Q: What exactly is a pro-biotic? Can this be obtained on its own to use as an additive to personal vitamin or mineral mixes?
Pro-biotics is commonly known as "friendly gut bacteria". This is generally used following an antibiotic treatment. The thought is to replace the flora of the intestine with good, if I could use that term, bacteria. It is just like in human beings -- if you are on heavy and extended use of antibiotics for a long time, your intestinal flora will be destroyed and people, especially children, at that point get diahrea.
In other words, when antibiotics are used, they kill all bacteria -- the bad that we want to eliminate, but also the good. The digestive system needs bacteria to function. The body will eventually rebuild its own bacteria, but we want to speed up the process by the use of a pro-biotic.
A pro-biotic as used in the animal world is really very similar to yogurt. Pro-biotics are used with many different kinds of animals. You can buy the product for horses, caged birds, chickens and turkeys, and of course the pigeon supply houses all have their own superior brands available to you.
You asked if it can be used simultaneously with vitamins. Like they say, "No Problem". Just don't have any bleach or chlorine in the water because you will kill the bacteria before the birds have a chance to drink it.