Three things prevent most common colics. Plenty of water, and plenty of roughage, and plenty of movement. To insure plenty of water, you of course must provide it, and then you encourage them to drink it. One, by keeping it fresh and clean, and 2, by providing enough salt. Those hard salt blocks just don't do it well enough. It's better to provide loose salt free choice, or put a good tablespoon (a horse's average daily requirement) in the grain feeding once a day, wetted so it will stick. Roughage is good grass hay or good pasture. Movement means not stuck in a stall more than they are out. I have followed these rules for the past 20 years, with 16-24 horses at a time, and had 2 colics in that time. One, a mare that had just shipped in, and the other a new mare with a hefty load of entroliths in the gut. Lost that second one.