Ruminants are less sensitive to mycotoxins than other species, since rumen metabolism exerts a protective function by degrading a large part of the mycotoxins ingested in the feed. However, some of these toxic substances can still have negative effects on productivity.
Ekaitz Maguregui Matellanes
Area Veterinary Manager
Milk is one of the most consumed foods from animal origin worldwide, with an annual production of 852 Mt (2019). Milk should be examined for different toxic compounds that can contaminated it, and mycotoxins are one of the most important.
Mycotoxins are secondary metabolites resulting from the reproductive process of different fungal species. These metabolites are toxic for different species including ruminants and humans.
Despite the fact that ruminants are less sensitive to mycotoxins than other species, because the ruminal metabolism exerts a protective function by degrading a large part of the mycotoxins ingested with feed, some of these toxic substances can still have negative effects on productivity.
The most important mycotoxins for ruminants include aflatoxins (AFB1, AFB2, AFG1, AFG2), trichothecenes (T2, DON, Zea) and fumonisins (FB1 and FB2). AFB1 is of greater concern because it is metabolized in the liver to AFM1 and excreted through the milk. AFM1 is an important hazard for public health due to its carcinogenic effects for humans.
2.EFFECTS OF AFLATOXINS IN DAIRY CATTLE
Aflatoxins are produced by fungi of the Aspergillus genus and there are four main types: AFB1, AFB2, AFG1 and AFG2. Aflatoxins are the most resistant to the degradation produced by the rumen flora, furthermore, the metabolite resulting from their degradation, known as aflatoxicol (AFL), also causes adverse effects on the animal.
The effects related with aflatoxins in ruminants include suppression of the immune system, hepatotoxicity, and digestive problems, as well as carcinogenic and teratogenic effects. In the case of AFB1, it is metabolized in the liver to AFM1, and excreted through the milk. Aflatoxin M1 has a carcinogenic and toxic potential comparable to that of AFB1. Additionally, aflatoxins can accumulate in different tissues where it also has carcinogenic effects.
The presence of aflatoxins in feed has a direct effect on productive performance of ruminants, as it makes them more prone to suffer from other digestive disorders because the immune system is suppressed, and reduces both milk production and quality.
3.RISK OF AFLATOXINS FOR PUBLIC HEALTH
AFM1 is the hydroxylated metabolite of AFB1, whose metabolization is catalyzed by cytochrome P450 enzymes in the liver of ruminants. This metabolite constitutes a significant risk to human health due to their carcinogenic effect, in fact, it is categorized as group 1 human carcinogen by the International Agency for Research on Cancer (IARC), which means that there is enough evidence to conclude that it can cause cancer in humans. AFM1 is absorbed in the intestine and has been proved to be carcinogenic for the liver in humans.
The average conversion rate from AFB1 in feed to AFM1 in milk rates from 0.3% to 6.2%, depending on the breed, feed composition, digestibility, and health status, among others.
Governments worldwide have stablished maximum limits to the presence of AFM1 in milk. In the European Union (EU), the maximum limit is 0.05 ppb. However, several studies around the world have proved that these limits are not always accomplished, especially in developing countries. Studies carried out in Nigeria (Suliman & Abdalla, 2013), Sudan (Susan et al., 2012), Iran (Sefidgar et al. 2011; Panahi et al. 2011) and Pakistan (Hussain & Anwar, 2008) showed that more than the 90% of the samples were over the EU limits. Another study made in Latin America (Torres et al. 2020) showed that the 59% of the samples were above the EU limits.
Mycotoxins are one of the main risks for animal production and their presence is difficult to control, indeed it is estimated that around the 25% of the world’s food crops are contaminated with mycotoxins. Aspergillus, an aflatoxin-producing fungal genus, grows at temperatures of 25⁰C and with a relative humidity of 70%, which means that can grow in nearly all over the world and contaminate the crops, raw materials and feeding stuffs
One of the most common measures to prevent the negative effects of mycotoxins in animals is the use of effective mycotoxin binders, such as the molecule Silicoglycidol. This molecule avoids the absorption of these toxic compounds along the digestive tract.
Chart 1. Concentration of AFM1 in the control group (CON) without challenge, the challenge group (AF) contaminated with AFB1, and the experimental group (AF+C) challenged with AFB1 and supplemented with Silicoglycidol.
The efficacy of Silicoglycidol was proved in a trial carried out by the Iowa University (2018), which showed how it was able to reduce the excretion of AFM1 in milk when it was fed to dairy cattle.
4.1Silicoglycidol – reduction of the excretion of AFM1 in milk in dairy cattle
12 dairy cattle were used for the trial divided in the following experimental groups for 9 weeks:
•Control group: basal diet, without challenge and without binder.
•Challenge group: basal diet + challenge (2,500 µg of aflatoxin/cow/day)
•Experimental group: basal diet + challenge (2,500 µg of aflatoxin/cow/day) + mycotoxin binder at a dose of 10% of dietary dry matter.
The mycotoxin binder molecule that was used during the trial was Silicoglycidol, which is a modified aluminum silicate that was patented in 1988 by the company Biovet S.A.
The presence of AFM1 in milk was examined in the three batches. The results showed that, by using Silicoglycidol in cows fed an aflatoxin-contaminated diet, the presence of AFM1 in milk was reduced by27% (chart 1).
The presence of AFM1 in milk has severe consequences for humans due to its carcinogenic effect. So, to establish effective preventive measures and surveillance is necessary.
Mycotoxin binders such as those based on Silicoglycidol have proved to effectively reduce the presence of AFM1 in milk by 27%.
By using this mycotoxin-binding molecule, the presence of AFM1 in milk can be reduced and, at the same time, the negative effects produced by mycotoxins in dairy cattle. Besides, Silicoglycidol can also prevent the productive losses associated with mycotoxins.
“Silicoglycidol is marketed under the brand name Alquerfeed Antitox by Biovet S.A.”
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•Ismail, Amir & Akhtar, Saeed & Levin, Robert & Ismail, Tariq & Riaz, Muhammad & Amir, Mamoona. (2015). Aflatoxin M1: Prevalence and decontamination strategies in milk and milk products. Critical reviews in microbiology. 42. 1-10. 10.3109/1040841X.2014.958051.
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