Automated Long-Term Total Collection Versus Indicator Method to Estimate Duodenal Digesta Flow in Cattle

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Abstract
Four steers, fitted with re-entrant duodenal cannulas, were used to compare digesta flow as measured by automated total collection (ATC) with flow estimations based on chromium oxide (Cr2O3) and lignin concentrations of representative samples of 24-h collection of digesta. In two successive periods, each steer was fed about 4 kg/d of either an all-forage or an 80% sorghum grain diet. Duodenal digesta samples were automatically taken and pooled every 2 h, during the 3- to 6-d total collections. For animals adapted to the collection procedures, there was no consistent evidence of flow inhibition in the first 24 h of a long-term total collection. Flow rates of duodenal digesta and dry matter (DM), estimated by Cr2O3 and lignin were 15% greater and more variable than those measured by ATC. Digesta flow rates measured by ATC averaged 65 liters/d in steers fed the forage diet and 42 liters/d in the same steers receiving the grain diet. Apparent ruminal DM disappearance, calculated from direct measurements by ATC was 44% for the grain diet and 37% for the forage diet. Ruminal DM disappearance, based on Cr2O3 and lignin, was about 25% lower than the ATC values. The data indicate that the use of total collection procedures should include replication over days. Duodenal flow rates suggested a 24-h cyclic pattern of digesta flow for the grain diet, with a peak about midnight followed by a period of low flow before the onset of the light hours. Chromium oxide showed a similar flow pattern, but flow rate decreased more rapidly following the midafternoon peak. With the forage diet, 24-h patterns were only observed for Cr2O3 and lignin concentrations in duodenal digesta, which appeared different from the Cr2O3 concentration pattern with the grain diet. Diurnal variation of digesta flow was greater than day-to-day variation. Because of the diurnal variation, spot-sampling techniques must be considered very carefully, since inadequate sampling could easily misrepresent total collection samples and flow estimates. The data also suggest caution in the use of lignin as a marker in grain diets, and of Cr2O3 as a marker in forage diets for partitioning digestion in the duodenum of ruminants. Copyright © 1985. American Society of Animal Science . Copyright 1985 by American Society of Animal Science

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