I'm very sorry to hear about your horse ;-(
I have a number of ponies and they are all susceptible to laminitis. I have to closely monitor their diet and reduce their intake of grass. I check them daily by feeling their crest and heat in their feet. If they are even just a tiny bit lame or thick in their neck I pull them from grass completely for a few days or week.
The main concern is the sugar content in the grass, hay or other feeds given. I have found it easiest to let them graze during the night, the sugar levels are at their lowest (highest during the afternoon, rising from about 10am).
The sugar levels in the grass literally change by the hour and can be affected by many things. Many people think because the grass is short it is safer, grass that is moisture stressed is higher in sugar and grass that is having new flushes of growth.
Another thing to be mindful of is that your pony/horse does not have to be fat to get laminitis or founder. Laminitis can be caused by stress or even concussion laminitis from working on hard surfaces.
Hay is also something to be wary of, it depends on when the grass was cut as to how much sugar is in it. If it was cut in the afternoon it will be higher in sugars, if it was cut during the night it should be lower. The best way to be safe is to soak your hay to remove the excess sugars. I only do it for 30 minutes, it removes enough and does not leave the hay smelling or tasting yucky (especially in hot weather).
I have a success story you might be interested to hear about ;-)
My daughter has a stunning little welsh pony. Last October we took him to his first ever show. He did very well on the day and won his classes. However 2 days later he went down with stress laminitis. I called the vet immediately.
We bandaged his feet with pads, stabled him on a thick bed of straw, medicated him and monitored him closely. Despite our best efforts Ted kept having mini episodes every 2 days, where he seemed to get worse. After a few weeks I had him out in a day yard and the pads off his feet. He was better than when he first got sick, but still could hardly walk. We trucked in sand so he could dig his feet in and find hoof angles that he felt comfortable on.
We then got x-rays done of his feet. Both front feet had developed founder --- 18% rotation of his pedal bone! They also thought his hind feet had also rotated to some degree but did not x-ray them. Others have explained the different between laminitis and founder, so I wont repeat it, but there is a difference.
You don't trim the feet during an acute episode so once the vet felt he had stabilised we called in a master farrier. He looked at the x-rays with the vet (I was not present) and he arrived at my property grim faced. He said he would trim the pony to make him comfortable for now, but he did not expect to see me again as he recommended I put him down. I did not put shoes on him.
I spoke to the vet after this and she also recommended I put him down. It was heart breaking to know I was running out of options. However he had not given up and still had a bright eye, so I wanted to try more.
I researched every single thing I could and spoke to as many people as I could. Credit must go to gallop and barefoottrimmer from Y!A, who gave me much encouragement.
On Monday I booked Ted in to be put down at 10am on Thursday. I had researched some treatments and decided to try a few things. I discussed them with my vet and she did not think they were a good idea. I told her he was about to be dead, so I had nothing to lose.
Long story shorter (lol) I started the treatments on Mon night and by Wed lunch time he was walking the best he had in weeks. I phoned the vet clinic and cancelled his appointment.. the vet was stunned!
I nursed him carefully for a number of months and he slowly returned to his old self. He was wanting to run and play and I was concerned he would cause more damage. However I allowed him to "play" on a grassed area and he was trotting, cantering and bucking.
Now Ted is attending pony club and is trotting freely with a small rider and even jumping small jumps on soft sand. He has more get up and go than all of the other ponies and I have to hold him back on the lead. In the paddock he canters and even gallops with his mate.
We trim his feet every 3 or 4 weeks, that is very important now as his hoof grows very quickly and if we don't keep them short his feet crack back badly. He had a dent in his hoof from where the pedal bone dropped, now his hoof looks normal to anyone who does not know.