Document Type

Thesis - Open Access

Award Date


Degree Name

Doctor of Philosophy (PhD)


Animal Science


Experiments designed to study the potentiation of antibiotic in swine were conducted over a two-year period. During the two years, 344 crossbred pigs were used in three separate experiments to study the effects of calcium sources and levels, sulfate sources and levels, and phosphorus levels in diets containing different levels of chlortetracycline. The first experiment was divided into three two-periods. During the first two weeks 50 g/ton of chlortetracycline in the diets increased gain of pigs from 0.68 to 0.72 kg. per day. Pigs fed diets containing chlortetracycline gained significantly faster when the source of calcium was sulfate rather than carbonate. In the second period, pigs receiving a higher calcium diet with antibiotic grew significantly faster than those fed a low-calcium diet. During the third two-week period pigs fed a calcium carbonate diet achieved gains significantly greater than those fed a calcium sulfate diet. On an accumulative basis (0-6 weeks) there were no significant differences among treatments in either average daily gain or feed efficiency. Diets containing three levels of calcium (0.3, 0.7 and 1.1%) with and without 100g/ton of chlortetracycline were used during the first four-week period of Experiment 2. In the second period (2 weeks) all diets contained 0.3% calcium. Pigs fed the antibiotic diets received 200 g/ton of chlortetracycline. Blood was collected from all pigs at the beginning of the experiment, at the end of the first period and at the end of the second period. Over the entire six-week period antibiotic fed pigs gained significantly (P<.01) faster and required less feed per Kg. gain than pigs fed diets without antibiotic. Pigs fed diets of 0.3 and 0.7% calcium responded significantly (P<.05) better to antibiotic than those fed the high calcium diet. Blood serum calcium was similar among all treatments at the first and third blood collections. At the second collection pigs on the lowest dietary calcium level showed blood serum calcium levels significantly higher than the others. Serum chlortetracycline at the second blood collection increased linearly with decreasing levels f dietary calcium. Serum chlortetracycline at the third collection followed the same pattern as the second and was closely correlated with the dietary calcium levels of the first period. Several methods of potentiation of chlortetracycline were studied in the third experiment which was conducted for ten weeks. The diets included increasing levels of sodium sulfate, calcium diet. All diets contained 200 g/ton chlortetracycline. Blood was collected at the beginning of the experiment after pigs were fasted overnight and fed for five hours and again two weeks later. Chlortetracycline significantly (P<.05) increased daily gain. At both sampling periods the lowest values of blood serum calcium were found in pigs fed the very high (1.8%) phosphorus diet. At the first collection blood serum from all pigs, except those fed the calcium sulfate supplemented diets, contained chlortetracycline levels which were significantly higher (P<.05) than the controls. At the second collection only serum from pigs fed the low calcium diet and the two very high phosphorus diets had chlortetracycline values significantly higher (P<.05) than controls. Increasing amounts of sodium sulfate in the diet caused a linear increase of blood serum chlortetracycline in the blood serum. At both collections, blood serum chlortetracycline was also significantly (P<.01) high when pigs were fed the high phosphorus diets.

Library of Congress Subject Headings

Swine -- Feeding and feeds

Antibiotics in animal nutrition




Number of Pages



South Dakota State University