30% protein is alot for horses who are not very active. It's best for broodmares, young, growing horses, and horses in intensive training or competitions. Often people feed their pleasure horse a high protein feed and start having behavior problems. Quality feeds for most horses doesn't need more that 11-13% protein. I feed my growing colt this Triple Crown feed and, since he's behind in his growth, utilizes the protein and has no problems. A friend had a 4 yo gelding and was having constant rearing, dancing, charging problems and right before he sold him, realized he was feeding too high a protein.
You can research this, I'm not pulling it out of my ear!!
"Bread may feed my body, but my horses feed my soul." ~~anonymous