Dogs often have loose motions and there can be loads of reasons for it - reactions to food, scavenging, drinking manky water, hard exercise etc. If they fall ill with a bad bout of diarrohea and are passing blood or mucus then a vet trip is in order but if it's just loose motions in an otherwise healthy dog then the most likely cause is what they are eating - either scavenging or a reaction to their actual food. It's extremely unlikely to be anything serious in a young, healthy dog with no other symptoms so try not to worry too much about anything like that. I find with my lot their poo can change throughout the day, it tends to be firmer in the morning and looser as the day goes on, particularly if they've been running around a lot.
