Fusarium which produce mycotoxins in cereal crops that af- fect humans and animals.
harvesting process. Many of these fungi and yeasts are acid tolerant and micro-aerobe and hence easily adapt to the silage environment. Perhaps the most prominent example of silage moulds is the Penicillium roqueforti group, able to produce a variety of mycotoxins (among others mycophenolic acid, patulin, and penicillic acid) exerting strong antimicrobial effects. Destabilisation of the rumen microbiota impairs rumen fermentation and fatty acid production and increases the risk for rumen acidosis. Typical signs of a persistent (subclinical) rumen acidosis are wasting, lameness and reduced fertility, increased somatic cells counts and mastitis and a reduced milk yield, particularly in high producing dairy cows. Again, the impact on animal health and well-being, and the economic losses associated to mycotoxin exposure are a major concern.
of mucus and the adherent defensins (endogenous antimicrobial peptides), the integrity of the intestinal barrier with its tight junction network, protective efflux carrier system and ultimately the architecture of the intestinal villi, the visible sign of damage of the intestinal tissues. The overall and economically important result is an impaired nutrient utilisation, a reduced growth rate and lower productivity of animals that appear at first sight clinically healthy. Chronic, subclinical inflammatory reactions also decrease the resilience of animals to infectious disease (resulting in an undesirable high use of antibiotics) and even the ability, to react with the required immunological response to vaccination programmes. Impairment of gut health and the risk of a persistent inflammatory syndrome is also an animal welfare concern, as it may lead to (endotoxin-induced) inflammation and vascular endothelial damage at tail tips, ears and claws.
Mycotoxins in the diet of ruminants While in monogastric animals the intestines are a target site for mycotoxin ingested with feed, in ruminants the ruminal microbiome (rumen microorganisms) is the first site of exposure. The ability of rumen bacteria to enzymatically degrade and inactivate many mycotoxins, established the assumption that ruminants are less sensitive to many mycotoxins known to affect the health on monogastric animals. However, the real-life exposure scenario of ruminants very often includes preserved feeds such as silages and haylage. During storage, these feed materials are regularly colonised by Penicllium and Aspergillus and other fungal species (up to 80 fungi and yeasts species have been reported) which are soil-borne and are introduced during the
Mycotoxins in the food chain The most prominent example of a human health concern is the contamination of dairy milk with Aflatoxin M1, a main metabolite of Aflatoxin B1 contaminating diverse feed and food commodities. Aflatoxin M1 retains the mutagenic potential of aflatoxins and is probably also carcinogenic when exposure occurs in the early phase of life. As infants are often high consumers of dairy milk products in comparison to their body weight, strict statutory limits for AFM1 have been introduced for all products intended for infant nutrition as a precautionary measure. In addition, several countries have also established statutory limits for other mycotoxins that may occur in edible tissue of animals (for example Ochratoxin A, which has a very long serum half-life and accumulates in kidneys of exposed animals). However, a comparison of the exposure levels for all mycotoxins revealed that animal- derived products (except for AfM1 in dairy milk) only contribute a small percentage towards the overall human exposure to mycotoxins from food and beverages.
Species-specific approach required Mycotoxins are globally the most frequently occurring undesirable contaminants of animal feeds. The lack of efficient measures to prevent fungal invasion and mycotoxins contamination at the pre-harvest stage under current agricultural practice and the ongoing climate change that increase the vulnerability of crops to fungal invasion, make it unlikely that effective avoidance strategies can be implemented soon. In turn, numerous strategies to reduce the impact of mycotoxins on animal health via functional feed additives have been developed. Such mitigation strategies require a species-specific approach and should consider all exposure scenarios even specific transgenerational transmission routes such as the intra-uterine, intra-ovum and early life exposure with colostrum and milk.
Literature references available on request. ▶ MYCOTOXINS | NOVEMBER 2021 19
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