
Hi Lisa,
it's difficult to determine what exact amounts of anything dogs should eat - even same size/sex littermates wont necessarily require the same amount of food.
If this were my dog I'd stop the the current food now, feed a bland home prepared diet for a couple of days instead (white fish or boiled chicken with stodgy rice or mashed potato) to let his tummy settle, then gradually reintroduce the food in smaller quantities and, yuk, poo watch intensely! Any sign of a return to sloppy motions then I'd be inclined to suggest that for some reason this food does not agree with your youngster and look to introduce an alternative :)
If his system is upset or shooting this diet from one end t'other then he's not getting the true benefit of the food anyway and, if due to a sensitivity to any of the ingredients rather than too much quantity, it could have the result of making him intolerant to certain foods whether in the near future or further down the line.
regards, Teri