well aware of what you are saying ian and cant understand what aids in humans has to do with ybs in pigeons ,i have diabetas as well for a number of years and have it in control ,as for young birds with crop retention more inclined to think its down to feeding rather than disease and the one you disposed of how did it get it and what was it and what did you do for it that you had to dispose of it ,i am more inclined to think that it came from the parents that was feeding it and not from any were else no one is getting away with these symptoms have it in my own loft were before i go to work i handle all my young birds and can still feel feeding in them one or two grains not a lot but they should be empty and beleive me when i say this 99% of lofts have the same its nothing major more of a condition than disease