Mycotoxins in dairy cattle

MYCOTOXINS AND DAIRY CATTLE

María Rodríguez-Blanco, Sonia Marín, Vicente Sanchis, Antonio J. Ramos Applied Mycology Unit, Department of Food Technology, ETSEA-University of Lleida, UTPV-XaRTA, Agrotecnio, Spain antonio.ramos@udl.cat

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Mycotoxins are low molecular weight secondary metabolites produced by certain genera of filamentous fungi under environmental conditions that are favourable for their synthesis (Bennett and Klich 2003).

Contamination of raw materials used for the formulation of feed with mycotoxins is a worldwide problem that causes significant economic losses.

Furthermore, the intake of contaminated feed may lead to acute or chronic intoxication in the animals and may also contribute to its consumption

The main mycotoxins that can be

by humans, due to the possible

found contaminating feed and feed

transfer of these compounds to

materials are aflatoxins (AFs),

animal products such as milk,

deoxynivalenol (DON), fumonisins

meat or eggs (Fink-Gremmels

(FBs), ochratoxin A (OTA), T-2

2008a; Pinotti et al. 2016).

toxin and zearalenone (ZEN).

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Toxic effects of mycotoxins in dairy cows Ruminants are considered to be relatively resistant to mycotoxins, as ruminal microorganisms are able to degrade these compounds to less toxic, or even biologically inactive, compounds at normal exposure levels (Fink-Gremmels 2008b).

However, it should be noted that the rumen’s degradation capacity can become saturated or affected by changes in the diet or as a result of metabolic diseases (Fink-Gremmels 2008b). Therefore, consumption of feed contaminated with these compounds can affect the health status of dairy cows.

Some of the negative effects caused by mycotoxins in cattle are listed in Table 1.

Table 1. Main toxic effects in dairy cows derived from the consumption of feed contaminated with AFs, FBs, ZEN and DON.

MYCOTOXIN

TOXIC EFFECTS

AFLATOXINS

Impaired liver functions, reduced feed intake and milk production (Fink-Gremmels 2008b), decreased feed efficiency, immunosuppression, reduced reproductive performance (CAST 2003).

FUMONISINS

Reduced feed intake and milk production, mild hepatocellular lesions, immunocytotoxicity (Fink-Gremmels 2008b).

ZEARALENONE

Reproductive problems, infertility, reduced milk production and hyperestrogenism (Kallela and Ettala 1984).

DEOXYNIVALENOL

Reduced food intake and milk production (Jouany and Diaz 2005).

Liver alterations • AFs • FBs (mild hepatocellular lesions)

Immunological alterations • AFs (immunosuppression) • FBs (immunotoxicity)

Reproductive problems • AFs • ZEN (infertility and hyperestrogenism) Reduced feed intake • AFs • FBs • ZEN • DON

Reduced milk production • AFs • FBs • ZEN • DON

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Mycotoxins in feed for dairy cattle Dairy cows need fiber, proteins,

Among the materials included in

Silage is an important part of the

water, vitamins and minerals as

the formulation of dairy rations,

diet of dairy cows, as it usually

fundamental nutrients in daily

energy-rich components represent

represents a high percentage of the

diets. Furthermore, it is necessary

the main potential source of

final ration. These materials can be

to include a sufficient amount of

mycotoxins.

contaminated in the field, in post-

forage in their feed to maintain a functional ruminal microbiota. In addition, high amounts of energyrich components are needed, as they are essential to achieve high milk production and maintain the animal’s weight (Gonçalves et al.

2015).

The great variety and variability of ingredients used in diets increases the risk of exposure to a wide range of different mycotoxins.

AFs, FBs, OTA, trichothecenes, and ergot alkaloids have been found contaminating some of these components such as cereals, soybeans, peanuts, or cottonseed.

Fodder is the second source of mycotoxins, and preserved feeds such as silage, hay and straw are the third (Fink-Gremmels,

2008a).

harvest stages, as well as during storage.

Aspergillus, Fusarium, Alternaria and Penicillium are some of the filamentous fungi frequently found contaminating silage, so mycotoxins such as AFs, FBs, ZEN, trichothecenes, mycophenolic acid and roquefortine C can be detected in this raw material (Storm et al. 2008; Driehuis et al. 2008; Schmidt et al. 2015).

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Mycotoxin carry-over to milk In addition to the direct effects on animal health, one of the main problems associated with the presence of mycotoxins in animal feed is their possible carry-over to products derived from animals, such as milk.

AFM1 is detected in milk approximately 6 hours after consumption of the contaminated feed. Peaks of toxin can be detected 24 and 48 hours later if the intake of the feed continues and it disappears almost completely 72 hours after the withdrawal of the contaminated feed (Rodrigues 2014).

When dairy cows consume feed contaminated with aflatoxin B1 (AFB1), a part is broken down in the rumen to aflatoxicol, and another part reaches the liver where it is metabolized by liver enzymes through hydroxylation, hydration, demethylation and epoxidation.

Presence of AFM1 in milk after consumption of contaminated feed 6 hours

24 hours

48 hours

72 hours

The hydroxylation of AFB1 results in aflatoxin M1 (AFM1) and some of this compound is eventually excreted through the milk (Dhanasekaran et

First detection

Detection of peaks if intake continues

al. 2011).

Complete disappearence after removal of the contaminated feed

Liver metabolism

Hydroxylation

AFB1

Excretion of AFM1 in milk

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The transfer rate from AFB1 in feed to AFM1 in milk can vary from 1-2% in low yielding cows to 6% in high yielding cows (Britzi et al. 2013; RodrĂ­guezBlanco et al. 2019).

Carry-over rate from AFB1 in feed to AFM1 in milk

1-2 %

6%

Low yielding cows

High yielding cows

FACTORS THAT MAY AFFECT THE CARRY-OVER RATE

Lactation day (Veldman et al.

1992) Species Health status Ingestion and digestion rate Liver biotransformation capacity Integrity of the mammary alveolar cell membranes (FinkGremmels 2008a; Britzi et al.

2013)

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Monitoring AFM1 in milk has increased, especially since this toxin was classified as a human carcinogen (Group 1) by the International Agency for Research on Cancer (IARC) (IARC, 2012).

To minimize the exposure of AFB1 in humans, different countries have established regulations for maximum allowed concentrations of AFM1 in milk.

The European Commission and the Codex Alimentarius Commission (EC 2006; Codex

Alimentarius 2001) established a limit of: 50 ng/kg AFM1 in raw milk, heat-treated milk and milk for dairy product fabrication.

25 ng/kg AFM1 in infant milk and follow-on milk.

AS FOR THE TRANSFER OF OTHER TOXINS TO MILK, FEWER STUDIES HAVE BEEN CARRIED OUT

The European Food Safety Authority (EFSA) reported that the carry-over of FBs to milk is limited and does not contribute

In other countries such as the

significantly to total human exposure (EFSA 2005).

United States, the maximum

Similarly, as regards to ZEN, EFSA reported

limit is:

that the carry-over rate of this toxin to

500 ng/kg toxin in raw milk.

25 ng/kg in baby milk products.

The maximum limits of AFB1 established in feed for dairy animals (5 Âľg/kg) are aimed at reducing the presence of AFM1 in

milk is very low (EFSA 2004).

On the other hand, several studies have shown that DON is transformed to de-epoxy-deoxynivalenol (DOM1) in the rumen (CotĂŠ et al. 1986; Seeling et al. 2006; Keese et al.

2008) and that the part that is not metabolized is excreted in the milk at a very low rate (Prelusky et al. 1984).

milk due to the transfer from feed to milk.

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Reduction of mycotoxin contamination Despite the limits for mycotoxins established in different countries to reduce the level of exposure to these compounds, their presence in food and feed is usually unavoidable.

Mycotoxin contamination can occur

The implementation of good agricultural practices, good manufacturing practices, good hygiene practices and good storage practices is essential to reduce mycotoxin contamination.

at any point in the feed production chain, so strategies have been developed to prevent its occurrence as well as to eliminate them from contaminated products. However, they are very stable compounds and difficult to remove.

The problem of mycotoxins in feed

Physical treatments:

can be addressed from a preventive point of view, by avoiding post-

Some of the physical treatments that have been tested are

harvest mycotoxin production

thermal inactivation or the application of UV light (CAST 2003).

in crops, by controlling feed storage conditions, or once the

Chemical treatments:

contamination of the products

Among the chemical methods, treatments with acid/base

has occurred, by applying different

solutions or the use of additives have been successfully employed

technological strategies.

(CAST 2003).

Although it should be noted that the use of chemical methods of mycotoxin detoxification is prohibited in the EU. Biological treatments: Moreover, biological methods based on the detoxifying action of microorganisms, such as yeasts, moulds, bacteria and algae, may represent in the future a more suitable alternative for the elimination of mycotoxins (EU 2018; EFSA 2013)

Another strategy, widely used in the field of animal nutrition, consists of adding adsorbent compounds to the feed, which bind to the toxins during its transit through the gastrointestinal tract, reducing its absorption, promoting its excretion or modifying its mechanism of action.

Its use has already been authorized by the EU (EC, 2009).

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