Keeping horses off rain-soaked or frozen pasture is critical if you want to maintain healthy grass plants. During the winter, plants stop growing and horses will continue to graze pastures down until little grass is left. Soon you’ll be left with bare spots that will turn to mud as soon as it starts to rain. Another reason to keep horses off pastures during the winter is to keep the soil from becoming compacted. When horses step on wet or soggy pastures, the soil is pressed down, squeezing out the space between soil particles and eliminating the pockets of air that allow roots to grow and water to penetrate. Finally, horse’s hooves, with or without shoes, can trample existing plants and dig up divots of dirt. And weeds usually are quick to move into these areas.