Evaluation of internal markers for estimating duodenal digesta flow in ruminants: acid detergent fibre and lignin disappearance at the lower gastrointestinal tract

摘要

Most of published studies carried out for estimating organic matter (OM) rumen digestibility (OMRD) use research animals fitted with simple t-typc cannulas and an external or internal marker for estimating the duodenal digesta flow. Compared to external, the internal markers have the advantage of occurring naturally in diet and, consequently, they flow intimately associated with digesta (Titgemeyer 1997). Porter and Singleton (1971a) reported from a study with sheep fitted with re-entrant duodenal cannula that lignin degradation takes place entirely in the stomach. Thus, in digestibility studies where total faeces output is measured, duodenal digesta flow may be estimated based on both faeces output and the ratio of lignin concentration in faeces and in duodenal digesta. However, sulphuric acid lignin (ADL) is present in low concentrations in duodenal digesta and the precision of duodenal flow estimates is usually compromised. This study evaluated the disappearance at the lower gastrointestinal tract and, consequently, the potential use of acid detergent fibre (ADF), in comparison with ADL, as an internal marker for estimating duodenal digesta flow in cattle.