundation of all equine diets. Unfortunately, forage quality varies a lot. So if your hay or pasture isn't ideal, you will need to fill the gaps with a feed. Also, if your horse has dental issues or has advanced age, your horse will likely need senior feed, chopped hay or soaked cubes. Since a horse being used as an athlete isn't performing a natural function, a man made concentrate is often needed, and the amount of that will vary horse to horse, job to job.
Second, quality matters. It matters in hay, pasture and feeds. Fact is, you don't save money by buying the cheapest feed you can find. A horse has a small stomach compared to his size, and considering forage is the bulk of what you need to feed, there isn't a lot of space for cheap grain feed in bulk. Your horse pays the price when you have to feed too much to meet their needs by not being able to digest all the poor quality mix or by suffering from colic. You feed less of a quality ration, and your horse can actually use all of what he is getting. Don't forget this applies to hay, as well. Just because it is hay doesn't mean it is suitable hay. Just because it looks okay doesn't mean it meets the needs of the horse. You can usually have your soil or hay tested through your local extension agent if you have concerns.
Third, mixing together concoctions of oats, corn, oil and other feeds isn't usually needed once you find the right concentrate. Invest one good feed and good forage. HOP likes Buckeye Safe and Easy Performance, but this isn't something everyone can find, and as we said, no single feed works for all horses (lactating mares, growing foals and seniors and extreme athletes, for example). For most horses, I really like this particular feed "tag," as it has all the things I look for in a ration: high fats, low starch, alfalfa meal, beet pulp and probiotics. . .safe for even metabolic horses (13% NSC -sugar and starch), nutritionally dense ingredients without molasses or corn, things find cause more issues than anything else. Do not assume because a feed is a pellet it is a quality feed. Look at the tag. Often they are still just a sweet feed with what I call "floor sweepings" on the tag.
Usually, if you have the right forage, your horse has dental issues addressed and receives a good grain ration, nutritional supplements will not be needed beyond access to a good quality loose mineral and salt.
If you see a horse not keeping a good condition, look first to adding more forage, better forage and then to changing the feed. Add oils and powders and extras only if all else fails, or you may simply be masking a serious nutritional deficit.