Dairy producers feeding aflatoxins every day: is this a manageable problem?
Picture 1 – Maize harvested in Argentina in 2016; Copyright© Newton Padovani, Nutriad International
Dairy producers robbed by aflatoxins
Mycotoxin contamination of dairy feeds is a worldwide problem for farmers as mycotoxins can increase the incidence of disease and reduce production efficiency in cattle (Coulombe 1993). The economic losses caused by aflatoxins are many and multi-faceted. All toxigenic fungi cause plant yield loss and mycotoxin contamination of the feed reduces animal productivity due to health problems. In addition, the contamination of crops and animal products (e.g., milk) is costly from a human health perspective. The cost of prevention, sampling, mitigation, litigation, and research also contribute to the losses associated with aflatoxins. The impact of aflatoxin due to lost maize yield in the USA has been estimated to be around $225 million/year. Due to the constant global climate change and varying weather conditions in different regions of the world, the economic losses from discarded contaminated milk are unpredictable yet real and significant. In addition to the cost of lost milk revenue due to the discarded milk, the dairy producer must also suffer the cost of proper disposal of the contaminated milk.
Aflatoxins: clearly toxic for ruminants
Aflatoxicosis is the disease caused by the consumption of high levels of aflatoxins by dairy cows. There are usually no visual symptoms of aflatoxicosis at low levels of intake and as a result, the problem is often unnoticed. However, high concentrations of aflatoxins or prolonged exposure at low levels cause visual symptoms in cattle especially in young calves. Beef and dairy cattle are more susceptible to aflatoxicosis than sheep and horses. Young animals of all species are more sensitive to the effects of aflatoxins than mature animals. On the other hand, the effects of aflatoxins in pregnant and growing animals are less than those in young animals, but more than those in mature animals kept at maintenance (e.g. breeding males). Feed refusal, reduced growth rate, and decreased feed efficiency are the predominant signs of chronic aflatoxin poisoning. In addition, listlessness, weight loss, rough hair coat, and mild diarrhea may be observed in affected animals. Anemia along with bruises and subcutaneous hemorrhages are also frequent symptoms of aflatoxicosis. Aflatoxicosis may also impair reproductive efficiency, including abnormal estrous cycles (too short or too long) and increased abortions. Other symptoms include impaired immune system response, increased susceptibility to other diseases, and rectal prolapse.
The diagnosis of aflatoxicosis is often difficult because of the variation in clinical signs, gross pathological conditions, and the presence of secondary infectious diseases due to a suppressed immune system. In addition, under commercial conditions, more than one mycotoxin may be present in any contaminated feed making the definitive diagnosis of aflatoxicosis difficult. The effects of aflatoxin contamination as the disease progresses depend upon the severity of induced liver damage. The prognosis is usually poor once overt symptoms are seen. Treatment should be directed at the severely affected animals in the herd and measures should be taken to prevent further poisoning. Unfortunately, most lactating cows with positive aflatoxins in milk will not exhibit strong visual symptoms, and as such, aflatoxicosis prevention is always the best way to tackle the problem. The carry over rate of aflatoxins from contaminated feed into milk in dairy cows is generally on average 1–2%. However, the carry over rate of aflatoxin M1 into milk can reach up to 6.2% in high yielding cows which consume significant amounts of concentrated feeds (Veldman et al., 1992).
Aflatoxins and legislations
There is a wide legislative framework regarding mycotoxin monitoring in the food supply chain as most of them are carcinogenic to animals and humans. Aflatoxin B1 is the most naturally occurring carcinogenic compound known (EFSA, 2004). Aflatoxin B1 is considered to be a human carcinogen (classified in group 1 by the International Agency for Research in Cancer [IARC]), and genotoxic. Aflatoxin M1 is the natural metabolite of aflatoxin B1 and has a high carry-over rate to animal products such as milk. Fresh milk is regularly checked for aflatoxin M1; concentrations of M1 above 0.5 μg/kg (0.5 grams in 1000 tons of milk) in the US are considered undesirable and such milk cannot be used for products that go into the human food chain and must be discarded. European legislation (EC) No 1881/2006 is even stricter and concentrations of M1 in milk above 0.05 μg/kg (0.05 grams in 1000 tons of milk) in the EU are considered undesirable for human consumption. It should be noted that aflatoxin M1 is not only found in dairy milk, but also in breast milk of nursing mothers. The FDA aflatoxin limit in dairy feeds including immature animals is 20 μg/kg (20 parts per billion [p.p.b.]) which is equivalent of 20 g of aflatoxin in 1000 tons of feed. European limit of aflatoxin B1 in dairy feeds is 5 μg/kg (5 parts per billion [p.p.b.]).
The information on possible adverse health effects of aflatoxin M1 in humans is scarce. The limited experimental animal studies carried out to determine toxicity and carcinogenicity of aflatoxin M1 appear to indicate that it has a hepatotoxic and a hepatocarcinogenic potential. The acute toxicity of aflatoxin M1 appears to be similar or slightly less than that of aflatoxin B1 but its carcinogenic potency is probably one or even two orders of magnitude lower than that of aflatoxin B1 (Henry et al, 2001).
Based on European regulation EC 1060/2013, every producer of anti-mycotoxin feed additive containing bentonite (1m558) with the quality specified in the regulation can claim that their product has a proven anti-aflatoxin B1 effect based on the non-holder specific EU registration of the bentonite product. However, this legislation is only valid in the European Union and can be only used as a reference in other parts of the world.
Economic evaluation of mycotoxin deactivators
Production losses due to mycotoxin contamination are clearly subject to a number of factors and uncertainties. The losses are hugely variable in time and difficult to estimate. However, the effects of the contamination are often significant and can be long lasting.
The economic impact of mycotoxins is difficult to estimate even after an outbreak of mycotoxicosis. The most important losses are probably those associated with long-term under-performance. Estimates of this can be made on the basis of the information provided earlier. A simple simulation model was developed that allows for the estimation of production and financial losses due to the long-term sub-clinical impact of mycotoxins in dairy cattle.
Under these assumptions the model predicts that on a herd-basis, mycotoxin contamination will cause losses in milk income of approximately 12 % and that the addition of an efficient mycotoxin deactivator will restore losses to just 3 % under the income level achieved in the absence of mycotoxins. Total farm revenue changed with similar percentages but variable costs or the operation costs increased by 3 % in the presence of mycotoxins. The annual return over variable costs decreased from 14.5 to 7.6 % due to the presence of mycotoxins.
The cost of the mycotoxin deactivator for a continuous treatment throughout lactation and dry period was estimated at $ 28/cow. The application of this mycotoxin treatment leads to an improvement in returns over variable cost to 12.3 % due to an improvement in revenue of $ 225/cow. Consequently, the return on investment (ROI) of the use of a mycotoxin treatment is approximately 7:1.
The assumptions associated with these simulations are considered to be rather close to the current US operational conditions. The model can be adapted to other economic situations - for instance those applicable to the EU, Middle East or Latin America. However, following a number of simulations, it appears that the economic returns of mycotoxin deactivators under conditions where contamination is suspected will easily be equal or superior to the rather conservative estimates obtained with these analyses. The addition of specific feed additives to animal feeds is a very common and economically valuable method to prevent mycotoxicoses in animals and carry-over of mycotoxins to human food chain.
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Article made possible through the contribution of Radka Borutova and Nutriad International