Keeping a horse out in pasture is the best and most natural way to keep a horse, but there are several natural and man-made conditions that you must be aware of and protect your horse from. Make sure the horse has plenty of fresh water.
Many people forget to give their horses water when horses are pastured.
A healthy horse drinks 25 to 30 gallons of water each day. Check the food supply. Just because the horse is outside grazing doesn't mean there is sufficient food. You may need to supplement with hay or pellets. Make sure the horse has shelter from the weather.