Gastrointestinal tract ruminant species

In species where reabsorption of drugs from the gastrointestinal tract increases the half-life of elimination, salivary secretion represents another important excretion route. The large volume of alkaline saliva produced by ruminants offers the possibility of trapping the acidic drugs. Exhalation of products of drug metabolism, such as carbon dioxide and water, can also account for drug excretion. 

In most species, chloramphenicol is rapidly and almost completely absorbed from the gastrointestinal tract. This route of administration provides antibiotic levels in blood comparable witli or higher than die intramuscular or the subcutaneous routes. The only known exception is in ruminants in which the drug is destroyed by the rumen microflora. 

The absorption, distribution, metabolism and excretion of ochratoxin A have been summarized previously by the Committee as follows (Annex 1, reference 153). Ochratoxin A is efficiently absorbed from the gastrointestinal tract, mainly in the small intestine. Information from a number of species shows that it is distributed via the blood, mainly to the kidneys, with lower concentrations being found in liver, muscle and fat. Transfer to milk has been demonstrated in rats, rabbits and humans, but little is transferred to the milk of ruminants, owing to hydrolysis of ochratoxin A into phenylalanine and ochratoxin alpha by the rumenal microflora. The major metabolite of ochratoxin A in all species examined is ochratoxin alpha, formed by hydrolysis of the peptide bond. Ochratoxin alpha and minor hydroxylated metabolites that have been identified are all reported to be less toxic than ochratoxin A itself. Ochratoxin A is excreted in urine and faeces, and the relative contribution of each of these routes in different species is influenced by the extent of the... 

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