The Effects of Antibiotics in the Weanling Pig Diet on Growth and the Excretion of Volatile Phenolic and Aromatic Bacterial Metabolites

The purpose of this study was to investigate the effects of dietary antibiotic supplementation on the fecal urinary excretion of volatile phenolic and aromatic bacterial metabolites by the weanling pig, and to determine if a relationship exists between an exposure to these metabolites and growth performance. Wealing pigs were fed a basal diet, supplemented with either 110 ppm chlortetracycline, 110 ppm sulfamethazine and 55 ppm penicillin, 40 ppm lincomycin sulfate, or no antibiotics, for 30 days. Pigs on the chlortetracycline-sulfamethazine-penicillin diet on the average tended to grow at a faster rate, attained a higher percentage weight gain, and weighed slightly more than pigs on either the lincomycin sulfate or no antibiotic diets. Under all treatments, p-cresol was the predominant metabolite of the volatile phenolic and aromatic metabolites detected in feces and urine, with the urine accounting for 88% of its total daily excretion. Pigs on the chlortetracycline-sulfamethazine-penicillin diet excreted less urinary p-cresol than pigs on either the lincomycin sulfate or no antibiotic diets. Total p-cresol excretion expressed on the metabolic body size, resulted in significant treatment differences. Regression analysis of percentage body weight gain on urinary p-cresol excretion gave a negative correlation coefficient (r = -0.73). The results suggest that intestinal p-cresol production may be responsible for depressing the growth of the weanling pig.