SPECIAL STORY FEED & ADDITIVE MAGAZINE May 2023 55 tic acid will improve aerobic stability of the silage by preventing proliferation of undesirable yeast and mold keeping silage highly nutrient and hygienic. In grass silage, the main challenge is acidification— in which case an adequate amount of homofermentative lactic acid bacteria (LAB) should be applied. A combination of homo- and heterofermentative lactic acid bacteria guarantees not only optimal fermentation but also enhanced aerobic stability. Application of inoculant bacteria Silage inoculants are generally applied as the forage is being picked-up or baled, using a specific applicator. While the forage will already have a range of naturally occurring bacteria on them including lactic acid bacteria species, the microbial community present may not drive optimum fermentation and may even have high levels of detrimental bacteria. The aim with an inoculant is to supply a sufficient amount of selected strains with known effects on fermentation to help ensure that fermentation proceeds rapidly and in the right direction. The rate of 100 000 (1 x 105) colony forming units (cfu) per gram of fresh forage will provide enough microorganisms to dominate fermentation. If a silage inoculant has a lower level than this, or does not even specify a cfu count, then there may be insufficient bacteria to really influence silage fermentation in positive way. Be aware that not all inoculant bacteria are equal. Even within the same species, there is wide variation in what effect the bacteria will have on fermentation. Products and the published evidence of efficacy should specify the actual strain numbers to provide assurance to customers. Quality of the packaging and storage conditions are also important. These should prevent exposure to oxygen, moisture and heat that could reduce the viability of bacteria. Follow manufacturer instructions on storage and use and ensure that application is even and comprehensive over the whole forage. PRESERVATIVES The use of organic acids such as propionic and formic acids are aimed at lowering the silage pH to make it less favorable for undesirable bacteria such as Clostridia. Other organic acids and their salts including potassium sorbate and sodium benzoate target the growth of yeasts and mold fungi either in fermentation or during feed out. There needs to be sufficient amount of the additive to provide a concentration in the bulk forage that will actually be sufficient effect on the growth of those undesirable organisms. That rate is typically at 5 to 10 kg of active ingredient per ton of forage to preserve the silage or around 1 to 2.5 kg/ton to restrict yeast amount at feed out. Compare those values to what is actually contained in a product that claim a preserving affect.
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