Silage inoculants are a crucial component of ruminant nutrition, with these bacterial solutions providing a reliable and efficient way of preventing silage spoilage and preserving its nutritional value. But while their use has been well established, Chr. Hansen believes industry knowledge surrounding these additives might need some updating.
According to the company’s Product Manager for Silage, Dr. Ivan Eisner, current popular methods for producing silage, while effective, can take much longer than necessary. As he explained to Feedinfo in a recent sit-down, the use of newer silage inoculants containing selected bacterial strains can help cut down silage storage before feeding from months to just a matter of days.
In this Industry Perspectives, he tells us more about the advances in silage inoculants that the industry might be missing out on and how Chr. Hansen is using its vast knowledge of bacteria to push the envelope in this area. He also touches on key differences between fermentation enhancers and aerobic stability enhancers, why choosing the right strain of bacteria is so vital to the silage production process, how the use of inoculants can impact producers’ carbon footprint, and much more.
[Feedinfo] You’ve stated that the industry’s knowledge about silage inoculants is “out of date”. Why do you think that is?
[Dr. Ivan Eisner]The ancient Egyptians understood that moist forage could be stored for an extended period if well compacted in silos. But it was the work of Finnish Professor Artturi Virtanen that demonstrated how compacting and sealing aided preservation and that nutrients could be conserved by adding certain chemical acids. This showed that a low pH aided good fermentation. Early lactic acid bacteria (LAB) were therefore selected for their capacity to reduce pH rapidly.
However, dairy producers often observed that natural fermentation would occur without the need for LAB inoculants to be added simply by establishing and maintaining anaerobic conditions. But the results were not always consistent. The reason being that even if compaction and sealing are executed with perfection, more than 30% of the total silage volume is made up of air. The presence of oxygen will inherently allow undesirable or even pathogenic microorganisms to grow and metabolise, competing with good LAB for nutrients. This postpones the onset of lactic acid production, reduces the nutritional value and prolongs the storage period of silage before it can safely be opened and fed to animals.
However, there are now silage inoculants containing lactic acid bacterial strains that can actively scavenge the oxygen and create an oxygen-free environment in less than 24 hours. This makes it possible to start feeding new silage after one week of storage instead of the 2-3 months usually required. SiloSolve® FC with Oxycap® Technology from Chr Hansen offers just that.
[Feedinfo] Speaking of lactic acid bacteria, there appears to be a difference between fermentation enhancers and aerobic stability enhancers. What are the main points to remember here?
[Dr. Ivan Eisner] Well, both are based on lactic acid bacteria. However, there are different types of lactic acid bacteria: homo- and hetero-fermentative. In general terms, homo-fermentative lactic acid bacteria convert crop sugars into lactic acid. The fermentation process is improved with these bacteria, yet aerobic stability is often jeopardised because the lactic acid may serve as a nutrient source for yeasts at aerobic exposure (when the silage is fed to the cows). In contrast, hetero-fermentative lactic acid bacteria convert crop sugars into lactic and acetic acid. Acetic acid – which most of us know as vinegar – is a very effective antifungal compound. The hetero-fermentative lactic acid bacteria therefore typically enhance both the fermentation and the aerobic stability of silage by reducing aerobic spoilage organisms, such as yeast and moulds. These biological silage inoculants must be applied to the crops as they are harvested (i.e., before being loaded and compacted into the silo or bunker). Hetero-fermentative bacteria also produce other molecules, such as ethanol, 1,2-propanediol and others.
[Feedinfo] You mentioned that chemical additives can also be used for the preservation of silage. How do these compare to biological silage inoculants?
[Dr. Ivan Eisner] There are other acids that can work as aerobic spoilage inhibitors, e.g. sorbic or propionic acid or salts thereof. These chemicals can also be applied during harvest or even during the feeding of the silage. However, to ensure they are effective, these acids typically need to be applied in high doses. This can result in them being corrosive to the equipment and posing a risk to the operator during handling. In contrast, a lactic acid bacteria-based silage inoculant is applied as a dry powder or as a water-based solution, with only a few grams per ton needed. The reason being that the lactic acid bacteria will multiply rapidly during the early stages of fermentation and create the fermentation acids "as they grow".
[Feedinfo] Why is selecting the right bacterial species so important for the fermentation process?
[Dr. Ivan Eisner] First of all, it is important to know what we want to achieve in the end. Do we only want to have silage that doesn’t contain butyric acid, the end product of fermentation by Clostridia? Or do we want to have butyric acid-free silage that doesn’t heat up after we open the silage bunker and start feeding? Or have we run out of silage from the previous season, and cannot wait two months until the new silage is ready to be fed? By selecting the right bacterial species and combining them into a final product, we can control fermentation and direct the silage according to our targets and, most importantly, the requirements of our animals.
[Feedinfo] I’ve read that you distinguish not only between different bacterial genus and species but also different strains of bacteria. Could you elaborate what this means?
[Dr Ivan Eisner] Yes, this is a topic that can be tricky to explain. So, within homo- and hetero-fermentative bacteria we can select between different genus and species to influence the fermentation process to achieve a specific outcome. However, even within the same species of bacteria we have identified completely different properties. We refer to such differences by the strain "ID", or license plate, if you prefer. So, when reading the label, the genus and species will provide you with a hint as to the type of silage inoculant being employed, i.e. whether it is a fermentation enhancer only or a fermentation and aerobic stability enhancer in the same product. However, the "ID", or license plate, reveals more details. Chr. Hansen offers different Lactococcus lactis strains, DSM11037 and NCIMB30117. Although they belong to the same genus and species, these two strains have completely different modes of action.
[Feedinfo] Can you explain the science behind how a combination of homo- and hetero-fermenting strains of bacteria can be useful in silage production? Talk to us about the “additive” vs “multiplicative” effect of using different strains in silage inoculants.
[Dr. Ivan Eisner] The additive effect is when two or more different strains work in the silage independently of each other: one produces lactic acid and reduces the pH of the silage, and another one produces acetic acid to prevent aerobic spoilage of the silage. This silage will have a low pH and prolonged aerobic stability after opening. The multiplicative effect is a synergistic effect: one strain enhances the effect of another. This silage will have superior characteristics, far better compared to the effect of each individual strain and even beyond the additive effect of the combined strains.
[Feedinfo] With thousands of different strains of bacteria out there – and each one behaving differently in the broad variety of conditions involved in silage making – what other exciting opportunities in this area is Chr. Hansen exploring?
[Dr. Ivan Eisner] The opportunities are enormous. We have already brought flexibility to our customers by offering them silage inoculants that can answer their individual requirements. Now they can start to feed the silage when they need it, without waiting the traditional 2 to 3 months until it is fermented. We can also help them reduce their carbon footprint by lowering silage waste. This means that they could potentially use a smaller agricultural area to produce silage for the same number of animals. This could also mean buying less feed (concentrates, compound feed), which could help improve bottom lines. In addition, we can make silage producers less dependent on the weather because our silage inoculants can help improve silage even in less optimal conditions. At the end of the day, it is our current and future mission to help unlock the full potential of silage for animals by unlocking the vast possibilities bacteria can offer.
Published in association with Chr. Hansen