Effect of molasses on fermentation quality of wheat straw ensiled with perennial ryegrass.

Context: Insufficient supply of silage has limited the development of animal husbandry in Tibet, where natural pasture may not meet requirements. Although wheat (Triticum aestivum L.) straw could be a supplementary forage, it is difficult to ensile. Mixing perennial ryegrass (Lolium perenne L.) and adding molasses may help to facilitate successful ensilage. Aims: The objectives were to determine the proper mixing ratios of wheat straw and perennial ryegrass for silage, and to evaluate the effects of different levels of molasses on fermentation quality. Methods: In Experiment 1, wheat straw was ensiled without perennial ryegrass or mixed at ratios of 4:1, 3:2 and 2:3 (fresh-weight basis). Fermentation quality was evaluated when the laboratory silos were opened after 7, 14, 30 and 60 days. In Experiment 2, a mixture of wheat straw and perennial ryegrass (2:3) was treated with 0%, 3%, 4% and 5% molasses (fresh-weight basis) and ensiled. Fermentation quality was determined at 7, 14, 30 and 60 days. Key results: In Experiment 1, inclusion of perennial ryegrass significantly (P < 0.05) increased lactic acid and water-soluble carbohydrate contents and the lactic acid:acetic acid ratio, and significantly (P < 0.05) decreased pH and contents of ammonia-nitrogen, acetic acid, butyric acid and total volatile fatty acids. The 2:3 mixture of wheat straw ensiled with perennial ryegrass was judged the best, with the highest lactic acid content and lowest pH and butyric acid content (P < 0.05). In Experiment 2, molasses addition significantly (P < 0.05) increased lactic acid, water-soluble carbohydrate and dry matter contents, and significantly (P < 0.05) decreased pH and ammonia-nitrogen content compared with the control. Trace amounts of propionic and butyric acids were observed in all silages. Fermentation quality was similar among all treatments with added molasses. Conclusions: Considering the costs of additives, 3% molasses was most suitable for practical application when ensiling wheat straw with perennial ryegrass at an optimum ratio of 2:3. Implications: This work may help to inform producers on efficient utilisation of wheat straw for silage making by demonstrating successful ensiling with perennial ryegrass and added molasses. With increasing demand for animal products, natural pasture may not meet the requirements for rapid development of husbandry. We found that ensiling wheat straw with perennial ryegrass favourably affected fermentation quality, with optimum ratio 2:3, and that molasses (3–5%) further improved the fermentation quality of mixed ensilages. The work provides practical guidance for expanding forage sources and improving forage utilisation efficiency. [ABSTRACT FROM AUTHOR]