PSIV-25 - Investigating the use of cover crop inclusion and preservation in silages with addition of molasses, homofermentative and heterofermentative bacterial mixes

Abstract: The use of cover crops in agriculture has had positive effects on soil health and sustainability. In the western US, utilizing cover crops for silage production provides many of the same soil health benefits while providing forage for ruminants, serving multiple sectors with the same water cost. Therefore, the aim of this study was to determine effects of mixed grass and legume silage combined with different inoculants on silage quality and in vitro rumen fermentation. Four silage mixes (100% sorghum [0SB], 67% sorghum + 33% soybean [33SB], 33% sorghum + 67% soybean [67SB], and 100% soybean [100SB]) were prepared and 6 treatments were applied to each mix: homofermentative lactic acid producing bacteria (LB), heterofermentative lactic and acetic acid producing bacteria (LB+), molasses, molasses and LB (MLB), molasses and LB+ (MLB+), and no inoculant (control). Silage mixes plus inoculants were made in triplicate, vacuum sealed in plastic bags, and ensiled for 60 days at 25°C. Once bags were opened, 200 mg air-dried of each silage treatment were incubated in 14 mL of buffering media and 4 mL of rumen inoculum. Each incubation spanned for 48h with gas production measured at 0, 2, 4, 8, 12, 18, 24, 36, and 48-h post-incubation. Total gas production (TGP), pH, ammonia and total volatile fatty acids (VFA) were determined. Ammonia concentrations were higher when samples were inoculated with LB, and the lowest for MLB+ (P < 0.05); however, no differences were observed between silage mixes (P >0.05). Total VFA concentrations were similar across treatments (P > 0.05). However, butyrate was higher for 33SB silages mixes inoculated with MLB (P > 0.05). Valerate concentration was higher for all treatments inoculated with molasses (P < 0.001). Isobutyrate and Isovalerate levels were only different when comparing between silage concentrations, where 0SB silages had the highest concentration (P < 0.05). Although no differences were observed on TGP (P > 0.05), pH of samples incubated with no inoculant, LB, and LB+ were higher than all samples inoculated with molasses (P < 0.001). In conclusion, the use of mixed grass and legume silages with up to 33% soybean inclusion appear to be beneficial to ruminal fermentation. However, variable results might be produced depending on the inoculant used. The incorporation of these cover crop varietals and their subsequent inclusion in silos for livestock feed represents a viable and effective application for producers currently utilizing cover crops in their operations.