I haven't seen this before. It appears to begin with one of the veins on their backs turning dark and progresses to an open sore and finally scabs over. They are six weeks old and seem to be putting on weight well and act normal. About half of the birds are exhibiting these lesions in different stages. I doubt there is much I can do now as far as treatment is concerned seeing how they are only two weeks away from the plucker. Anyone have any idea on the cause? Starts out like this. See the dark vein on the haunch? Progresses to this.... Thought I would post here instead of the emergency section, seemed more appropriate. Mod please move if you disagree.