Comparative study of chloramphenicol absorption in calves after oral, intra-ruminal and intra-abomasal administration

The mechanisms responsible for the rapid decline of chloramphenicol plasma levels after oral administration in young calves during their first weeks of life were investigated. Chloramphenicol was administered by stomach tube, to four 2 week old calves on three consecutive days at a dose of 50 mg/kg. The plasma levels increased daily to a peak value on the third day. The minimum therapeutic concentration of 5 μg/ml, however, was barely obtained. Simultaneous estimation of the ruminal contents showed a parallel increase in chloramphenicol concentration. Thus it can be assumed that there is an inefficient absorption of chloramphenicol from the forestomachs of young calves. Chloramphenicol was not metabolized by the ruminal contents until the calves were 9 weeks old. Finally chloramphenicol was administered to 7 week old calves by the intra-abomasal route, intraruminal route and by mouth. Only with the intra-abomasal method could a therapeutically effective level be reached. This indicates that the rapid decline of chloramphenicol plasma levels in calves during their first weeks of life could be attributed to the delayed reticulo-rumen emptying and to inefficient absorption from the forestomachs.