MONENSIN CONCENTRATIONS MEASURED IN FEEDER CATTLE USING ENZYME-IMMUNOASSAY

Thirty heifers were fed a ration containing 30 g monensin/ton. Fecal, urinary and seral samples were collected at varying intervals prior to and after initiating administration of the monensin-containing feed, and monensin concentrations were determined using a modified indirect enzyme immunoassay. Fecal samples contained measurable (mu g/g; ppm) c oncentrations of monensin in most samples. The majority of sera and ur ine samples contained monensin at ng/ml (ppb) concentrations, which we re above background levels prior to monensin feeding. Twelve head were fed monensin at 60 g/ton and 90 g/ton for 5 d with collection of simi lar samples. Higher concentrations of monensin were detected with incr easing ration amounts in all 3 sample types. Enzyme Immunoassay for mo nensin in these biological samples identified presence of the feed add itive.