I live in seedy toe central here in PA, I see lots and lots and lots of people with some nasty seedy toe problems. I'm assuming you're inquiring because you think one of your horses has seedy toe.
The best thing you could possibly do for prevention with a mud hole pasture is to keep your horse inside at night with a deep bedding of either kiln dried pine shavings, or kiln dried corn cob bedding to dry out those feet. However, this definitely isn't always possible depending on your setup.
If you're just looking for prevention on a pasture only setup, gelatin supplements can go a long way, and magnesium supplements can be a lifesaver on a foundered horse prone to hoof issues. Pick out all those tiny stones you see in the white line to make sure no abscesses form, and I like to use Farriers Fix just on the soles of their feet. It adds a small, short term protective barrier from all the poop and nasty stuff lurking in pastures. Pine tar and turpentine solutions are caustic enough to do the same thing, but its nasty stuff and stains the hell out of clothes... Ask me how I know that! Some horses can get sensitive with pine tar and turpentine on their frogs as well.
If you notice one of your horses gets a nasty, infected looking toe crack, (You'll know because the toe crack will be dark) get it CLEAN! If you're not comfortable hacking away at your horses hoof with a knife and nippers, which is totally understandable, then use something rigid and thin to pick out every ounce of dirt possible. Screwdrivers, O Ring picks and scratch awls all work great for this. If some hoof wall flakes off in the process, don't worry about it. Its better to let it fall off than to trap dirt.
Wire brush the daylights out of his foot. You can get little welders toothbrushes at any hardware store and they work at treat. Once the cavity is clean as you can get it, my two favourite remedies are Keratex hoof putty or copper sulfate crystals with hoof packing.
The Keratex stuff is just medicated paraffin wax. Its absolutely divine, if you can get it out! You may need to employ a hot forge or a stove top to melt the wax before pouring it on, but if you get it in there it should last for a few days. It creates a great barrier so moisture and dirt can't just make their way back in.
If you can't melt the keratex wax, which is a fairly common problem, you can get some copper sulfate crystals, pour them into the cavity, and then seal them in with a hoof packing of choice. Lots of people like magic cushion, but I find Forshners stays in a bare foot better. If you don't mind the drying time, I've heard of people using silicone caulking too! You just want to keep the poop out, and the medication in. This method would likely have to be redone daily if not twice daily depending on how soupy your pastures are.