Effects of conservation method on condensed tannin content, ruminal degradation, and in vitro intestinal digestion of purple prairie clover (Dalea purpurea Vent.)

Abstract

In situ and in vitro experiments were conducted to evaluate the effect of forage conservation method on the chemical composition, ruminal degradation, and intestinal digestion of purple prairie clover (PPC), which was conserved as freeze-dried forage (FD), silage (SIL), or hay (Hay). In situ dry matter (DM), neutral detergent fiber (NDF), and crude protein (CP) degradabilities were determined by incubating the forages in three rumen-cannulated heifers for 0, 1, 2, 4, 8, 24, 48, and 72 h. Intestinal DM and CP digestions were estimated by incubating 12 h ruminal in situ residues in a modified three-step in vitro procedure. Ensiling decreased (P < 0.001) extractable condensed tannins (CT) but increased (P < 0.001) protein- and fiber-bound CT compared with FD and Hay. The ruminal disappearance of CP at 8 and 24 h was affected by conservation method (P < 0.001), ranked as SIL > FD > Hay. The effective degradability of DM was lower (P < 0.001) for Hay than for FD and SIL. Ensiling lowered (P < 0.001) whereas haymaking increased (P < 0.001) intestinal digestion of CP compared with the fresh PPC. There were no differences in intestinal DM digestion among the three conserved forages. The results suggest that PPC conserved as Hay may conserve the biological activity of CT via preserving extractable CT more than as SIL, thus having the potential to improve protein utilization in ruminants.