This is what we feed our 17h, 1300lb horse. A minuscule amount. For comparison, Mathilda is six inches shorter, 300 pounds lighter, and gets twelve times the amount of food (1 cup vs 3 quarts). They both eat three times a day.
Rodney is fat. Not just ‘in good flesh’. He sports pokeable pads of podge on parts of his body.
Ingredients:
Yup, 2 horses, 3 bags of feed.
We would have them both on Senior for digestibility, but Mathilda refuses to eat all Senior. She gets half grain as a compromise. Rodney gets a taste of grain so his system is familiar should he ended up getting a mouthful by mistake – say I let him in for pen time & forget to take out the leftovers.
BTW, this is M’s old feed pan. We bought her a new one to see if she prefers the taste of new plastic. She does. Silly cow. (Although, in her defense, she eats inside, so her pan is no longer rainwater fresh. Still.)
Virtual Brush Box 
I finally have all mine on the same feed – Safechoice Senior (the only senior my old guy will eat). The others will eat anything that looks like grain.