How do you put weight on a thin horse?

There are posts all over any horse related message board asking this question. The answer is simple. Feed it.

Now, people spend all kinds of money on all kinds of feed, supplements, builders, and boosters. On an otherwise healthy horse, you don't need any of it.

I said, "otherwise healthy." This assumes that:
1. You are not feeding a senior horse with special needs (see previous post)
2. Skinny horse has been dewormed more than once in the past year, i.e., on a schedule approved by your vet, been PowerPac'd, or had a fecal to determine appropriate treatment.
3. Skinny horse has had teeth floated by a professional within the past year, so that you are certain he is able to get the most from his food.
4. Skinny horse has had vaccinations on schedule and, if difficult to put/keep weight on, skinny horse has had bloodwork/CBC to make sure skinny is not a result of underlying infection.
5. Skinny horse is just "skinny" and not a "2" or worse on the BCS chart. A severely malnourished, starved horse will need supportive care including all of the above, and more.

So let's say you pick up Skinny Minny from the sale barn, you can see her ribs and backbone, but she's not emaciated; she's just too thin for you to think about riding. You could dump high calorie feed into her, but why? First of all, a horse's body is designed to GRAZE up to 20 hours per day; your feeding 2 or 3 or 4 meals of sugary grains every day doesn't maximize her metabolism.

Here's a tried and true practice: Turn the horse out on good grass pasture. Let her eat to her heart's content. Ranchers out west have done it for years and years, and you don't hear about the remudas losing horses to colic and founder. Let me say it again: A horse is designed to graze. They will eat at a slow, steady pace - they will be able to roam and build muscle exercising at will - Let your skinny horse chill out and be a horse for 30 or 60 days, and I promise you, weight, shine, and a better attitude will come out of it.

If you are still worried about colic/founder: Fill them up on hay the night before you turn out. In the middle of summer on unmowed, ungrazed grass, nothing is starchy enough to cause founder unless - as I have said - you have underlying health issues already at work.