We use probiotic yoghurt for all manner of sicky chicken problems. Seems to work well but never use it on sour crop as it makes it worse as it can go off in the crop. Gail Dumelow reckons it's a little wonder cure and other swear by it. I administered it in desperation after the vet pronounced Lucy terminal having heard of people using a spot to get chicks digestive systems started ASAP. We use it on all our chicks at day two and use unmedicated chick crumb (can't do that with broody reared as mum won't let us near them). Other say it's complete rubbish, but I know what I saw. A chick hunched up pooing blood and guts one day and jumping around happy as Larry the next.