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Yeasts to reduce mytotoxin absorption in ewes

Scientists in the INRA Herbivore Research Unit, working in collaboration with the company Alltech, have shown that addition of the modified yeast cell wall of S. cerevisiae to the diet of ewes could reduce the absorption of a mycotoxin, Aflatoxin B1, thus contributing to preserving the health and well-being of the animals.

Colonies de Saccharomyces cerevisiae, levure de panification, sur milieu nutritif gélosé. © CAIN Anne-Hélène
Updated on 02/12/2013
Published on 06/06/2012

Mycotoxins: from St. Anthony's fire to endocrine disruptors

In the past, mycotoxins were responsible for massive, often fatal, intoxications among both animals and humans. The epidemics of "St Anthony's fire" that affected Europe between the Middle Ages and the 18th century – although the last episode occurred in 1951 in France – were the most famous manifestations of this type of poisoning. The ingestion of toxic alkaloids secreted by a fungus of rye, Claviceps purpura, or ergot, triggered dementia and blood circulation disorders that could even progress to gangrene. Today, thanks to modern crop protection methods, stock management and the controls put in place, mycotoxins no longer cause such spectacular and severe outbreaks of poisoning in Europe. However, despite these preventive measures, an absence of mycotoxins still cannot be guaranteed, mainly in cereals but also in other plant products. Entry into the food chain of toxic molecules – a carcinogenic compound such as Aflatoxin B1 (AFB1) or an endocrine disruptor such as zearalenone – may constitute a real risk factor in both humans and livestock.

A research objective: to reduce the bioavailability of toxic compounds

Because physicochemical methods to eliminate mycotoxins from plant raw materials are little effective and expensive, INRA researchers have been focusing for several years on techniques that might be able to reduce the bioavailability of mycotoxins in the digestive tract of animals by fixing these substances and thus facilitating their excretion in the faeces. During previous studies, also performed in partnership with Alltech, the scientists achieved an in vitro demonstration of the sequestering – or fixing – potential of the yeast cell wall (YCW) of S. cerevisiae.

In the context of a new partnership (CIFRE thesis project), the scientists have demonstrated the efficiency of the sequestering potential of YCW in vivo in ewes using low doses of mycotoxin (60 micrograms AFB1 per kg feed) similar to those naturally encountered in farms. To achieve this, 16 dairy ewes were divided into four equivalent groups and received the same diet for a long period (21 days) which was either mycotoxin-free (control group), contained the mycotoxin alone (AFB1 group), the absorbent alone (YCW group) or the mycotoxin supplemented with YCW extracts (AF+YCW group). During the same period, the researchers measured the zootechnical parameters of the animals (body weight, milk yield, fatty acid, protein and lactose contents of the milk). They then assayed and compared the quantities of toxin found in the faeces and urine of the animals 24 hours after they had ingested the last dose of mycotoxin, and then for the next three days. They thus evidenced that the AF-YCW group displayed mycotoxin levels in the faeces that were nearly twice as high as those in the AF group (170.4 ± 20.9 µg versus 109 ± 16 µg), and a reduction of the mycotoxin level in the urine (15.9 ± 6.1 µg versus 25.7 ± 7.3 µg), thus demonstrating a weaker absorption of aflatoxin in the presence of YCW. Growth rates and milk quality remained comparable between the different groups, thus underlining the safety of the YCW chelating agent obtained from yeasts.

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  • Firmin, S., P. Gandia, D. P. Morgavi, G. Houin, J. P. Jouany, G. Bertin and H. Boudra. 2010. Modification of aflatoxin B1 and ochratoxin A toxicokinetics in rats administered a yeast cell wall preparation. Food Additives and Contaminants 27(8): 1153-1160
  • S. Firmin, D.P. Morgavi, A. Yiannikouris And H. Boudra. 2011. Effectiveness of modified yeast cell wall extracts to reduce aflatoxin B1 absorption in dairy ewes. J Dairy Sci. 94:5611-5619