In general, pigs are considered highly susceptible to mycotoxin contamination, with young animals and female breeders being the most sensitive groups.
Aflatoxins can cause death when administered at high levels, but the greatest impact comes from reduced reproductive and performance capabilities, suppressed immune function and various pathological effects on organs and tissues.1 Piglets fed aflatoxin-contaminated diets which were vaccinated with ovalbumin, showed decreased cell-mediated immunity and impaired lymphocyte activation.2 Thymus weight and histopathology, as well as viable alveolar macrophages were negatively influenced.3,4 In addition, cases of aflatoxin carry-over in swine have been reported with residues found in porcine liver and muscle tissues.5
Agalactia (due to interference with the release of prolactin), feed refusal and consequent weight gain reductions are classical signs of ergot alkaloid intoxication.28,29,30 Other frequently noted symptoms have been observed in the cardiovascular and central nervous system because of increased blood pressure, causing vasoconstriction and strong uterotonic effects, resulting in stillbirths and reduced pregnancy rates.30,31 Recent studies suggest that carry-over of ergot alkaloids in pigs is negligible, as no residues were detected in meat, back fat and blood serum in animals fed the highest experimental dose of about 12 mg ergot alkaloids per day.32
Fumonisins exposure represents an issue in swine production. Numerous studies have confirmed the link between porcine pulmonary edema (PPE) and fumonisin intoxication.20 Severe lung edemas, liver and pancreas injuries, performance decreases and immune suppression were observed in exposed animals, even at low doses.20,21,22,23,24 Chronic exposure to fumonisin B1 (FB1), decreased the proliferation of undifferentiated porcine epithelial intestinal cells, altered the integrity of the intestinal epithelium and consequently facilitated the intrusion of pathogens into the body.25 Fumonisins impaire vaccination response, reduce the level of several specific antibodies and the period of vaccine protection. The carry-over of fumonisins in sow milk and pork meat (mainly liver and kidneys), may only occur after a high level of exposure over a longer period.5,21,26 On the other hand, the recently discovered hydrolyzed form of fumonisin B1 caused neither intestinal nor hepatic toxicity and did not impair the intestinal morphology of pigs.27
Hepatotoxic effects, decreased performance parameters, nephrotoxicity and necrosis are the major toxic effects caused by Ochratoxin A. In addition, pigs showed a significant and linear reduction of daily gain with increasing doses of ingested ochratoxin A.14,15,16 This mycotoxin was observed to suppress cell-mediated immune response in pigs, resulting in reduced macrophage activity and weakened stimulation of lymphocytes.17 Furthermore, ochratoxin A tends to accumulate in kidneys, liver and muscle tissues, as well as in blood serum and, therefore, it represents a potential hazard in the human food chain.15
Among animal species, pigs show a high sensitivity to deoxynivalenol (DON). Therefore, growth reduction (anorexia and decreased nutritional efficiency), impaired immune function (enhancement and suppression), and decreased reproductive performance (reduced litter size) are the most frequently observed effects.6 Moreover, it has been demonstrated that deoxynivalenol inhibits intestinal nutrient absorption and alters intestinal cell and barrier functions.7,8 The highest residues of deoxynivalenol were detected in bile, followed by the kidneys and serum. Residues were detected in the liver and in muscle tissue as well.9 Concerning influence on immunity, trichothecenes in general reduce lymphocyte proliferation, macrophage activity and antibody response to certain vaccinations and influenced immunoglobulin levels.10,11,12,13
Despite relatively low levels of acute toxicity, Zearalenone (ZEN) can have a significant impact on swine reproduction, as pigs are among the most sensitive species to this mycotoxin. Negative effects are due to the interaction of ZEN and its metabolites with estrogen receptors. ZEN increases the frequency of abortions and stillbirths in pregnant sows. In general, ZEN contaminated feed induces the swelling and reddening of vulva, false heats and false pregnancy.18 Studies investigating the carry-over of ZEN into meat and other edible tissues showed that there is only limited tissue deposition of this mycotoxin. Furthermore, no transfer of ZEN and its major metabolites into serum was detected after a ZEN administration of 56 ppb.19
About 80% of swine diseases are related to the mismanagement of feed quality, reproduction, housing conditions and biosecurity, with only 20% due to viral, bacterial or parasitic pathogens. Toxicological interactions between mycotoxins enhance the toxic effects even at low levels. Fusarium graminearum and Fusarium culmorum are known to produce several different fusariotoxins, including zearalenone and deoxynivalenol, which are known to interact synergistically in swine. In addition, the analysis of deoxynivalenol often indicates the co-occurrence of other fusariotoxins such as other trichothecenes (T-2 toxin, nivalenol, diacetoxyscirpenol), zearalenone and fumonisins.
A summary on the synergistic and additive effects of mycotoxins in pigs is presented in the figure below.
Figure 1: Synergistic and additive effects in pigs
AFB1 – Aflatoxin B1; Fb1 – Fumonisin B1; DON – Deoxynivalenol; OTA – Ochratoxin A; ZEN – Zearalenone; FA – Fusaric acid; DAS – Diacetoxyscirpenol; CPA – Cyclopiazonic acid; MON - Moniliformin
Red line: synergistic effect
Dashed line: additive effect
AFB1 – Aflatoxin B1 | AFM1 – Aflatoxin M1 | DON – Deoxynivalenol | FUM – Fumonisins | OTA – Ochratoxin A | T-2 – T-2 Toxin | HT-2 – HT-2 Toxin | ZEN - Zearalenone | Ergots – Ergot, Alkaloids