![Aerobic deteriorated silages (pooled data of farms 1 and 2): butyric acid bacteria (BAB) spore concentrations in relation to pH, mold count, nitrate concentration, and differences between silage temperature and ambient temperature (dT section−ambient ). Regressions ob- tained were a) BAB spores [log 10 most probable number (MPN)/g] = 1.26 pH − 3.55 [r 2 adj. = 0.75; root mean square error (RMSE) = 1.06]; b) BAB spores (log 10 MPN/g) = 0.727 molds + 0.01 (r 2 adj. = 0.87; RMSE = 0.781); c) BAB spores (log 10 MPN/g) = −0.0193 nitrate + 5.55 (r 2 adj. = 0.85; RMSE = 0.818); and d) BAB spores (log 10 MPN/g) = 0.244 dT + 1.21 (r 2 adj. = 0.72; RMSE = 1.13).](https://www.researchgate.net/profile/Giorgio-Borreani/publication/23410807/figure/fig1/AS:310175308238852@1450962965027/Aerobic-deteriorated-silages-pooled-data-of-farms-1-and-2-butyric-acid-bacteria-BAB_Q320.jpg)
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Low Permeability to Oxygen of a New Barrier Film Prevents Butyric Acid Bacteria Spore Formation in Farm Corn Silage
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The outgrowth of Clostridium spore-forming bacteria causes late blowing in cheeses. Recently, the role of air diffusion during storage and feed-out and the role of aerobic deterioration has been shown to indirectly favor butyric acid bacteria (BAB) growth and to determine the presence of high concentrations of BAB spores in farm tank milk. A new oxygen barrier (OB) film was tested and compared with conventional polyethylene (ST). The objective was to verify whether the OB film could prevent BAB spore formation in whole-crop corn silage during storage on 2 commercial farms with different potential silage spoilage risks. Two bunkers (farms 1 and 2) were divided into 2 parts along the length so that half the feed-out face would be covered with ST film and the other half with OB film. Plastic net bags with freshly chopped corn were buried in the upper layer and in the central part (CORE) of the bunkers. The silos were opened in summer and fed out at different removal rates (19 vs. 33 cm/d). Herbage at ensiling, silage at unloading, and silage after air exposure (6 and 15 d) were analyzed for pH, nitrate, BAB spores, yeasts, and molds. The BAB spores in herbages at ensiling were 2.84 log(10) most probable number (MPN)/g, with no differences between treatments or farms. Nitrate was below the detection limit on farm 1 and exceeded 2,300 mg/kg of fresh matter on farm 2. At unloading, the BAB spores in the ST silage on farm 1 were greater than 5 log(10) MPN/g, whereas in the CORE and the OB silages, they were approximately 2 log(10) MPN/g. The ST silage had the greatest pH (5.89), the greatest mold count (5.07 log(10) cfu/g), and the greatest difference between silage temperature and ambient temperature (dT(section-ambient)). On farm 2, the ST silage had the greatest concentration of BAB spores (2.19 log(10) MPN/g), the greatest pH (4.05), and the least nitrate concentration compared with the CORE and the OB silages. Pooled data on BAB spores collected from aerobically deteriorated samples showed a positive relationship with pH, mold count, and dT(section-ambient) and a negative relationship with nitrate concentration. A high concentration of BAB spores (>5 log MPN/g) was associated with visible spoilage, high pH values (>5.00), high mold counts (>5 log cfu/g), high dT(section-ambient), and nitrate below 1,000 mg/kg of fresh matter. We concluded that the use of a film with reduced oxygen permeability prevented the outgrowth of BAB spores during conservation and feed-out, and it could improve the microbiological quality of corn silage by eliminating the fractions of silage with high BAB spore concentrations.
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... Clostridium tyrobutyricum and other anaerobic or facultative anaerobic sporeformers (mainly clostridia and Paenibacillus spp.) can grow and multiply in this ecosystem in micro-niches with less inhibitory activity (Jonsson, 1989;Borreani et al., 2013). The increase in the anaerobic spore content of silage, due to air penetration, has been observed for whole-plant corn silage (Vissers et al., 2007a;Borreani and Tabacco, 2008), wilted alfalfa (Colombari et al., 2001), whole-plant grain sorghum (Tabacco et al., 2009), and grass silage (Jonsson, 1991;Vissers et al., 2007a). Furthermore, the multiplication of Paenibacillus spp. ...
... The pH value was determined through the use of specific electrodes. The nitrate content was determined in the water extract, through semiquantitative analysis, using Merckoquant test strips (Merck KGaA; Borreani and Tabacco, 2008). ...
... This suggests that these species have the capacity to outgrow in silage during aerobic deterioration, as previously suggested for C. tyrobutyricum in grass silage (Jonsson, 1991). Other authors (Vissers et al., 2007a;Borreani and Tabacco, 2008) suggested, on the basis of tests conducted with the most probable number (MPN) method, that the aerobic deterioration of corn silage led to an increase in butyric acid bacteria, which in turn produced gas under anaerobiosis on lactate acetate agar. Borreani et al. (2013), in trials on the deterioration of corn silage, then found the outgrowth of Paenibacillus macerans, which was identified by 16S-DNA sequencing as the dominant anaerobic and facultative anaerobic sporeformer isolated on an RCM medium. ...
The occurrence of Paenibacillus and Clostridium spores in silage is of great concern for dairy producers because their spores can contaminate milk and damage processed milk and semi-hard cheeses. Spoiled silage is considered to be the main contamination source of the total mixed ration (TMR), feces of dairy cows, and consequently bulk tank milk via the contamination of cow teats by dirt during milking. The presence of an anaerobic and facultative anaerobic sporeformer population in different matrices (soil, corn silage, other feeds, TMR, feces, and milk) and its transmission pathway has been studied on 49 dairy farms by coupling plate count data with 16S-DNA identification. The different matrices have shown a high variability in the anaerobic and facultative anaerobic spore count, with the highest values being found in the aerobically deteriorated areas of corn silages. Clostridium tyrobutyricum, Paenibacillus macerans, and Paenibacillus thermophilus were detected in all the matrices. The TMR spore count was influenced by the amount of spoiled corn silage in the TMR and by the care taken when cleaning the spoiled silage before feed-out. Most of the farms that prevent the presence of visible moldy silage in the silo and carefully clean to remove molded spots were able to maintain their TMR spore counts below 4.0 log spores/g. When a level of 4.5 log spores/g of TMR was exceeded, the feces presented a greater contamination than 3.0 log spores/g. Moreover, the higher the number of spores in the feces was, the higher the number of spores in the milk. Most of the farms that presented a feces contamination greater than 5.0 log spores/g had a higher milk spore contamination than 1,000 spores/L. Careful animal cleaning and good milking practices have been found to be essential to maintain low levels of contamination in bulk tank milk, but it has emerged that only by coupling these practices with a correct silage management and cleaning during TMR preparation can the contamination of milk by spores be kept at a low level. It has been found that aerobically deteriorated silage has a great capacity to contaminate TMR and consequently to increase the risk of milk spore contamination, even when routine milking practices are adopted correctly.
... LBD occurrence is a relevant defect in the production of one of the greatest Italian excellences, the Grana Padano PDO, indeed, LBD might cause huge economic losses (15-35% of total production showed this problem). During the fermentation process, LBD can be faced by the addition of lysozyme to the milk (up to a maximum of 2.5 g per 100 kg of milk), recommended to control clostridia outgrowth, minimizing the butyric fermentation risk (Borreani & Tabacco, 2008;Brasca et al., 2013;Neviani, Bottari, Lazzi, & Gatti, 2013;Soggiu et al., 2016;Zucali et al., 2015), as also allowed by the production specification of Grana Padano PDO (Disciplinare Grana Padano PDO, 2017). In recent times, however, greater attempts have been made to limit the use of lysozyme due to the possible selection of dairy flora: when low spore numbers are present (<500 spores/L), lysozyme addition can be suitable for the LBD regulation, while in the case of higher spore numbers, higher lysozyme doses may also inhibit the desired fermentations. ...
... The spore contamination level can be under the method's limit of detection and this consideration must be applied also to the results of the analysis of MPN method, which despite having a lower limit of detection (about 300 spores/L) it is only an estimation. Actually, the threshold value of spore concentration in milk causing late blowing is between 600 and 1000 spores/L (Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna, 2020) but some authors reported that even low numbers of spores (less than 50 spores/L) would be enough to cause the LBD development during the cheese ripening (Borreani & Tabacco, 2008;Doyle et al., 2015;Klijn et al., 1995;Lavilla et al., 2010;Talbot et al., 1994;Zucali et al., 2015). Moreover, spores are often organized in clusters, so the aliquot (1 mL out of approximately 70 mL of milk brought into our Institute for the routine spore count analysis) of the sample used for the MPN dilutions might not truly be representative of the actual spore content (Bergère & Sivelä, 1990). ...
In the dairy industry, the late blowing defect in medium and long ripened cheeses causes important economic losses. This cheese defect, caused mainly by the anaerobic spore former Clostridium tyrobutyricum, is characterized by gas production resulting in holes formation in the paste, and in unpleasant aromas related to the butyrate production. Since longtime, the reference method used to detect the presence of total spore number in milk is the Most Probable Number (MPN), a semi-quantitative method which measures the bacterial growth and the gas production after heat treatment of the samples. This method often gives uncertain results, it requires long incubation periods and fails to differentiate between different species of spore-forming bacteria. A TaqMan real-time quantitative PCR targeting the phosphotransacetylase gene (pta) for C. tyrobutyricum was previously developed as an alternative technique to the traditional method, faster and more specific, and therefore of great interest to preventively determine the contamination of milk by C. tyrobutyricum. The aim of this work was the validation of this quantitative real-time PCR protocol for the C. tyrobutyricum detection in milk. Following the method validation, 120 samples of UHT and raw milk artificially contaminated with C. tyrobutyricum spores were analyzed in increasing concentrations, relating the results of the molecular method with those obtained by the MPN. Finally, 144 raw milk samples with a possible natural contamination were analyzed and demonstrated a positivity rate of 15.28% (CI95% 10.31-22.05%).
... To retard oxidative deterioration of a food product, one strategy is to lower the localized concentration of oxygen in a food package. Over the years, a variety of packaging materials showing low oxygen permeability have been designed [76][77][78] . Despite this, long-term durability is a problem that has yet to be fully solved. ...
Smart packaging materials enable active control of parameters that potentially influence the quality of a packaged food product. One type of these that have attracted extensive interest is self-healable films and coatings, which show the elegant, autonomous crack repairing ability upon the presence of appropriate stimuli. They exhibit increased durability and effectively lengthen the usage lifespan of the package. Over the years, extensive efforts have been paid to the design and development of polymeric materials that show self-healing properties; however, till now most of the discussions focus on the design of self-healable hydrogels. Efforts devoted to delineating related advances in the context of polymeric films and coatings are scant, not to mention works reviewing the use of self-healable polymeric materials for smart food packaging. This article fills this gap by offering a review of not only the major strategies for fabrication of self-healable polymeric films and coatings but also the mechanisms of the self-healing process. It is hoped that this article cannot only provide a snapshot of the recent development of self-healable food packaging materials, but insights into the optimization and design of new polymeric films and coatings with self-healing properties can also be gained for future research.
... Silo length implicitly suggests that the ensiled mass, which tends to occupy this dimension more than width or height, is subjected to a better feed-out management. At the same time, it is intuitive that the daily removal of the silage surface exposed to air limits the growth of yeasts, thus avoiding aerobic spoilage and consequent restart of clostridia activity [28]. The comparison of MPNld data distribution within each kind of silo reinforces the beneficial effect of this removal, especially in the hot season ( Figure 4). ...
At feed-out, aerobic spoilage of silage enables an increase in anaerobic spore-forming bacteria (ANSB) that may enter the total mixed ration (TMR). The aim of our study was to understand whether in hot summers the silage structures and management may affect the level of ANSB in milk for long-ripening cheese production. A survey of silage facilities, management, and their relationships with silage, TMR, feces, and milk ANSB most probable number (MPN) content was conducted in the Po Valley during summer months. Silo type did not affect the mean ANSB, but only the wideness of their value distributions, with a narrow range for bags and a wider range for bunkers. The unloading equipment affected the ANSB count; the front-end loader with cutter was associated with a lower ANSB count—probably as a result of the reduced surface left after daily silage removal. Silo length and daily removed face width were the main factors affecting contamination of silage by spore-forming bacteria during summer, with longer silos and wider surface removal reducing ANSB contamination—probably as a consequence of reduced aerobic spoilage at the silage surface. The silage contamination by spore-forming bacteria within a log10 2 MPN g−1 allowed a low concentration of spore-forming bacteria at the farm bulk milk tank level. Fecal ANSB levels did not factor into the regression that explains the ANSB in farm milk. It has been found that silage facilities’ features and their management are an important first step to reduce the extent of ANSB contamination at the farm level.
... The authors also related the better hygienic quality of the silage, due to the lower yeast count in the silage sealed with the polyamide film. Borreani and Tabacco et al. (46) related high counts of fungi and yeasts in silage with heating of the ensiled mass in the silo, suggesting that the higher silage temperature (Table 4) and lower aerobic stability of the silage sealed with the DF110μm film (Table 5) can be attributed to the higher oxygen permeability of this film. ...
The objective of this study was to evaluate the efficiency of different double-sided plastic films on chemical and fermentation characteristics, dry matter digestibility, aerobic stability, physical and dry matter losses in corn silages stored in bunker silos. This was a completely randomized experimental design consisting of three treatments: DF110µm - double-sided polyethylene with 110 µm thickness; DF200µm - double-sided polyethylene with 200 µm thickness; and DFBO - oxygen-impermeable film consisted of double-sided polyethylene with 80 µm thickness overlaid with a translucent vacuum polyamide film with 20 µm thickness. The use of DF200µm film increased the ruminal dry matter digestibility by 4.58% and reduced the silage temperature by 3.1 °C, as well as the physical losses of the corn silage were reduced by 118.9 g kg-1 DM using DFBO and 95 g kg-1 DM with DF200µm; DFBO resulted in the highest aerobic stability (127 hours) of corn silage. The use of DF200µm and DFBO is recommended for preserving corn silage in bunker silos.
... Only species with relative abundance > 1% are listed yeast and mold growth in well-fermented silages not treated with any antifungal chemicals due to its strong antifungal properties at low pH environment (Courtin and Spoelstra 2010). Butyric acid is a fermentation product of Clostridium butyricum, but it is considered undesirable in ensilage because of its poor palatability (Borreani and Tabacco 2008). Our study detected butyric acid in the first three days of fermentation, suggesting insufficient suppression of clostridial growth during the early phase of ensilage, probably due to the high NO 3 level and moisture content (Pahlow et al. 2003). ...
This study investigated the effect of inoculating Lactobacillus (L.) plantarum PS-8 in fermentation of alfalfa silages. We monitored the fermentation characteristics and bacterial population dynamics during the ensiling process. PacBio single molecule real time sequencing was combined with propidium monoazide (PMA) treatment to monitor the viable microbiota dynamics. We found that inoculating L. plantarum PS-8 may improve the silage quality by accelerating acidification, reducing the amounts of clostridia, coliform bacteria, molds and yeasts, elevating the protein and organic acid contents (except butyrate), and enhancing lactic acid bacteria (LAB) while suppressing harmful microorganisms. Some significant differential abundant taxa were found between the PMA-treated and non-treated microbiota. For example, the relative abundances of L. brevis, L. plantarum, and Pediococcus pentosaceus were significantly higher in the PMA-treated group than the non-PMA-treated group, suggesting obvious differences between the viable and non-viable microbiota. It would thus be necessary to distinguish between the viable and non-viable microbial communities to further understand their physiological contribution in silage fermentation. By tracking the dynamics of viable microbiota in relation with changes in the physico-chemical parameters, our study provided novel insights into the beneficial effects of inoculating L. plantarum PS-8 in silage fermentation and the physiological function of the viable bacterial communities.
... When yeast and acetic acid bacteria raise both the pH (≥ 4.5) and temperature (40°C) of aerobically challenged silage, the growth of undesirable microorganisms is facilitated, such as bacilli (Muck, 2010), L. monocytogenes (Driehuis et al., 2018), clostridia (Borreani and Tabacco, 2008), and molds, which complete the silage deterioration (Borreani et al., 2018). ...
The aim was to screen and optimize low-cost lignosulfonates (LST) as legume silage and hay preservatives to decrease losses of DM and nutritive value due to spoilage. In experiment 1, we evaluated the effects of untreated silage (0%), sodium lignosulfonate (NaL) and magnesium lignosulfonate (MgL) applied independently at 0.5, 1, and 1.5 (% w/w, fresh basis) and INO (Pediococcus pentosaceus and Lactobacillus plantarum; 5 and 4 log cfu/fresh alfalfa g, on high moisture alfalfa (Medicago sativa L.) silage nutrient preservation. Data were analyzed as a randomized complete block design (RCBD; 5 blocks) and linear and quadratic polynomial contrasts were used to determine dose rate effects for NaL and MgL and orthogonal contrasts for INO effects. At opening (d 229), both MgL and INO increased DM loss (~13.7 vs 11.3% of DM) due to a lower production of lactic acid (~7.55 and 7.83 vs 9.23% of DM, respectively) which resulted in a higher pH relative to untreated silage (~4.41 and 4.46 vs 4.33; respectively). The high acidification in untreated silage resulted in additives not reducing further the proteolysis that occurred relative to control, measured as NH3-N (~11% of N). Overall, all additives tested failed to improve the preservation of high moisture alfalfa silage nutrients. In experiment 2A, we determined the minimum inhibitory (MIC) and minimum fungicidal concentration (MFC) of 4 sodium lignosulfonates [Sappi (NaSP), Sigma-Aldrich (NaAl), Beantown (NaBT), and Spectrum (NaUM)], 1 magnesium lignosulfonate [Sappi (MgSP)], 2 chitosan sources [naive (ChNv) and microparticles (ChMp)], and propionic acid (PRP; positive control) against 3 molds and 1 yeast isolated from spoiled alfalfa hay. Our results showed that both chitosans had the strongest fungicidal activity against all the fungi tested with exception of M. circinelloides at both pH 4 and 6. Among lignosulfonates, we found that NaSp was the most antifungal and was further optimized to produce LST. However, none of the lignosulfonates inhibited the molds or yeast at pH 6. Across additives, PRP inhibited all fungal strains at both pH levels. In experiment 2B, we used a factorial combination of three preservatives (LST, ChNv, and PRP) and 5 concentrations (0, 0.25, 0.5, 1, and 2% w/w fresh basis) to determine the effects of their application on the preservation of nutrients in high moisture alfalfa hay. Data were analyzed as a RCBD replicated five times. After 23 d of aerobic storage, LST and PRP prevented DM losses to the same extent with doses as low as 0.25% compared with the untreated hay (~1.61 vs 24.0%). This was explained by reduced mold counts for as low as 1% LST (< 2.0) and as low as 0.5% PRP (< 2.0) compared with untreated hay (6.76 log cfu/fresh g). However, ChNv did not affect DM loss or molds count (~23.2% and 6.59 log cfu/fresh g, respectively). Also, DM digestibility was increased for at least 0.25% LST (71.1) and 1% PRP (71.4) compared with untreated hay (69.3%). As a consequence, both LST and PRP increased total VFA with doses as low as 0.25% compared with the untreated hay (93.6 and 95.1 vs 83.3 mM, respectively). In summary lignosulfonates initially tested did not improve the preservation of nutrients in high moisture legume silage but an optimized lignosulfonate showed promise as a low-cost preservative for high moisture legume hay.
... When yeast and acetic acid bacteria raise both the pH (≥ 4.5) and temperature (40°C) of aerobically challenged silage, the growth of undesirable microorganisms is facilitated, such as bacilli (Muck, 2010), L. monocytogenes (Driehuis et al., 2018), clostridia (Borreani and Tabacco, 2008), and molds, which complete the silage deterioration (Borreani et al., 2018). ...
The aim was to screen and optimize low-cost lignosulfonates (LST) as legume silage and hay preservatives to decrease losses of DM and nutritive value due to spoilage. In experiment 1, we evaluated the effects of untreated silage (0%), sodium lignosulfonate (NaL) and magnesium lignosulfonate (MgL) applied independently at 0.5, 1, and 1.5 (% w/w, fresh basis) and INO (Pediococcus pentosaceus and Lactobacillus plantarum; 5 and 4 log cfu/fresh alfalfa g, on high moisture alfalfa (Medicago sativa L.) silage nutrient preservation. Data were analyzed as a randomized complete block design (RCBD; 5 blocks) and linear and quadratic polynomial contrasts were used to determine dose rate effects for NaL and MgL and orthogonal contrasts for INO effects. At opening (d 229), both MgL and INO increased DM loss (~13.7 vs 11.3% of DM) due to a lower production of lactic acid (~7.55 and 7.83 vs 9.23% of DM, respectively) which resulted in a higher pH relative to untreated silage (~4.41 and 4.46 vs 4.33; respectively). The high acidification in untreated silage resulted in additives not reducing further the proteolysis that occurred relative to control, measured as NH3-N (~11% of N). Overall, all additives tested failed to improve the preservation of high moisture alfalfa silage nutrients. In experiment 2A, we determined the minimum inhibitory (MIC) and minimum fungicidal concentration (MFC) of 4 sodium lignosulfonates [Sappi (NaSP), Sigma-Aldrich (NaAl), Beantown (NaBT), and Spectrum (NaUM)], 1 magnesium lignosulfonate [Sappi (MgSP)], 2 chitosan sources [naive (ChNv) and microparticles (ChMp)], and propionic acid (PRP; positive control) against 3 molds and 1 yeast isolated from spoiled alfalfa hay. Our results showed that both chitosans had the strongest fungicidal activity against all the fungi tested with exception of M. circinelloides at both pH 4 and 6. Among lignosulfonates, we found that NaSp was the most antifungal and was further optimized to produce LST. However, none of the lignosulfonates inhibited the molds or yeast at pH 6. Across additives, PRP inhibited all fungal strains at both pH levels. In experiment 2B, we used a factorial combination of three preservatives (LST, ChNv, and PRP) and 5 concentrations (0, 0.25, 0.5, 1, and 2% w/w fresh basis) to determine the effects of their application on the preservation of nutrients in high moisture alfalfa hay. Data were analyzed as a RCBD replicated five times. After 23 d of aerobic storage, LST and PRP prevented DM losses to the same extent with doses as low as 0.25% compared with the untreated hay (~1.61 vs 24.0%). This was explained by reduced mold counts for as low as 1% LST (< 2.0) and as low as 0.5% PRP (< 2.0) compared with untreated hay (6.76 log cfu/fresh g). However, ChNv did not affect DM loss or molds count (~23.2% and 6.59 log cfu/fresh g, respectively). Also, DM digestibility was increased for at least 0.25% LST (71.1) and 1% PRP (71.4) compared with untreated hay (69.3%). As a consequence, both LST and PRP increased total VFA with doses as low as 0.25% compared with the untreated hay (93.6 and 95.1 vs 83.3 mM, respectively). In summary lignosulfonates initially tested did not improve the preservation of nutrients in high moisture legume silage but an optimized lignosulfonate showed promise as a low-cost preservative for high moisture legume hay.
A common method of silage production in Europe is based on the use of cylindrical bales wrapped with polyethylene films. In this study, several modifications of composition of these films were tested for their impact on the microorganisms involved in the ensiling process. Different additives, including nanosilver particles and microcellulose, were analyzed upon the first stage of the experiment. In the second stage, the usability of recycled polyethylene as a film component was assessed. The forage value after ensiling was determined during storage, based on analyses of the content of crude fiber, nitrate nitrogen, total protein, sugars, acids (lactic, acetic, butyric and propionic), pH and dry matter. Microbial forage quality was evaluated by analyses of growth of lactic acid bacteria (LAB) compared to the number of undesirable aerobic bacteria, yeasts and molds. Film properties were also characterized. No statistically significant (p < 0.05) differences were shown for the tested film formulae as compared to standard commercial films. In the second experimental stage, an elevated pH and a slightly higher content of acids were observed for the tested films than for the control sample. In addition, for standard PE film supplemented with nanosilver, a higher number of LAB was detected on the inner surface of the film and in the ensiled material.
Context Consumers require nutritious and safe animal products, particularly milk and meat. Forage silage is a major source of feed for dairy cattle. However, inappropriate silo preparation and management can affect silage nutritional quality and may lead to fungal growth and mycotoxin production. Aims We aimed to determine the nutritional quality of different forage silages in dairy farms from four regions in northern Tunisia where silage production is a common practice, and to screen for the presence and concentration of 23 mycotoxins. Methods Six different forage silage types from 27 silos were sampled 100 days after ensiling. Samples were taken from upper, middle and lower sections of the silo. The pH and nutritional values of the silages were determined. The QuEChER method was used to extract mycotoxins, and they were identified and quantified through liquid or gas chromatography with tandem mass spectrometry. Key results Silage pH ranged from 4.4 to 7.8, and dry matter content of forage biomass from 15% to 47%. Values of pH of silage samples varied among the silo levels (P = 0.001), whereas nutrient contents of silage biomass were similar among the three levels. Only five Fusarium mycotoxins (deoxynivalenol, two enniatins, beauvercin, HT-2 toxin) were detected at different concentrations depending on the silo level. Oat, oat + triticale and oat + sulla silages were the most heavily contaminated with mycotoxins. Biomass in the upper silo level was the most co-contaminated. Conclusions High pH (>4) and dry matter content (>30%) indicate low quality silages; therefore, the silages were generally of low quality. Although the evaluated silages were contaminated with five of the targeted mycotoxins, their concentrations were so low that they do not represent a risk to the health of dairy cattle. Implications Forage biomass should have a dry matter content of 20–30% on the day of silo filling. It is important to sample silage from the upper, middle and lower sections of the silo to screen for mycotoxins. In future studies, the transfer of detected mycotoxins to milk should be determined.
Mathematical equations are presented for a model of the processes of air infiltration and oxidation loss occurring when silage is stored in horizontal clamps, driven by a combination of pressure differences and diffusion. The limited information available about parameters of the model is discussed. Results suggest that air enters a clamp owing to pressure differences but distributes itself throughout the clamp by diffusion. These mechanisms account for levels of surface waste and invisible oxidation loss which are typically measured in silage clamps. The model suggests that it should be possible to almost eliminate these types of loss, either by thorough consolidation of the ensiled material, or possibly by improved sealing with plastic sheeting. In practice, consolidation appears to be the most practical approach to the reduction or elimination of losses, since the required density levels are known to be achievable in practice. It is less likely to be possible to improve sealing significantly, particularly between plastic sheet and coated concrete clamp wall.
A mathematical model is presented for oxygen flow, heat transfer, and yeast growth at the exposed face of bunker silos. The model considers the diffusion of oxygen and conduction of heat within the silage mass; volume flow is neglected. A single comparison of yeast counts and temperatures with measurements by previous authors shows areas of good agreement, but much more experimental work is needed to determine the conditions in which diffusion is the primary mechanism of oxygen infiltration. The model predicts a rapid influx of oxygen early in aerobic exposure followed by a decrease in oxygen levels deep within the silage. Higher silage densities and a faster removal rate from the exposed face are predicted to mitigate aerobic deterioration substantially, while treatment with propionic acid in the outermost layer still results in extensive deterioration under the treated layer.
The numbers of bacteria belonging to Enterobacteriaceae (enterobacteria), lactic acid bacteria, Bacillus- and Clostridium spores were enumerated in manure and on manured and NPK-fertilised silage crops. The enterobacteria were biochemically characterised by means of the Minitek system (BBL). More than 90% of the enterobacteria on crops belonged to the genus Enterobacter. A majority of these (72%) were identified as E agglomerans. Manuring did not increase the number of enterobacteria on silage crops. E coli was the most frequent species in manure but was present at 10−3 times that of the total number of enterobacteria on the crop one week after manuring. The number of Bacillusspores was 20–40 times higher on manured crops and the number did not decline with time, whereas Clostridium spores, coliforms capable of growing at 44°C and E coli were reduced 6, 40 and 20 times respectively between manuring and harvesting (7 weeks).
Mechanical harvesting increased the number of Bacillus spores and coliforms capable of growing at 44°C on NPK fertilised crops probably due to soil contamination. Enterobacteria and lactic acid bacteria increased during wilting. The most representative enterobacteria on wilted crops was a specific biovariant, possibly E agglomerans or Rahnella aquatilis.
Cattle slurry (50 m3 ha−1 equivalent to 68 kg N ha−1) was applied to grassland plots 70 d (early application) and 34 d (late application) before ensiling and the retention and survival of slurry and epiphytic micro-organisms on the growing herbage were examined and compared with those on herbage from corresponding fertilizer-treated plots. The populations of lactic acid bacteria, enterococci and enterobacteria on herbage increased dramatically after slurry application. Thereafter, numbers of lactic acid bacteria declined, although they were always higher than on untreated herbage. Number of enterobacteria also declined but were higher on chopped grasses at ensiling [106 colony-forming units (CFU) g−1 fresh matter (FM)] than they were on hand-cut. unchopped herbages at all previous sampling times. Clostridia numbers were lowest on untreated and highest on slurry-treated herbage, particularly after the late application (>103 CFU g−1 FM). Herbage was harvested 70 d and 34 d after slurry application, chopped and ensiled in laboratory silos. All herbages, irrespective of treatment, had low dry matter (DM) values (ranging from 149 to 170 g kg−1 FM) and fairly low water-soluble carbohydrate (WSC) concentrations (130 g kg−1 DM or less). The initial rate of pH decline up to 4 d was most rapid in slurry-treated herbages, with all pH values falling to < 4. 5 by day 4 and remaining there until day 21. However, after 90 days the pH values of all silages had risen to > 4. 5. accompanied by a marked decline in lactic acid concentration. Lactic acid-fermenting Clostridia increased in numbers, reaching peak values of 107 CFU g−1 FM by day 21, remaining high until opening, and were probably responsible for increases in butyric acid levels in all silages, with the highest concentrations occurring in those prepared from slurry-treated herbages. The results suggest that, although some faecal lactic acid bacteria may have beneficial effects in the early stages of fermentation, Clostridia from slurry can survive on herbage for extended periods. The results indicate that the potential for growth of Clostridia in silage may be independent of source or size of the initial population even at tow pH, if other conditions are favourable.
The quality of silage from crops fertilized with cattle manure and an inorganic fertilizer was compared in experiments from 1985 to 1989. Manure was spread either as farmyard manure (FYM, 25t ha−1) or as slurry (20-50t ha−1). Crops were direct cut (approximately 200 g DM kg−1) or wilted (approximately 300 g DM kg−1), precision chopped and ensiled in experimental silos. Silage was treated with 4 kg 85% fonnic acid t−1 fresh matter (FM), an inoculant or no additives. The use of manure, particularly FYM, resulted in more Bacillus spores on crops at harvest compared with fertilized crops. Clostridium spores increased as a result of manuring in 1989 only on FYM-treated crops. Differences in the chemical composition of crops were usually small between fertilizer treatments. The quality of silage from slurry-dressed crops, compared with that of silage from fertilized crops, varied between years. The FYM resulted in reduced silage quality, i.e. high pH values (> 4·5), high ammonia N (> 150 g kg−1 total N) and butyric acid (> 6·3 g kg−1 water) concentrations, and high numbers of Bacillus (105 g−1 FM) and Clostridium spores (105 g−1 FM). The concentration of lactic acid was low (≤ 12 g kg−1 water). Wilting and additives generally improved silage quality and reduced the differences between treatments. However, the efficiency of the inoculant on farmyard manured crops was limited.