Mycotoxins in swine feed
Mycotoxicosis in swine
Pigs are considered highly susceptible to mycotoxin contamination, with young animals and female breeders being the most sensitive groups. Mycotoxin can cause clinical symptoms or subclinical decreasing animal performance leading to great economic losses.
Effects of mycotoxins in swine / mycotoxins symptoms in pigs
Mycotoxins target many organs and tissues and systems, liver, gut, kidneys, reproductive and immune system. The outcome is decreased performance, higher sensitivity to pathogens and reducing vaccination response.
Symptoms vary considerably depending on which mycotoxin is responsible and can range from fertility and reproductive problems, reduced productivity, suppressed immunity and various pathological effects on organs and tissues.
Zearalenone and pigs
Zearalenone (ZEN) can have a significant impact on reproductive performance, 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, disturbing hormonal homeostasis.
ZEN can cause abortions, light litters and stillbirths In addition, ZEN contaminated feed induces the swelling and reddening of vulva (hypoestrogenism), false heats and pseudopregnancy. Studies investigating the carry-over of ZEN into meat and other edible tissues showed that there is only limited tissue deposition of this mycotoxin.
Table 1. Effects of ZEN in swine | Source: BIOMIN
Affects reproduction cycle, conception, ovulation and implantation
Atrophy of ovaries
Effects of zearalenone on swine fertility
Pigs are very sensitive to zearalenone (ZEN). ZEN increases the frequency of abortions and stillbirths in pregnant sows. In general, ZEN-contaminated pig feed induces:
- swelling and reddening of the vulva
- false heats
- false pregnancy
Effects of zearalenone on gilts
Due to their undeveloped endocrine system, gilts are even more sensitive to ZEN’s estrogenic effect. The results of ZEN ingestion are hyperaemia and vulva swelling (hyperestrogenism); uterus mass increase; ovarian follicle atresia and atrophic ovaries; vaginal or rectal prolapse. Hyperestrogenism would delay oestrus onset and would compromise fertility in subsequent reproductive life of gilt.
- hyperaemia and vulva swelling (hyperestrogenism)
- uterus mass increase
- ovarian follicle atresia and atrophic ovaries
- vaginal or rectal prolapse.
Effects of aflatoxins on pigs
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.
Piglets fed aflatoxin-contaminated diets which were vaccinated with ovalbumin, showed decreased cell-mediated immunity and impaired lymphocyte activation. Thymus weight and histopathology, as well as viable alveolar macrophages were negatively influenced. In addition, cases of aflatoxin carry-over in swine have been reported with residues found in porcine liver and muscle tissues.
Effects of fumonisins on pigs
Numerous studies have confirmed the link between porcine pulmonary edema (PPE) and fumonisin intoxication. Severe lung edemas, liver and pancreas injuries, performance decreases and immune suppression were observed in exposed animals, even at low doses. 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.
Fumonisins impair 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. 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.
Effects of ochratoxin A on pigs
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. This mycotoxin was observed to suppress cell-mediated immune response in pigs, resulting in reduced macrophage activity and weakened stimulation of lymphocytes. 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.
Effects of deoxynivalenol on pigs
Pigs show a high sensitivity to deoxynivalenol (DON). The most frequently observed effects of deoxynivalenol consumption in swine are:
- Growth reduction (anorexia and decreased nutritional efficiency)
- Protein synthesis inhibition
- Gut barrier disruption
- Impaired immune function (enhancement and suppression)
- Decreased reproductive performance
Deoxynivalenol inhibits intestinal nutrient absorption and alters intestinal cell and barrier functions. 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. Concerning influence on immunity, trichothecenes in general reduce lymphocyte proliferation, macrophage activity and antibody response to certain vaccinations and influenced immunoglobulin levels.
Synergistic effects of mycotoxins in pigs
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 Figure 1.
Reproductive performance of sows exposed to Fusarium toxins
In a recent trial contracted by BIOMIN at the University of Berlin, the reproductive performance of sows was evaluated in the presence of DON and ZEN during a long-term (three-cycle) exposure to Fusarium toxins. Sows were allocated to one of three different groups (Table 2).
Table 2. Summary of trial groups and diets | Source: BIOMIN
Feed not contaminated
Feed contaminated with DON at high levels and ZEN at medium levels
Feed contaminated with DON at high levels and ZEN at medium levels and supplemented with Mycofix® Plus
The presence of mycotoxins impaired different reproductive performance parameters as shown in Figure 2. The most commonly used index for assessing reproductive performance is the number of weaned piglets per sow per year. Farrowing rate and wean to estrus interval both affect this index. The presence of mycotoxins, especially ZEN, increased the returns to heat of inseminated sows and decreased the farrowing rate.
The drop in feed intake affected the body condition score of the sows at weaning and milk yield. Underweight sows need more days to come into estrus after weaning. This decreases the number of farrowings per year, meaning there are fewer weaned piglets produced per sow per year. In addition, lower milk yields could compromise litter growth and weaning weights, resulting in lower weights at slaughter or more days in feed.
The presence of mycotoxins also compromised piglet quality (Figure 3). The percentage of underweight piglets (<1.2 kg) increased, implying that mycotoxins have a negative effect on embryo development and maternal nutrition. The negative effect on piglet quality accompanied with a depletion of milk yield may result in higher pre-weaning mortality and lower weaning weights.
However, a sound recovery was observed when Mycofix® Plus was applied.
Diagnosis of mycotoxicosis in pigs
Mycotoxicoses are caused by ingestion of mycotoxins, inhalation or contact with the skin. The effects of mycotoxins in swine are diverse, varying from immunosuppression to death in severe cases, depending on toxin-related (type of mycotoxin consumed, level and duration of intake), animal-related (animal species, sex, age, breed, general health, immune status, nutritional standing) and environmental (farm management, biosecurity, hygiene, temperature) factors. This fact often impedes correct attribution of problems caused by mycotoxins.
Much attention should be given to the so-called “conditioned” diseases—for example, Erysipelas, E.coli, Salmonella, Influenza, Pasteurella and Streptococcus. These diseases are triggered by a stress stimulus. Mycotoxins have been shown to be a sufficient and necessary condition to set aflame such infections.
Mycotoxin risk management for pigs
When it comes to counteracting mycotoxins, pig industry tends to think of toxin binders or mycotoxin binders first. (Learn the truth about mycotoxin binders).
However, clay mineral binders are not an effective answer to all major mycotoxins. Especially not against Trichothecenes since their structures are not suitable for adsorbing by binders.
Biotransformation using microbes and enzymes is the most effective strategy. It provides reliable protection for pigs against Fusarium mycotoxins by biodegrading mycotoxins into non-toxic metabolites. The transformation is fast, specific and irreversible.
In addition to biotransformation, a bioprotection strategy is also important. Variety of feed additives is available that contains plant and algae extracts to provide a hepato-protective effect and to overcome the immune suppression caused by mycotoxins.
A combination of different strategies can counteract the negative effects of mycotoxins in pigs more completely, especially in cases of multi-mycotoxin contamination with the poorly absorbed Fusarium mycotoxins in swine feed.