I can announce that we have now completed our trial of dried horse poo as a fuel on our multi-fuel stove.
100% Burns well, doesn't smell (not that we noticed, anyway), and keeps the fire in all night. If you only burn wood with it, you can use the ash on the garden / veg plot, or whatever, and put the nutrients back in the soil after extracting the energy.
I don't know what else there is to say, really.
Oh, the ponies were stabled on hay half the time and out on grass the other half of the time. I collected a few buckets full of 'kidneys', dried them and then burned them.