subject: Silage Additives [print this page] Silage Additives Silage Additives
There are three categories of Silage additives.
I. Stimulants of fermentation (microbial inoculants, enzymes, fermentable substrates),
II. Inhibitors of fermentation (acids, other preservatives), and
III. Nutrient additives (ammonia and urea).
STIMULANTS OF FERMENTATION
a) LAB: Natural populations of lactic acid bacteria (LAB) on plant material are often low in number and heterofermentative . The concept of adding a microbial inoculant to silage was to add fast growing homofermentative lactic acid bacteria (hoLAB) in order to dominate the fermentation resulting in a higher quality silage. The organism(s) from microbial inoculants must be present in sufficient numbers to effectively dominate the fermentation. Thus the most commonly recommended inoculation rate supplies 100,000 (or 1 x 105) organisms per gm of wet forage. Most microbial inoculants are available in powder or granular form.
Use a metered liquid sprayer to evenly disperse the inoculant on the forage. Unused liquids should be discarded after a period of 24 to 48 h because bacterial numbers begin to decline. Application to forage at the chopper is highly recommended in order to maximize the time that microorganisms have in contact with fermentable substrates. Inoculants applied in a liquid may be more advantageous since bacteria are added with their own moisture to help speed up fermentation. Storage is an important aspect of a high quality inoculant that contains live microorganisms. Inoculants should be kept in cool dry areas away from direct sunlight. Moisture, oxygen and sunlight will decrease stability of inoculants. Opened bags of inoculants should be used as soon as possible.
Recently, Lactobacillus buchneri, a heterolactic bacteria capable of producing lactic and acetic acid, has been included as an inoculant for improving the aerobic stability of silages. Aerobic stability was markedly enhanced and improved with increasing inoculation rate.
b) ENZYME ADDITIVES: A variety of enzymes, particularly those that digest plant fiber and starch have used as silages additives. Silage additives may contain single enzyme complexes, combinations of enzyme complexes and combinations of enzyme complexes and LAB. Plant fiber-digesting enzymes (cellulases and hemicellulases) are the most widely used enzyme additives.
There are two primary reasons for adding fiber-digesting enzymes to silage. First these enzymes could partially digest the plant cell walls (cellulose and hemicellulose) yielding soluble sugars which could be fermented by LAB to lower the silage pH. This would stimulate silage fermentation and improve fermentation quality by increasing the rate and extent of decline in pH, increasing the concentration of lactic acid, improving the lactic acid:acetic acid ratio (which is indicative of greater efficiency of fermentation), and hence reduce DM losses. A faster decline in pH would also limit degradation and deamination of forage proteins and reduce ammonia production. Second, partial digestion of the plant cell wall may improve the rate and/or extent of digestibility. In order for the first event to take place the rate of cellulose hydrolysis must coincide
MOLASSES. Molasses has been used as a fermentation stimulant. Molasses is a by-product of the sugar-cane and sugar-beet industries and contains 79% soluble carbohydrates; 45 to 50%, of which sucrose is the main component. Molasses provides a relatively cheap source of fermentable carbohydrate for lactic acid bacteria and has been applied at a rate of 40-80 lb per ton of fresh forage.
