Apart from the threat to human health, mycotoxins are associated with economic losses for both crops and animals, including ruminants. Ruminants seem to be more resistant to mycotoxicosis than monogastrics, but clinical signs of acute mycotoxicosis such as reduced feed intake, decreased milk production, and liver damage have also been observed in cattle.
Fumonisins
Geographic distribution. Fumonisins can cause illness and poor performance of livestock all over the Europe (Germany, France, UK, Italy).
Source of contamination. The majority of fumonisin positive samples are found in cereals: corn and corn derived products, wheat, barley and oats. Silage and hay can be heavily contaminated with fumonisins due to bad storage condition that allow Fusarium mould to grow. The fermentation process of DDGS production does not destroy mycotoxins, hence, this important raw material for the dairy sector can be a source of fumonisin contamination of feed.
Negative effects. Fumonisin B1 has been shown to be toxic to sheep, goats, beef cattle and dairy cattle. Because of greater production stress, dairy cattle may be more sensitive to fumonisin than beef cattle.
Fumonisins are water-soluble polar compounds, and their absorption from the gastrointestinal tract is very low (about 1%). Fumonisins are degraded by the rumen flora only to very minor extent, and thus seem to be absorbed in the small intestines of ruminants in the same ratio as in monogastric species. Smith and Thakur (1996) and Caloni et al. (2000) found that fumonisin B1 is eliminated from the body mainly unmetabolised. Ingestion of feed containing 75 ppm fumonisin B1 daily for 14 days by Jersey cows increased serum cholesterol concentration and decreased feed intake and milk production (Richard et al., 1996). Holstein and Jersey dairy cattle fed diets containing 100 ppm fumonisin for approximately 7 days prior to calving and for 70 days thereafter demonstrated lower milk production (6 kg/cow/day), explained primarily by reduced feed consumption (Diaz et al., 2000). Fumonisin carryover from feed to milk is thought to be negligible (Scott et al., 1994). The liver and the kidneys are the target organs for fumonisin toxicity in ruminants. Toxic threshold levels still need to be defined, but normally they exceed 10 ppm (up to 100 ppm per kg feed), reflecting again the very low bioavailability of fumonisins in comparison to other Fusarium toxins (Fink-Gremmels, 2005).
Carryover. Available data on carryover of fumonisins from animal feeds into milk indicate that transfer is limited and thus residues in animal tissues contribute insignificantly to total human exposure (Opinion of the Scientific Panel on Contaminants in Food Chain on a request from the Commission related to fumonisins as undesirable substances in animal feed). Maximum limits in feed. The EU recommendation to the maximum limit in feed for adult ruminants is 50 ppm (Table 1).
Detoxification of mycotoxins
Many fungal species are capable of simultaneously producing several mycotoxins. Therefore, an individual grain may be naturally contaminated with more than one mycotoxin. Moreover the incorporation of numerous grain sources, which are each contaminated with a different mycotoxin, into a single feed may result in a diet that contains a number of different mycotoxins. Hence, poor livestock performance and/or disease syndromes, reported in commercial operations, may be due to additive, synergistic interactions between multiple mycotoxins.
Prevention of mould infection is the most desirable method of reducing mycotoxins in feeds, although contamination often is unavoidable, even with the best agricultural practices. Therefore, several strategies have been developed to reduce post harvest product contamination. Some of these methods involve early identification and segregation of grossly infected kernels to identify and to reject spoiled grains. Another strategy is the use of detoxifying agents, which prevent absorption of mycotoxins in animals. Many companies and researchers have tried to find means of detoxifying mycotoxin contaminated grains. Most of the treatments have been found to be either too expensive or to have side effects on the end products that reduce the benefits of detoxification. The addition of inorganic adsorbents, along with vitamins, proteins, and trace elements added to feed, have the most positive effects. The adsorbents bind and immobilize the toxins holding them in the intestinal tract, allowing them to be eliminated in urine and faeces.
Conclusions
Dairy farmers face some significant dilemmas. Diarrhoea, lowered feed consumption, mastitis, estrus errors, etc. may be a part of one or more mycotoxins impacts on the dairy animal. However, none of them are unique to fungal toxins and most may more often occur as a result of other factors. Similarly, if one takes the research on ruminal degradation of mycotoxins at first sight, it would seem that ruminants are uniquely protected against these fungal metabolites. How then, can it be that staggers, slobbers, abortion, loss of production can all be induced by a dietary application of certain toxins at levels consistent with what is found naturally under farm conditions?
Various mycotoxins appear to have considerable immunotoxic potential, depending on the level of exposure. The idea that mycotoxins can potentiate or antagonize the action of other mycotoxins is no longer a supposition. It has been proven extensively in the literature. We have little ability to predict what might happen when four or five or more toxins are present together in the animal’s ration. The effects of long-term feeding of mycotoxins at low levels also have not been well characterized.
Key conclusions
Ruminants seem to be more resistant to mycotoxicosis than monogastrics, but clinical signs of acute mycotoxicosis such as reduced feed intake, decreased milk production, and liver damage have also been observed in cattle
In Europe the different climatic conditions among the northern, middle and southern parts favours the development of different fungal species The diet of a dairy cow generally includes both forages and concentrates, which can increase the probability of multiple mycotoxin contaminations Prevention of mould infection is the most desirable method of reducing mycotoxins in feeds, although contamination often is unavoidable, even with the best agricultural practices. Therefore, the use of detoxifying agents, which prevent absorption of mycotoxins in animals can reduce post harvest product contamination
Abstract
The inclusion of numerous feedingstuffs of various geographical origins into a dairy cow feed may result in a number of different mycotoxins in a diet. A microbial population including bacteria, protozoa and fungi in the rumen seems to be effective in mycotoxin metabolism in this section of the cow digestive tract. However, mycotoxin metabolites produced in the rumen may be equally or even more toxic than the initial contaminant for the animal itself as well as for the milk consumers.
The article describes the negative effects of the main mycotoxins such as aflatoxins, fumonisins, zearalenone, Trichotecenes, ochratoxin A, citrinin, patulin and ergot alkaloids on a dairy cow performance. A unique summary of mycotoxins carryover from feed into milk is introduced together with European advisory levels of mycotoxins in feed for dairy cattle.
More and more often dairy cow nutritionist suspect moulds in the raw material such as silage, hay, grains are causing a mycotoxin challenge to the cows. The use of inorganic adsorbents has positive effects on a cow performance. They bind and immobilize the mycotoxins holding them in the intestinal tract, allowing them to be eliminated in urine and faeces. Kemin Europa N.V. already experienced the cows yield had risen by 2 litres per head per day within one week with clay-based mycotoxin adsorbent Toxfin®.
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