In situ evaluation of the ruminal and intestinal degradability of extruded whole horse beans.

Abstract

Four rumen and proximal duodenum fistulated non-lactating Holstein cows were used to determine the effect of extrusion at 120 degrees C of whole horse beans (Vicia faba cv Talo) on in vitro nitrogen (N) solubility and in situ degradation of dry matter (DM) and crude protein (CP) in the rumen and intestine. Cows were fed a ration of 30% whole horse beans (WHB) and 70% Italian rye-grass hay. The degradation of DM and CP was estimated using nylon bags suspended in the rumen for 2, 4, 7, 16, 24 and 48 h; the effective ruminal degradability of DM and CP was evaluated assuming a ruminal outflow rate of 0.06/h. Bags incubated in the rumen for 16 h were introduced into the small intestine through the duodenal cannula and subsequently recovered in the feces. Extrusion of WHB reduced N-solubility in buffer solution (21.1 vs 74.9%). Processing diminished the effective rumen degradability of DM (74.6 vs 80.4%) and CP (70.2 vs 89.2%). Meanwhile, the amounts of DM and CP digested in the intestine increased: 9.6 vs 1.4% and 25.2 vs 3.0% respectively. Therefore, feeds containing extruded WHB increase the availability of dietary proteins in the intestine compared with diets containing raw WHB.