Inclusion of Red Osier Dogwood in High-Forage and High-Grain Diets Affected in Vitro Rumen Fermentation

Red osier dogwood (ROD) is an abundant shrub plant in Canada and other places in the world. It is rich in antioxidants such as quercetin, gallic acid and tyrosol. The objective of this study was to evaluate the effects of substituting barley silage with ROD in high-forage (HF) or high-grain (HG) diets on gas production (GP), dry matter (DM) disappearance (DMD) and fermentation characteristics in ruminal batch cultures. The study was a randomized design with 2 media pH (5.8 vs. 6.5) × 4 doses of ROD. An additional treatment of monensin and tylosin was added as a positive control for each pH level. The basic diet consisted of 60% barley silage and 40% barley grain for HF or 15% silage and 85% grain for HG diet. The barley silage was partly replaced with ROD at 0, 3, 6 or 12% in both diets (DM basis). Each diet was incubated for 24 h in culture bottles with three replicates for each treatment combination, and three runs on different days. The GP and DMD were greater (P<0.01) with media pH 6.5 vs. pH 5.8. The DMD linearly (P<0.01) decreased at pH 5.8 with increasing levels of ROD. Increasing ROD levels also linearly (P<0.01) decreased total VFA concentration and the proportion of propionate, and increased (P<0.01) the acetate to propionate ratio (A:P) at pH 5.8. Compared to the antibiotic treatment, the inclusion of ROD resulted in lower (P<0.02) DMD at pH 5.8, and a greater (P<0.01) proportion of acetate but a lower (P<0.01) proportion of propionate. These results indicated that the DMD of diets and the fermentation pattern were adversely affected by ROD at pH 5.8. However, the increased A:P along with the decreased DMD at pH 5.8, suggested a lower impact on fibre digestion than on starch digestion by ROD. Feeding ROD may therefore potentially reduce the incidence of rumen acidosis resulting from feeding HG diets to ruminants by decreasing starch digestion in the rumen.