You stated that it is better to breed resistant chickens... How do I do that, if I don't know who has it and who doesn't. Also can those chickens be purchased??? if so where???
Thank you for your input I am trying to understand all of this.
Immunity or *resistance* is when the body is able to fight off a germ. Vaccines do this by artificially exposing a person or animal to a germ, generally a germ that has been weakened so it hopefully won't cause the actual disease. Natural immunity comes from being exposed to a germ in the environment and the body fights it off. We are exposed to a ton of germs every day that our immune systems fight off, just like chickens come across lots of germs every day but they don't always gets sick.
Unless you have lab testing done to specifically look for antibodies to a germ, there isn't a way to know if a bird is *resistant* to a particular germ. So there is no way to really buy or sell *resistant* birds since you can't tell for sure. And stress is a huge factor in whether or not a bird gets sick. Buying a bird and bringing it home can be stress enough for a bird to get sick, because it's in a new environment and not accustomed to your husbandry methods yet.
If all your birds intermingle with one another and one bird gets sick, chances are all the other birds have been exposed to the same germ. If the birds get sick and recover, then theoretically they shouldn't get sick again if they are exposed to that exact same germ again. And theoretically, if you have birds that never got sick, even though they were still around the sick birds, then chances are they have also been able to build up an immunity to the germ.
For best results of breeding for *resistance* you would only breed the birds that did NOT show any symptoms, but were still exposed to the sick bird.
As ChicKat mentioned, serious breeders tend to cull ill birds. Fortunately chickens are also considered food, so their lives are not taken in vain and their bodies can go for a utility purpose. If you are not willing to cull, then at the very least, you should not hatch from birds that have gotten sick - unless it's an illness like fowl pox which is pretty benign. Although I have heard of some old time breeders that will even cull birds that wind up with pox.
I have seen too many backyard people hatching from birds that routinely cycle through a respiratory illness several times a year and all they are doing is perpetuating birds that are prone to illness. Breeding from birds that routinely get antibiotics, because the owners give antibiotics every time something looks wrong with a bird, is also a way to perpetuate a flock more prone to illness. Best thing is not to breed from these birds, no matter how attached you are to them. Breeding from healthy birds is the best bet.
