Suitability of anaerobic fungi culture supernatant or mixed ruminal fluid as novel silage additives

Abstract

This study investigated silage quality characteristics and ruminal fiber degradability of grass and straw ensiled with either anaerobic fungi (AF) supernatant with active fungal enzymes or mixed ruminal fluid as novel silage additives. Compared to control silages, AF supernatant improved the quality of grass and straw silages as evidenced by decreased pH, acetic acid concentration, and dry matter losses. Likewise, mixed ruminal fluid enhanced lactic acid fermentation, which further resulted in lower pH of the treated grass silage. The ruminal fiber degradability was determined using in situ incubations and, compared to controls, the cellulose degradability was higher for grass silage with AF supernatant, whereas ruminal degradability of straw silage was reduced by this treatment. In contrast, mixed ruminal fluid did not influence fiber degradability of silages in the rumen. Concluding, both novel additives improved silage quality, whereas only AF supernatant enhanced ruminal fiber degradability of grass silage and therefore may represent an approach for improving forage utilization by ruminants. Key points • Enzymes of anaerobic fungi supernatant improve quality of grass and straw silages. • Mixed ruminal fluid enhances lactic acid fermentation when ensiling grass and straw. • Enzymes of anaerobic fungi supernatant increase ruminal grass silage degradability.

Mixed ensiling of drought‐impaired grass with agro‐industrial by‐products and silage additives improves the nutritive value and shapes the microbial community of silages

“…It is conceivable that additional sugars released during fungal fibre degradation in the silos were metabolized into lactic acid. Surprisingly, the effect was also present for the InactAF treatment, so clarification is needed regarding the mode of action as the active components were not present in the heat‐inactivated additive and such effects have not been observed in our previous studies (Hartinger et al, 2022; Hartinger et al, 2024). In contrast to these findings, the pH was not as low as in CON silages, which is unexpected because lactic acid predominantly contributes to the pH decline in silages (Kung et al, 2018) and also disagrees with previous findings on AF‐treated grass silages (Hartinger et al, 2022).…”

“…Immediately after opening the vacuum bags, a cold‐water extract was prepared from each silage according to Hartinger et al (2022). Briefly, a 50 g sample was taken and mixed with 100 mL of distilled water in a jar, sealed, and placed in the fridge at 4°C for 24 h. Then, the content was filtered through three layers of gauze (Wilhelm Weisweiler GmbH & Co. KG, Münster, Germany) and the pH was directly measured using a calibrated pH meter (S40‐K SevenMulti™ pH meter, Mettler Toledo, Vienna, Austria).…”

“…Three different silage additives were used, that is, AF, RF, and LAB. The AF was obtained as described by Hartinger et al (2024). Briefly, the AF was derived from the fungal strain Feramyces DF1 (GenBank accession number MW907584), which was isolated from deer rumen content.…”

“…These silages were then ensiled without a silage additive (CON) or with either fresh AF, InactAF, fresh RF, InactRF or LAB. The applied concentrations were 100 g/kg DM for RF and InactRF as well as 10 g/kg fresh matter (250,000 colony-forming units per g fresh matter) for the LAB, which corresponds to previous ensiling trials (Hartinger et al, 2022) or to the manufacturer's recommendation. For AF and InactAF, a dosage of 250 g/kg DM was applied, which is higher than in previous ensiling experiments (Hartinger et al, 2022) and was chosen to investigate whether the beneficial effects on silage quality and ruminal in situ degradability observed before (Hartinger et al, 2022) can be further enhancedespecially since AF constitutes a novel silage additive candidate for which no knowledge on optimal dosages exists.…”

“…Recent research from our team found the addition of anaerobic fungi culture supernatant (AF) or mixed ruminal fluid (RF) to be a tool to improve the silage fermentation quality in grass silages: Both additives resulted in lower silage pH and reduced dry matter (DM) losses. Furthermore, AF had significantly improved the in situ fibre degradability, which was attributed to a fibre‐cleaving effect of fungal enzymes in the silage (Hartinger et al, 2022). Besides these two additives, other studies have suggested that lactic acid bacteria (LAB) could promote the silage fermentation in forages with unfavourable properties, including those with rather low water‐soluble carbohydrate (WSC) concentrations (Guo et al, 2023), which may also apply to drought‐impaired forages.…”