The meal is far too large for one sitting, so spreading it out is good. Beyond that I would make sure that he is up to date on dental, dewormer, and vet checkups. After that I would research everything you have him on and find out if it is necessary. Make sure that there is nothing in there that was used to treat something in the past and is no longer needed. If the grass is no good then keep constant source of hay for him. If the minis are pigs and you need to regulate how much they eat you may need to separate them. Also a constant source of fresh water. The hay is very dry and they will need to drink more with the hay rather than the fresh grass. Also check his poop is there lots of undigested food, is it loose? It should be balls of poop not a cow pie, if the balls splat when they hit the ground they are still too loose.