The oldest hen I've seen still breeding was 11 years old. She didn't seem to have any problems. But then again, I had a hen who was four years old become egg-bound and die. Seemed that she didn't breed for six months or so, then when she tried again she didn't make it. It seems to affect the males diffrently, I have a male fantail who is 11 years old, and he's as active as ever, courts everything that moves, lol.
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David and Kellie Dittmaier
Haven's Loft
www.haven-lofts.cityslide.com