We raise our poultry together from day one, chickens, turkeys etc etc and haven't had any problems to date. However, they can pass disease from one to another. For holiday turkeys we like them in the 9 to 10 month range, you can have them sooner but we like ours better filled out. Our guest of honor this year is a Midget White tom and he will be 10 months old in Nov. Turkeys need a higher protein feed to start than chickens, we start ours on 28% game bird starter for the first 3 months, then 20% chick start n grow until 6 months. If you want them to finish quicker then go to a 18% grow n finish to processing time. At 6 months ours are out with the flock and have free choice 16% poultry layer, plenty of fresh greens and all the bugs etc they can find.
Actually I got a little ahead of myself here since you are new to turkeys. There are two types. The Broad Breasted and the Heritage. The Broad Breasted will finish much larger and in less time (about 5 months). They are basicly your home raised "butter ball". They normally don't self reproduce. The heritage types are the "old time" turkeys, they will self reproduce and keep you in turkeys as long as you want. The heritage come in different sizes from the Midget White, toms about 20 pounds to the White Holland and Standard Bronze in the 35 to 40 pound range.
Taste wise, the home raised Broad Breasted is better than store bought, the heritage is the best tasting hands down. This year the Americian Livestock Breeds Conservancy did a blind taste test and the Midget white won with a store bough Butterball last. We have raised the Broad Breasted before and agree with the results 100%.
Steve in NC