In Japan, condensed barley distillers soluble (CBDS) is a widely known liquor byproduct that contains a high level of protein and is used as a supplementary protein feed for cattle. The present study evaluated the effects of CBDS feed on rumen fermentation and plasma metabolites in Japanese Black cows. Applying a replicated 3 × 3 Latin square design, nine cows were offered CBDS and hay (CBDS-t), soy bean meal and hay (Soybean-t) and only hay (Hay-t) over 35 days. We collected ruminal fluid and plasma just before feeding and at 3 h after feeding. The concentrations of propionate and butyrate in the rumen before feeding were lower in the CBDS-t than in the Soybean-t group (P < 0.05). However, after 3 h, the concentrations were higher in the CBDS-t than in the Soybean-t and Hay-t groups (P < 0.05). Although, there were no differences in the compositions (% mol) of propionate and butyrate in the rumen and the concentration of plasma β-hydroxybutyric acid before feeding between treatments, after 3 h they were significantly higher in the CBDS-t than in the Soybean-t and Hay-t groups (P < 0.05). These results indicate that feeding CBDS promotes rumen fermentation and butyrate metabolism.
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