A mathematical model of the aerobic deterioration of silage

A mathematical model of the aerobic deterioration of silage is described that includes the physical processes of gas and heat Rows, as well as an established model of microbial growth and the associated chemical changes. Yeasts and acetic acid bacteria are included in the growth model. The version of the model described relates to a cylinder of silage subject to forced aeration, a common experimental configuration. The model was very sensitive to variations in insulation thickness and yeast growth rate, and to initial pH, especially when maize was the forage. Great care is needed when selecting input data for use in the model to be sure that the physical and chemical properties are accurate. The model solution was sensitive to grid size, but with 361 cells, the maximum grid resolution that could be used on a 486 series PC, solutions were achieved with an acceptably small loss of accuracy. The model predicted the results of an experiment on silage deterioration quite accurately. However, the model also predicted that considerable spatial gradients of parameters, such as temperature, pH, and lactic acid, would occur. This indicates the need for care when taking samples or making temperature measurements in deterioration experiments. The model is potentially a useful tool in predicting the optimal time and position to take samples for analysis in a time-course experiment.     

A mathematical model of the aerobic deterioration of big-hale silage and its implications for the growth of Listeria monocytogenes

Aerobically spoiled silage has often been shown to harbour dangerously high levels of Listeria monocytogenes. This paper investigates the dynamics of aerobic deterioration in a silage bale as it occurs close to a site of damage to the cover. The underlying aim was to enable prediction of the extent of the silage that may become suitable for Listeria growth during the course of storage. In order to meet these objectives, a model was formulated that represents the microbiology of the deterioration process and the transport of oxygen and heat through the silage. The geometry of the system was exploited to ensure that the model is computationally tractable. The model was used to evaluate the effect of silage pH and puncture size on the risk of Listeria contamination. Although the hazardous fraction was seen to be relatively insensitive to the initial pH of the silage, it increased rapidly with puncture size. However, a small puncture can result in the 'loss' of a considerable fraction of the bale because of the relatively long time scale over which bales are stored.     

A model of aerobic fungal growth in silage.

The components of a simulation model of mesophilic and thermophilic yeast and mould growth in aerobically deteriorating silage are presented. The purpose of the model is to examine the relative roles of yeasts and moulds in deterioration and the factors affecting aerobic stability. Information for the model was based on literature studies. Growth of the fungi was assumed to be affected by temperature, pH, water activity, and lactic and acetic acid concentrations. The substrates utilized in the model, in order of preference, were water-soluble carbohydrates, ethanol, lactic acid and acetic acid. Gas movement and heat transfer were not considered. Consequently, oxygen and carbon dioxide concentrations were assumed to be those for open air, and the heat of respiration retained in the silage was set as a constant percentage of that released by fungal growth.
Based on the relationships developed for the model, pH affects yeast growth minimally and does not affect mould growth at all. Water activity over the range in silage affects yeast growth more than mould growth, but affects neither one strongly. Undissociated lactic and acetic acids decrease growth rate and may be important factors in silage stability. Compared with moulds, yeast growth rates are less affected by suboptimum temperatures but are more sensitive to temperatures in excess of the optimum.
A succeeding study compares the model with published aerobic deterioration studies and examines the predicted succession of microbial groups and the variation in silage stability as affected by silage parameters, initial temperature, and initial microbial populations.     

Effects of formic acid and potassium diformate on the fermentation quality,chemical composition and aerobic stability of alfalfa silage

The objective of this study was to evaluate the efficacy of potassium diformate (KDF) as a potential additive for alfalfa silage. Fresh alfalfa was untreated or treated with formic acid (4 g/kg fresh weight, FW) or three concentrations of KDF (4, 5.5 or 7 g/kg FW). After 60 days of ensiling, the addition of formic acid and greater levels of KDF (5.5 and 7 g/kg) effectively reduced silage pH and inhibited the undesirable bacteria, indicated by lower butyric acid, ethanol, ammonia N concentrations and microbial populations (including enterobacteria, yeasts, moulds and clostridia). Additives decreased the dry‐matter loss, and more water‐soluble carbohydrates were preserved in the silages with formic acid or potassium diformate than in the control. Alfalfa silages treated with formic acid at 4 g/kg FW or potassium diformate at 5.5 or 7 g/kg FW were classified as the highest quality silage based on the higher Flieg's point (above 70) and remained stable for more than 9 days during aerobic exposure. Potassium diformate is recommended as an effective additive for alfalfa silages at a level of 5.5 or 7 g/kg FW under the humid and hot conditions of southern China.     

The microbiological and chemical composition of silage over the course of fermentation in round bales relative to that of silage made from unchopped and precision-chopped herbage in laboratory silos

The composition of baled silage frequently differs from that of comparable conventional silage. A factorial experiment was conducted with three wilting treatments (0, 24 or 48 h) × three ensiling systems [unchopped grass in bales, unchopped grass in laboratory silos (LS), precision-chopped grass in LS] × six stages of ensiling to (i) confirm that the fermentation of unchopped grass in LS could be used as an adequate model for baled silage fermentation, (ii) quantify the differences between baled silage and silage made from precision-chopped herbage across a range of dry-matter contents and (c) quantify the fermentation dynamics within the various treatments. The onset of fermentation as evidenced by the accumulation of fermentation products and the decline in pH were slower ( P  < 0·05) in baled silage compared with silage made from precision-chopped herbage. Furthermore the pH ( P  < 0·001) and overall concentration of fermentation acids ( P  < 0·01) were lower while ammonia-N concentration was generally higher in baled silage, making it more conducive to the activities of Clostridia , Enterobacteria and yeast. Numbers of Enterobacteria were higher ( P  < 0·001) in baled silage in the early stages of ensilage and persisted in baled silage at the end of the storage period. The implications of a slower onset of fermentation in baled herbage are greater in farm practice, as the fermentation would be further restricted by a more extensive wilting of the herbage prior to ensiling.     

Aerobic deterioration of grass silage: the need to couple models and experiments

A mathematical model of the aerobic stability of grass silage is presented. The model is shown to predict as well as more complex models previously published. Sensitivity analysis performed on model parameters suggests that current understanding of the temperature dependence of yeast growth needs to be advanced in order to produce more accurate models of deterioration. Inhibition of yeast growth by organic acids is identified as a critical process worthy of further investigation. We discuss how model validation experiments must identify different yeast species and track their growth separately. Such experiments should also attempt to minimize or measure heat losses.     

The aerobic stability of silage: key findings and recent developments

When silage is exposed to air on opening the silo, or after its removal from the silo, fermentation acids and other substrates are oxidized by aerobic bacteria, yeasts and moulds. The aerobic stability of silage is a key factor in ensuring that silage provides well‐preserved nutrients to the animal with minimal amounts of mould spores and toxins. In this paper, key findings and recent developments are reviewed, and findings of recent research are integrated in terms of four themes: (i) the most significant biochemical and microbiological factors, (ii) physical and management factors, (iii) type of additive and (iv) silo sealing. The development of yeasts and moulds during plant growth, and during field wilting or storage, and the concentration of undissociated acetic acid in silage are important microbiological and biochemical factors affecting aerobic stability. Silage density and porosity are key physical factors that affect the rate of ingress of oxygen into the silage mass during the feed‐out period. A target for potential silage aerobic stability is 7 d including time in the feed trough. To achieve this target, speed of harvest should be coordinated with packing tractor weight to achieve a minimum silage density by the time of feed‐out of 210 kg DM m^?3, maximum proportional porosity of 0·4 and a rate of silage removal, which matches or exceeds the depth of air penetration into the silo. The use of additives to increase aerobic stability is advisable when there is the risk of these objectives not being met. Novel microbial approaches to solving the problem of silage aerobic deterioration are needed.     

Effect of stage of maturity and chop length on the chemical composition and utilization of formic acid-treated ryegrass and formic acid silage by sheep

Two areas of an early-heading perennial ryegrass cv. Cropper were harvested by either a precision-chop or a flail harvester at around 50% ear emergence (15 May 1978) and 14d later (29 May). Formic acid (85%) was applied at the rate of 2·2 litres t^-1. Mature crossbred wethers were used in a 2 × 2 factorial design to determine the effect of stage of maturity and method of harvesting (chop length) on the in vivo digestibilities of formic acid-treated grass in experiment 1 and formic acid silage in experiment 2. Apparent digestibility coefficients were determined at a fixed level of feeding for both grass and silage and at ad libitum access to feed for silage only. There were no significant differences in the concentrations of crude protein (CP), ether extract (EE), acid-detergent fibre (ADF) or acid-detergent lignin (ADL) in grass or silages of differing chop lengths but the later cut forages had significantly higher ADF and ADL concentrations and lower CP concentrations than the early-cut forages. The ADF and ADL concentrations were also higher in the silages than in the corresponding grasses. In general, the fermentation characteristics of precision-chopped silage were better than for the corresponding flail-cut silage but date of harvest was a more important determinant of quality and the late, flail-cut silage had the highest butyrate and ammonia N concentrations and the highest pH (411) of any treatment. There was a significantly higher intake of precision-chopped as compared with flail-cut silage with both the early-and the late-cut silage but there were no significant differences attributable to stage of maturity (i.e. date of harvest) or significant interaction between chop length and maturity. The slightly increased intake of early harvested, precision-chopped silage as compared with late precision-chopped silage was not significant. Dry matter digestibility (DMD) of the grass decreased at a rate of 0004 units d^-1 post 50% ear emergence. The results of experiment 2 indicated a decrease of 0·207 units d^-1 in silage fed at a similar level. The late-cut silage (DMD 0·292, mean of both harvesting treatments) thus had a significantly lower digestibility than the corresponding grass (mean DMD 0·247). Chop length had a variable influence on the DMD of both grass and silage fed at a fixed level but treatment differences were non-significant. However, a trend towards higher digestibility of flail-cut as compared with precision-chopped silage was apparent and this became statistically significant when the animals were allowed ad libitum access to feed. This may be a response to the generally lower intake of flail-cut silage.     

Separating the effects of forage source and field microbiota on silage fermentation quality and aerobic stability

This study attempted to separate the effects of forage source and field microbiota on silage fermentation quality and aerobic stability. Single samples of grass, red clover and maize were used. Field microbiota was obtained by centrifugation of microbial suspensions of the three samples. The intact forages were dried and sterilized by heating at 60°C for 3 h + 103°C for 15 h, inoculated in a 3 (forage) × 3 (inoculum) design and reconstituted to a dry‐matter level of 400 g kg^?1 before ensiling. After ensiling for 71 d, subsamples were subjected to an 8‐d aerobic stability test, which included temperature and pH measurements. Bacterial community analysis was performed on samples before and after ensiling by 16S rRNA gene amplicon sequencing. Forage source had a marked effect on the levels of lactic acid, acetic acid, ammonia‐N and 2,3‐butanediol, but microbiota source only affected the acetic acid concentration. The forage and microbiota as well as their interactions affected silage stability variables. The maize microbiota improved silage stability, whereas silages made from the maize forage had the poorest stability. Bacterial community analysis revealed higher abundance of lactic acid bacteria on the maize forage, with Lactococcus and Leuconostoc being the dominant genera. These preliminary results suggested that fermentation quality is mainly affected by forage source, whereas the aerobic stability is affected by both forage and field microbiota.     

Effects of different additives on fermentation quality and aerobic stability of Leymus chinensis silage

This study investigated the effects of different additives on fermentation quality and aerobic stability of Leymus chinensis silage. Treatments included (i) no additive, (ii) 3 mL kg^?1 formic acid (FA), (iii) 6 mL kg^?1 FA, (iv) 5 mL kg^?1 acetic acid (AA), (v) 10 mL kg^?1 AA, (vi) 2 mL kg^?1 propionic acid (PA), (vii) 4 mL kg^?1 PA, (viii) 5 mL kg^?1 butyric acid (BA), (ix) 10 mL kg^?1 BA, (x) 1.0 g kg^?1 potassium sorbate (PS), (xi) 1.0 g kg^?1 sodium benzoate (SB), (xii) 1 × 10⁸ colony‐forming units (cfu) kg^?1 Lactobacillus (Lb) plantarum LP (LP), (xiii) 1 × 10⁸ cfu kg^?1 Lb. brevis LB (LB) and (xiv) 1 × 10⁸ cfu kg^?1 Lb. buchneri NCIMB40788 (Fresh). Each additive treatment was based on fresh matter (FM). Results showed that all additives decreased pH values. All additives except Fresh decreased ammonia‐N content (p < .001). Both LP and LB increased lactic acid content (p < .001). Butyric acid content increased with FA (3 mL kg^?1) and BA, but decreased with PA, PS, SB, FA (6 mL kg^?1), AA, LP, LB (p < .001). FA (3 mL kg^?1), AA (10 mL kg^?1), PA, BA, PS, SB and Fresh improved aerobic stability (p < .001). After 8 days exposure to air, the pH value and yeast count were lower in FA (3 mL kg^?1), BA (10 mL kg^?1), SB treatments than in other treatments. Overall, AA outperformed all other additives in improving fermentation quality. Sodium benzoate and AA could be used as an effective additive to improve aerobic stability of L. chinensis silage.     

Lactic acid bacteria strains for enhancing the fermentation quality and aerobic stability of Leymus chinensis silage

Leymus chinensis is an important grass in China and Russia. Six lactic acid bacteria (LAB) strains (LB, LPL1, LPL2, LPL3, LCL and WH) from L. chinensis silage were screened and identified and their effects on fermentation quality were investigated. All six strains were grown at 6·5% NaCl and pH 4·00. Strains LPL1, LPL2 and LPL3 were identified as Lactobacillus plantarum, and LB, WH and LCL were classified as Lactobacillus brevis, Weissella hellenica and Lactobacillus casei respectively. The six isolated strains and a commercial inoculant (Lactobacillus buchneri) were added to L. chinensis for ensiling at densities of 500 and 600 kg m^?3. The control was sprayed with the same volume of distilled water. The effects of the strains on fermentation quality after 45 d ensiling and aerobic stability during 8 d of exposure to air were evaluated. The 600 kg m^?3 silage had lower pH, butyric acid, ammonia nitrogen content and coliform bacteria counts than the 500 kg m^?3 density silage (P < 0·05). The six isolated strains decreased pH, butyric acid content and increased lactic acid content, and all inoculants increased L. chinensis silage aerobic stability except LCL (P < 0·05). The fermentation quality of L. chinensis silage increased with higher ensiling density. The LAB strains improved the fermentation quality, and high‐quality silage could be obtained at low ensiling density with the addition of the LAB strains. The strains improved the aerobic stability; Lb. buchneri and Lb. brevis showed the best performance.     

Effect of Lactobacillus buchneri 40788 on the fermentation,aerobic stability and nutritive value of maize silage

The effect of adding Lactobacillus buchneri 40788, a heterofermentative lactobacilli, to whole‐plant maize and its effect on fermentation and aerobic stability of the resulting silage were evaluated. Whole‐plant maize (380 g DM kg^–1 fresh weight) was ensiled in laboratory silos after the following treatments: untreated, L. buchneri 40788 at 1 × 10⁵, 2·5 × 10⁵, 5 × 10⁵, and 1 × 10⁶ colony forming units g^–1 of fresh forage or, a commercial inoculant containing homolactic acid bacteria, a single species of propionibacteria and enzymes. Addition of L. buchneri 40788 resulted in a decrease in lactic acid concentration but increased the concentration of acetic acid in silage and markedly decreased the numbers of yeasts present in the silage. All levels of L. buchneri 40788, increased the aerobic stability of silages but the effect was greatest for the two highest levels of inoculation. Treatment with the commercial inoculant had no effect on the fermentation or aerobic stability of silage. On‐farm treatment of maize silage with L. buchneri 40788, stored in a bag silo, resulted in changes in fermentation that were similar to those observed in laboratory silos. Treatment decreased the numbers of yeast in silage and increased aerobic stability (+25 h) of the silage when exposed to air. Treatment had no effect on the dry‐matter intake of silage fed to sheep. These results showed that treating silage with L. buchneri 40788 can increase the aerobic stability of maize silage in laboratory and farm silos.     

Chemical, physical and microbiological changes during composting of the water hyacinth

An investigation of the physical, chemical and microbial population changes that occurred during the composting of water hyacinth was carried out. After 11 weeks of composting, the compost turned black, had decomposed and had no smell. The pH was 7 and the highest temperature reached, of 40 degrees C occurred in the first week. The initial carbon/nitrogen ratio was 17.61 and this increased to 18.12 by the end of the composting. The coliform population declined greatly from 8.11 to 5.85 MPN (log)/g and fecal coliforms and Escherichia coli were not detected in the final product. Bacteria were the dominant microbes in the compost followed by actinomycetes and fungi. Mesophillic microorganisms were present in higher numbers than thermophillic microorganisms throughout the composting. The highest cellulase and xylanase activities in the compost of 6.67 and 10.24 U/kg DW, respectively were detected in the second week which was related to the temperature. Bacillus sp. strain B4 was isolated and investigated for cellulase and xylanase using agro-industrial residues as substrates during Solid-State Fermentation (SSF) processes. Corncob and rice straw were good substrates for the production of the enzymes with a maximum cellulase of 1.19 U/gDW and xylanase activity of 2.54 U/g DW, respectively. The activities of both enzymes were stable and maximum at 50 degrees C. This study indicated that agro-industrial residues should be mixed with water hyacinth for composting to facilitate the development of a thermophilic phase during the composting process and to improve the product. Bacillus sp. strain B4 can be used as a starter strain.     

The effects of lactic acid bacteria on the fermentation,aerobic stability and nutritive value of maize silage

Maize was harvested at one‐third milk line (297 g kg^?1 DM) stage. All inoculants were applied at 1 × 10⁶ cfu g^?1 of fresh forage. After treatment, the chopped forages were ensiled in 1·5‐L anaerobic jars. Three jars per treatment were sampled on days 2, 4, 7, 12 and 90 after ensiling, for chemical and microbiological analysis. Homofermentative LAB‐inoculated silages had lower pH and higher lactate:acetate ratio (except for Lactobacillus plantarum/Pediococcus cerevisiae and L. plantarum/Propionibacterium acidipropionici) than the control and both heterofermentative LAB‐inoculated silages. Both L. buchneri inhibited yeast growth and CO₂ production during exposure of silage to air. The L. plantarum/P. cerevisiae, L. plantarum (Ecosyl) and L. plantarum/Enterococcus faecium‐inoculated silages had higher dry‐matter digestibility than the control and L. buchneri‐inoculated silages. Inoculants did not affect digestibility of neutral detergent fibre, except for L. buchneri (Biotal), organic matter nor ME content of silages. The LAB silage inoculants generally had a positive effect on maize silage characteristics in terms of lower pH and shifting fermentation toward lactate with homofermentative LAB or toward acetate with L. buchneri. The use of L. buchneri can improve the aerobic stability of maize silages by the inhibition of yeast activity.     

Effect of sward height on the fermentability coefficient and chemical composition of Guinea grass silage

There is a high correlation between sward height and pasture sward structure. Therefore, in tropical grasslands, taking sward height into account has been a much better strategy in rotational stocking management than considering pre‐defined days of growth. Similarly, sward height could be used to determine the moment when tropical grasses present the best ensilability parameters. This study aimed to identify the sward height at which Panicum maximum cv. Mombaça (Guinea grass) provides the highest fermentability coefficient (FC) and to define the combination of additives that best improves the chemical composition of silage. Two trials were carried out in Selvíria, MS, Brazil, from 2015 to 2016. The first year was used to identify the highest FC, and the second year was used to identify the best combination of eight additives (citrus pulp [CIP], homofermentative and heterofermentative LAB, their combinations and control). Statistical analyses were performed using SAS (p < .05), and one contrast was defined as silage with CIP vs. silage without CIP. The height of 130 cm resulted in the highest FC (31.01). Silages inoculated with CIP had better quality than silages without CIP, due to the high crude protein (8.3 vs. 7.3% DM), DM recovery (98.6 vs. 93.3% DM), low pH (3.92 vs. 4.91) and NH₃‐N values (2.49 vs. 14.73% total N). Sward height is a consistent parameter for determining the time of ensiling Guinea grass, and the inclusion of CIP is necessary to raise the silage quality.     

A meta‐analysis comparing standard polyethylene and oxygen barrier film in terms of losses during storage and aerobic stability of silage

A meta‐analysis was undertaken of 51 comparisons of standard polyethylene film with oxygen barrier (OB) film in covering systems for bunker silos, unwalled clamp silos and bales. Mean losses of DM or OM during storage from the top 10 to 60 cm of bunker and clamp silos were 195 g kg^?1 for standard film and 114 g kg^?1 for OB film systems (41 sets of data, P < 0·001), while mean total losses of DM from baled silage were 76·8 g kg^?1 for standard film and 45·6 g kg^?1 for OB film systems (10 sets of data, P < 0·001). Top surface silage judged subjectively to be inedible was 107 and 29·6 g kg^?1 for standard film and OB film systems respectively (5 sets of data, P = 0·02). Aerobic stability was 75 h for silage stored under standard film system and 135 h for silage stored under OB film system (11 sets of data, P = 0·001). It is concluded that the OB film system reduces losses from the outer layers of silos and from bales and increases the aerobic stability of silage in the outer layers of silos.     

The effects of pressure and stage of ensilage on the mechanical properties and effluent production potential of grass silage

Direct-cut grass silage was ensiled without compression in laboratory silos for 0–75 d. On occasions during this period, the silage was subjected to creep compression tests at three pressure levels for a period of 5 h and effluent production was measured. Precision-chopped Italian ryegrass ( Lolium multiflorum ) was ensiled in the first experiment, whereas flail-harvested perennial ryegrass ( Lolium perenne ) was ensiled in the second. Pressure levels were 11·3, 16·9 and 22·5 kPa for Experiment 1 and 5·7, 11·3 and 16·9 kPa for Experiment 2. Moisture contents of the ensiled herbage were 815 and 856 g kg⁻¹ for Experiments 1 and 2 respectively. The consolidation of the grass silage was described by a Burgers body model. Effluent production was more closely related to strain than to compressibility. Linear regression equations for the relationship between strain and effluent production are presented. There was a significant positive linear relationship between pressure and effluent production at each silo opening time in both experiments. The time course of effluent production was fitted to a negative exponential curve. The time that elapsed before effluent release in each experiment was a function of both pressure and time after ensilage. The results of the experiments were compared with the predictions of two models of effluent production. Reasonable agreement between predicted and actual effluent production could be obtained provided the measured material parameters were used and immediate saturation of the forage was assumed. Using the models highlighted the need for a better understanding of saturation development in the silage.     

Effects of Lactobacillus buchneri isolated from tropical maize silage on fermentation and aerobic stability of maize and sugarcane silages

This study was aimed to perform a screening of Lactobacillus buchneri strains from maize silage and use them as inoculant in maize and sugarcane silages. In all, 151 lactic acid bacteria (LAB) strains were isolated from whole‐plant maize silage, and their identification was based on the sequence analysis of 16S rDNA. In total, 15 strains were categorized to the L. buchneri group and eight of these were selected based on growth rate and fermentation pattern. The selected strains were evaluated on fermentation and aerobic stability of maize and sugarcane silages. For maize, the inoculated silages had lower pH and higher LAB population, but lower acetic acid concentration in comparison with the untreated control silage. For sugarcane silage, the strains 56.1, 56.4 and 40788 resulted in highest dry‐matter (DM) content and lowest DM losses. However, only the strain 40788 showed lowest counts of yeasts and moulds. Sugarcane silages inoculated with the strains 56.9, 56.26 and the untreated control silage showed highest concentrations of lactic acid and ethanol, besides the great DM losses. Even so, for both crops, the aerobic stability was not affected by inoculation. After air exposure, all silages increased temperature and had high population of yeast and moulds. Nevertheless, the strains 56.1 and 56.4 are promising for use as a silage inoculant.     

Effects of potassium sorbate and sodium benzoate at two application rates on fermentation and aerobic stability of maize silage

This study evaluated two potassium sorbate (PS) and sodium benzoate (SB) application rates in improving the aerobic stability of maize silage. Treatments included no additive, the addition of PS at 1 and 2 g kg^?1 fresh matter (FM) and the addition of SB at 1 and 2 g kg^?1 FM. Four replicates of each treatment were ensiled in 15‐L plastic jars. The silages were analysed for their fermentative characteristics and were subjected to an aerobic stability test with pH and yeast and mould count measurements. Considering fermentation quality and aerobic stability, both additives were effective. The PS was more active against yeasts during aerobic exposure. When the additives were applied at 2 g kg^?1, the silages were more stable (256 h, on average) than those with 1 g kg^?1 (119 h, on average) and control (61 h). Aerobic deterioration was more pronounced in the controls than in the treated silages. Silages treated at 2 g kg^?1 had consistent effects on pH values and yeast counts over 288 h of aerobiosis. Overall, PS and SB applied at 2 g kg^?1 were more effective in improving aerobic stability.     

Effects of maize meal and limestone on the fermentation profile and aerobic stability of smooth bromegrass (Bromus inermis Leyss) silage

Chemical‐compositional characteristics of crops are crucial factors affecting the fermentation profile and aerobic stability of silages. To evaluate the effects of starch content and buffering capacity, fresh smooth bromegrass was ensiled alone (control), with 9% maize meal (MM), or with a mixture of 9% maize meal and 1.5% limestone (MX) on a fresh matter basis in sealed plastic bags. After 1, 3, 14 and 56 days of ensiling, triplicate bags of each treatment were opened for chemical and microorganism analyses, and then the samples ensiled for 56 days were placed in polyethylene containers to evaluate their aerobic stability. During the early days of ensiling, the mixtures of maize meal and limestone favoured lactic acid bacteria growth, lactic acid production and decrease in pH values. After 56 days of ensiling, the MX‐treated silages had significantly higher (p < .05) lactic acid, ammonia‐N and buffering capacity compared with the silages treated with other additives. The aerobic stability of MM‐treated silages was significantly lower (p < .05) than that of the control silages, but the MX‐treated silages showed higher (p < .05) aerobic stability than the other groups. The changes of organic acids and pH in the MX‐treated silages were also delayed, which inhibited the growth of aerobic bacteria and yeasts. These results indicate that maize meal improved the fermentation profile of smooth bromegrass silage but had a negative effect on its aerobic stability; however, limestone played important roles in both accelerating fermentation and the improvement of aerobic stability.