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THIS IS A TWO PART ARTICLE. PART I AVAILABLE AT
http://www.agricultureinformation.com/discuss/threads/forage-preservation-part-1.5316/
Stage of growth
Crops should be cut at a proper stage of maturity as it is the most important factor for controlling the silage quality. The appropriate stage of growth for cutting different fodder crops for silage making is Sorghum - Flowering to dough stage; Maize - Milk to dough stage;Oat - 50% flowering to dough stage;Grasses - Early flowering stage
The “ideal” dry matter content
The “ideal” dry matter content of the forage depends on the type of silo. The recommended levels of dry matter in forages at ensiling are- 30 to 40% for bunker silos; 35 to 50% for tower silos; 40 to 50% for wrapped round bales. Often, wilting a green forage for 24 – 48 hours to increase dry matter is highly desirable, because wilted silage requires less lactic acid production and will stabilize at a higher pH level than silage that has a lower dry matter content. This is the case because higher dry matter content increases the concentration of soluble dry matter in the silage, and the resulting increase in osmotic pressure inhibits bacterial growth. Thus fermentation stops in wilted silage because of the high acidity, high osmotic pressure combination (rather than high acidity alone in silage with lower dry matter content). Thus wilting has a “sparing” effect on the level of sugar and the level of fermentation needed to stabilize the silage. As a result, wilting is particularly important when the ensiled forage is a legume, which has a relatively low level of fermentable sugars as compared to grass or corn.
Additives for effective ensiling of nutrients
Various types of additives can be used to improve or inhibit the fermentation or supplement nutrients needed by ruminants to be fed as silage. Propionic acid, formaldehyde, etc. have been used to increase the rate of lactic acid fermentation and produce stable silage. Carbohydrate sources such as molasses, whey, yeast and other energy-rich ingredients have also been used as additives to increase the fermentation and feeding value of silage. Common additives are as follows,
Molasses:Legumes and certain grasses are rather low in sugar content. Adding molasses definitely improves the quality of silage by increasing lactic and acetic acid production. It also increases the palatability and nutritive value of the silage. Molasses may be added (3.0 to 4.0 per cent of the green weight of the forage) in either liquid or dehydrated form. Molasses and starches when added in the form of grains supply the silage bacteria with ample food so that fermentation proceeds normally.
Urea: Adding urea at a level of 0.5 per cent of fresh forages is recommended. The very idea of adding urea is to enrich the silage with nitrogen as cereal forages are mostly deficient in this element.
Limestone: This is calcium carbonate and may be added at a level of 0.5 to 1.0 per cent to maize silage to increase acid production. It neutralizes some of the initial acids as they are formed allowing the lactic acid bacteria to perform longer and to produce more desirable acids. Sodium metabisulphite: Sulphur dioxide (SO2 a gas) is a very good antibacterial preservative. It also improves carotene content.
Organic acids: Propionic and formic acids are used for enhancing preservation of forages without the loss of palatability. These are costly and when added, the following guidelines may be observed: Add 1 per cent propionic acid to the forage in the field at the time of harvest or at the chopper. Limit the presence of oxygen by using a sound well built silo.Prevent dilution of organic acid treated silage by rain and cover it with plastic when it is stored outside.
Silos
The different types of silos generally used are: (i) pit silo, (ii) tower silo, (iii) trench silo, (iv) Bunker silo, (v) Clamp silo (vi) Plastic silo and (vii) Silage bag. The silo must provide a solid surface to permit consolidation of the ensiled material and elimination of air. It must protect the silage from water. In India, pit silo is the most common.
Chopping
Crop should be chopped before ensiling. For good silage, the shorter the chop length, the better is the quality. Chopped silage is more palatable to livestock and has little chance of secondary fermentation.
Filling of silo
Silo should be filled rapidly and should not be left open. It should be sealed as soon as possible. Packing is important to create anaerobic conditions. It should be thoroughly pressed so that no air pocket is left in the silo otherwise chances of mould formation will be there which will spoil the silage. After filling, silo should be covered with polythene sheet followed by that of a layer of soil, etc.
Removal of silage
After 45 days of ensilage, the silage can be removed for feeding to animals. Care should be taken in removing the silage from silo. It should not be allowed to deteriorate after the silo is opened for feeding. Covers should be kept firmly in place as long as possible and the minimum face should be exposed at one time.
Silage quality
A good-quality silage should have the following characteristics: (i) pH 3.8-4.2 (ii) ammonical nitrogen of total N – less than 10% of total N, (iii) butyric acid- less than 0.2%, (iv) lactic acid -8 to 12% of dry matter,For desirable fermentation, the forage should be rich in water soluble sugar (more than 5% on dry-matter basis).
CHANGE IN FORAGE COMPOSITION IN A SILO
Loss of soluble carbohydrates and proteins
As dry matter is lost during silage-making, forage composition also changes. The changes in dry matter composition are due primarily to the fact that the most valuable nutrients (soluble carbohydrates and proteins) are also the first to be lost during respiration and fermentation and in the effluents (juices). Fiber on the other hand remains essentially unaffected by the naturally occurring fermentation process in a silo. Thus the overall effect of these losses is to increase the proportion of fiber; the percentage of both the acid detergent fiber (ADF) and neutral detergent fiber (NDF) tend to be higher in silage than in freshly cut forage.
Changes in the protein (nitrogen) fractions
Silage-making change the protein fraction of forages. Respiration is responsible for protein breakdown. As plant cells die after cutting, proteolytic enzymes break down large proteins into smaller soluble compounds including: peptides, amino acids (the building blocks of proteins) and ammonia. In addition, enterobacteria have proteolytic enzymes that remain active even after the pH has dropped to 5.0. Thus most of the protein degradation that takes place in a silo occurs within the first 24 to 72 hours. By the time pH is about 4.0, proteolytic enzymes have lost 65 to 85% of their activity. Consequently, a rapid drop in pH is desirable to reduce the amount of protein breakdown in a silo. Although limiting protein solubilization and ammonia production in a silo is desirable, one should realize that this process is relatively similar to what happens in the rumen of a cow after ingesting silage. Not all soluble protein and ammonia produced in the silo are necessarily lost. Ammonia and amino acids are needed for microbial synthesis in the rumen. Another nitrogen transformation that may occur during hay or silage-making results from the browning reactions that take place when excess heat is produced. Excess heat cause chemical reactions that combine amino acids with plant sugars (usually derived from hemicellulose) to form a compound resembling lignin. This reaction results in increased levels of acid detergent fiber (ADF) and acid detergent insoluble protein (ADIP). Excess heat is an indication of aerobic degradation due to the presence of air (oxygen) in a silo.
Contact Details :
Mr. Bheru Lal Kumhar (Prajapati)
S.R.F.
M.Sc. (Agriculture) Agronomy, (NET)
Krishi Vighan Kendra, Borkheda Kota
(Agriculture University, Kota) Pin code 324001
Mob.- 9413105314
http://www.agricultureinformation.com/discuss/threads/forage-preservation-part-1.5316/
Stage of growth
Crops should be cut at a proper stage of maturity as it is the most important factor for controlling the silage quality. The appropriate stage of growth for cutting different fodder crops for silage making is Sorghum - Flowering to dough stage; Maize - Milk to dough stage;Oat - 50% flowering to dough stage;Grasses - Early flowering stage
The “ideal” dry matter content
The “ideal” dry matter content of the forage depends on the type of silo. The recommended levels of dry matter in forages at ensiling are- 30 to 40% for bunker silos; 35 to 50% for tower silos; 40 to 50% for wrapped round bales. Often, wilting a green forage for 24 – 48 hours to increase dry matter is highly desirable, because wilted silage requires less lactic acid production and will stabilize at a higher pH level than silage that has a lower dry matter content. This is the case because higher dry matter content increases the concentration of soluble dry matter in the silage, and the resulting increase in osmotic pressure inhibits bacterial growth. Thus fermentation stops in wilted silage because of the high acidity, high osmotic pressure combination (rather than high acidity alone in silage with lower dry matter content). Thus wilting has a “sparing” effect on the level of sugar and the level of fermentation needed to stabilize the silage. As a result, wilting is particularly important when the ensiled forage is a legume, which has a relatively low level of fermentable sugars as compared to grass or corn.
Additives for effective ensiling of nutrients
Various types of additives can be used to improve or inhibit the fermentation or supplement nutrients needed by ruminants to be fed as silage. Propionic acid, formaldehyde, etc. have been used to increase the rate of lactic acid fermentation and produce stable silage. Carbohydrate sources such as molasses, whey, yeast and other energy-rich ingredients have also been used as additives to increase the fermentation and feeding value of silage. Common additives are as follows,
Molasses:Legumes and certain grasses are rather low in sugar content. Adding molasses definitely improves the quality of silage by increasing lactic and acetic acid production. It also increases the palatability and nutritive value of the silage. Molasses may be added (3.0 to 4.0 per cent of the green weight of the forage) in either liquid or dehydrated form. Molasses and starches when added in the form of grains supply the silage bacteria with ample food so that fermentation proceeds normally.
Urea: Adding urea at a level of 0.5 per cent of fresh forages is recommended. The very idea of adding urea is to enrich the silage with nitrogen as cereal forages are mostly deficient in this element.
Limestone: This is calcium carbonate and may be added at a level of 0.5 to 1.0 per cent to maize silage to increase acid production. It neutralizes some of the initial acids as they are formed allowing the lactic acid bacteria to perform longer and to produce more desirable acids. Sodium metabisulphite: Sulphur dioxide (SO2 a gas) is a very good antibacterial preservative. It also improves carotene content.
Organic acids: Propionic and formic acids are used for enhancing preservation of forages without the loss of palatability. These are costly and when added, the following guidelines may be observed: Add 1 per cent propionic acid to the forage in the field at the time of harvest or at the chopper. Limit the presence of oxygen by using a sound well built silo.Prevent dilution of organic acid treated silage by rain and cover it with plastic when it is stored outside.
Silos
The different types of silos generally used are: (i) pit silo, (ii) tower silo, (iii) trench silo, (iv) Bunker silo, (v) Clamp silo (vi) Plastic silo and (vii) Silage bag. The silo must provide a solid surface to permit consolidation of the ensiled material and elimination of air. It must protect the silage from water. In India, pit silo is the most common.
Chopping
Crop should be chopped before ensiling. For good silage, the shorter the chop length, the better is the quality. Chopped silage is more palatable to livestock and has little chance of secondary fermentation.
Filling of silo
Silo should be filled rapidly and should not be left open. It should be sealed as soon as possible. Packing is important to create anaerobic conditions. It should be thoroughly pressed so that no air pocket is left in the silo otherwise chances of mould formation will be there which will spoil the silage. After filling, silo should be covered with polythene sheet followed by that of a layer of soil, etc.
Removal of silage
After 45 days of ensilage, the silage can be removed for feeding to animals. Care should be taken in removing the silage from silo. It should not be allowed to deteriorate after the silo is opened for feeding. Covers should be kept firmly in place as long as possible and the minimum face should be exposed at one time.
Silage quality
A good-quality silage should have the following characteristics: (i) pH 3.8-4.2 (ii) ammonical nitrogen of total N – less than 10% of total N, (iii) butyric acid- less than 0.2%, (iv) lactic acid -8 to 12% of dry matter,For desirable fermentation, the forage should be rich in water soluble sugar (more than 5% on dry-matter basis).
CHANGE IN FORAGE COMPOSITION IN A SILO
Loss of soluble carbohydrates and proteins
As dry matter is lost during silage-making, forage composition also changes. The changes in dry matter composition are due primarily to the fact that the most valuable nutrients (soluble carbohydrates and proteins) are also the first to be lost during respiration and fermentation and in the effluents (juices). Fiber on the other hand remains essentially unaffected by the naturally occurring fermentation process in a silo. Thus the overall effect of these losses is to increase the proportion of fiber; the percentage of both the acid detergent fiber (ADF) and neutral detergent fiber (NDF) tend to be higher in silage than in freshly cut forage.
Changes in the protein (nitrogen) fractions
Silage-making change the protein fraction of forages. Respiration is responsible for protein breakdown. As plant cells die after cutting, proteolytic enzymes break down large proteins into smaller soluble compounds including: peptides, amino acids (the building blocks of proteins) and ammonia. In addition, enterobacteria have proteolytic enzymes that remain active even after the pH has dropped to 5.0. Thus most of the protein degradation that takes place in a silo occurs within the first 24 to 72 hours. By the time pH is about 4.0, proteolytic enzymes have lost 65 to 85% of their activity. Consequently, a rapid drop in pH is desirable to reduce the amount of protein breakdown in a silo. Although limiting protein solubilization and ammonia production in a silo is desirable, one should realize that this process is relatively similar to what happens in the rumen of a cow after ingesting silage. Not all soluble protein and ammonia produced in the silo are necessarily lost. Ammonia and amino acids are needed for microbial synthesis in the rumen. Another nitrogen transformation that may occur during hay or silage-making results from the browning reactions that take place when excess heat is produced. Excess heat cause chemical reactions that combine amino acids with plant sugars (usually derived from hemicellulose) to form a compound resembling lignin. This reaction results in increased levels of acid detergent fiber (ADF) and acid detergent insoluble protein (ADIP). Excess heat is an indication of aerobic degradation due to the presence of air (oxygen) in a silo.
Contact Details :
Mr. Bheru Lal Kumhar (Prajapati)
S.R.F.
M.Sc. (Agriculture) Agronomy, (NET)
Krishi Vighan Kendra, Borkheda Kota
(Agriculture University, Kota) Pin code 324001
Mob.- 9413105314
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