I think it is important to add a bit more information to my last post. Spring (and fall) weather is often a time when I see an increase in the number of colic's. One year, the late Dr. Dave Catlin & I were discussing the frequency of colic's we both saw in the spring & fall. We were scratching our heads about it then came to the conclusion that it is likely water related. In other words, warm days & cool nights...the horses are probably not drinking as well as they should be on the cool nights, then with the warm days - their reserve just isn't there so they develop an impaction...from mild to severe. A couple of things you can do to be proactive, 1) CHECK your water supply at least daily if not more frequently (I was just talking to a client yesterday whose outdoor, auto waterer was dry - for the first time since it was installed at least 6 years ago. It turned out to be a pump issue. Also, I have had issues in the past with my auto, year round waterer's freezing.) Automatic waterer's are wonderful time savers, BUT they must be checked at least 1x/day everyday!, 2) add a small palm full of salt to your horses' supplements every day in the spring & fall to encourage an increase in water consumption. As well as ALWAYS having free choice salt AND a mineral available (loose or block is fine, just PLEASE DO NOT use a combo salt/mineral block - these are phony in the sense that they would have to consume way more salt than is normal to get their mineral needs met).
Signs of colic: colic is simply abdominal discomfort. There are MANY things that can cause colic or abdominal discomfort, everything from the dreaded large colon volvulus or twist or to a much more mild displacement or simply gas or an impaction. These are just a few of the things that can cause colic. It stands to reason that for as many things there are that cause colic, there are many signs horses give us that they have abdominal discomfort or colic. It is not always, and in fact not common to display what most people know which is down, thrashing, rolling from side to side, standing then laying or throwing themselves down. That is certainly one sign but USUALLY always there are much more subtle signs first. It can be as simple as irritably swishing the tail (when there are for sure NO bugs), very subtly lifting a hind leg (& sometimes kicking at their belly), pawing (for no other reason such as boredom, loneliness - when tied by themselves, etc), not eating when they normally would and sometimes something so subtle as curling their upper lip (not to be confused with the flehmen response when a horse curls its' upper lip in reaction to certain smells). The key is to KNOW YOUR HORSE. Know your horse's normal behaviors, that is the only way you will know abnormal. And PLEASE, listen to your instincts, if their is some behavior that seems abnormal, trust yourself that you are seeing what you are seeing, continue to observe & respond if necessary.