Fighting mycotoxins with lactic acid bacteria?

Inoculation with lactic acid bacteria may prevent mycotoxins from contaminating silage, but research findings are mixed.

Mature Technologist Checking Quality Of Cattle Feed Lucerne (alf
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Some lactic acid bacteria may bind mycotoxins; scientists are looking for the right ones

Researchers believe that another microorganism already common in the ensiling process — lactic acid bacteria — could help keep mycotoxins out of cattle feed, but more work may be necessary to identify the most effective strains.

A recent study on the subject, due out in April’s edition of the journal Animal Feed Science and Technology, could find no trace of the mycotoxins zearalenone and tenuazonic acid a month after scientists treated silage with lactic acid bacteria, even though the raw corn was contaminated with both toxins at harvest. However, the lactic acid bacteria had seemingly no effect on aflatoxins, contradicting previous research that indicated lactic acid bacteria could reduce aflatoxins in silage.

“We have to find the bacteria that are able to bind” mycotoxins, said Antonio Gallo, lead author on the paper and faculty at Italy’s Catholic University of the Sacred Heart. But this could prove trickier than it may seem. It’s not just that they need bacterial strains capable of countering mycotoxins; they also need bacteria that grow well in the variable and complex conditions that occur within silage, without causing stress to the fungi that produced the mycotoxins in the first place.

Managing mycotoxins in silage is already a challenging task, Gallo said, because of the sheer quantity of silage needed to keep a dairy operation running.

“If we have mycotoxins in concentrate — corn meal, soybeans, raw materials, we can discard it or reduce its use. I can substitute more easily,” Gallo said. “It’s much more difficult to manage in silage because we have to use it.”

Prior research, Gallo said, showed promising results when raw materials were treated with lactic acid bacteria before ensiling — fungal growth and the production of mycotoxins, especially aflatoxin, were reduced. These bacteria have specialized polysaccharides in their cell walls that allow them to bind mycotoxins, likely because the bacteria and the fungi that produce mycotoxins compete for the same food sources, Gallo said.

But since the initial set of studies, the results of additional work on the topic have been mixed — sometimes showing no effect against aflatoxin, and in other cases causing an increase in fusarium toxins.

Finding the correct strain of bacteria, Gallo said, is the likely solution. By increasing the types of bacteria tested in future research, he hopes to identify the most promising species and then test it in a variety of conditions and materials beyond just corn silage to determine if it might be an appropriate solution to a longstanding problem.

“To counteract the effects of mycotoxins in silage, we have to adopt the best practices possible,” he said.

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