The objective of the work is to evaluate the effects of four chemical additives on fermentation quality, aerobic stability, and in vitro ruminal digestibility of total mixed ration (TMR) silage. TMR containing 15% spent mushroom substrate, 25% soybean sauce residue, 45% napiergrass (Pennisetum purpureum (L.) Schum.), and 15% concentrate was ensiled with the following: (1) no additives (control), (2) potassium sorbate (PS, 0.1%), (3) sodium benzoate (SB, 0.1%), (4) sodium diacetate (SDA, 0.5%), and (5) calcium propionate (CAP, 0.5%) based on fresh weight. All silos (10 L) were opened for fermentation quality, in vitro ruminal digestibility analysis after 60 days of ensiling, and then subjected to aerobic stability test for 9 days. All TMR silages were well-conserved, as indicated by low pH, butyric acid, and ammonia nitrogen contents. During aerobic exposure, SDA was more stable with higher (p < 0.05) lactic acid and acetic acid contents and lower (p < 0.05) yeast counts than other TMR silages. In addition, SDA significantly (p < 0.05) increased cumulate gas production and in vitro dry matter digestibility compared with the control. Overall, SDA is recommended as additives to improve fermentation quality, in vitro ruminal digestibility, and aerobic stability of TMR silage prepared with local food by-products.
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.
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