SAMPLING TECHNIQUE FOR COLLECTION OF EXPIRED CO2 IN STUDIES USING NATURALLY LABELLED 13C IN CALVES

Abstract

Natural isotopic labelling of animal metabolic processes presents great advantages over the use of artificially enriched compounds. These advantages include the use of natural diets, low cost and easiness of handling, sampling and disposal. Changes in the 13C/12C ratio of expired CO2 after ingestion of a test meal containing a variable proportion of C3 and/or C4 plant-derived products permits measurements of the immediate oxidation of dietary carbohydrates. A breathing device for collection of expired CO2 and purification techniques are described. The breath-sampling device is composed of a polypropylene enclosure and a rubber bag. The rubber bag is blown up by the animal and a sample of the expired gas is transferred to a sampling glass holder in which a vacuum had been previously achieved. Sample purification of expired CO2 is done by differential freezing. Key words: Breath device, carbon 13, calf