Effects of Dietary Antibiotics and Uric Acid on the Growth of Chicks

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Abstract
One-day-old (Vantress × Arbor Acre) male chicks, fed a diet containing 2% uric acid, showed a significant weight depression after 4 weeks. This growth depression was not observed in chicks that received the same uric acid-containing diet but supplemented with 11 mg/kg of bacitracin and 44 mg/kg of procaine penicillin G. It is proposed that uric acid depresses growth by acting as an irritant and thus interfering with the absorption of nutrients from the intestinal tract; or uric acid inhibits the microbial biosynthesis of known vitamins or other nutrients essential to the host. Chemical analyses of the intestinal contents revealed an increased degradation of uric acid in the tract of the “uric-antibiotic”-fed chicks. No significant reduction or elevation was noted in the level of serum uric acid in any of the chicks. Antibiotic assays showed rapid penicillin inactivation in the tract, but persistence of the bacitracin. Although the beneficial response and increased uricolysis were observed in the “uric-antibiotic”-fed chicks, the level of antibiotic was lower in these birds. A growth response was obtained with diets supplemented with bacitracin only when an “old” environment appeared to have been established.