The horse leaves receipts of its gut balance every day. The droppings are receipt number one: normal formed balls mean balance; loose manure or hard little balls are deviations worth noting. Free faecal liquid — when liquid runs separately and soils legs and tail — is a sign of hindgut imbalance. Gas and rumbling after feed changes is a signal. Note deviations with the date on your phone. At any sign of colic, contact a vet immediately.