Italian Scientists Show that even Good Quality Silage Can Develop Clostridia Contamination at Feedout

Clostridia, or butyric bacteria, contamination in silage always has financial consequences for the farmer, being the loss of dry matter or direct financial penalties on milk prices which are applied in certain cheese-making regions. A recently published study (Borreani et al., Journal of Applied Microbiol., 2009) shows that, even when the analysis of fresh silage shows low clostridia count, the silage can become heavily contaminated at feedout, due to aerobic instability, a phenomenon that can easily go unnoticed as long as analysis are performed on fresh silage.
Professor Giorgio Borreani, an expert in silage for many years, has looked into aerobic spoilage and clostridia spore formation in more detail and demonstrated that even a very clean and easily ensiled silage such as corn or sorghum (high cut and rapid acidification typically prevent contamination), could develop clostridia contamination. In this study, corn silage analysis showed only a few hundred clostridia spores per gram of fresh silage. But after air exposure, this count skyrockets, with up to 5 million spores/g after a hundred hours in lab conditions.

In an attempt to prevent aerobic spoilage and clostridia development, the scientists have tested two different microbial additives: an homofermentative lactic bacteria (L. plantarum), and the anti-fungic bacteria L. buchneri NCIMB 40788*. While L. plantarum had no effect on aerobic spoilage (the evolution of yeast, mould and clostridia development after silo opening is similar to untreated silage ), the silos that were treated with L. buchneri NCIMB 40788 were stable up to 300 hours after air exposure: clostridia spores did not develop (see graph).

(From Borreani et al., 2009)

Explanations...

Clostridia, responsible for butyric acid production in silage and milk, are spore-forming bacteria : when the environment is unfavorable to their development, they transform into inactive, resistant spores, waiting for more favorable conditions to multiply. In the case of corn silage, the bacteria already present on the forage rapidly enter an inactive phase due to the rapid acidification of the silage and do not have time to multiply in the silo, hence a very low level of contamination and the absence of butyric acid. At the time of feedout, the fermentation process is reactivated by the presence of oxygen: first yeast, and then mould thrive and grow in the presence of oxygen and the silo temperature rises up to 45°C. As a result, the pH rises (aerobic microorganisms consume lactic acid). In this non acidic environment, clostridia start to develop. The anti-fungic activity of L. buchneri NCIMB 40788 prevents these fermentations and stabilizes the pH under 5 units for more than 300 hours (see graph). In this case, clostridia remain inactive in the silage at feedout. Consequently, forage dry matter and nutritional quality are preserved and the risk of clostridia contamination in milk is prevented.

* L. buchneri NCIMB 40788 is present in silage additives from the Lalsil range which are designed for high dry matter forages : Lalsil® Fresh and Lalsil® Dry. Its anti-fungic and silage aerobic stabilization effects have been largely demonstrated.

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Hafiz Wasi Khan

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  07/04/2009

To achieve effecient results is always an art may be in hay making and its storage or silage making and its preservation. To me this article just shows that the farmer should not sleep and not be satisfied once he opens silage for using which is to be opened and covered from one side every day till the whole silage is used.The contamination due to one kind or the other type of bacteria is imminent as silage contains considerable moisture level in it.Its preservation to get high standard silage requires a watchful eye on it throughout its usage. The message is ok and timely however the writer wants to convince usage of certain product to achieve the same which may be ok thinking in term of business.
I always use 1% solution of Na Cl to spray the outer surface exposed after removal of required silage before covering it again and I never found any problem.
This helps me in the following ways
1. requirement of NaCl of my animals is minimized
2. It improves the taste of silage
3.Due to its alkaline nature It prevents any mold formation on the exposed area due to any acid which is exposed for sometime while removing silage for animals use

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