if they are in good weight, they have enough calories. If they are fat, that in and of itself can sap energy.
I've dealt with this with Rio all his life. It really is about making sure there are no physical reasons - bloodwork (already done), saddle, hocks, feet, etc, and then finding what motivates them to actually *move*.
It may be something as "simple" as starting the process with a good gallop. It may be as (mentally) difficult as REALLY hauling off with the whip to really make them understand "yes, I DO mean it."
No, you can't just add enough oats to provide more energy to an easy keeper.
You have my permission to talk to ET about this in relation to Rio, as she's seen what it sometimes takes to get him going.
______________________________ The CoTH CYA - please consult w/your veterinarian under any and all circumstances. - ET
One thing to consider is that often EPSM horses lack energy as they simply cannot process the startches into energy and need the fat for energy. Many EPSM horses will look undeveloped muscle wise, but I have seen some that were "easy keepers" So this may be something you want to explore as a possibility
I have a paint mare that I used to to feed Triple Crownd Low Starch. She did not need it but I wanted her to get the vitamins. I have since switched her to Pennfields All Phase which is a vitamin supplement for horses that dont need grain. I give her 1 quart of all phase and 1 quart of los starch 2xs a day. She can still be lazy but some horses are just this way. I have a good story to tell but it would take forever, the out come was that it was just the horses tempermant. This lady spent tons on money on blood work and all sorts of supplements some which made the horse sick. Always consult your vet first.
I most certainly would not be whipping a horse that doesn't have energy to go. Good lord. Dalpal is doing the right thing by trying to modify and fix the diet first. I've had health issues that made me tired and sluggish and I know what it feels like to just.not.have.the.energy.to.go.one.more.step. Hardly seems fair to get whipped for that. Horses cannot communicate in words what is bothering them. I'm the first to crack a horse a good one for obvious disobedient behavior but this certainly doesn't sound like an applicable case to me.
I also would suggest an all-round vitamin/mineral supplement like SmartVite, Accel, or Equi-VM or something comparable.
I have a huge easy keeper on free choice hay and grass, and he gets three pounds of Pennfield's All Phase for vitamins and minerals. As long as he's in work, he keeps the hay and grass calories sufficiently burned off (e.g. doesn't get fat). In turnout, he frequently watches his pasturemate buzz around with a bemused "why on earth are you exercising of your own free will?" look on his face, but under saddle he has plenty of good, focused energy. I think Deltawave's questions of history and at-liberty behavior are good ones.