Silage Inoculants: What are they?

What is silage?

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ilage is those round bales of hay you see on farms. Or you may have seen those plastic-covered mounds held under by a layer of tyres. Silage is simply forage that is being preserved for a later date, such as in the winter when there is a deficiency in feed.

Many forages can be ensiled (turned into silage); there’s alfalfa silage, barley silage, wheat silage, corn silage, oat silage etc. And there are several forms which silage can take when stored, for instance in concrete silos, as round bale haylages, bagged, covered in plastic, or on bunkers.

The successful preservation of the forage relies upon avoiding spoilage, which is achieved through fermentation. That’s where silage inoculants come in…

What are silage inoculants?

Silage inoculants are microbes, mainly bacteria, that are added to the silage to keep the forage preserved for longer, otherwise it will become spoiled. Essentially, they serve to lengthen the ‘shelf life’ of forage by preventing the growth of bad bacteria, yeasts, and moulds.

There are four generations of silage inoculants. This means there are four groups of microbes which are added to silages, each serving different purposes in the overall fermentation process.

Let’s discuss them…

1^st Generation Inoculants – Lowering pH

These bacteria are homolactic meaning they only produce lactic acid. They play a role in decreasing pH through all the acid they produce. 1^st gen inoculants include enterococci, pediococci, and lactobacillus species such as Lactobacillus plantarum.

The reduction in pH is essential for stopping the growth of unwanted bacteria, yeasts and moulds as well as inhibiting cellular respiration within the plant cells in the forage as this would have deprived the silage of its sugars (glucose).

But what about when the silage is exposed to oxygen? The low pH is going to be offset as the microbes start using up the lactic acid and sugars for growth. 1^st gen inoculants alone are not enough to keep the silage insured against spoilage as it’s still quite aerobically unstable.

This is where 2^nd gen inoculants come in…

2^nd Generation Inoculants – Aerobic stability

So now our silage has 1^st and 2^nd generation inoculants. 2^nd gen inoculants, including Lactobacillus buchneri and propionibacteria species are bacteria that is heterolactic. They produce acetic or propionic acid, converted from lactic acid.

Acetic and propionic acid act as fermentation inhibitors, stopping yeasts and moulds from utilising the sugars and lactic acids for their growth. Thus, the silage is made more aerobically stable.

But what about the fibre digestibility of the forage? Are the microbes improving digestibility so that feed efficiency is improved for the cows and sheep?

This is where 3^rd gen inoculants come in…

3^rd Generation Inoculants – Fibre digestibility

So now we have 1^st, 2^nd, and 3^rd generation inoculants in our silage. 3^rd gen inoculants, including Lactobacillus buchneri, provide enzymes which break down the tight bonds between lignin, cellulose, and hemicellulose in plant cell walls. This renders the fibre more digestible for the ruminants. One such enzyme is feruloyl esterase.

But what about improving health and performance of animals? Can microbes be added to enhance gut health?

This is where 4^th gen inoculants come in…

4^th Generation Inoculants – Probiotics

Now our silage has all 4 generations of inoculants. 4^th gen inoculants are probiotic microbes, serving to improve overall growth and health, particularly in the gut. These include bacteria such as lactobacilli and enterococci species and fungi such as saccharomyces and aspergillus species.

Thanks to these inoculants, silage can be preserved in good condition for when extra feed is needed for the ruminants.

See you in my next article Xx

Sources:

McAllister, T.A. 2019, AVBS2004 Animal Nutrition, lecture: Evolution and role of silage inoculants in ensiling, lecture PowerPoint slides, Agriculture and Agri-Food Canada Research Centre, Lethbridge, Alberta

Addah, W,Baah, J, Okine, E.K., McAllister, T.A. 2014, ‘Silage Inoculants – Are They WorthThe Money?’, WCCS Advances in Dairy Technology, vol. 26, pp. 193-206