John Imo it's very hard to tell how many it affects when it's amoungst your team they might look ok but you can't see what's going on inside them and pigeons canny talk to tell you how there feeling I would say it varies every year as to how many get the full blown symptomsThis year my ybs were very good up to the first YB race where I sent 30 and on the Monday after the race I must have had about 6 to 8 throw up there grub and then the droppings went bad and the weight loss etc now I hope your not going to tell that I should have pulled the heeds aff them because these same ybs can go on and score well from 450miles as ylgs that's a fact I've proved it and by the way surely some of these top athletes that you see winning gold medals at the olympics must have had illness when they were young so I would say if you've got confidence in the young pigeon you must give it a chance these days.