首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 33 毫秒
1.
A farm-scale trial to compare the effectiveness of polythene bags and wrapping of big bale silage was monitored for Listeria monocytogenes contamination. There was no significant difference between the level of L. monocytogenes found in wrapped and bagged big bale silage, but the work confirmed that big bale silage is prone to contamination by Listeria organisms, and that the degree of Listeria contamination could be significantly reduced by the removal of obviously spoiled material prior to feeding.  相似文献   

2.
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.  相似文献   

3.
Listeria monocytogenes contamination is associated with silage that has been subjected to aerobic deterioration. A laboratory ensiling system based on plastic tube silos, which permit aerobic spoilage to take place in a controlled manner, is described. This system gives a high degree of consistency between replicates. Parameters measured over a 90-d ensiling period were pH, L. monocytogenes and Enterobacteriaceae counts and percentage spoilage. The system may be suitable for assessing the effectiveness of additives on parameters, such as aerobic spoilage and L. monocytogenes , which are not easily measurable in field studies. The study confirmed the relationship between the presence of Listeria spp. and Enterobacteriaceae in aerobically spoiled silage, showing that the latter group of bacteria may be useful as indicators of the potential risk of L. monocytogenes contamination of silage.  相似文献   

4.
A mathematical model is presented that predicts the time-course of aerobic deterioration in grass and whole-crop maize silages. The model predicts the stability of the silage taking into account the buffering capacity of the silage, the initial contents of organic acids and ethanol, pH, the initial temperature and the initial populations of the microorganisms. The specific processes simulated include the growth of yeast and acetic acid bacteria, the oxidation of fermentation products, the consumption of oxygen and the production of carbon dioxide, the rise in temperature. and the increase in pH.
The deterioration of silage is seen to be initiated by acetic acid bacteria or by yeast, or by both groups together. The factors that determine which groups will prevail are the dry matter contents and the chemical composition of the silage. The output of the model is validated by comparison of the simulated data with data from published work on the deterioration of silage.  相似文献   

5.
Use of big bale silage and haylage can be difficult on farms where daily forage consumption is comparatively low as speed of deterioration of forage after bale opening may be faster than feed-out rate. Production of smaller bales at harvest is possible, but expensive and work-intensive. Therefore, a pilot study of rebaling forage stored in big bales to smaller bales was conducted. Three separate experiments were included, where microbial and chemical composition of silage and haylage was studied before and after rebaling. In Experiment III, residual big bale forage stored and opened together with rebaled forage was included. Results showed that rebaled haylage and silage had higher yeast counts compared to initial forage; however, residual bales in Experiment III had yeast counts similar to rebaled forage, indicating an effect of storage time rather than of rebaling. In Experiment II, mould counts were higher in rebaled compared to initial silage, but not in haylage. Chemical composition was similar in initial and rebaled forage except for ammonia-N. In Experiment III, ammonia-N was higher in rebaled compared to initial and residual forage and was the only chemical variable affected by rebaling. Bale temperature during aerobic storage followed ambient temperature until day 6–8 in Experiment I and until day 14 in Experiment III where ambient temperature was lower. In conclusion, rebaling can be done without large changes in chemical composition of the forage, but yeast and mould counts may be higher in rebaled forage, and this risk should be considered when using this procedure.  相似文献   

6.
A laboratory method for ensiling grass in bags, which simulates the aerobic deterioration found in big bale silage, is described. These conditions selectively encouraged the multiplication of naturally occurring listeria. All grasses ensiled in this way gave detectable numbers of listeria, usually L. monocytogenes , indicating that these bacteria are a normal part of the microflora of grass. The results from the laboratory silage were comparable to those found in the same grass ensiled in big bales on the farm.  相似文献   

7.
A model of aerobic fungal growth in silage.   总被引：7，自引：0，他引：7  
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.  相似文献   

8.
The occurrence of Listeria spp. in pasture grass and grass silage made with various additives and preservation techniques is reported. Silage samples were collected three times (in November, February and May) from eighty dairy farms. The prevalence of Listeria spp. in pasture grass samples was 0.647 and in silage samples 0.227. Only two species, L. monocytogenes and L. innocua were observed. Listeria spp. Were isolated from the silage at least once at thirtynine farms (0.488), and L. monocytogenes at twenty-seven farms (0.338). The occurrence of Listeria was highest among the silage samples collected in November (0.288). Silages preserved with acids had the lowest prevalence of Listeria (0.194). Silages preserved in tower silos were most often free of Listeria, only 0.056 being positive. The highest prevalence of the Listeria spp. (0.324) was detected in clamp silage. The results of chemical analyses of silage statistically reflect the frequency of Listeria.  相似文献   

9.
An experiment investigating changes in fermentation variables and microbial composition during storage of small‐bale silage and haylage was performed. Haylage was defined as silage with a dry‐matter (DM) content exceeding 500 g kg?1. Grass was wilted to three different DM contents, and baled into silage (350 g DM kg?1), haylage with a low DM content (550 g kg?1) and haylage with high DM content (700 g kg?1) in small rectangular‐shaped bales (0·80 m × 0·48 m × 0·36 m) that were individually wrapped. Bales were stored for short (2 months) or long (14 months) periods before opening and sampling. Silage had higher concentrations of fermentation products and a lower pH than either of the two haylage types. In general, long‐term storage influenced all fermentation variables except concentrations of butyric acid and succinic acid, and yeast counts were higher after 14 months than 2 months of storage. However, silage changed in more fermentation variables during storage than the two haylage types. Although differences between short‐ and long‐term stored silage were found, linear correlations between short‐ and long‐term stored bales were present for all chemical variables. Pearson's correlation coefficients were highest for lactic acid, followed by pH.  相似文献   

10.
  相似文献   

11.
Aerobic stability is an important feature in the evaluation of silages. The aims were to investigate the chemical and microbiological changes that occur in sugar-cane (Saccharum spp.) silage after aerobic exposure, to identify the major species of yeasts associated with the aerobic deterioration process and to select lactic acid bacteria (LAB) strains that can improve the aerobic stability of this silage. Fourteen wild LAB strains belonging to Lactobacillus plantarum, L. brevis and L. hilgardii were evaluated using experimental silos. Silage samples were collected at 0, 96 and 216 h after aerobic exposure to determinate the DM, WSC, pH, products of fermentation, to evaluate the silage temperatures and to identify yeast species associated with the aerobic deterioration of silage. The strains tested were able to modify the fermentative and chemical parameters and the diversity of yeasts species of silage after aerobic exposure. There was no association between the facultative or obligatory heterofermentative fermentation patterns and the increased aerobic stability of silage. Aerobic stability of sugar-cane silages was associated with high acetic acid and 1,2-propanediol concentrations. L. hilgardii UFLA SIL51 and UFLA SIL52 strains promoted an increase in aerobic stability of silage.  相似文献   

12.
The effectiveness of the polyethylene stretch‐film barrier to air infiltration is the major factor affecting the preservation of silage in bales. Three separate experiments investigated the effects of the number of layers of stretch‐film cover, film colour, stretch extent, film type and frequency of bale handling on gas composition, surface mould growth and conservation characteristics of baled grass silages. Monitoring gas composition in bales during ensiling proved useful for assessing the success with which wrapped bales were stored anaerobically. Under good storage conditions the early stages of ensiling were characterized by the rapid reduction of O2 concentration in the bale and the creation of a CO2‐rich environment. However, wrapping bales in only two layers of stretch‐film failed to create the anaerobic conditions required for a successful fermentation and the inhibition of visible fungal growth. In contrast, a minimum of four layers of stretch‐film were required to achieve suitably anaerobic conditions, but the additional benefits of applying more layers were relatively small. Under temperate climatic conditions with moderate solar radiation, film colour had little effect on the gas composition in baled silage. Likewise, the extent of stretching applied to the film at wrapping and film type had no influence on gas composition, baled silage quality or mould development. However, frequent mechanical handling of bales after wrapping had a negative effect on gas composition and surface mould growth, and thus should be kept to a minimum.  相似文献   

13.
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.  相似文献   

14.
A quantitative model of the ensilage process in lactate silages   总被引：2，自引：1，他引：1  
A model of the ensilage process is presented which can be used to predict silage quality in lactate silages. The model simulates the major microbial and biochemical processes during ensilage, including aerobic respiration, hydrolysis of hemicellulose. growth and death of lactic acid bacteria and their production of lactic and acetic acids, reduction in pH, change in soluble sugar content, increase in osmotic potential, and proteolysis. The model is designed to operate on mixtures of grasses, legumes, or whole-plant corn. Parameters for the model are developed from published silage experiments and pure-culture bacterial studies. The model gives reasonably accurate predictions of key silage quality parameters, but further experimental work is needed on growth of lactic acid bacteria and on plant-enzyme proteolysis. Predicted final pH depends primarily on the pH at which bacterial growth and death rates are equal. Initial bacterial concentration affects the time to rapid pH change, while maximum bacterial growth rate affects the rate of decline thereafter.  相似文献   

15.
A simulation model of the growth and fermentation of lactic acid bacteria and clostridia in silage is described. The model is used to predict the occurrence of a well-preserved lactate silage or a poorly-preserved clostridial silage. Results of the model are compared with published experimental studies not used in the model's development. The results are summarized with maps showing the combinations of initial water-soluble-carbohydrate content, crop buffering capacity, dry matter content, temperature, initial pH, and initial population of lactic acid bacteria which result in a clostridial silage. The specific processes modelled include the growth and death of lactic acid bacteria and clostridia; the use of substrate and accumulation of fermentation end products; release of ammonia; and change in silage pH.  相似文献   

16.
A second cut of lucerne was wilted to 500 g DM kg−1 and either left untreated (control) or treated with formic acid (4.5 1 fresh forage t−1) or with a commercial inoculum of lactic acid bacteria (105 colony forming units (cfu) g forage−1). The forages were ensiled in 2-t capacity silos for 8 months, and later fed to six lambs (mean initial weight 27.7 ±1.60 kg) in a 3x3 duplicated Latin square with 27-d periods. Portions of the untreated and additive-treated forages were also ensiled in laboratory silos at 25 ° C for intervals up to 42 d. Results from the laboratory silos showed that the major increase in ammonia-N in silage occurred between 40 h and 7 d of fermentation; during this period, both formic acid and the inoculant produced a smaller increase in ammonia-N, than did the control. The pH of inoculated silage declined from 5.74 to 4.57 in 7 d, but it took 14 d for the pH of the control silage to fall below 5.0. Formic acid treatment immediately reduced the silage pH from 5.74 to 5.10 ( P < 0·01); the pH then remained unchanged until 21 d, after which it decreased slightly. When compared with control, lambs fed formic acid-treated silage consumed more ( P < 0·05) digestible organic matter; the response was associated with a trend towards decreased concentration of ammonia in plasma. Inoculation of lucerne silage did not ( P < 0·05) affect voluntary intake but increased ( P <0.05) apparent digestibility of fibre and tended to increase N retention.  相似文献   

17.
Data from thirty-three experiments conducted at three ADAS Experimental Husbandry Farms were used to compare unwilted non-additive-treated silage with silage treated with formic acid, a formalin and formic-acid mixture, a calcium-formate and sodium-nitrite mixture, a formalin and sulphuric-acid mixture and wilted silage made without or with formic acid or a formalin and formic-acid mixture.
Formic acid significantly reduced pH and wilting significantly increased silage pH compared with other treatments. Formalin-acid mixtures significantly reduced pH compared with untreated silage. Formic acid in conjunction with formalin or wilting significantly increased water-soluble carbohydrate in silage compared with other treatments except wilting. Formic acid either alone or combined with either formalin or wilting significantly reduced silage butyric acid content compared with other treatments. Formic acid treatment either alone or combined with formalin significantly increased lactic acid as a proportion of total silage acids compared with other treatments except sulphuric acid-formalin.
All treatments significantly increased silage dry matter (DM) intake compared with untreated silage and intakes of wilted silage were significantly greater than of unwilted silage. Daily liveweight gains on all treatments were significantly higher than on untreated silage.
Herbage water-soluble carbohydrate necessary for successful preservation as silage without additive use was approximately 30 g (kg DM)−1 and with additives containing formic acid it was approximately 25 g (kg DM)−1.
It is suggested that formic acid application to unwilted silage either alone or in conjuction with formalin was the best treatment for improving subsequent preservation as silage, and that animal performance was enhanced by addition of acid-formalin additives to unwilted herbage or formic-acid application to unwilted or wilted herbage.  相似文献   

18.
Three feeding trials with big bale silage were carried out to determine whether previously established intake differences between artificially dried Italian ryegrass cultivars could be repeated under differing conditions of food preparation and presentation. The silage was prepared in 2 consecutive years from the same field crop and fed to groups of cattle in both years. The second year silage was also fed to sheep indoors. All animals were fed ad libitum and the voluntary intakes recorded for groups of cattle and individual sheep. Chewing activity was also recorded on all groups of sheep.
The chemical composition of the two cultivars as fresh grass was similar in 1984 but there were small differences in 1983 with Tarquin showing slightly higher organic matter digestibility (DOMD) and lower dry matter and water-soluble carbohydrate compared to RvP. The only consistent differences in silage composition between cultivars was a slightly higher level of modified acid detergent (MAD) fibre in RvP compared to Tarquin. Despite these small differences the voluntary intake of cattle fed Tarquin was 19% higher than RvP in the first year and 35% in the second, while sheep showed a similar difference of 40% with the second year silage.
Recording of jaw activity with sheep showed that animals spent 40% more time eating and 27% more time ruminating RvP than Tarquin per unit of food eaten. This suggested that the intake differences, which were independent of digestibility, were related to the physical resistance of the feed to breakdown by chewing. These differences depend on the structural characteristics of the plants and were associated with differences in leaf/stem ratios and MAD-fibre content. These are less likely to be affected by the method of conservation or feed presentation and, although the degree of difference between the cultivars changed with the different procedures, the inherently higher intake of Tarquin persisted.  相似文献   

19.
The fermentation quality of small‐bale silage and haylage for feeding to horses in Sweden, and using a conventional high‐density hay baler, was investigated in two experiments. Treatments studied were use of additives (inoculants containing lactic acid bacteria and a chemical additive consisting of hexamethylenetetramine, sodium nitrate, sodium benzoate and sodium propionate), the influence of dry‐matter (DM) content of wilted herbage and the effect of number of stretch film layers on fermentation pattern and aerobic stability. All silages and haylages were made from predominantly Timothy swards and were well fermented as indicated by low levels of ammonia and butyric acid. Values of pH were higher and concentrations of organic acids were lower in haylages than in the silages. This was not considered to be indicative of a poor fermentation in the haylage but of a restricted fermentation due to the high DM content of the herbage. The additives enhanced aerobic storage stability because of inhibition of mould growth. The only statistically significant effect of varying the number of stretch film layers was a higher content of CO2 inside the bales when ten layers of stretch film were applied compared with six layers.  相似文献   

20.
Challenges to ensiling are coming from a wide spectrum. Faster harvest rates are making it more difficult to achieve target silage densities. Larger harvest equipment is increasing soil compaction and rural road issues. Older silos are too small and are overfilled, creating safety issues, or temporary piles are placed on bare ground permitting soil contamination. Mycotoxins and other pathogens in silages are still a problem. Global warming may affect the forage crops grown and crop characteristics as well as rates of silage fermentation and aerobic deterioration. Silage as an input to bio‐refineries has an unclear future. Silage analysis is challenged by sampling and knowing what components truly predict nutritional value. The future holds many opportunities for both ensiling and silage research. Robotic harvesting will release more labour for silo packing, and there are opportunities to develop tools to estimate silage density during filling. Total mixed ration silages should allow more by‐products in rations. The development of novel silage additives to improve silage hygiene or increase nutrient availability appears promising. Predicting the onset of aerobic deterioration with quick tests for lactate‐assimilating yeasts or silage temperatures seems possible. Metabolomics and metabonomics, in addition to the microbiome tools in development, put us at the cusp of being able to see which microorganisms are active in the silo and rumen and what compounds of significance they are producing. This could lead to many advances in silage quality including reduced microbial toxins, better hygiene and improved utilization by livestock.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号