PSX-B-8 - Effect of supplementing red osier dogwood extract on in vitro gas production, feed digestibility and fermentation characteristics of high-forage diet

Red osier dogwood (ROD) is native shrub plant in Canada and rich in bioactive compounds. The objective of this study was to evaluate the effects of ROD extract supplementation in a high-forage (HF) diet on gas production (GP), dry matter (DM) disappearance (DMD) and fermentation characteristics in batch cultures with varying media pH. The study was a completely randomized design with 4 levels of ROD extract (0, 1, 3 and 5% of substrate) × 2 media pH (5.8 and 6.5) factorial arrangement. The study was conducted in three replicate experiments. Substrate contained 60% barley silage and 40% barley concentrate (DM basis). Inoculum was obtained from 2 ruminally fistulated beef heifers offered the HF diet. Substrate (0.5 g DM) ground (1 mm) was incubated for 48 h in a culture bottle. Data were analyzed using Mixed procedure of SAS with fixed effects of treatments and random effect of experiment. There was no interaction between media pH and level of ROD on GP, DMD and fermentation characteristics. Increased media pH (5.8 vs. 6.5) increased (P < 0.01) GP (averaged 164 vs. 275 ml/g substrate), DMD (50.6 vs. 60.6%), and total VFA production (63 vs. 71 mM). Increasing ROD extract levels did not affect GP but linearly (P = 0.05) decreased DMD from 62.1 to 58.9% at pH 6.5. Although total VFA production was not affected, increasing ROD extract linearly (P < 0.01) increased the proportion of acetate (47.9 to 49.7%) and propionate (20.5 to 22.3%) at pH 5.8; whereas at pH 6.5, acetate to propionate ratio quadratically (P = 0.04) changed to be lower with 3% ROD extract (2.08) than other treatments (2.21). These results indicated that supplementation of HF diet with ROD extract may improve fibre digestion at low media pH, and improve fermentation efficiency at high media pH.