Well I'm sure the vets know what they are doing. They are monitoring him very closely and are doing everythign in their power to save him, I'm sure they know more about him and what's going on with him than the rest of us. They have brought him this far, where most horses would never have made it off the track, so I won't worry too much about the carrots for now. Laminitis is not always caused by the sudden ingestion of an excessive amount of soluble carbohydrates, often is is caused by excessive weight bearing in one limb due to severe lameness in the other may result in the good limb developing laminitis. This is what happened to him, it was a result of his excesive weightbearing on the left "good" leg when he had several days of discomfort and infection in his broken leg, not his diet. I'm sure they won't risk his life over carrots..


What are the causes of laminitis?
Many "triggers" of laminitis have been identified. The most common cause is the sudden ingestion of an excessive amount of soluble carbohydrates. This is where the horse engorges itself on a lush pasture or breaks into the feed shed and helps itself to the grain. Obese or overweight horses that have little exercise are very vulnerable. Excessive concussion on a hard surface has also been implicated. Laminitis can be a rapid sequel to toxic conditions such as retained placenta or Salmonella enteritis. Older horses that develop Cushing's disease, a hormonal disorder have an increased susceptibility to the condition. Hypothyroidism can also be a predisposing factor in its development. Excessive weight bearing in one limb due to severe lameness in the other may result in the good limb developing laminitis. Therapies using corticosteroids can cause laminitis.

It's only related to a metabolic disorder in the fact that obese horses sometimes get it, and they are usually obese by ingestion too much grain, etc. Horses rarely are overweight just from eating hay.