Things to check for when you’re concerned about your horse’s weight.
☐ Does his teeth need done?
☐ Does he have ulcers?
☐ Up to date on worming?
☐ How much, and what kind, of grain is he receiving?
☐ What is the fat content of said grain?
☐ How much, and what kind, of hay is he receiving?
An underweight horse is something to be concerned about. It’s a sign of an underlying problem. Whether that problem is poor diet, or something as serious as ulcers. Good luck! Hope this helped.