Effects of sugar sources and doses on fermentation dynamics, carbohydrates changes, in vitro digestibility and gas production of rice straw silage

Abstract

To elucidate the differences of various sugar sources and doses on rice straw silage, the effect of molasses (M, direct substrate) and fibrolytic enzyme (E, indirect substrate) with four doses on fermentation dynamics, carbohydrates and in vitro digestibility was evaluated. Molasses (0, 2, 3 and 4% of fresh weight) or fibrolytic enzyme (0, 0.02, 0.04 and 0.06%) were applied to fresh rice straw ensiling for 3, 6, 9, 15, 30 and 60 days. All additives increased lactic acid content and lactic/acetic acid, reduced pH, NH 3-N content of resulting silage (p < .05). The highest lactic acids, residual sugar and fibre degradation were observed in 0.06%E (p < .05). M-treated silage had higher dry matter (DM) content, in vitro digestibility of DM and neutral detergent fibre, and less DM loss, acetic acid, butyric acid and in vitro gas production (GP) than other treatments. Both sugar sources effectively improved fermentation quality. Fibrolytic enzyme induced free sugar release from fibre, especially from hemicellulose, while molasses showed a potential dose effect to decrease ruminal energy waste by increasing digestibility and decreasing GP in vitro. 3%M, 4%M and 0.04%E produced moderate silage based on V-score, and 4%M is recommended for rice straw silage, indicated by intermediate fermentation quality and higher in vitro digestibility. HIGHLIGHTS Low WSC limited fermentation Sugar sources reduced fibre with various mechanisms Molasses decreased in vitro gas production with a dose effect ARTICLE HISTORY

Using γ-ray irradiation and epiphytic microbiota inoculation to separate the effects of chemical and microbial factors on fermentation quality and bacterial community of ensiled Pennisetum giganteum

“…Similar fermentation patterns were observed between M I C I and M II C I silages, as well as between M I C II and M II C II silages, which might be interpreted that even if M I contained insufficient LAB (<10 5 cfu/g FW), the chemical quality of material (mainly WSC content) still determined the natural fermentation. Our previous study (Zhao et al, 2019) also found that sugar supplementation improved the fermentation quality of rice straw lacking LAB. Meanwhile, under the same epiphytic microbiota (M I or M II ) inoculation, changes of chemical composition had marked effects on the fermentation parameters of P. giganteum silage (M I C I vs. M I C II or M II C I vs. M II C II ).…”

Comparative profiling of lactic acid bacteria isolates in optimized and spontaneous fermentation of cowpea leaves

“…Zhao et al. (2019) reported a slow transition of homofermentation to heterofermentation which he solved by addition of molasses. In the current study, the fermentation in spontaneous process was originally dominated by the homofermenter ( L. lactis ) before the obligate heterofermenter ( L. brevis and genus Leuconostoc ) dominated the intermediate stage.…”

Application of lactic acid bacteria producing antifungal substance and carboxylesterase on whole crop rice silage with different dry matter

“…After harvesting, the rice straw commonly is preserved by making silage or hay. However, it has poor content of soluble carbohydrate after separating from its grains, which results in a low fermentation quality when it is preserved as silage [ 8 ]. The LAB cannot grow optimally with low content of soluble carbohydrate leading an inability to drop the pH rapidly during ensiling [ 9 ].…”