Before the collection of eggs for breeding, hens infected with Mycoplasma gallisepticum (MG) were treated with chlortetracycline (CTC). In experiment 1, they were administered with three preparations of CTC daily for two five-day periods with an inter mission for 30 days in between. In addition, they were injected intramuscularly with 200mg of dihydrostreptomycin (STM) four times, 15, 25, 45, and 55 days after the beginning of treatment. As a result they turned to be negative for the whole-blood plate agglutination test. No MG was isolated from chicks hatched from eggs laid by them.
In experiment 2, hens were fed a diet containing 2.5% CTC daily for two five-day periods with a 20-day intermission in between. In addition, some of them were injected with 200 mg of STM concurrently by the intramuscular route. As a result, it was presumed that CTC could display a destructive effect upon MG without the aid of STM.
