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Mycotoxins: Ruminant Production and Welfare

To minimize the risk of mycotoxin contamination different measures can be taken by the farmer. The first strategy is to prevent the mycotoxin contamination of crops in the field and during storage. Because it is very difficult to prevent mycotoxin contamination either pre-harvest or during storage of feeds, several products are available to protect the animal against ingestion of mycotoxin contaminated feed.

Jesse STOOPS & Anne GODERIS
Nutrex nv- Belgium

nutrexMycotoxins are toxic metabolites produced by molds and are able to cause intoxications in animals. The major mycotoxins with well-known toxic effects are alfatoxins (AFL), trichothecenes (TCT), zearalenone (ZEA), fumonisins (FUM), ochratoxins (OT) and ergot alkaloids. Sensitivity towards mycotoxins varies according to animal species, sex, breed, age, general health, immune status, etc. In general, ruminants are considered to be less susceptible to many mycotoxins compared to monogastric animals, because the ruminal microbiota provides the first line of defense by converting mycotoxins into less toxic metabolites. However, production (e.g. milk and beef), reproduction and growth can be impaired when ruminants are exposed to mycotoxin contaminated feed for extended periods of time or when multiple mycotoxins are present. It is likely that ruminant rations are contaminated with multiple mycotoxins. The ruminant diet consists of silage made from forage crops and (wet) by-product. Therefore, ruminants are exposed to a broad range of mycotoxins, originating from a pre-harvest contamination (e.g. Fusarium species) as well as from a post-harvest contamination (e.g. Penicillium or Aspergillus species). Exposure to a cocktail of mycotoxins can have synergetic effects, increasing the negative impact on animal’s performance.

SUSCEPTIBILITY OF RUMINANTS TO MYCOTOXINS
The sensitivity of ruminants to mycotoxins largely depends on the pre-systemic elimination of ingested mycotoxins by the rumen microbiota. Rumen protozoa and rumen bacteria can metabolize different mycotoxins into less toxic compounds. In a healthy ruminant, DON is rapidly converted in the rumen into de-epoxyde, which is less toxic. However, the detoxifying capacity of the rumen microbiota is limited and varies with changes in the diet or as a consequence of metabolic disorders like rumen acidosis. Furthermore, not all mycotoxins are subjected to enzymatic cleavage by the rumen microbiota. Some mycotoxins could pass the rumen unchanged, such as FUM and ergot alkaloids, and some mycotoxins are converted in the rumen into metabolites with an equal or more toxic activity than the parent molecule. For example, ZEA is converted into the even more potent alpha-zearalenol. On the other hand, various mycotoxins (e.g. patulin) exert an antimicrobial effect, and impair and modify the rumen microbiota.

Clinical mycotoxicosis in ruminants is associated with mycotoxins that are not (completely) degraded by the rumen microbiota. These mycotoxins can reach the duodenum where they are absorbed, resulting in a high mycotoxin load. Ruminants are more susceptible to mycotoxins in the transition period or in other phases of stress, such as high environmental temperatures. Also high yielding cows are considered to be more sensitive due to the greater dry matter intake, which lowers the rumen pH and increases the rate of passage. This results in less time for detoxification of the mycotoxins by the rumen microbiota.

PREVENTION MEASURES
To minimize the risk of mycotoxin contamination different measures can be taken by the farmer. The first strategy is to prevent the mycotoxin contamination of crops in the field and during storage. Because it is very difficult to prevent mycotoxin contamination either pre-harvest or during storage of feeds, several products are available to protect the animal against ingestion of mycotoxin contaminated feed. Nutrex developed a product, Free-Tox, that protects the animal against the harmful effects of a broad spectrum of mycotoxins. The product is a combination of specially selected and processed silicates (i.e. acid activated bentonite), yeast cell walls, and organic acids and salts.

An in vivo trial was set up to investigate the ability of Free-Tox to prevent or reduce the negative effects when dairy cows were subjected to naturally mycotoxin contaminated feed. A four week trial was performed on 110 dairy cows (average of 118 days in milk). The ration consisted of corn silage (30 kg), pulp (7 kg), grass silage (8 kg), wheat (3.5 kg), protein premix (3.3 kg) and concentrate (2 kg). Moreover, soy bean meal was used as protein corrector. Within this protein corrector Free-Tox was dosed at 7.5 kg/ton to achieve a daily dose of 25 g/cow/day. Before onset of the trial, the average milk production was 24 kg/day. During the treatment period, the milk production was increased to 26.2 kg/day (Figure 1). Also on protein content there was a marked effect. Free-Tox increased the protein content with 1%, from 33.9 g/kg to 34.2 g/kg (Figure 2). In conclusion, Free-Tox protects the animal against the negative effects of mycotoxins, resulting in more milk with a higher protein content.

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