Effect of inclusion of grasses and wet hulless-barley distillers' grains on the fermentation and nutritive quality of oat straw- and straw-grass silages in Tibet

In order to enlarge the feed resources in Tibet, oat straw was conserved as silage by combining with tall fescue and wet hulless-barley distillers' grains (WHDG). In Experiment 1, oat straw was ensiled with four levels of tall fescue (0, 20, 40 or 60% of fresh weight) in laboratory silos for 30 days. Ensiling oat straw with tall fescue significantly increased (P < 0.05) lactic acid and water-soluble carbohydrate contents, and significantly (P < 0.05) decreased acetic acid, propionic acid, butyric acid and total volatile fatty acid concentrations. The values of pH and ammonia/total N decreased with the increase in tall fescue ratios. There were no significant differences (P > 0.05) in pH value between 40 and 60% tall fescue inclusion silages. To maximise the use of straw, it was suggested that 40% tall fescue inclusion was proper for further study. In Experiment 2, mixture of tall fescue and oat straw (6/4) were ensiled with 0, 10, 20 or 30% WHDG, triplicate silos for each treatment were opened on 7, 14, 30 and 60 days after ensiling, respectively, the fermentation characteristics and in vitro rumen degradability were analysed. WHDG addition significantly improved the fermentation quality of mixed silages, indicated by significantly lower (P < 0.05) pH, ammonia/total N, butyric acid and propionic acid concentrations and significantly higher (P < 0.05) DM and lactic acid content than the control. WHDG addition silages also showed higher crude protein contents, and lower neutral detergent fibre and acid detergent fibre content. These results suggest that adding WHDG to mixture of oat straw and tall fescue before ensiling appears to be a feasible strategy to improve the fermentation and nutritive quality of straw-grass silage.