"Lack of tolerance" should mean that there's zero tolerance for drug residue in the eggs. Nobody would recommend mixing Ivermectin with detergent!!! There is demonstrated parasite resistance to fenbendazole in horses, for example, and getting a measured dose into each chicken in the flock for five days running is problematic, IMO. Big commercial flocks get meds in their drinking water (greatest good for the greatest number) but I'm just not happy with that approach for my small home flock, and b individuals getting less than optimal drug dosages, promotes drug resistance. Mary