Chlortetracycline and Oxytetracycline at High Levels in a Protein Supplement for Growing-Finishing Swine

Additions of chlortetracycline at levels from 50 to 250 gm. per ton of protein supplement fed to healthy pigs on concrete resulted in a highly significant (P<0.01) increase in gains. Differences in gains between lots fed the different levels of antibiotic were not statistically significant. Similar additions of oxytetracycline at those levels for pigs on pasture failed to increase gains significantly. Average daily feed intake was increased by both antibiotics at all levels, but feed efficiency was not consistently improved.