One of the main goals of silage making should be reducing shrinkage (dry matter losses) during the preservation process, according to Adegbola Adesogan, researcher at the University of Florida.
Adesogan says dry matter (DM) losses occur during the three main stages of silage preservation, which are (1) the aerobic respiration stage before the silo is sealed; (2) the anaerobic fermentation stage after sealing; and (3) the aerobic feed-out stage after the silo is opened. “Heating and spoilage during feed-out is one of the greatest contributors to DM losses,” he says. “Spoilage occurs when yeasts and molds that were dormant during fermentation begin to grow and convert nutrients into carbon dioxide and heat after air enters the silo.”
Additives can be used to reduce DM losses and heating in silages. Adesogan summarizes the characteristics and purpose of various silage additives:
- Organic acids – Adding organic acids rapidly acidifies forages and prevents the growth of Clostridia and Enterobacteria that increase DM losses and protein degradation during ensiling. Propionic acid is the most commonly used organic acid in the U.S., due to its strong antifungal activity. Propionic acid should be applied at the chopper to ensure uniform distribution throughout the forage. Because it is more expensive than silage inoculants, propionic acid should be used when quality silage is required from large acreages in a short period of time.
- Ammonia and urea – Ammonia is very effective at increasing bunk life because it inhibits the growth of spoilage-causing organisms in silage. It also increases crude protein concentration of silage and may improve digestibility. Urea can be used as a silage preservative and is safer to handle and apply than ammonia. Silages treated with ammonia or urea will have high soluble nitrogen concentrations.
- Enzymes – Amylase is useful for degrading starch into sugars. Cellulases or xylanases degrade cell walls into sugars. Sugars released by the enzymes increase growth of silage bacteria and, in some cases, fiber degrading enzymes also increase forage digestibility. These enzymes usually are most effective on low-lignin feedstuffs such as cereal silages and immature, cool-season grasses.
- Inoculants – Inoculants are added to silage to dominate the epiphytic (natural) population of bacteria on plants that cause DM losses by inefficient fermentation of sugars. The three main types of inoculants are (1) homofermentive; (2) homolactic; and (3) heterofermentive. Combination inoculants often incorporate homofermentive bacteria to reduce DM losses and heterofermentive bacteria to increase bunk life.