Certainly. One good one is this article below. I'm reading The Chicken Health Handbook 2nd Edition which makes reference to the Hellevad hen which was breed over many years to be disease resistant. Being interested in the topic, I found this online.
http://www.poultryworld.net/Breeder...en-could-hold-key-to-robust-health-WP008850W/
Such an "aha!" moment when what is natural is proving to not only be sustainable but actually far better. Problem with today's antibiotic free chicken is that it's only the first batch of what will eventually be a much healthier bird. Too bad there aren't more breeders who have been breeding this way already who's stock we can use to jump start this process within our own flocks.