Horses will sometimes start passing a looser stool (not actual diarhea), more frequently as they get close to foaling (within ten days) because the baby is so big, there just seems to be less room in them to hold feces. I think that the phenomenon looks like diarhea because stuff is coming out before the colon has a chance to leach the last bits of water out that it would normally do. Stuff is just getting pushed out as it gets there.
I hope that made some sense. Horses certainly aren't goats and you need to go by what the good goaters here say, but I'm betting that the same thing applies sometimes.
In horses this loose, frequent stool is not an accurate foaling predictor because it can vary depending on the position of the foal. But it usually does mean that baby (or babies!) will be there soon
I'm going to post a thread on a question I have about predicting imminent birth. Lets see if anybody knows the answer to my question!