Fodder Preservation Strategies: Hay and Silage Making

Fodder Preservation Strategies: Hay and Silage Making

 Sanjay Kumar¹, Savita Kumari² and Rajni Kumari³

  ¹Associate Professor, Department of Animal Nutrition

  ²Associate Professor, Department of Veterinary Microbiology

   ³Senior Scientist, DLFM, ICAR-RCER, Patna

Bihar Veterinary College, Bihar Animal Sciences University, Patna, Bihar

 The rain fall in India is seasonal. As a result, abundant grass is available in rainy season, all of which are not properly utilized. A good amount of fodder also can be produced during this season through proper selection of plant material and proper cultural practices. To satisfy the needs of the stock during the lean months, viz, November-December and April-June, an adequate amount of the surplus grass available during the rainy season must be conserved. The ideal and simple of method of conservation is to drive off the moisture in the fresh grass with artificial heat and store the product as dried fodder for use when required, unfortunately a considerable capital expenditure is involved in this process. In practice the moisture in grass is reduced through exposure to sun and wind, and hay is obtained. To combine cheapness and simplicity and yet ensure at the same time a product of high feeding value and virtually independent of weather conditions at the time, natural fermentation must be used and the process of ensilage adopted. There lies the choice of the farmer, dried grass, hay or silage.

SAILAGE

Silage is the product obtained by controlled fermentation of green fodder crop under anaerobic condition in a container called silo, and the process is called ensiling. The major changes which occur during ensiling are the fermentation of sugars from acids and the breakdown of some of forage protein to simpler compounds, including ammonia. This fermentation occurs during the first two to three months, after that the silage remains practically unchanged for another 12-18 months.

Advantage of silage making:

1. Crops can be ensiled when the weather does not permit curing them in to hay or dry fodder.
2. The use of silage generally makes it possible to keep more animals on a certain area of land.
3. At low expenses silage furnishes high quality succulent feed for any season of the year.
4. From weed crops, which would make poor hay, satisfactory silage can be produced, ensiling process kills many kinds of weed seeds.
5. Crop from given area can be stored in less space as silage than as dry fodder, silage contain 230 kg DM/M3 as against 66 kg/m3 in hay.
6. Stemmy forage crops when converted in to silage become soft and are better utilized by the stock.
7. Many undesirable things present in a fresh crop are eliminated after ensiling.

Biochemical changes in the ensiling process

1. Respiration:When the plant is harvested or separated from the soil, photosynthesis soon stops but respiration continues in the living cell. When a green crop is put in to a silo, the cells of plants are alive and the respiration will continue as long as oxygen is available and as a result H2O + Co2 will be produced along with a considerable amount of heat. Simple carbohydrates are partially lost during this process. The rise in temperature depends upon the degree of compaction of mass. With greater compaction the entry of air is stopped and the Co2 accumulation takes place. The aerobic respiration can thus be reduced by treading with human feet or running tractor wheels over the ensiled green mass in silo pits. Air pockets should carefully be avoided. The wasteful activities of aerobic micro-organisms and oxidative plant enzymes are suppressed by the anaerobic condition, acid fermentation then occur, resulting in the inhibition of the proteolytic activities of spore bearing bacteria.
2. Enzymatic reactions: biochemical changes in the plants are very much influenced by the enzymes in them. These enzymes have the property of spending up chemical reactions. The carbohydrates under anaerobic conditions give rise to many substances, including a number of organic acids through a chain of enzymatic processes. The organic acids commonly found in silage are acetic, propionic, butyric and lactic acids. The first three are quite volatile and are usually referred to as volatile acid of silage and the lactic acids as nonvolatile acid. Acetic acid is largely responsible for the smell and taste of vinegar. Propionic acid has similar properties. Butyric acid has most objectionable odour and is responsible to a large extent for the offensive smell, sometimes met with in badly preserved silage. Lactic acid has a sharp but pleasant acid taste. IN making it is desirable that a considerable amount of acid is produced.

 Lactic acid fermentation:

On the death of the living cells in the ensiled material fat, protein and carbohydrate are able to diffuse out in the plant sap and become food for the microorganisms present. Some of them can grow in presence of oxygen, some in absence of oxygen and some can’t grow in presence of oxygen. The microorganisms of most concern in silage making are bacteria and fungi. Amongst fungi are yeasts and moulds. Which are probably not of much importance except in surface layer of silage. The lactic acid bacterial plays a much important role in ensiling process and are widely distributed and are sometimes present the fresh crop. They can grow best at 27 C – 37 C temp. They also grow best in low concentration of oxygen or in the absence of oxygen. They all produce lactic acid from sugar glucose, but other sugar also fermented and other acids beside lactic acid may be produced in small quantities. However, the most important characteristics of the lactic acid bacteria from the point of view of preservation crop is ensiled, the lactic acid bacteria can start to grow almost at once on the sugars of the expressed plant sap and if they multiply rapidly they will use up the fermentable sugars and produced so much acid that undesirable bacteria are prevented from developing. The higher the proportion of homofermentive lactic acid bacteria, the more rapid will be the decline of PH, since homofermentive bacteria quantitatively convert soluble sugars to lactic acid, and homofermentive produce Co2, mannitol, ethanol and acetic acid in addition lactic acid. The proportion of homofermentive to heterofermentive lactic acid bacteria is important in crops poor in water soluble carbohydrate.

1. Secondary fermentation/Butyric acid fermentation: This can occur both during and after lactic acid fermentation. It results in the degradation of amino acids and lactic acid. The undesirable bacteria include the group that produces butyric acid. They grow in the absence of oxygen or below pH 4, spores of butyric acid bacteria present the soil and occur in silage soil contamination and will be slow to start growth compared with lactobacilli. If they do get a chance to multiply, they will produce various volatile acids from carbohydrates as well as Hydrogen and Co2 and they can also attack the lactic acid and convert it into butyric acid and gases. The proteolytic enzyme of butyric acid bacteria decomposes the protein and produces various amines such as tryptamines, phenyethylamines and histamine. Many of those are toxic to the animals if absorbed in to the blood. The final end product of protein degradation is ammonia which is volatile and may be lost from the silo in gaseous form.

Factors responsible for the activity of butyric acid bacteria are:

1. In adequate degree of acidity on account of slow development of lactobacilli.
2. Deficiency of easily fermentable carbohydrates in the crop this is most likely to occur with young leafy grass or legumes at the pre-bloom state of growth when they contain high percentage of protein and less of soluble carbohydrates.
3. Possibility that very leafy crops become so rapidly compacted that the condition become anaerobic and tend to favour the butyric acid organisms.
4. Rain water might have percolated through the silage and diluted or carried away the lactic acids which act as a preservative.

Other objectionable features of the bacteria producing butyric acid in that they can decompose proteins and proteolytic enzymes of the butyric acid bacteria liberate ammonia and derivatives of ammonia from the protein.

1. After Fermentation:According to woodford (1972) there are three types of fermentation viz. lactic acid fermentation, secondary fermentation and after fermentation. After fermentation is the fermentation which occurs under aerobic conditions when a silo is opened for feeding. Fermentation is merely an aerobic microbial degradation of residual sugars and of lactic acid in the silage.

 Other Changes

1. Alcohol formation: Alcohol is produced by the enzymes of yeast during the fermentation of sugar. The amount of alcohol is normally in much lesser quantities and when it combines with organic acid pleasant smelling esters are forms.
2. Colour formation: one of the most obvious phenomenon of ensiling is the alteration of colour of the ensiled crop. Sometimes the crop becomes dark brown or black; this is because of the high temp. resulting in the charring of the organic compounds. It commonly occurs when rather dry or stemmy material is not tightly packed and an excess of air is able to carry the oxidation changes too far, causing the development of excessive heat. When the temp. in the silo is moderate the silage tends to yellowish or brownish green and sometimes even golden in colour. This is due to the action of the organic acid on the chlorophyll, which losses its magnesium and is converted into a brownish pigment-phaeophytin.
3. Loss of vitamins: The yellow pigmented carotene of the green plant is fairly easily oxidized. Hence if excessive oxidation takes place in the silo, there may be a serious loss of this valuable constituent of green crops, but it is easily decomposed under the conditions prevailing even in the best made silage.
4. Loss of mineral matter: A part of the mineral may be leached out and lost, but a large proportion will remain unchanged or simply take part in some new combination.
5. Development of moulds: When silage becomes mouldy through of fungi, a profound change takes place. The organic acids are neutralized by ammonia produced through the breakdown of proteins and then decomposed, Mould material is usually found on the surface layer of silage, but if the process has been correctly carried out, it should not be more than 2.5 cm thick. Owning to the faulty packing, sometimes patches are found even in well-furnished silo.
6. Rate of changes in silage: In silage changes occur quite rapidly and can be detected within 24 hrs. and may reach a maximum within a week. The speed with which the reaction takes place depends on the condition of the crop, the weather and the method of filling up of silo.

Methods for the control of changes:

The relative deficiency of fermentable sugars can be corrected by adding a sugar or practically all the bacterial activity can be prevented by adding an acid to the crop to bring the pH value below 4.

Addition of sugar: When the lactic acid in silage is about 1-2 % the product is invariably well preserved and palatable, because the pH value in usually below 4 and there is no butyric acid. About 1-2 % of sugar is required to produce this amount of lactic acid. The common source of sugar used for silage making is molasses.

The quantity normally recommended for short leafy grass or protein rich fodder crops like Lucerne or berseem is 15 liters of molasses dissolved in 15 liters of water for each tone of crop. If the crop had received heavy nitrogenous manuring contains a large proportion of cover or other legumes it will be very rich in protein and the amount of molasses should be increased to about 3 times more than the above mentioned dose. The amount of water used is adjusted to the state of the crop and the temp. so that an even distribution of sugar solution is obtained through the silo.

Addition of acid: The method of making silage by using acid additives was first developed by prof. A. I. Virtanen in Finland and the process has come to be known as AIV method of silage making. In this method mixture of strong mineral acids, HCL and H2So4 are added. The mixture of conc. Acids is first diluted to a suitable level with water. About 55-60 lit of diluted acid are then sprayed on each tone of the crop in such a way that the contact between the crop and acid is as complete as possible.

Addition of preservative:

Sodium Metabisulphite: It causes partial sterilization and is sprinkled at the rate of 4 to 8 kg/1000 kg of forage as ensiling proceeds.

Salt: It makes the silage more palatable. There is no evidence that it stimulates or retards bacterial activity. At the most it might speed up the release of juice from the cells by plasmolysis and thus help to provide condition suitable for fermentation in the early stage.  Factors affecting the nutritive value of silage:

1. DM of the crop: Dry matter of the crop should be within 30-35 %. If the crop contains high moisture level the undesirable fermentation will take place resulting in the production of more butyric acid instead of lactic/acetic acid.  Again, if the crop is too dry, compaction will be improper, and more oxygen will be available for oxidation, as a result there will be more Mould growth.
2. Nature of the crop: The species, stage of growth and the physical state of the crops are important factors affecting the nutritive value of silage. In order to obtain good quality silage crops are important factors affecting the nutritive value of silage. In order to obtain good quality silage crops are important factors affecting the nutritive value of silage. In order to obtain good quality silage crops should be harvested at on shortly after ear pre following stage emerging stage of growth as digestibility falls rapidly with increasing herbage maturity. Quality of the silage is dependent on the production of lactic acid which in turn is dependent upon the soluble sugars present in the crop. Therefore crops like maize, jowar, oats etc. are excellent for silage making. High protein grass crops and legumes are difficult to ensile satisfactorily because of low soluble carbohydrate content and because of their high buffering capacity. The physical nature of crop at the time of ensiling is an important factor in the fermentation process, chopping and brushings tends to produce more favorable condition for microbial activity than leaving the material long.
3. Effluent production: In most silos free drainage occurs. Effluent production depends largely on the initial moisture content, but it will obviously increase if rain water enters into the silo. Effluent contains sugar, soluble nitrogenous compounds, minerals and organic acids produced during fermentation. These nutrients are highly digestible and are of high nutritive value to the animals. It is necessary to reduce the effluent production and one way in doing this is to will the crop before animals. It is necessary to reduce the effluent production and one way in doing this is to will the crop before ensiling.

Characteristics and classification of silage

Silage quality is a measure of ensiling process, the amount of nutrient loss and relative palatability.

Physical properties:

Colour: Colour is an important index of quality. Good silage should be yellowish green, dark brown or charred black material often found is usually the result of excessive heating, poor packing or sealing or too low moisture content. If the moisture content is too high, the silage usually appears deep green to black.

Odour & texture: Good silage does not have any strong objectionable odour. It is palatable to livestock. However, it should be fed carefully to caws to prevent off flavour in milk. Strong butyric acid, ammonia or musty odour indicates a considerable loss in feed value. Very wet silage usually has strong odour indicating inferior quality. Silage containing stubble, foreign matters or fodder cut at too late stage will naturally be less palatable and nutritious.

Degree of wetness: Silage having high moisture content (75% or more) contains less feed value per kg than silage having less moisture. If juice runs freely when silage is squeezed in hand, it indicates that the material has high moisture content.

Chemical properties: The quality of silage is more readily assessed by determining its pH value, which should be less than pH 4.2 with this degree of acidity, there is almost invariably more lactic acid (3-13 % of the DM) and volatile acid and butyric acid is present only traces. In general, the butyric acid concentration of good silage is less than 0.2 % and the ammoniac nitrogen content less than 11% of the total nitrogen.

CLASSIFICATION:

Silage can be classified broadly in to the following 3 groups

Grade – I: CP ranges over 15 % and prepared from young grass and legumes.

Grade – II: CP range from 10-12 % prepared from grasses at ear emerging stage and cereal/legume crops.

Grade – III: CP below 10 % prepared from grasses at sending stage.

Step for making good silage:

1. Avoid bad weather at the time of harvest

One should avoid the rainy days, in the rainy days the crop will be too wet and it will be difficult to complete the whole operation of harvesting of crop, filling and sealing of silo etc.

2. Asses the quality of crop to be harvested:

Quality of harvested crop will depend upon the number and kind of animlas to be fed and the length of feeding period. The number and size of silo pits have to be regularized accordingly so that there can be a regular supply of feed particularly during lean months.

3. Check the conditions of silo:

The silo walls must be smooth perpendicular strong and rigid and must prevent the entrance of air if the walls are not smooth and perpendicular cavities will from along the walls as the mass settles and the adjacent silage will get spoiled. The walls must be strong and rigid to withstand the outward pressure on walls exerted by the silage when it settles.

4. Growth stage of the crop:

The crop should be neither dry nor have high water content. In the former case it will not pack well in the silo and in the latter case the silage is apt to be very sour or it may even be spoilt. For preparing good silage forage crop with solid stem should be selected so that only small amount of air will remain in the mass after it has settled. If hollow stemmed crops are used, the cut forage must be trampled with special case to force out as much air as possible, the type of crop affects the quality of silage, but the condition of crop affects the quality even more.

5. Pre wilt the forage if needed:

Wilting of young succulent grass and legumes for few hours before ensiling is very much important. The moisture content should not be more than 70-75%. It encourages butyric acid type of fermentation; moreover, the amount of liquid effluent from the silage is reduced.

6. Chop the crop if needed:

For proper consolidation the crop should be chopped into short lengths before ensiling. When chopped the proportion of the material immediately available for bacterial fermentation is much higher and consequently acid production occurs much more rapidly. Chopped pieces should not exceed 4-5 in length.

7. Decide mixture of legumes and other forage crops ahead:

Good silage can be made from a mixture of legumes. e.g. Lucerne, soyabean with a suitable proportion of sorghum, maize and cowpeas mixture, paddy straw with berseem etc. The mixture can be in the following ratio, Sorghum + Lucerne=1:3, paddy straw + berseem=1:5, paddy straw + water hyacinth=1:4, Maize + Cowpea=1:3

8. Addition of molasses, salt etc.

Addition of molasses to leguminous forage crops improves the quality silage. Salt ads taste to the silage.

9. Proper filling of silo:

To ensure good silage, it is very essential that the chopped material is distributed uniformly throughout the silo. The material should be trampled, specially well near the wall, as the fictions with the wall retards setting, it is believed that keeping the centre higher than the outside while filling the upper part of the silo lessens the tendency of the silage to draw way from the walls as it settles. To avoid a large amount of spoilage at the top for last few meters the silage should be leveled off and tramped thoroughly. It will if leveling, trampling, additions of additives etc are done after every 30 on layer of packing. No matter what the method followed is, if the forage is too dry water should be added.

10. Covering and sealing of silo:

One the pit is full it should be covered with wet straw, sawdust and other materials and plastered with 15-30 on thick layer of soil. The loss at the surface can be reduced to minimum if the forage is covered with chop roll roofing like polythene sheets after proper trampling and leveling. After covering weights much as pacing slabs, concrete posts, wooden legs etc. should be kept for better compaction. Finally, a simple roof some kind should be devised to keep off the rain.

11. Intermediate checking of silo:

It is advantageous to check the seal from time to time, flatten if down and seal any cracks. There should be a small door near the surface of the silage to allow the Co2 to escape. Very rarely poisonous yellow nitrogen dioxide gas is formed in silage soon after filling apparently being produced from nitrate in the forage.

Hay Making

A forage plant when preserved through reducing the moisture content to the level at which plant tissues are dead or dormant is termed as hay. The characteristics of good hay are:

1. Hay must be leafy and green to brown in colour.
2. It should be soft and palatable.

• It should be free from moulds, weeds and dust.

1. It should have pleasant smell and aroma.
2. It should not be containing more than 15% moisture.

Advantage of Hay Making

1. The hay provides the nutritious feed to the livestock as compared to straws.
2. The good quality legume hay may reduce the cost of animal production by replacing certain amount of concentrate in the ration.
3. The fodders can be harvested at the stage when there is maximum accumulation of nutrients in the plant.
4. The ration of the animals can be balanced with the help of good quality hay.
5. More quantity can be stocked on less space.

Crops for Hay Making: The legumes crop which have soft, thin and palatable stem like berseem, Lucerne, oat, cowpea, soyabean, anjan and sudan grasses etc. are preferred for hay making. Some self-grown grasses during mansoon season are also used for this purpose. Thick stemmed crops like maize and jowar are not suitable for hay making as it will take longer time for the stems to dry. The non-leguminous crops contain less proteins, minerals and vitamins, hence not a good choice for hay making.

The stage of maturity of the crop at the time of cutting is very important as far as nutritive value of the hay is concerned. An early cut means more nutritive value but less yields. Late cutting on the other hand will result in less nutritive value but more bulk.

Method of Hay Making: The crop used in hay making are processed to reduce the moisture level below 15 percent. The fodder crop is cut when 2/3^rd of the entire crop is in flowering stage. The harvested forages can be processed using different ways to reduce the moisture content to a safe level for preservation under sun drying or artificial drying. After harvesting, the forage is dried with frequent turning of the material. The forages are sometime pooled together to form a poola or chaffed to reduce the size. These poolas are then kept vertically in the field for effective drying. Sometime the fodder crops after harvesting is spread over the barbed wire fencing or boundary wall. It is tilted once or twice before storage for proper curing. In case of chaffing, the chaffed fodder is spread in 5-6 inch layers on pucca floor or polythene sheets with frequent turnings till the moisture reduced to desired level. Within 4-5 days the hay is ready and can be stored in dry place. Leguminous hay contains 9-15% DCP and 50-60% TDN.

Losses during hay making: The main aim of hay making is to reduce the moisture content of the herbage to a safe level (about 15%) and to retain its nutritional characteristics. Various factors are responsible for the loss of some nutritional characteristics of the forage. Following losses occurred during hay making:

1. Physical losses: The leaves of forage plants are rich in proteins and also more palatable than that of the stem usually get separated from the plant during the process of drying. The physical losses are variable depending on the handling and processing of hay making.
2. Chemical losses: The fresh forage plant contains various chemical constituents apart from the water. The loss of water is desirable during the process of hay making while the loss of other components which may reduce nutritional value is undesirable. The losses of chemical constituents which are brought about by plant enzymes, respiration activity and processing method are difficult to measure in field conditions.
3. The enzymes act on soluble carbohydrates and convert them into carbon dioxide and water.
4. The plant proteases start working immediately after the harvesting and are responsible for the loss of nitrogenous fraction.
5. The vitamins A, D and E are most affected by during process. The carotene, a precursor of vitamin A is unstable in light and air. A considerable loss of carotene occurs from the action of lipoxidase.
6. The chemical constituents of nutritional importance like carbohydrates, nitrogenous substances and vitamins etc. are known to reduce during the process of hay making.

Storage of Hay: The hay should be stored in cool and dry place. Improper storage will result in loss of leaves, green colouring matter and carbohydrates or vitamins by fermentation, leaching and shattering etc. So, care should be taken to avoid losses particularly of leaves during storage and handling of hay.