Can low levels of mycotoxins deteriorate your animal health and profitability?

Wednesday, April 6, 2022


Can low levels of mycotoxins deteriorate your animal health and profitability?

 

Radka Borutova DVM, PhD, Alltech mycotoxin management team

 

 

Mycotoxins are poisons produced by moulds and frequently occur in a variety of feedstuffs. The high frequency of occurrence, along with the concentrations at which they occur, suggest that mycotoxins are routinely consumed by animals, causing sub-clinical symptoms that subsequently result in production losses. Mycotoxins are most often found at low levels, which may result in the sub-clinical reduction of meat, milk and egg production; increase in disease incidence and severity and impairment of reproductive performance in breeding animals. Consequent increasing expenses with inappropriate veterinary therapies further jeopardise the final profit of the animal producer. The effects in different animal species are dependent on the level of mycotoxins in the diet, the duration of feeding and the interactions of the mycotoxin with other mycotoxins or stresses that may activate or accentuate these responses. Unfortunately, the most common and difficult mycotoxin challenges occur when rations contain low levels of mycotoxins and, thus, all health effects are sub-clinical. The animals mostly affected by sub-toxic concentrations of mycotoxins are those that are less susceptible to the effects of mycotoxins, namely ruminants and poultry. Both ruminants and poultry the ability to partially detoxify some mycotoxins in their gastrointestinal tract. However, because this ability is not 100% effective, some quantity of these mycotoxins can reach the blood system and target tissues, resulting in sub-clinical health and reproduction injury. In this article, we will explain why and how even low — and many times underestimated — concentrations of mycotoxins in feed can cause deleterious health effects in farm animals.


Acute mycotoxicosis outbreaks are rare events in modern animal production. However, low mycotoxin doses that, very often, are not detected are responsible for reduced efficiency of production and increased susceptibility to infectious diseases. A more likely scenario is to find mycotoxins at lower levels interacting with other stressors leading to sub-clinical losses in performance, increases in the incidence of disease and reduced reproductive performance. To the animal producer, these sub-clinical losses are of greater economic importance than losses from acute effects, but again even more difficult to diagnose.


Definition


Sub-clinical: describes an early stage or mild form of a medical condition, no symptoms of which are detectable.


Adverse health effects associated with the contamination of feed materials with mycotoxins may lead to acute intoxications, which can be life-threatening. More frequent are sub-acute and, often, sub-clinical alterations of organ function that impair weight gain and reduce productivity. Significant effects of low mycotoxin concentrations can be observed on the immunity and antioxidant systems, which often remain undetected.


Effects on the immune system


While growth impedance and reduced productivity are of economic importance, the intrinsic activity of many mycotoxins on the immune system of the animals is of increased concern. The presence of moderate–low amounts of mycotoxins in daily feed rations increases the susceptibility of animals to viral, bacterial and parasitic diseases (Bondy and Pestka, 2000). This increased susceptibility requires increased therapeutic intervention with antibiotics and anti-parasitic drugs. This, in turn, increases the costs for animal healthcare and the use of anti-infective agents, particularly antibiotics, with a concomitant increase in the risk of induction and spread of antimicrobial resistance. The immunosuppressive effects of mycotoxins may also result in incomplete protection of farm animals against viral diseases following vaccination, as antibody formation is impaired.


Scientific evidence


According to Swamy et al. (2002), feeding grains naturally contaminated with deoxynivalenol reduced growth, altered brain neurochemistry, increased serum immunoglobin (Ig) concentrations and decreased organ weights in starter pigs. Some of the deoxynivalenol-induced changes in neurochemistry and serum Ig concentrations were prevented by the feeding of Mycosorb® at appropriate concentrations, although this was not reflected in increased growth rate under these experimental conditions. If we extrapolate this study to the real farm conditions, we might see that the growth rate of the animals was not affected, while the immune system functions were. This can have a detrimental consequence on any medical actions of veterinarians, as decreased responsiveness of animals to medical treatment may harm their performance in the field.


In the study of Verbrugghe et al. (2012), the researchers investigated the effect of Mycosorb on performance and Salmonella typhimurium colonisation of piglets given diets containing low levels of T-2 toxin (83 ppb). The presence of 83 ppb T-2 toxin in the feed had a strong negative impact on growth. This negative effect was significantly counteracted by the inclusion of Mycosorb at 1 kg/ton. During the first 18 days that piglets were exposed to only T-2 toxin contaminated diets, Mycosorb improved the ADWG by 35%. After the exposure of piglets to S. typhimurium, while still being fed T-2 toxin contaminated diets, Mycosorb improved the ADWG by 56%. This improvement was highly significant and, in addition, piglets that were fed a contaminated diet and challenged with S. typhimurium but protected with Mycosorb slightly over-performed the control group of piglets.


Effects on antioxidant status


Induction of cellular oxidative stress, resulting from an increase in the production of oxygen and hydrogen radicals and a depletion of cellular defence mechanisms such as glutathione, is common following exposure to many mycotoxins (Surai, 2002). Cellular oxidative stress and enhanced radical production cause lipid peroxidation and cellular necrosis. Many mycotoxins also affect the transport of vitamins and provitamins, which encourages lipid peroxidation, impairs vital cellular function and induces programmed cell death (apoptosis) followed by cell necrosis (Fink Gremmels, 2008). Incorporation of mycotoxins into membrane structures causes various detrimental changes that are associated with peroxidation of long-chain polyunsaturated fatty acids (PUFAs; lipid peroxidation). This causes alterations in membrane permeability, flexibility and other important characteristics determining membrane function. Moreover, it is not currently clear if mycotoxins stimulate lipid peroxidation directly by enhancing free radicals production, or if the increased tissue susceptibility to lipid peroxidation is a result of a compromised antioxidant system (Surai, 2006; Figure 1).
 

Figure 1:  The main mycotoxin toxicity mechanisms (Surai, 2006)
 
Sub-clinical effects of mycotoxins can be seen in:


1)  Immune system


    •  Antibody titers after vaccination: A test that measures the presence and number of antibodies in blood. These antibodies may be against a particular type of tissue, cell, bacteria, virus or other external substance.


    •  Phagocytic activity: Counts of immunocompetent cells that are capable of phagocytosis. Phagocytosis is a process in which phagocytes engulf and digest microorganisms and cellular debris; an important defence against infection.


    •  Phagocytic index: Ability of immunocompetent cells to ingest foreign particles (bacteria, cells damaged by virus, tumorous cells, dead cells).


    •  Immunoglobulins (Ig): A protein produced by plasma cells and lymphocytes and characteristic of these types of cells. Immunoglobulins play an essential role in the body's immune system. They attach to foreign substances, such as bacteria, and assist in destroying them. The classes of immunoglobulins are termed immunoglobulin A (IgA), immunoglobulin G (IgG), immunoglobulin M (IgM), immunoglobulin D (IgD) and immunoglobulin E (IgE).


    •  Lymphocytes: A white blood cell (leukocyte) that plays a large role in defending the body against disease. Lymphocytes are responsible for immune responses. There are two main types of lymphocytes: B cells and T cells. The B cells make antibodies that attack bacteria and toxins, while the T cells attack body cells themselves when they have been taken over by viruses or have become cancerous. Lymphocytes secrete products (lymphokines) that modulate the functional activities of many other types of cells and are often present at sites of chronic inflammation.


    •  Chemotactic index: Represents the ability of the macrophages to move towards pathogen invasion sites.


2)  Antioxidant status


    •  Uric acid: The end product of purine metabolism and is normally excreted through the urine. High levels are noted in infections, kidney disease, high protein diets and with toxaemia in pregnancy.


    •  Glutathione: One of the most important cellular antioxidants.


    •  Antioxidant enzymes [Glutathione peroxidase (GPx), Superoxide dismutase (SOD), Thioredoxin reductase (TrxR), Catalase]: Molecules capable of slowing or preventing the oxidation of other molecules


    •  Malondialdehyde (MDA): The end-product of lipid peroxidation by reactive oxygen species. It is, therefore, used as a biomarker for oxidative stress of an organism.


    •  Gama-glutamyl transferase (GGT): Known to be involved in the transfer of amino acids across the cellular membrane and in glutathione metabolism. Serum GGT activity is widely used as an index of liver tissue integrity or a marker of liver dysfunction. Serum GGT activity may be an early marker of oxidative stress.


    •  Selenium: An essential trace mineral that functions largely in the form of proteins, called selenoproteins. These act as enzymes and help prevent damage to cells in the body by oxidants in the environment or those produced by normal metabolism.


    •  Vitamins (E, A): Lipid-soluble antioxidants that protect membranes from oxidation by reacting with lipid radicals produced in the lipid peroxidation chain reaction.


3)  Blood biochemistry


    •  Activities of liver enzymes [Alanine-aminotransferase (ALT), Aspartate-aminotransferase (AST), Lactate-dehydrogenase (LDH), Glutamic-oxaloacetic transaminase (GOT), Glutamic-pyruvic transaminase (GPT)]: Activities are widely used as an index of liver tissue integrity or a marker of liver dysfunction.


    •  Sphinganine to sphingosine ratio (Sa/So): In serum and urine, these are sensitive biomarkers of sub-clinical fumonisin B1 (FB1) exposure in animals. These free sphingoid bases are toxic to most cells, affecting cell proliferation and inducing apoptosis or necrotic cell death, and are associated with hepatotoxic and nephrotoxic effects.


    •  Total protein: Total amount of protein in the blood. It also measures the amounts of two major groups of proteins in the blood: albumin and globulin.


    •  Albumin/globulin ratio: The ratio of the concentrations of albumin to globulin in blood serum.


    •  Total cholesterol: A steroid metabolite found in the cell membranes and transported in the blood plasma of all animals. It is an essential structural component of mammalian cell membranes, where it is required to establish proper membrane permeability and fluidity. Cholesterol is an essential component for the manufacturing of bile acids, steroid hormones and several fat-soluble vitamins.


    •  HDL-C/Total-C: HDL-C tends to carry cholesterol away from the arteries and back to the liver, where it is passed from the body. It removes excess cholesterol from arterial plaque, slowing its build-up.


Scientific evidence


Antioxidant capacity in the intestinal mucosa of weanling piglets fed diets containing deoxynivalenol and the efficacy of Mycosorb was measured in the study by Van Le Thanh et al. (2015). Without a mycotoxin management solution, the inclusion of DON increased jejunum lipid peroxidation levels. Pigs consuming Mycosorb during the DON challenge had the lowest levels of jejunum MDA as compared with pigs that were not protected from DON.

 

Veterinarians should pay attention to:
 

    •  Very-difficult-to-see symptoms with little or no awareness.


    •  The immunity system being the only thing apparently affected.


    •  Many diseases that are incorrectly diagnosed as the primary problem due to low levels of mycotoxins that usually cause immunosuppression.


    •  No adequate response to vaccination = low titers of antibodies.


    •  Live vaccines that can have harmful effects on an animal (they have a potential to become active and cause disease, especially in animals with a weakened immune system; live vaccine is able to create immunosuppression or cause abortions in pregnant individuals).


    •  Antibiotics used as therapeutics not performing, even if used at a higher dosage or for longer periods.


    •  The transference of antibodies from breeding animals to offspring being impaired.


    •  Respiratory diseases of unknown origin or that are difficult to diagnose.
 

Table 1.  Differences between sub-acute (sub-clinical) and clinical symptoms caused by mycotoxins

 

 

Diagnosis of mycotoxin problem


    •  There are no "safe" or "unsafe" levels of mycotoxins. Low–medium levels might be much more dangerous because they are underestimated and cause sub-clinical effects, such as immune-suppression or suppression of antioxidant system functions.


    •  There is a need for reliable and readily available laboratory diagnosis of mycotoxins in feedstuff. Many mycotoxins are present in so-called "masked" or "conjugated" form, which cannot be analysed by routine analytical methods. Synergistic and additive interactions between more mycotoxins or mycotoxins and infectious agents should be taken into consideration. Alltech 37+® embraces new technologies and innovations to equip farmers and feed manufacturers with the ultimate protection tool against mycotoxin challenges. By providing actionable advice backed by data, we can now help to make more informed decisions to mitigate the threat from mycotoxins, changing the nature of business operations for the better.


    •  Veterinarians, feed company representatives and other people involved should ensure that feed samples are correctly taken, identified unmistaken and submitted to reliable analytical laboratories.


    •  Feed companies would be well advised to perform tests of either unprocessed grain or the final (pelleted or crumbled) product regularly to ensure the wholesomeness of their product. Attention to the possibility of occurrence of mycotoxins should be of particular concern. Rapid test kits based on the ELISA method and lateral flow device (LFD) are already used worldwide. Alltech® RAPIREAD™ embraces new technologies and innovations to equip farmers and feed manufacturers with the ultimate protection tool for the threat of mycotoxins. Connecting modern hardware and technology across multiple devices, Alltech RAPIREAD is a fully integrated rapid test platform that prioritises production, performance and profitability. By providing actionable advice backed by data, Alltech can now help anybody make more informed decisions to mitigate the threat from mycotoxins, changing the nature of business operations for the better.


Conclusion


It is clear that there are no safe levels of mycotoxins in animal feed. Unfortunately, it is not possible to entirely prevent the production of mycotoxins before harvest of agricultural crops, in storage or during processing operations. Nevertheless, consulting nutritionists and veterinarians, along with applying mycotoxin management solutions from Alltech, can help to minimise the effects of mycotoxin challenges.

 


For more of the article, please click here.


Article made possible through the contribution of Radka Borutova and Alltech

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