Fermentation Quality and Bacterial Ecology of Grass Silage Modulated by Additive Treatments, Extent of Compaction and Soil Contamination

Abstract

New technologies related to the identification of bacterial communities in fresh forage and silage may give valuable detailed information on the best practices to produce animal feeds. The objective was to evaluate how management conditions during silage making manipulate the profile of bacterial communities and fermentation quality of grass silages. Silages were prepared from mixed timothy and meadow fescue grass using two compaction levels. As an additional treatment the grass was contaminated with soil and feces prior to tight compaction. Four additive treatments with different modes of action were applied: control without additive, formic acid-based additive, homofermentative lactic acid bacteria and salt-based additive. After 93 days the silos were opened, samples were taken and routinely analyzed. DNA extraction was carried out and PCR amplification of the bacterial 16S rRNA gene V4 region was performed using universal primers. The silage pH was higher for loose than tight compaction and higher for non-contaminated than for contaminated silages. Great shift was observed in bacterial profiles from fresh material towards silage. Lactobacillus genus was barely found on the relative abundance of fresh grass but became predominant in the final silage along with Sphingomonas genus. Use of additives improved fermentation quality and modified the bacterial profiles of grass ensiled under different management conditions.

Fermentation quality and bacterial ecology of red clover dominated silage modulated by different management factors

“…The effects included significant differences in pH (4.51 vs 4.55), lactic acid (59.9 vs 57.0 g/kg DM) and acetic acid (30.8 vs 36.2 g/kg DM), and proportion of ammonia N in total N tended (P<0.06) to increase (53 vs 56 g/kg N). The responses to contamination were not as clear as in Franco et al (2022) indicating that the raw material characteristics in the current experiment were more resistant to contamination, or that the contaminants were less competitive. However, in both cases, increased acetic acid production was noted, and it probably contributed to the increased aerobic stability of the silages (234 vs. 374 h for non-contaminated and contaminated silages, respectively; P<0.01).…”

“…The only fermentation characteristic that was significantly (P<0.03) affected by compaction was the sum of all fermentation acids, which was higher for loosely rather than tightly compacted silages (95.8 vs. 91.9 g/kg DM). Limited responses to intensity of compaction have also been obtained earlier in pilot scale silos (McEniry et al, 2007;Franco et al, 2022). Use of airtight laboratory silos may not mimic sufficiently farm scale silos regarding the effects of compaction, which could explain the limited responses to compaction in the current experiment.…”

“…The standard analytical methods used for dry matter (DM), ash, crude protein, water soluble carbohydrates (WSC), neutral detergent fibre, buffering capacity, organic matter digestibility, pH, ammonia-N, lactic acid, volatile fatty acids (VFA), formic acid, ethanol and microbial counts as well as the conduction of the aerobic stability test based on heat accumulation are described in detail by Franco et al (2022).…”

“…Various investigations have used integrated 16S rRNA sequencing to analyse the microbiome of fermented feeds to better comprehend biological mechanisms that underpin silage production systems (Guo et al, 2018;Xu et al, 2019). The identification of bacterial communities in the fresh biomass used as the raw material and subsequent silages provides new insights into the understanding of the silage fermentation process (McAllister et al, 2018;Bai et al, 2020;Li et al, 2021;Wang et al, 2021), as each and every particular bacterial community can modulate nutritional composition, hygienic quality and overall ensiling process of the feed and influence ensiling losses (Franco et al, 2022).…”

Metataxonomic analysis of the uterine microbiota associated with low fertility in dairy cows using endometrial tissues prior to first artificial insemination

“…Because the bacteria to which cows are exposed are strongly affected by the farm environment, proper implementation of hygiene practices is important in regulating the uterine microbiota [32]. In terms of feeding management, the fermentation condition of silage [42][43][44] and feed content, especially the ratio of roughage to compound feed [34,35], should be considered because of their signi cant effect on the composition of the gastrointestinal microbiota. Thus, maintaining a suitable uterine microbiota rea rms the importance of going back to basics and provides a new perspective on reproductive management.…”