Silage fermentation is the conversion of plant sugars to acids by lactic acid bacteria (LAB). This process drops the pH, stabilizing and preserving the forage, in effect, “pickling” the forage.
Lactic Acid Bacteria (LAB) and Fermentation, What Happens?
- The LAB population needs to be 100 trillion/ton of crop before pH will start to decline in silage. Such levels are rarely seen on crops entering the silo.
- The natural LAB population can range from non-detectable to several million colony-forming units (CFU) per gram of fresh forage. The natural LAB populations vary from field to field and within a particular field.
- Normally, counts of LABs are highest on corn and lowest on alfalfa. Corn: 10 billion to 1 trillion per ton of crop. Alfalfa: 1 billion to 100 billion per ton of crop.
- Higher concentrations of LAB should result in a more rapid rate of pH decline in the initial stage of ensiling, limiting the action of ammonia producing plant enzymes.
- More nutrients are retained in the silage when fermentation is rapidly completed. The best quality silage generally has lactic acid as the dominant acid.
- Crops are best preserved by maintaining an anaerobic (oxygen free) environment and a low pH.
Intake and Bunk Life
- In studies where silage composition was related to intake, increasing lactic acid content usually is associated with improved silage intake.
- Silage intake decreases with increased butyric acid concentrations.
- Silage with high lactic acid content tend to be more stable.
- Generally molds do not proliferate within a mass or properly preserved silages, due to a low pH.
- It is the production of lactic acid and the resulting drop in pH which preserves silage in storage and at the same time improves stability in the feed bunk.
- When the lactic acid bacteria use all the sugar in the crop or the pH gets low enough to stop their growth (yeast and clostridia), the stable process begins. FYI — Since molds can grow in a collected sample, it should be dried or frozen and delivered to the lab quickly for processing.
Preserving Protein Quality
- Proteolysis is the break down of bypass, no-degradable proteins to soluble, degradable non-protein nitrogen (NPN). Alfalfa silage (haylage) is particularly susceptible to proteolysis.
- Low pH prevents the growth of undesirable bacteria and inhibits plant enzymes that break down proteins. Proteolysis reduces bypass protein — which is not good.
- Maximum proteolysis occurs at pH 5.5 to 6.0. At pH 4.0, proteolysis rates are only 15-35% of the maximum rates. This, a very rapid fermentation will reduce protein breakdown. Minimizing proteolysis maximizes profitability.
Bad Bacteria — Clostridia, Bacilli and Listeria Bacteria
- A clostridial silage is characterized by butyric acid levels greater than lactic acid levels, ammonia-nitrogen (N) levels greater than 10% of total N, pH above 5.0 and an odor characteristic of butyric acid (rancid smell) or ammonia.
- Using clostridia silages in the ration can reduce dry matter intake and disrupt rumen ecology. Cows may go off feed and milk production can be depressed.
- Clostridia do not grow well at low pH or in low moisture conditions.
- Making the silage environment favorable for rapid growth of lactic acid bacteria helps to prevent clostridial spoilage. There is no substitute for good forage management.
- Bacilli are a group of bacteria that start to grow when the pH is above 5.0. Although they may not initiate deterioration, the bacilli are important in extending aerobic spoilage.
- Listeria cause a disease to the nervous system (listeriosis, or circling disease) in animals and humans and an induce abortions and death. Listeria are sensitive to low pH. Clostridia, bacilli, listeria – a low pH slows or stops them all!
- Heterofermentative lactic acid bacteria are LABs that produce carbon dioxide, ethanol, and/or acetic acid in addition to lactic acid. They also produce heat.
- Heterofermentative bacteria can cause up to a 24% loss of sugar dry matter (DM).
- Homofermentative lactic acid bacteria (those that produce only lactic acid) cause no dry matter loss.
- A completely homofermentative silage fermentation could provide up to a 4 point improvement in dry matter recovery over a completely heterofermentative one.
- Another advantage of homofermentation is a more effective lowering of pH. Lactic acid is the strongest acid produced by lactic acid bacteria.
- The lower pH reduces proteolysis, an unwanted microbial activity. For both crop preservation and animal performance, homofermentation is more desirable.
Whether crop condition is ideal or not, we have a full line of bacterial inoculants designed to optimize forage and silage preservation. Talk with your Northside dairy specialist or agronomist for recommendations.
Safety = Good Working Equipment + Capable And Attentive Operators
While Functional equipment is an important part of farm safety, most accidents actually occur due to distracted, overtired, or unprepared operators. Keep these tips in mind to avoid accidents when operating equipment and machinery on your farm.
- Read and comply with the manual. Thoroughly read the manual for all equipment. Your new tractor may function differently than your old one, for example. Then, comply with the instructions and rules.
- Keep your slow-moving emblem (SMV) clean, visible and properly mounted. A clearly visible sign can prevent rear-end collisions —and it’s the law.
- Dress appropriately. An untied shoelace, flowing long hair and stray threads from an old shirt have, in the past, led to injuries when operating equipment. Dressing appropriately can mean reducing risk of such injuries.
- Ensure you’re well rested. Fatigue when operating machinery can be dangerous. Take breaks from work when you need rest.
- Adjust equipment accordingly. This means keeping all guards, shields and access doors in place when operating equipment, and making necessary alterations to equipment to fit operational conditions.
Article Refrences
University of Wisconsin: Silage inoculants: What the research tells us about when and how to use them
Hay & Forage Grower: The Mystery and Magic of Silage Inoculants