Join Date: Jul 2008
Location: South of No-where
Its hard to say if that will be enough because flake sizes differ depending on the bales size and how tightly they are packed. It is best to feed by weight rather than volume.
The best way to do it is figure out the weight you want your pony to be at. Then take that weight and figure out what 1-1.5% of that would be and you have your range of the proper amount of hay to feed per day. Then take that and divide it into 2 or more feedings (more the better). For example - if the horse's ideal weight is 1000 lbs, then that would be 10-15 lbs of hay. 10 would be the absolute minimum for gut health, so its best to feed a bit more than that and 15 would be the maintenance amount for your average horse of that size. A 800 lb horse would be 8-12 lbs per day.
Try to find low-glycemic hay as well, its better than the higher sugar stuff. If you are not sure what level your hay is at and can't test it - then soak it for an hour before feeding to take off the extra sugars.
Unfortunately I do not know how much grass they get using the grazing muzzle. I would assume that depends on how lush and long your pasture's grass is. If it was my horse and they were off pasture all night - I would take the formula above and feed 50% of the calculated amount. So for a 800 lb horse I would feed 4-6 lbs of soaked hay for the overnight feeding and then adjust it from there depending on how they do.
All I pay my psychiatrist is cost of feed and hay, and he'll listen to me any day!