Composition and Intestinal Digestibility of Rumen Fermented Feeds and Duodenal Digesta in Cows Using Bag Techniques

Abstract

Three rumen-cannulated and five duodenal-cannulated lactating Holstein cows were used to compare the chemical composition and oodegraded dietary protein digestibility of unfermented feedstuffs isolated in two different ways, from polyester bags (in situ rumen-fennented and in vitro pepsin-digested) or from duodenal-collected digesta, respectively. There was a good resemblance between the chemical composition of unfennented feedstuffs isolated from polyester bags and duodenal digesta, irrespective of whether a complete or hay diet was fed. Using the polyester bag isolated 00- degraded dietary protein and mobile bag for intestinal digestion, the digestibility of this fraction ranged from 36.6 to 37.9% for the hay diet and from 64.5 to 65.2% for the complete diet. The corresponding values for duodenal-collected digesta were 42.6 to 43.2% and 56.5 to 56.9% for the hay and complete diets, respectively. The results suggest that the factor for undegmded dietary protein digestibility used by some of the new protein evaluation systems is too high.