I think if you're taking your chicks out to a part of your yard where other birds have not been, it would be safer in regard to picking up the cocci.
Depending on how old your chicks are and how many there are, if they are just babies (6 weeks or so?) I'd start with about a teaspoon or so per bird. Mix it into their food. Some of them really like the yogurt from the start and others look at it and start shaking their heads
like they're trying to get if off their beaks, they seem to know its wet and will stick to their beaks! As they get used to it and older, you can increase the amount up to say a tablespoon per adult bird. My birds would eat much more than that if I let them and they don't care if it gets on their beaks. In fact, the sling it all over the place and get it on their faces and the faces of their pen mates. It all gets cleaned up in short order. I can't afford to feed them a lot of it or I would. I start them on it while in the brooder within the first week of their little lives.
I use Mountain High yogurt. It has 5 different strains of bacteria in it so yes, its a really good one and my birds absolutely love it! I'm not saying yogurt is a cure for cocci (I haven't had any cocci in my flock at all but I guarantee you, if I did, I would TRY to cure it with the yogurt), but definitely a preventive and its all natural!