240 of 39-week-old laying hens were randomly divided into four treatment groups consisting of 6 replicates of 10 laying hens in one-factor design, respectively. The laying hens were given either a basal diet or a basal diet supplemented with 0.02%, 0.04% and 0.06% quercetin. The experiment lasted for 8 weeks. E. Coli, Salmonella, Pasteurella, E. faecalis, Staphylococcus aureus, Proteusbacillus vulgaris, Pseudomonas aeruginosa, Enterococcus were tested strains in vitro using Oxford cup method. This study was...