A Multi-Sensor Mini-Bioreactor to Preselect Silage Inoculants by Tracking Metabolic Activity in situ During Fermentation

The microbiome in silage may vary substantially from the onset to the completion of fermentation. Improved additives and inoculants are being developed to accelerate the ensiling process, to enhance fermentation quality, and to delay spoilage during feed-out. However, current methods for preselecting and characterizing these amendments are time-consuming and costly. Here, we have developed a multi-sensor mini-bioreactor (MSMB) to track microbial fermentation in situ and additionally presented a mathematical model for the optimal assessment among candidate inoculants based on the Bolza equation, a fundamental formula in optimal control theory. Three sensors [pH, CO2, and ethanol (EtOH)] provided data for assessment, with four additional sensors (O2, gas pressure, temperature, and atmospheric pressure) to monitor/control the fermentation environment. This advanced MSMB is demonstrated with an experimental method for evaluating three typical species of lactic acid bacteria (LAB), Lentilactobacillus buchneri (LB) alone, and LB mixed with Lactiplantibacillus plantarum (LBLP) or with Enterococcus faecium (LBEF), all cultured in De Man, Rogosa, and Sharpe (MRS) broth. The fermentation process was monitored in situ over 48 h with these candidate microbial strains using the MSMB. The experimental results combine acidification characteristics with production of CO2 and EtOH, optimal assessment of the microbes, analysis of the metabolic sensitivity to pH, and partitioning of the contribution of each species to fermentation. These new data demonstrate that the MSMB associated with the novel rapid data-processing method may expedite development of microbial amendments for silage additives.

Nutritive Value and Preference of Guinea-Grass Ensiled with or without Additive by West African Dwarf (WAD) Goats

A study was designed to investigate silage additives’ effect on preference and nutritive value of five weeks re-growth guinea grass by West African dwarf (WAD) goats. The silages of five weeks re-growth guinea grass were made without additive (T1), with cassava peels additive (T2), and with fermented epiphytic juice of lactic acid bacteria in Panicum maximum (FEJPM) additive (T3). The effects of silage additives on preference, voluntary feed intake, growth, digestibility, and nitrogen utilization were assessed using 18 growing WAD goats (BW: 5.88±0.26 kg) in a completely randomized design. Dry matter was significantly (p<0.05) higher in T2 silage (40.70 g/100g) than in T1 silage (39.00) and T3 silage (34.60). Crude protein values were similar (p>0.05) in T1 and T3 silages (10.63 and 10.72 g/100g DM) that were significantly lower (p<0.05) than that in T2 silage (12.54 g/100g DM). The silages of guinea grass had acceptable physical attributes in terms of color, odor, and texture, with pH values ranging from 3.87- 4.97. T1 and T3 silages were rejected, whereas T2 silage was accepted well by the experimental WAD goats. Average daily feed intake (ADFI) was significantly (p<0.05) the highest in the WAD goats fed T2 silage (303.30 g/day), and the lowest (p<0.05) was found in WAD goats fed T1 silage (271.60 g/day). Similar to the ADFI, the highest average daily gain (ADG) was found in WAD goats fed T2 silage (37.25 g/day), and the lowest ADG (p<0.05) was found in WAD goats fed T1 silage (24.50 g/day). Feed conversion ratio (FCR) of WAD goats fed T2 silage (8.15) was superior to those of WAD goats fed T1 silage (13.63) and T3 silage (9.66). Crude protein and dry matter digestibility values were higher (p<0.05) in WAD goat fed T2 silage (68.24 and 63.87%, respectively) than in WAD goats fed T1 and T3 silages. Nitrogen intake and balance were significantly (p<0.05) the highest in WAD goats fed T2 silage (12.41 and 8.68 g/day, respectively), and these variables were similar in WAD goats fed T1 and T3 silages. Nitrogen retention was not affected by the silage additives. It was concluded that cassava peels were better than FEJPM as a silage additive since it improved fermentative quality, acceptability, feed intake, and digestibility of guinea grass silage by WAD goats.

Effect of Lactic Acid Bacteria on the Nutritive Value and In Vitro Ruminal Digestibility of Maize and Rice Straw Silage

A study was conducted to determine the effects of lactic acid bacteria (LAB) on nutritive value and in vitro rumen digestibility of maize and rice straw silages. Two identical experiments were carried out for each of the two silages. A total of five treatments were used for each experiment: (1) negative control (NC); (2) positive control (PC); (3) Lactobacillus plantarum (LPL); (4) L. paracasei (LPA); and (5) L. acidophilus (LA). Each treatment was then divided into four ensiling periods: 3, 7, 20, and 40 days with three replications. The LPL treatment had significantly higher dry matter (DM), lower ammonia-N, and a lower number of fungi on maize silage after 40 days (p < 0.05). On the other hand, the LA treatment increased DM and CP content, reduced NDF and ADF contents compared to NC, and also produced more lactic acid compared to the other LAB-treated rice straw silages. Results of the in vitro rumen fermentation of maize silages showed no significant differences in DMD after LAB inoculation. However, higher DMD and ruminal ammonia-N were shown by rice straw ensiled with L. acidophilus. In conclusion, silage additives, which could improve the ensiling process of maize and rice straw, appeared to be different and substrate specific.

Fermentative characteristics and chemical composition of cochineal nopal cactus silage containing chemical and microbial additives

The objective of this study was to evaluate the fermentative characteristics and chemical composition of cochineal nopal cactus silage additives with urea or Lactobacillus buchneri (LB), as well as the association of both additives in four storage times (7, 15, 60 and 120 days) and during aerobic stability, with evaluations at 0, 48 and 96 h. Four silages were used: no additive, addition of 2% urea, addition of LB and addition of 2% urea and LB. The study was divided into two experiments: the first experiment evaluated the silages at different storage times, and the second experiment evaluated the silages during the aerobic stability test. In both experiments, the experimental design was completely randomized in a factorial scheme (4 × 4 and 4 × 3) with three replicates per treatment. After the ensiling process, lactic acid bacteria predominated in all treatments. The concentration of lactic acid increased significantly from 60 days of ensiling. The concentration of acetic acid varied significantly between the storage times only for the silages treated with urea and LB alone. The silage treated with urea maintained a constant pH value up to 120 days of storage. During the 96 h aerobic stability test, no breaking in the stability of silages was observed. The exclusive or associated use of urea and LB promotes improvement in the fermentative characteristics of cochineal nopal cactus silage, without major alterations in the chemical composition or interfering with the aerobic stability of the silages.

Effects of Additive Type on Fermentation and Aerobic Stability and Its Interaction with Air Exposure on Silage Nutritive Value

As farm profitability and sustainability of animal production are largely affected by overall losses of dry matter and nutritive value of silage from field to trough, the objective of the study was to assess the effects of different additive types on fermentation, aerobic stability (ASTA) and changes in in vitro organic matter digestibility (IVOMD) and metabolisable energy (ME) of grass and grass–clover silage exposed to air. Three trials were performed, where grass and grass–clover forages were treated with biological and chemical additives and ensiled in 1.6-L glass jars. Upon silo opening, fermentation characteristics, yeast counts and ASTA were determined as well as changes in IVOMD and ME during subsequent air exposure for up to 336 h. All silages were well preserved. The ASTA was improved by Lactobacillus buchneri-containing additives in all trials and by chemical additives in trial 3. In untreated silage, aeration reduced IVOMD and ME but variable effects of additives were observed. The nutritive value was maintained throughout aeration by all additives in trial 1, whereas in trial 3, only chemical additives were successful. A strong negative linear relationship across trials was detected between the extent of aerobic deterioration and changes in ME during air exposure (r = −0.756, p < 0.001). Silage additives improving aerobic stability have the potential to prevent the loss of nutritive value of grass and grass–clover silage during feed-out.

Varying ensiling conditions affect the fermentation quality and abundance of bacterial key players in lucerne silages

The successful ensiling of lucerne (Medicago sativa L.) depends on a rapid acidification in the silo and consequently relies on a sufficient proliferation of, particularly homofermentative, lactic acid bacteria. Similarly, growth of spoilage bacteria, such as enterobacteria and clostridia, must be suppressed and silage additives are therefore frequently applied to promote favourable conditions during ensiling. Three silage additives or soil were applied during lucerne ensiling and investigated for their effects on silage quality characteristics and abundances of total bacteria as well as the bacterial key players Lactobacillus spp., homofermentative Lact. plantarum, heterofermentative Lact. buchneri, Clostridium spp. and Enterobacteriaceae after 30 days of storage. Inoculation with viable Lact. plantarum resulted in highest concentration of this species and excellent silage quality, i.e. high lactic acid concentration coupled with low acetic acid and ammonia-nitrogen concentrations. A sodium nitrite and hexamine-based additive did not support growth of lactic acid bacteria, which was also apparent by higher pH and low lactic acid concentration. No effect of treatments was found on spoilage-related enterobacteria and clostridia, even not when adding soil to lucerne to increase initial clostridial contamination. However, soil treatment resulted in increased ammonia-nitrogen and acetic acid concentrations. Consequently, among the bacterial key players, lactic acid bacteria concentrations were related to silage quality. Regarding spoilage bacteria, however, alterations in silage quality characteristics were not reflected in the abundances of enterobacteria and clostridia. Future investigations should underpin the present findings and help to understand how silage additives affect microbial key players and silage fermentation.

Ergosterol and polyphenols: Potential biochemical indicators of silage safety

Background: Silage, one of the most important feed sources for cattle, is vulnerable to contamination by spoilage moulds and mycotoxin production because ensilage forage crops are excellent substrates for fungal growth. Whereas there are many factors involved in mycotoxins contamination such as biological factors, harvesting, storage, and processing conditions, the climate is the most important factor. Silage additives can improve the safety of silage and inhibit moulds and other detrimental silage microorganisms; however, their efficacy varies with the type and level of toxigenic fungi contamination. Several studies provided evidence showing that the presence of various mycotoxins was correlated with the presence of ergosterol in cereals and feedstuffs. Therefore, ergosterol ( ERG ) has been suggested as a potential indicator of fungal contamination with polyphenols concentration analysis allowing accurate prediction on silage safety. The main goal of this study was to use the ERG and polyphenols content as potential biochemical indicators to predict the silage safety in ensiled grasses. The study was carried out using ten orchardgrass varieties (untreated and treated with biological and chemical additives). The determination of the samples was performed on high-performance liquid chromatography using UV detection (ERG) and spectrophotometer UV/VIS (polyphenols). Results: Interestingly, in the silage ‘Bepro’ was the unique variety that no presented content of ERG (0.0 mg kg -1 dry matter) in comparison with other varieties in the first cut in 2012. The biological additives reduced the content of ERG in both cuts in 2012 compared with untreated silage. In contrast, the chemical additives in silage grass had a negative effect ( P < 0.05) by increasing the ERG and polyphenols content in comparison with untreated silage. Conclusions: These results of this study provide indisputable evidence that silage contaminated with fungi increase the concentration of polyphenols, which prove a progressive deterioration of silage quality. In consequence, ERG and polyphenols seem to be relevant as a rapid method for screening silage safety.