Pumpkin is not terribly high in sugars and is definitely low in fats. Further, it has a decent amount of potassium, at .4 grams per cup.
While that is higher in a human context, it poses little to no disruption to a horse’s daily intake, as hay typically yields 8.5 grams per cup. Horses are potassium-eating machines.
Further, pumpkins (the flesh and the seeds alike) contain a number of beneficial vitamins and properties, many of which you can find marketed in dietary supplements, such as:
Carotenes: Helps with developing eyes/vision and strong bonesFatty acids: These are necessary components that are excellent for heart healthFiber: Well known to help aid in digestionMinerals: Calcium, copper, phosphorus and potassium, all of which are part of a body’s essential nutrients for healthy functioning