Effect of Chlortetracycline on Methemoglobinemia Resulting from the Ingestion of Sodium Nitrate by Ruminants

In vitro fermentation data obtained by use of an artificial rumen technique showed that 0.5 to 1.0 ppm of chlortetracycline was sufficient to suppress nitrate reduction and subsequent nitrite accumulation. Chlortetracycline fed at the rate of 10 mg. per lb. of feed was partially effective in retarding methemoglobin formation in cattle receiving high-nitrate rations for 2-week periods. When fed to sheep for longer periods, however, chlortetracycline provided partial protection only during the first 2 weeks of the 6-week experimental period. Thus, feeding 10 mg. of chlortetracycline per lb. of feed, although offering some protection at the onset against the methemoglobinemia resulting from the ingestion of rations high in nitrates, did not provide continuous protection.