Purple prairie clover (PPC; Vent.) containing 84.5 g/kg DM of condensed tannin (CT) was ensiled without (Control) or with polyethylene glycol (PEG) for 76 days, followed by 14 days of aerobic exposure. Changes in fermentation characteristics were determined and bacterial and fungal communities were assessed using metagenomic sequencing. Addition of PEG that deactivated CT at ensiling increased ( < 0.05∼0.001) soluble N, non-protein N, lactic acid, total volatile fatty acids, ammonia N, deoxynivalenol (DON) and ochratoxin A (OTA), but decreased ( < 0.001) pH and water soluble carbohydrates. Concentration of DON and OTA increased ( < 0.001) for both silages with the extent of increase being greater for Control than for PEG treated silage during aerobic exposure. The PEG treated silage exhibited higher ( < 0.01∼0.001) copy numbers of total bacteria, , yeasts and fungi than Control. Addition of PEG decreased ( < 0.01) bacterial diversity during both ensiling and aerobic exposure, whereas it increased ( < 0.05) fungal diversity during aerobic exposure. Addition of PEG at ensiling increased ( < 0.05) abundances of and, but decreased ( < 0.01) abundances of and Filamentous fungi were found in the microbiome at ensiling and after aerobic exposure, whereas the were the dominate bacteria after aerobic exposure. In conclusion, CT decreased protein degradation and improved aerobic stability of silage. These desirable outcomes likely reflect the ability of PPC CT to inhibit those microorganisms involved in lowering silage quality and in the production of mycotoxins. The present study reports the effects of condensed tannins on the complex microbial communities involved in ensiling and aerobic exposure of purple prairie clover. This study documents the ability of condensed tannins to lower mycotoxin production and associated microbiome. Taxonomic bacterial community profiles were dominated by the after fermentation, with a notable increase in as a result of aerobic exposure. It is interesting to observe that condensed tannins decreased bacterial diversity during both ensiling and aerobic exposure but increased fungal diversity during aerobic exposure only. The present study indicates that the effects of condensed tannins on microbial communities lead to a reduced lactic acid and total volatile fatty acids production, proteolysis and mycotoxin concentration in the terminal silage and an improved aerobic stability. Condensed tannins could be used as additive to control unfavorable microbial development and maybe enhanced feed safety.
This study was conducted to evaluate the use of exogenous enzymes as a potential means of improving the ruminal digestion (i.e., degradability) of alfalfa hay and rice straw. Twenty six enzyme-additives were examined in terms of protein concentration and enzymic activities on model substrates. The exogenous enzymes contained ranges of endoglucanase, xylanase, β-glucanase, αamylase, and protease activities. Six of the enzyme additives were chosen for further investigation. The enzyme additives and a control without enzyme were applied to mature quality alfalfa hay substrate and subsequently incubated in rumen batch cultures. Five of the enzyme additives (CE2, CE13, CE14, CE19, and CE24) increased total gas production (GP) at 48 h of incubation compared to the control (p<0.05). The two additives (CE14 and CE24) having the greatest positive effects on alfalfa hay dry matter, neutral detergent fibre (NDF) and acid detergent fibre (ADF) degradability were further characterized for their ability to enhance degradation of low quality forages. The treatments CE14, CE24, a 50:50 combination of CE14 and CE24 (CE14+24), and control (no enzyme) were applied to mature alfalfa hay and rice straw. For alfalfa hay, application of the two enzyme additives, alone and in combination, increased GP compared to the control at 48 h fermentation (p<0.05), whereas only CE14 and CE14+24 treatments improved GP from rice straw (p<0.05). Rumen fluid volatile fatty acid concentrations throughout the incubation of rice straw were analyzed. Acetate concentration was slightly lower (p<0.05) for CE14×CE24 compared to the control, although individually, CE14 and CE24 acetate concentrations were not different from the control. Increases (p<0.05) in alfalfa hay NDF degradability measured at 12 and 48 h of incubation occurred only for CE14 (at 12 h) and for CE14+24 (at 12 and 48 h). Similarly, ADF degradability increased (p<0.05) with CE14 and CE14+24. As for rice straw, increased DM degradability was observed at 12 and 48 h of incubation for all enzyme treatments with an exception for CE14 at 12 h. The degradability of NDF was improved by all the enzyme treatments at either incubation time, while ADF degradability was only enhanced at 48 h. Overall, the enzymes led to enhanced digestion of mature alfalfa and there was evidence of improved digestibility of rice straw, an even lower quality forage.
Cereal grains rich in starch are widely used to meet the energy demands of high-producing beef and dairy cattle. Bacteria are important players in starch digestion in the rumen, and thus play an important role in the hydrolysis and fermentation of cereal grains. However, our understanding of the composition of the rumen starch-hydrolyzing bacteria (SHB) is limited. In this study, BODIPY FL DQ starch staining combined with fluorescence in situ hybridization (FISH) and quantitative FISH were applied to label, identify and quantify SHB possessing active cell-surface-associated (CSA) α-amylase activity in the rumen of heifers fed barley-based diets. When individual cells of SHB with active CSA α-amylase activity were enumerated, they constituted 19-23% of the total bacterial cells attached to particles of four different cultivars of barley grain and corn. Quantitative FISH revealed that up to 70-80% of these SHB were members of Ruminococcaceae in the phylum Firmicutes but were not Streptococcus bovis, Ruminobacter amylophilus, Succinomonas amylolytica, Bifidobacterium spp. or Butyrivibrio fibrisolvens, all of whose amylolytic activities have been demonstrated previously in vitro. The proportion of barley grain in the diet had a large impact on the percentage abundance of total SHB and Ruminococcaceae SHB in these animals.
The chemical composition of barley grain can vary among barley varieties (Fibar, Xena, McGwire, and Hilose) and result in different digestion efficiencies in the rumen. It is not known if compositional differences in barley can affect the microbiota involved in the ruminal digestion of barley. The objective of this study was to characterize the in situ rumen degradability and microbiota of four barley grain varieties and to compare these to corn. Three ruminally cannulated heifers were fed a low (60% barley silage, 37% barley grain, and 3% supplement) or high grain (37% barley silage, 60% barley grain, and 3% supplement) diet. One set of bags was used to estimate dry matter (DM), starch and crude protein (CP) degradability. A second set was used to extract DNA from the adherent microbiota and visualize grain after incubation using scanning electron microscopy (SEM). DNA was subjected to amplicon 16S rRNA gene sequencing followed by analysis using QIIME. In the low grain diet, McGwire had the highest effective degradability (ED) of DM (P < 0.01). The ED of starch was highest (P < 0.01) for Fibar, McGwire, and Xena, but the ED of CP was not affected by variety. For the high grain diet, Xena and McGwire had the highest ED of DM (P < 0.01). The ED of starch was highest (P < 0.01) for Xena and Fibar. The ED of protein was highest (P < 0.01) for Xena and McGwire. Although the microbiota did not differ among barley varieties, they did differ from corn and with incubation time. Lactobacilli were dominant members of the mature biofilms associated with corn and barley and were accompanied by a notable increase in the lactic acid utilizing genera, Megasphaera. As none of the cattle exhibited subclinical or clinical acidosis during the study, our results suggest that lactobacilli play a more prominent role in routine starch digestion than presently surmised.
Agricultural operations generate large quantities of manure which must be eliminated in a manner that is consistent with public health guidelines. Meanwhile, construction and demolition waste makes up about 25% of total solid municipal waste. Co-composting of manure with construction and demolition waste offers a potential means to make manure safe for soil amendment and also divert construction and demolition waste from municipal landfills. Therefore, the archaeal, bacterial, and fungal microbiota of two different types of composted cattle manure and one co-composted with construction and demolition waste, were assessed over a 99-day composting period. The microbiota of the three compost mixtures did not differ, but significant changes over time and by sampling depth were observed. Bacillus and Halocella, however, were more relatively abundant in composted manure from cattle fed dried distillers’ grains and solubles. Proteobacteria and Bacteroidetes were enriched at day 0 and Firmicutes at day 99. The fungal genus Kernia was the most relatively abundant overall and was enriched at day 0. The concentration of 12 antimicrobial resistance determinants in the compost mixtures was also determined, and 10 of these determinants decreased significantly from days 0 to 99. The addition of construction and demolition waste did not affect the persistence of antimicrobial resistance genes or community structure of the compost microbiota and therefore co-composting construction and demolition waste with cattle manure offers a safe, viable way to divert this waste from landfills.
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