Effect of dietary aflatoxin on the uptake and elimination of chlortetracycline in broiler chicks.

Day-old broiler chicks were fed 0, 1.25, 2.5, and 5.0 micrograms aflatoxin/g of feed for 3 weeks. Chlortetracycline (CTC) was administered in the drinking water at a concentration of 50 mg/liter for 27 hr starting on Day 21. Three hours after initiation of the CTC treatment, birds receiving 2.5 and 5.0 micrograms/g dietary aflatoxin had significantly lower CTC in blood compared with the controls. At 12 and 27 hr after the initiation of CTC treatment, birds receiving any level of aflatoxin had significantly decreased blood levels of CTC compared with the controls. Intravenous injection of CTC of control birds and birds receiving 2.5 micrograms/g aflatoxin revealed a significant decrease in the elimination half-life of CTC and a significant increase in the total systemic clearance of CTC in the birds receiving dietary aflatoxin. Birds receiving 2.5 micrograms/g dietary aflatoxin also had a significant increase in the volume of gall bladder bile; however, this did not result in a greater amount of CTC being eliminated via bile. Studies on protein binding of CTC in the plasma of control birds and the plasma of birds receiving 2.5 micrograms/g dietary aflatoxin demonstrated that 60% more CTC is "free", or unbound, in the plasma of birds receiving no aflatoxin. These results suggest that aflatoxicosis lowers the plasma concentrations of CTC as a result of a decreased binding of CTC to plasma protein. This allows more unbound CTC to be available for elimination from the plasma by a means other than the liver, most likely via the kidney.