Effect of Three Levels of a New Antibiotic, Tetracycline, in a Swine Ration

An experiment was conducted with 30 Duroc pigs to compare three levels of tetracycline in a swine ration to a recommended level of chlortetracycline and a negative control. The levels of tetracycline were 10.85, 15.03, and 19.21 gm. per ton. Tetracycline at all levels used improved feed efficiency but did not improve rate of gains as compared to chlortetracycline and to the negative control. The increase in feed efficiency was greatest in the initial part of the trial. The optimal level of tetracycline appeared to be 15 gm. per ton of feed. Chlortetracycline failed to produce the responses observed in previous trials. This was associated with improved performance of the pigs on basal rations.