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1 Ecole Nationale Supérieure Agronomique, Laboratoire de Zootechnie et Qualité des Produits, Avenue de lAgrobiopole, 31326 Castanet-Tolosan, France
2 Ecole Nationale vétérinaire de Toulouse, Département Elevage et Produits, Laboratoire dAlimentation, Chemin des Capelles, 31076 Toulouse, France
Corresponding author: C. Bayourthe; e-mail: bayourth{at}ensat.fr.
A sampling and measuring device was set up to measure continuously the pH and the redox potential (Eh) of ruminal content in absence of any gaseous contamination (method 1). It was compared with a conventional suction device in which no precaution was taken to prevent air from coming into contact with the surface of collected samples (method 2). Two fistulated dry cows were used and fed a total mixed ration. Redox potential and pH measurements were performed repeatedly on collected samples using these 2 methods during a 9-h period; each period started 1 h before feeding. The partial pressure of oxygen (log fO2) was calculated from Nernsts equation using pH and Eh values. Results indicated that pH, Eh, and log f(O2) were affected by sampling method. In method 1, pH values ranged from 6.7 to 6.37 and Eh from 173.5 to 216.8 mV. In method 2, pH and Eh values varied, respectively, from 6.93 to 6.49 and from 111.3 to 139.5 mV. The partial pressure of oxygen was 106 times lower in samples that were continuously collected than in hand-samples. As a result, method 1 could make accurate measurements of pH and Eh of ruminal content.
Key Words: redox potential method of measurement rumen dairy cow
Abbreviation key: Eh = redox potential, log f (O2) = partial pressure of oxygen
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