I'm, not very experienced (1st time adult owner) but I don't think they all do? For example I've settled on feeding coblet Allen & Page Soothe and Gain and its a higher calorie feed but the calories aren't from sugar and starch, more from oil sources. Same for Copra and Equijewel too I believe.
It appears to be a mine field this feeding malarkey and a far cry from when i was a kid and it was just pony nuts! But i think it is now possible to find a feed that does what you want it to do? I'm sure someone with far more experience will pop on in a minute?