Always great to hear news of happy horses being ridden by happy owners who've educated themselves in good diet plans.
FWIW, i own a veterinary hosp so i frequently test my two known IR (both severe risks) horses and have a folder full of lab results showing "not IR" (because of strict diet & exercise) and then a short time later "severly IR" on same horse that i experimented w changing one small element (ie, a new supplement, a different batch of hay, one less ride a wk, etc). A piece of paper does not overrule what is standing in front of you on four legs!
A story no doubt everyone is sick of, is one of eventing my mare hard-core last year & winning enough to qualify for the Championships. My mare was a perfect 5 body condition w only a tiny bit of cutesy crest. She was maintained all season on chopped forage weighed at every serving. Her lab numbers were tight. I was smug that i kicked her IR's butt bc hey, she's a super fit eventer, right? Well, the first day of competition she was a roaring maniac (dressage was right next to Prelim's XC warm-up). We were fourth of god knows how many; it didnt matter, I had a real shot to win. The champ competitors were stabled in temp stalls on a hay field. My mare spent all night digging up her bedding to get to the grass nubs underneath. It was so little, what could it hurt, you know? The next morning she was very lethargic. I had to beat her around cross country when normally Im dragged around with aching biceps. I withdrew after she hit a jump so hard I thought she was going to get stuck on top of it. Something was very wrong bc my mare never, ever touches a jump. I drew blood within a day, and her insulin & glucose were the highest they'd ever been. Thats why she couldnt move at the show--she was likely foundering subclinically & I didnt recognize it. Looking back, i think that "little bit" of grass she dug up pushed her always-at-risk IR status over the edge.
A long tedious story but an important one. Insulin status can change day to day & be influenced by factors too numerous to count. I would not rely on one seemingly good lab result to let your guard down. Furthermore, horses do not need grass or treats to be happy. I have now two IR horses that are exceedingly happy living in drylots. Both go bananas when the bucket of ODTB cubes gets tossed around their paddocks so they can go "graze" for a few hours. One absolutely loves being worked or ridden and will literally free-jump 3'6" for a single white Tic-Tac (i have video proof). All i have to do is point to the jump a la Parelli-style and he springs over it w zeal, then runs over for his tiny mint. Then does it again. And again. But I digress...
Giving grass and treats make humans feel good. Being with you (their herd leader) and being treated clearly & correctly (like a horse) is what horses crave more than anything else. They'll do just fine with a balanced hay diet and a kind word & gentle stroke.
So resist the grass temptation! Or at the very least, be financially committed to re-test labs frequently to assess insulin/glucose/leptin(ideally) in order to thwart disaster before it strikes. Take it from me and my book of lab results: youre fine one day until you arent.
Kerry in NY
Pinky Sept 2014 IR/PPID
Tofurky Nov 2014 IR