Generally just picking their feet should be ok, but you should be aware of mud fever, especially if your horses have feathers, and horses with white legs seem to be particularly susceptible. I wouldn't hose the mud off unless you make sure to dry it thoroughly. If you can wait until the mud dries and then scrub the worst of it off around the bottoms of their feet, they should be alright. But, at the same time, we've had horses out year-round in the mud, and some of them never develop it (even ones supposedly susceptible). It's just something to watch for.
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