USE OF CHROMIUM-OXIDE IN DIGESTIBILITY STUDIES - VARIATIONS OF THE RESULTS AS A FUNCTION OF THE MEASUREMENT METHOD

The objective of the present study was to evaluate the agreement of tw o methods for the determination of chromium oxide in feed, duodenal co ntents and faeces in the investigation of feed digestibility. Four Hol stein steers fitted with permanent ruminal and duodenal cannulae were used in a 4 x 4 Latin square design experiment. Steers were fed diets varying in urea content three times daily, restricted at a level equiv alent to 2.5% of live body weight (dry matter basis). Faecal and duode nal fluxes of dry matter and nitrogen were estimated using chromium ox ide (Cr2O3) as a indigestible marker. The equivalent Cr2O3 concentrati on in the solution resulting from acid digestion of the samples was me asured by chromium determination by simple photometry at 350 nm and by flame atomic absorption spectrometry. Chromium concentrations in feed , duodenal contents and faeces and ruminal and total digestibilities o f dry matter and nitrogen were affected by the chromium determination methods used. Despite the fact that the AAS method is more precise and sensible, sometimes its utilisation is limited by availability of equ ipment. In this situation, the chromium determination by photometric m ethod can be a feasible alternative, since proper corrections in optic al density readings are done. (C) 1998 SCI.