Effect of mycotoxins on US milk production

The chances are very high that multiple mycotoxigenic moulds including Aspergillus, Fusarium, Penecillium and related toxins creep into silos and are present in corn silage at harvest and after ensiling. As ruminants consume forages, by-product feeds and wet feeds, they are exposed to a broader range of mycotoxins at concentrations that are perhaps higher than those found in dry grain mixtures. Under normal conditions, a multiple-toxin contamination is likely. Multiple toxins can have a synergistic effect, increasing the negative impact on the animals’ performance and health. Toxins from mould and fungus combined with bacterial toxins increase the negative health issues significantly.

Impact on rumen environment

While the rumen microorganisms can help in degrading a certain degree of toxins, rumen metabolites of such toxins may be equally or more toxic. It should always be considered that mycotoxins would adversely impact rumen environment and activity even before having an effect on the animals themselves. Decreases in ruminal motility, on DM, ADF and starch digestion and on microbial growth are some of the impacts seen in animals fed mycotoxin contaminated diets, directly impacting production and indirectly initiating other metabolic disorders.

However, a more likely scenario is to find mycotoxins at lower levels interacting with other stressors to cause more subtle symptoms leading to subclinical losses in performance, increases in incidence of disease and reduced reproductive performance. For the dairy producer, these subclinical losses are of greater economic importance than losses from acute effects, but even more difficult to diagnose. 
The following symptoms could be associated with multiple mycotoxins contamination and feed related stress:

• Below normal milk production
• Oxidative stress
• Increased incidence of disease (opportunistic)
• Reduced production efficacy
• Poor reproductive performance
• Little or no response to veterinary therapy
• Difficulty of diagnosis and masked toxins
• Pale enlarged fatty liver inconsistent dry matter intake.

“The biggest challenge in the mitigation of toxins contamination is the ability to properly detect the risk we are confronted with,” affirmed Prof Trevor Smith, University of Guelph, ON, Canada. With this mind Innovad developed a partnership with reliable laboratories utilising the most precise, rapid and accurate techniques (LC MS/MS ) to identify such risks. The company analysed 218 feedstuff materials (TMR, Corn silage, haylage, straw, cotton seeds, etc) collected from dairy farms throughout the north-eastern US states of Pennsylvania, New York and Vermont between September 2015 and March 2016.

The profile contamination and toxins occurrence of the dairy cow’s diet in this region is considerably linked to the presence of Fusarium fungi capable of producing an array of toxins such as DON, conjugated forms of DON, Zearalenone and Fumonisins (Figure 1). The toxins levels of DON and Zearalenone in lactating cows as shown in Table 1 are considered to be moderate to high (and sometimes very high). These levels lead to depressed milk yield and components, gut integrity disorders, poor feed conversion and impaired rumen function. The liver is the main organ that is able to deal with non-polar toxins, so it will need to be supported.

Figure 1 – Occurence of mycotoxins in analysed feedstuffs.

How to mitigate such risks

The best way to eliminate risks related to the concurrent presence of toxic contaminants along with all other stresses inherent to the cows’ production challenges seems to lay in a combination of actions – the cow’s metabolic support emphasising maintenance and balancing oxidative stress management, the essential organ (liver mainly) aid, the stimulation of rumen function and immune response, along with the reduction of mycotoxins adsorption and toxins toxicity through their bio- transformation.

Rumen microorganisms can do something to degrade a certain degree of toxins. However, rumen metabolites of such mycotoxins may be equally or more toxic. Besides, such activity is lower in case of rumen dysfunction, or the animal’s immune system being depressed (i.e. early lactation). It is then that the cow’s liver is affected and needs to convert the toxins into something benign that can be excreted. Hepatic bioconversions of mycotoxins will need to take place – risking liver overload – to change the polarity. The liver may not be able to detoxify all those components.

Mycotoxins are not the only toxic material that the animal has to cope with. The liver, the main detoxification organ, needs to clear and detoxify not only mycotoxins present in the feed, but also enterotoxins (toxins produced by bacteria – that are usually not checked for) and many other contaminants. Therefore, products that stimulate organ function can reduce the negative impact of the toxins. Various plant extracts, present in the product Escent, produced by Innovad, have been known to maintain and restore organ function in case of toxic stressors.

Oxidative stress

Considering that mycotoxins are among the stress factors that have a negative effect on pro and antioxidant balance in the body and especially in the cell, free radicals can get out of balance. This may lead to a situation where the cow is no longer able to quickly detoxify these products, leading to oxidative stress.

An animal’s oxidative balance is one of the many factors that can limit milk production. Dealing with oxidative stress requires more energy from the animal that could otherwise be used for milk production, growth, longevity, fertility and overall animal productivity. When the system is out of balance, the body initiates an oxidative chain reaction, resulting in oxidative stress. Once critical structural damage occurs, antioxidants may no longer be able to repair problems.

Mycotoxins appear to have a significant immunotoxic potential, depending on the degree of exposure. Gliotoxin produced by A. flavus acts as an immunosuppressive, being antibacterial and improving apoptosis. These effects can be enhanced further by T-2 toxin, as it inhibits phagocytosis of A. fumigatus conidia by macrophages. Direct effects of the T-2 toxin are seen in lower concentrations of plasma immunoglobulin and protein. Cows in phases of stress as in early lactation or due to high temperatures are particularly susceptible to mycotoxins because their immune system is already overtaxed. The system is less stressed when vital organs such as the liver are fully functional.

The rumen has great potential to eliminate toxins, if the microflora is well balanced and very active. In addition, the immune system can be activated directly. B-glucans, as extracted and concentrated yeast cell walls, can activate leukocytes and cytokines. The stabilisation of the immune system results in fewer cases of mastitis and a lower concentration of somatic cell count.

At the beginning of lactation, during high mobilisation of body reserves and with high feed bypass through the rumen, the cow can barely cope with an additional burden such as mycotoxin contamination. A multifunctional approach should be used in order to maintain and to stabilise the health of the cow naturally. As part of this approach Escent can keep the liver and kidney healthy, as well as keeping the rumen highly productive, resulting in more milk.