Activity gradient, Ca

Carboxylic lonophores and Efficiency of Feed Conversion by Livestock. A strong note of relevance to studies of the chemical and pharmacological properties of carboxylic lonophores derives from the large scale use of monensin as a livestock feed additive. The rationale is that carboxylic lonophores control endemic coccidiosis in the poultry gut (30) and promote a more favorable fermentation of cellulose in the bovine rumen (31). In either case, the net result is the economically important Increased efficiency of conversion of feed into meat. 

Pharmacokinetics of lonophore Absorption. We have developed a sensitive chemical assay for carboxylic lonophores (which will be published elsewhere) based on their ability to form lipid soluble complexes with cations. We can detect as little as 1 part per billion (ppb) monensin in 2 ml of blood plasma or tissue. For a comparison yardstick, current feeding regimens call for ca. 30 parts per million (ppm) in cattle feed (32) and as much as 100 ppm in poultry feed (33). 

ACS Symposium Series American Chemical Society Washington, DC, 1980. 

The Need for Increased Surveillance of the Exposure of Man to lonophores. From the lipid soluhllity of monensln and other lonophores, we would predict they should have no trouble equilibrating across biological membrane systems including the gut. This Is certainly the case for the two diverse species observed, the dog, a carnivore, and the rabbit, a herbivore. Accordingly, we infer that there Is ample opportunity for monensln and other carboxylic lonophores administered orally to livestock to distribute systemically and exert a pharmacological effect on the recipient animal. Furthermore, the resultant physiological effects may be part of the mechanism by which lonophores produce their Improved feed conversion efficiency. 

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