When forages are harvested for silage, anaerobic bacteria (i.e., lactic acid and acetic acid) are involved in the fermentation process. Weather, forage species, maturity, and harvest conditions can impact fermentation.
The goal of using an inoculant may be to improve fermentation efficiency in storage, improve aerobic stability once the silo is opened or both. Silage inoculants are additives that contain bacteria that manipulate fermentation.
There is an interaction between the crop and commercial inoculants, so only inoculants selected and labeled for a particular crop should be used on that crop. For example, do not use an inoculant labeled only for corn silage on alfalfa or grass haylage, or vice versa.
Read and follow product label directions, including application rates, storage, re-hydration, handling, and application. Product labels will detail colony forming units (CFU) per gram of forage to apply at recommended rates. Inoculants should be stored in a cool, dry place to maintain bacteria viability. Dead bacteria (also called non-viable) don’t work.
Be sure to properly calibrate the applicator. Inoculant application at the chopper usually works the best, especially with drier forage. Liquid products have an advantage over granular products because of more uniform application. Research suggests that liquid inoculants are more effective than dry inoculants when applied to haylage that has been wilted to lower moistures.
Remember, the application of a silage inoculant will not overcome the effects of poor silage management or poor weather conditions. The keys to good silage fermentation are harvesting at the correct moisture and chop length, quick and adequate packing, and sealing immediately after filling. However, under good management, commercial inoculants can be a valuable tool in silage systems.
Whether or not the benefits of using an inoculant are greater than the cost of the product can sometimes be a challenging question at the farm level. It is difficult for a farmer to see reduced dry matter losses and subtle improvements in animal performance, even when they exist. Are the increased gains or milk production due to the inoculant, or are they due to some of the many other management factors in silage and livestock management? University research, conducted by some of the silage experts, has shown that indeed some of the inoculant products work very well in certain situations. Many dairy, beef and sheep producers are now using haylage inoculants as a standard management practice.
Lactic Acid Bacteria
Lactic acid bacteria (LAB) are also known as homofermenters because they produce only one fermentation product: lactic acid. LAB inoculants are used to improve fermentation efficiency. Lactic acid is a strong acid that causes the pH of the forage to drop quickly, which minimizes dry matter losses (shrink). Dry matter losses in a well-managed bunker silo can typically be reduced from 15% to 12%–13%, a reduction of 2–3 percentage points. Since lactic acid contains almost as much energy as the original sugars in the forage, animal performance may be improved by using a LAB inoculant compared to not inoculating.
The most common LAB in commercial inoculants are Lactiplantibacillus plantarum, Enterococcus faecium, various Pediococcus species and other Lentilactobacillus species. Species and specific strains of LAB in commercial inoculants have been selected because they grow rapidly and efficiently and produce primarily lactic acid. There are significant genetic differences between LAB species and strains. Not all products are equally effective, but it is difficult to compare products. Ask company representatives to provide research that substantiates their claims for the product. Determine whether these claims are of value to the farm operation. Check whether the company can provide product quality control assurances.
If there is a high natural population of lactic acid bacteria, an inoculant is less likely to dominate the fermentation and provide a benefit. A long wilting time (>2 or 3 days), low silage moistures (<60%), rainfall during wilting and higher wilting temperatures, decrease the chances of an inoculant being successful, because these situations increase naturally occurring LAB. Therefore, the conditions for the greatest chance of an economic benefit from a haylage inoculant would be:
- first-cut and fall-cut (lower wilting temperatures)
- fast drying summer cuts (<1 day wilting), and
- higher moistures (65%–70%)
When forage in the windrow is rained-on, undesirable soil-borne bacteria are splashed onto the crop. It is sometimes difficult to dominate these undesirable bacteria with a commercial inoculant, and an inefficient fermentation may be the result. Also, because sugar is the principal food for LAB, low sugar levels in alfalfa can limit the success of inoculation. Rainfall will leach out some of the soluble sugars, which could be more limiting to a successful fermentation than inoculation.
Lentilactobacillus buchneri, formerly known as Lactobacillus buchneri
Some species of Lentilactobacillus bacteria produce both lactic and acetic acid. These are called heterofermenters because they produce more than one fermentation product. Lentilactobacillus buchneri are by far the most common heterofermenters used as silage inoculants. Acetic acid is much better than lactic acid at suppressing yeast and mould growth and slowing heat production once the silo is open. This means that the silage stays fresher for longer, which is also known as aerobic stability.
The increased acetic acid and aerobic (exposed to air) stability comes at the expense of increased fermentation dry matter losses. However, dry matter losses due to aerobic spoilage of corn silage are typically much larger than fermentation losses. In situations where spoilage at feed out is an issue, the use of L. buchneri inoculant on corn silage may result in less mould and mycotoxins, improved palatability and intake, and reduced total dry matter losses.
L. buchneri inoculants should be considered in situations where aerobic stability is a greater risk. Although L. buchneri inoculants could work similarly with alfalfa and grass haylages, aerobic stability is more of a problem with silages that contain large amounts of starch, such as whole-crop cereal silage and corn silage. High dry-matter corn silages, and bunk, pile or pit silos with large exposed surfaces usually have greater problems with aerobic stability and may benefit more from L. buchneri inoculants. The same may be true for the top loads in either vertical or horizontal silos. In tower silos, it is usually the bottom of the silo that is fed during the warmer summer temperatures, when there is increased risk of aerobic spoilage.
Another application where L. buchneri inoculants may be a benefit is in situations where corn silage is expected to be transferred from one silo to another. L. buchneri inoculants have also been shown to increase aerobic stability in high-moisture corn. Remember that aerobic stability is also improved by proper silage management practices, including recommended moisture and chop length, rapid filling and packing, sealing, face management, removal rate and feed bunk management.
Enzymes
Enzyme additives are sometimes included in inoculant products. Enzymes include cellulases, hemicellulases and amylases to help break down cellulose, hemicellulose and starch. In theory, these enzymes break down some of the fibre and starch sooner than normal, and therefore provide additional initial substrate for the bacteria to ferment. Research results are mixed. In situations where plant sugars are low and limiting to the fermentation, this may result in improvements. Product cost and effectiveness should be considered.