Rickettsiostasis in Fertile Eggs from Use of Antibiotic Residues in Poultry Feeds. ∗

Conclusions

The introduction of antibiotic mash containing aureomycin and terramycin, into the diet of a flock of laying hens resulted in progressively increasing resistance of the eggs to rickettsial growth, the resistance becoming almost complete at the end of 3 weeks. Similar dietary factors had no appreciable effect on the growth of Influenza A virus in eggs. These results, with other data submitted, indicate that fertile eggs obtained from commercial hatcheries may, under present conditions, be unsatisfactory for controlled microbiological studies.