I’m with NinaJD on the hay belly thing. I’ve got a mini who looks pregnant much of the time, and given a day on unlimited grass (like last week when I forgot I’d mowed the tall grass in the pen and turned him out in there…ewwwww!), he puffs up like a balloon animal. He’s not fat otherwise, so I don’t worry too much about it. He actually consumes very little. I can put two flakes of hay in his stall, and most of it will still be there in the morning, and he gets only a half-pound of low-cal feed twice a day–enough to hide his supplements but not enough to pack on weight. It’s just his body type. I only worry when he objects to moving around because that belly is just a burden. Could be you’ve just got a youngster who tends toward that shape. Could also be that he’s not quite grown into his body yet. If the vet is happy, then I wouldn’t be too concerned.
Horses In the Yard