Im not sure what the MOST common cause of laminitis is but i
know some of the things that could cause laminitis.
If your horse is overweight, resistant to insulin, has a high
porportion of grain in his diet, has had laminitis before, comes
from a bloodline prone to laminitis, has access to lush or improved
pastures (grazing rich pastures can lead to laminitis), has
cushings syndrome, or excessive fat on his crest area.
If your horse has any of the things above he could be at risk
for laminitis