The effect of medicated feed on the nasal microflora and weight gain of pigs.

Antimicrobial agents were added to the feed of swine for three weeks to determine the interrelationships of potentially pathogenic agents in the nasal tract, turbinate atrophy and weight gains. Bordetella bronchiseptica was not isolated from the groups fed the combination of chlortetracycline, penicillin and sulfamethazine. B. bronchiseptica was found in some pigs after the feeding trail, but this organism was not significantly associated with turbinate atrophy at the time of slaughter.Mycoplasma hyorhinis was not found in the nasal passages of the pigs that received feed containing high concentration chlortetracycline but was found in pigs that received other diets. Hemophilus suis was not significantly reduced by any of the treatments used. The organisms studied in the pigs were not isolated from the personnel handling the pigs.