Here at home we feed hay 24/7 on the ground by way of square bales which are actually rectangular. Since we only have one horse now she gets a half bale morning and evening plus a token amount of grain. Since she is 24 and retired that is all she needs. Trust me I am "knocking on wood" here, but we've had up to 6 horses here at one time and never had a case of colic.
Back when we were traveling with horses on trail riding camping trips, which we did 4-5 times of each year we used the nylon rope haynets and had great success with them.