PROCEDURE FOR SILAGE MAKING & PREVENTIVE MEASURES TO CONTROL SILAGE SPOILAGE
Dr. Rakesh Singh,TVO, Motihari
Silage is the fodder which is conserved by reducing pH through natural anaerobic fermentation and is used for feeding during scarcity period, drought or floods and for Utilizing surplus forage. The suitable crops are sorghum, maize and oat etc. During lean period feeding of silage acts as a green fodder and maintains livestock productivity.
Silage making means preservation of chaffed cereal green fodder in anaerobic condition by way of fermentation method. In anaerobic condition (no air inside pit/tank),with the help of micro organisms, sugar contained in green fodder is converted in to Lactic acid ,which help to preserve the green fodder for longer duration.
Respiratory function of living cells present in green chaffed fodder utilises Oxygen in air tight condition & releases water & carbon dioxide in closed environment in pit/tank. Due to Carbon dioxide releases in pit/tank, air inside is expelled outside as well as organism which depends on oxygen (Like bacteria & Fungi) cannot withstand in CO2 atmosphere in Tank/Pit. These effects in to preservation of chaffed green fodder in silo pit/tank as silage for longer duration (6 months or max. a year if good care is taken)
How Silage is prepared?
During the silage making process, the pasture is cut when the grasses contain the highest nutrient levels. This level is attained just before they are fully mature.
The reason why it is cut just before they are fully mature is that all forms of preserved grass, such as hay and silage, will have lower amounts of nutrients than fresh pasture, so everything must be done to make the end product be as nutritious as possible.
During Silage preparation, the grass is allowed to wilt in the field for a few hours to reduce the moisture content to around 60-75% as this is the optimum level. If the grass is left out longer, it may get too dry, or it may get rained on – and both these will reduce the efficiency of the fermentation.
SILAGE MAKING FOR SMALL HOLDERS
| Process in silage making
1. Selection of forage crops and their maturity stage 2. Steps in silage making |
| 1. Pit making: Firstly, a silage pit has to be dug for storing silage. The pit size may be determined based on the amount of silage to be stored. A pit with a dimension of 1 metre wide X 1 metre length X 1 metre depth can store 500 kilograms of silage. The location of pit should be free from water stagnation. The pit should be surrounded on all sides with thick plastic sheet. Pit can also be constructed using bricks and cement. |
2. Preparation of fermentation mixture:
3. Harvesting and transportation of crop (ensiling): Harvesting at proper stage but delay in transportation may lead to loss of excess moisture results in haylage (DM 70-80%) 4. Chaffing: |
| 5. Filling of silo and compaction:
Chaffed material should be spread evenly over entire surface of silo (the structure) and then compacted through trampling (in case of small silo). In case of large silo (trenches) the compaction can be done using tractor. It helps in rapid evacuation of air from the silo, thus checks the aerobic respiration and nutrient loss. 6. Properly sealing and covering of silo pit: It should be done in such a way that neither air enters in to the silo nor the gas comes out from the silo. It is better to use polythene sheet but care should be taken that entire surface of polythene sheet should be covered with straw or any other dried material up to 6-8 inch thickness to avoid the damage of polythene sheet by dog, cat or other animals. Make sure water does not enter the pit during rains. The silage will be ready in 45 to 60 days, depending on the types of material used. The silage of thin stem crop like oat becomes ready in 45 days while thick stem crops like maize, sorghum and bajra become ready in 60 days. Ideal silage is golden yellowish green colour with good aroma. After completion of incubation period the silo is opened for feeding. The whole silo should not be disturbed and it should be opened from one place/corner to avoid the loss of moisture and nutrients. Depending on the type of animal, stage of production and availability of silage it can be supplemented in the ration (5-25 kg per animal) of animal during lean period. After opening the pit, silage should be used within 30 days. |
Essential fodder crops for silage making-
To prepare best quality silage, cereal green fodder like Green fodder maize, Fodder sorghum, Bajara, Hybrid Napier, Sugar cane tops, Oat, Marwel etc are required. Preference for cereal green fodder (monocotyledons) is due to it has more sugar content than protein, as sugar is utilised in fermentation process to make lactic acid by microorganisms. These cereal fodder crops have hard stem, which takes more time for drying in making hay of these crops, so it is better to use these kinds of crops for making silage than hay.
Silage is storage system of green fodder which keeps all parts of fodder in appropriate condition for feeding than any other system of storage of fodder. Silage requires less space for storage as it is pressed in pit/tank than hay making. For daily cutting, transporting & chaffing of fodder in traditional way requires more labour &time but in case of silage, fodder cutting, transport, chaffing is done at one time only, so it is less labour & time consuming practice.
Land under fodder cultivation is emptied, and immediately it is used for plantation of other crops. So farmers’ can take more crops in same land in a year against traditional way where land is reserved for fodder until all crops is harvested. Silage is prepared in closed & air tight condition so there is no danger of fire. (In hay making, dry fodder is stocked & exposed for fire like situation) Due to lactic acid in silage, it is easily digestible to animals, so energy required for digestion is used for other purposes like milk production.etc. Silage is tasty & flavoured, so it increases appetite of dairy animals. Important thing behind to adopt silage is in scarcity it provide supply of fodder to dairy animals. Situations like drought, high rainfall & scarcity of fodder, farmers may use silage for feeding to dairy animals. (Rain fed area where shortage of green fodder is for March to June & in high rainy area or water logged lands, it is impossible to cultivate or harvest fodder) Due to treatment of additive for silage, farmers can supply energy, mineral & vitamins to dairy animals.
Planning for silage making-
There are two methods for silage making which are vastly used i.e. Pit method or tank method. These two methods are economically viable for dairy farmers. For planning of silage, following aspects needs to pay attention-
How many dairy animals farmer’s have?
How many days farmer’s have to feed animals with silage?
Is sufficient green fodder is available with farmer to prepare required silage?
On the above points, decide to plan for silage making,
there is example for you- -One dairy farmer has four adult milching dairy animals. He has to plan for silage for four summer months (i.e. March to June), so go through following points- There are four milking dairy animals Farmers have to make silage for four months i.e. 120 days Maximum per day feeding of silage is 20 kg per animal so per day feeding for four animals as 80 kg. So for four months i.e. 120 days for four animals requirement of silage is 9600 kg.This means 9600kg of chaffed green fodder is require to make silage for four dairy animals for four months. In one cubic foot in pit or tank (1 cubic foot = 1 foot long × 1 foot wide × 1 foot high),contains 16 kg of chaffed green fodder. To decide dimension of pit/tank for 9600 kg chaffed green fodder ,you may divide it with 16 kg, so you may have to make 600 cubic feet of pit/tank as 20 foot long × 6 foot wide × 5 foot high.
Pit/tank method for silage making-
Depending upon local situation like ground water level, number of animals & duration of feeding silage to animals, decide shape & size of constructing pit/tank for silage making. For pit method, select location for making pit at higher level on ground so that rain waer may not percolate in to pit. In rectangular pit, corner edges should be making round so that while filling & pressing chaffed fodder, air will not remain inside in the corners of pit or tank. Wall of pit/tank should be air proof to avoid air too come inside in pit /tank through cracks or crevices .To avoid this situation, plaster wall of silo pit or tank with cement or moistened soil.
If ground water level is nearer, then go for building tank for silage making than pit method. If plastering cement to the wall of pit/tank is uneconomical, then you may use HDPE plastic paper (200 micron) to cover pit/tank inside out position.
Treatment for Silage-
- For making best quality & balanced silage, needs proper treatment of additives like-
- Per ton of chaffed green fodder requires 1 kg Urea, 2 kg jaggary, 1 kg common salt, 1 kg mineral mixture & 1 litre of Whey.
- Prepare separate solution in 15 to 20 litres of water for Urea, Jaggary, Mineral mixture & common salt in separate pots/buckets & then spread it on layer of pressed chaffed green fodder while filling silo pit/tank.
Procedure for filling silo pit/tank-
When fodder crop is in cob stage or Tussling stage, harvest it for preparation of silage. Very mature stage is not good for preparing silage as its sugar content is decreased as well as fibre percentage in increased; this kind of fodder is less suitable for silage making.
After harvesting fodder crops, let it dry for 5-6 hours in shed so that moisture content of fodder will decreases from 80% to 65-70%.Care to be taken to avoid silage making in rainy days or crops containing dew drops in winter season because moisture is more in this situation so there may be chances for development of mould in silo pit during storage period.
Following steps to be taken while filling silo pit-
Prior to filling silo pit / tank, clean·& dry it.
Cover with plastic film inside pit/tank in such way that it will cover all sides of pit/tank.·
For making silage, chaffing of fodder is essential component. With the help of chaff cutter machine, make pieces of 1.5c.m. to 2 c.m. length of green maize.sorghum,sugarcane tops,marwel,Fodder bajara etc for filling silo pit.·
Prepare separate solution in 15 to 20 litres of water for Urea, Jaggary, Mineral mixture· & common salt in separate pots/buckets & then spread it on layer of pressed chaffed green fodder while filling silo pit/tank.
Start to fill chaffed green fodder in pit or tank.·
After making 4” thick layer of chaffed green fodder, press it with wooden plank(Like Mortar) in such a way that air will not entangled in chaffed fodder. Then sprinkle it with prepared solution of Jaggary, Mineral mixture, Urea, Common salt· & whey.
Follow the same procedure until filling of pit/tank 1 to 1.5 feet above the ground level(In pit).Then covet it from plastic film from all side carefully.·
Covet it with Trash, Wheat straw, Soil· & dry hay to protect it from entering rain water in to it. If possible to temporary arrangement of shed above the silo pit/tank.
It will require 45 to 60 days to make good quality of silage.·
Use of silage-
After 8-10 weeks, silage is ready as feed for animals. Open pit/tank initially from one side of for use. If it is not in use, then cover it carefully with plastic film so that air will not go inside in silage. Initially fed animals with 5-6 kg silage by adding it with chaffed green fodder to develop taste to animals. Once animal likes sweet-sour taste of silage; it will eat it with good liking.
Quality of Silage-
Mould- If silage while filling pit/tank, not well pressed; there will be growth of mould.
Odour- Good quality silage has sweet & sour taste.
Colour- Good quality silage has faint green or brownish colour. Rotten silage has black colour.
pH- Good quality silage has pH of 3.5 to 4.2.
Fermentation process:
During the fermentation process, the cut grass is chopped into even smaller pieces (0.5 inches or 1.3 cms) and then compressed to eject the oxygen more efficiently.
This is important because the microorganisms especially, lactic acid bacteria, grow best under anaerobic (oxygen-free) conditions.
When oxygen remains, plant enzymes and other bacteria react with the plant sugars and proteins to make energy, thus reducing the amount of nutrients in the final product.
Preserving technique:
After the fermentation process is done and once all of the oxygen is used up, lactic acid bacteria start to multiply. These are the bacteria that are needed to make the silage. They play a key role in turning the plant sugars into lactic acid causing the pH to drop (mixture becomes more acidic). Once the pH is around 4-5, the sugars stop breaking down and the grass is preserved until the silage is opened and exposed to oxygen.
If the pH isn’t low enough, a different kind of bacteria will start fermenting the silage, producing by-products (like ammonia) that taste bad to cows and sheep. Thus, the latter situation needs to be avoided at all costs.
Preventive Measures to Control Silage Spoilage
Preservation of surplus fodder as silagemakes it possible to have the green fodder availability throughout the year. Lactic acid fermentation is important for good silage production, but some undesirable bacteria can make entry during ensiling, which candegrade the quality of silage and cause economic lossesto the farmer. Safety control measures and additives may behelpful used in producing quality silage.
In developing countriesincluding India,livestock sector is one of the fastest growing segment of the agricultural economy. The supply of the green forage throughout the year is an economic priority to the farmers, in orderto maintain the production from the ruminant stock. But forage production is mostlyseasonal in many parts of the world, with surplus availability in harvesting season and shortage of fodder during dry season. Silage making is an option to preserve the green fodder to make the greens available throughout the year.Ensiling is based on natural lactic acid fermentation under anaerobic conditions. The most important foddercrops for ensiling are corn, sorghum, barleyand various othergrasses. Beside these crops various moist “by-products” of the food industry, such as apple pomace, beet pulp and brewer’s mash can alsobe used for silage preparation. Ensiling process has many steps which should be timed and controlled carefully to ensure successful ensiling.
Ensiling process and role of different bacterial groups during ensiling:
The ensiling process completes in the following steps: harvesting the crop (30-35%DM), chopping, loading into a silo, compacting and sealing to exclude air, storing and feed out phase (unloading for animal feeding). Biochemical and microbiological incidents can ariseduring the different stages of ensiling which may affect the silage quality. At first step of ensilingisthe enzymatic activity of intact plant cells whenresidual respiration occurs. The intact cellsuse glucose and fructose as carbohydrate source and consume oxygen entrapped in the silage.Early consumption of carbohydrates is detrimental for the subsequent anaerobic lactic acid fermentation. In initial phase of ensiling epiphytic aerobic flora such as Enterobacteria, yeasts and molds develop until oxygen has been entirely consumed or acidification is sufficient to stop their metabolism. At ensiling, the facultative anaerobic bacteria carry out a heterolactic fermentation which slightly decreases the pH of the silage.
As the conditions become anaerobic in silagepit, fermentation phase starts.This phase continue for several days or weeks, during which different groups of facultative aerobic or anaerobic microorganisms naturally found in plants compete for available nutrients. With gradual acidification,acid tolerant bacterial development start; convert water soluble carbohydrates into lacticacid. In well-processed silage, LAB dominate the fermentation, rapidly producing the low pH conditions that help to preserve the silage. In case of accidental soil incorporation in ensiled material, a long aerobic phase or slow acidification, the microbial communities in the silage will be dominated by Clostridia, yeasts, molds and accidentally incorporated pathogenic microorganisms such as Listeria sp.
As long as the pH is sufficiently low and anaerobiosis is maintained, storage phase lasts and few changes occur. Numbers of LAB and other viable microorganisms decline over time, except for some specialized species such as L. buchneri with continues to be active at low population densities. Some acid-tolerant microorganisms can survive this storage period in an almost inactive state (e.g. acid-tolerant yeasts) or as spores (e.g. butyric acid bacteria). Homofermentative lactobacilli such as L. plantarum and Lactobacillus curvatus tend to predominate in well preserved silage until the final stage of fermentation, when they are invariably replaced by heterofermentative species such as L. brevis and L. buchneri.
The fourth phase is the unloading or feedout phase. On opening of silos air penetrates into the silage depending on the density and porosity of the plant material and the rate of silage removal. This causes the growth of undesirable aerobic microorganisms initially present in the silage, such as yeasts and molds and an increase in pH.
Undesirable microorganisms and their metabolites-
Several undesirable microorganisms can grow during ensiling process which can affect silage quality and thus affect animal performance or both animal and human health. These microorganisms are known as spoilage microorganisms; responsible for silage degradation mainly induce economic losses.
Yeasts and molds: Yeasts are considered to be the most important groupamong the undesirable microorganisms of silage because they are involved in aerobic spoilage either during the aerobic phase at the beginning of ensiling or during the unloading phase. The organic acid metabolism pathways (succinic, citric and lactic acids) of yeasts restarts on exposure of silage to air; inducing a pH increase and allowing the growth of less acid-tolerant microorganisms. Yeasts present in silage convert WSC into CO2 and alcohols; impair silage quality and lead to a decrease in feed intake. The alcohol production also has negative effect on milk taste.
Moulds are eukaryotic micro-organisms and develop in part of silage where oxygen is present. Many mould species produce the large filamentous structures and coloured spores in silage..Penicillium (70%), Fusarium (47%) and Aspergillus (34%) are the most frequent mycotoxin-producing fungi isolated from corn silage. There metabolites remain in the silage even after the fungus has disappeared. More than 20 mycotoxins can be produced by Fusarium sp., mainly dioxynivalenol(DON), zearalenone (ZEN) and fumonisin (FB).
Chronic exposure to mycotoxins produce non-specific symptoms such as immune system impairment, increased infections and metabolic and hormonal imbalances. Ruminants are better protected than other animals against many mycotoxins but fumonisin B1 is only poorly metabolized in the rumen.In high producing dairy animals fed on silage-based diets with high levels of concentrates; the consequent acidificationof the rumen environment may increase the animal’s sensitivity to mycotoxins.
Butyric acid bacteria (BAB): Soil accidentally included with the plant material during silo filling is the source of Butyric acid bacterial contamination of silage. Endospore-forming bacteria of the genera Clostridium, especially C. tyrobutyricum and C. butyricum and Bacillus are main BAB found in silage.At a relatively low ph,BABconvert lactic acid into butyric acid, hydrogen and carbon dioxide. A typical “clostridial silage” is characterized by a high butyric acid content of more than 5 g/kg DM, a high pH (over pH 5 in low DM silages), and a high ammonia and amine content. Excess butyric acid from feeding butyric silages results in higher levels of plasma Ketones. Daily doses of over 50 – 100g of butyric acid can cause ketosis.Feeding butyric silage has long term negative effects on production, fertility and health, thus economy of the farm business.
Bacterial spores can survive the passage through the gastrointestinal tract in dairy cows. Bacillus cereusis an important spoilage microorganism in pasteurized milk and milk products and can lead to food poisoning.The occurrence of Clostridium in milk can lead to off-flavors and excessive gas formation in semi-hard or hard ripened cheeses.
Listeria: The presence of L. monocytogenes in silage, feces or both increases the risk of its presence in milk and hence of its transmission to humans. pH of silage over 4.5 increases the risk of presence of Listeria sp. In ruminants it could cause encephalitis, absorption or septicemia, even death.
E. coli (STEC):E. coli and higher prevalence of E. coli O157 or E. coli O157:H7 has been found in herds fed corn silage.At ensiling, insufficient anaerobiosis could delay the establishment of lactic acid fermentation, slowing the pH decrease andincreasing the survival of pathogenic E. coli, which is a food born pathogen.
Biogenic amines (BA): Putrescine, cadaverine and tyramine are main biogenic amines found in silage; derived from arginine, lysine and tyrosine, respectively. These are produced due to amino acid decarboxylation by enzymes of several lactic acid bacteria. Species of many genera present in silagesuch as Clostridia, Bacillus, Klebsiella, Escherichia and Pseudomonas can also cause biogenic amine production. Several factors such as temperature, oxygen availability and rapidity of pH decrease during the initial stage of fermentation results inthe formation of BA. Feeding of silage having BA acts as causative factors in ketonemia. BA presence in silage decrease the palatability and reduce DryMatter Intake (DMI) and cattle performance.
Strategies to limit silage degradation by undesirable microorganisms:
Spoiled silage has to be thrown out because till now no any measure has been develop to improve the quality of spoiled silage. Main factors which affect the quality during silage processing are the use of poor quality or immature plant material, insufficiently rapid filling (causes delay in establishment of anaerobiosis leading to weak silage acidification), and contamination by pathogenic or spoilage microorganisms. Preventive measures which should be taken care for quality silage production are discussed below.
Promoting acidification:Silage preservation is mainly based on acidification,whichdepends on anaerobiosis (promoting LAB fermentation), buffering capacity and DM of the crop. Soil incorporation in silage increases its buffering capacity, encourages the growth of aerobic microorganisms, whichreduce the quantity of hexoses and pentoses available for further LAB fermentation. This all leads to delay in silageacidification during which lactic acid is converted tobutyric acid, followed by pH increase and further spoilage due tosecondary fermentation by Clostridia. Mineral acids such as sulfuric and chlorhydric acids has been used to promote silage acidification and to limit the pathogenic microorganism growth.
Establishment of anaerobiosis during ensiling: For good silage production anaerobic conditions should be established as soon as possible in the silo. This can be achieved by rapid filling of silo and compaction of the silo to exclude the trapped air. Compaction of silage is easy with small particle size of crops. So chopping length plays an important role in good silage production, whilevery small particle size mayimpair the rumen function. For grass silage optimum chopping length is 4-6 cm. The corn silage prepared for dairy cow feeding should contain less than 1% of large particles (>2 cm), 8–12% of medium particles from 1 to 2 cm and less than 50% of very short particles (<6 mm). Harvesting of crop at appropriate dry matter is helpful to reduce effluent losses, which may impair anaerobiosis.
Prevention of air ingression during storage of silage:Silo should be sealed properly to avoid air ingression during storage, which can lead silage spoilage. A barrier made up of plastic sheets is helpful to prevent air ingressionand giveprotection against damage by birds, rodents and UV rays. To reduce spoilage of silage due to exposure during feed-out phase,silage requirement and silo pit dimensions should be calculated prior to silage making.
Improving the aerobic stability of silage: To improve aerobic stability of silage chemical additives like formic acid, silage additives containing partially neutralized acids in salt form (nitrites, sulfates) in association with formol-based preservatives can be used.Bacterial additives like Lactobacillus buchneri and Lactobacillus plantarumPediococcusacidilactici, Pediococcus cerevisiae and Propionibacterium acidipropionici can alsobe used during ensiling to improve the silage quality. Bacterial inoculants also limit pathogen development andproduce substances which may have antimicrobial potential (H2O2, ethanol, diacetyl, exopolysaccharides) and antibacterial peptides such as bacteriocins.
Prevention of pathogen introduction during harvesting and ensiling of crop:Entry of soil in the silage is the source of butyric acid bacterial/ pathogen contamination. Crops should be harvested 4 weeks after manure application takingcare to prevent contamination by soil.
Reference-On Request
SILAGE MAKING: AN EMERGING ENTERPRISE FOR DAILY SECTOR
SILAGE MAKING: AN EMERGING ENTERPRISE FOR DAILY SECTOR
