Nutritional impact of mycotoxins in food animal production and strategies for mitigation

Mycotoxins are toxic secondary metabolites produced by filamentous fungi that are commonly detected as natural contaminants in agricultural commodities worldwide. Mycotoxin exposure can lead to mycotoxicosis in both animals and humans when found in animal feeds and food products, and at lower concentrations can affect animal performance by disrupting nutrient digestion, absorption, metabolism, and animal physiology. Thus, mycotoxin contamination of animal feeds represents a significant issue to the livestock industry and is a health threat to food animals. Since prevention of mycotoxin formation is difficult to undertake to avoid contamination, mitigation strategies are needed. This review explores how the mycotoxins aflatoxins, deoxynivalenol, zearalenone, fumonisins and ochratoxin A impose nutritional and metabolic effects on food animals and summarizes mitigation strategies to reduce the risk of mycotoxicity.

Dose-Effect of Zearalenone on the Localization and Expression of Growth Hormone, Growth Hormone Receptor, and Heat Shock Protein 70 in the Ovaries of Post-weaning Gilts

Zearalenone (ZEA) has an estrogen-like effect, which can injure the reproductive system of animals, causing infertility, and abortion in sows. However, the underlying mechanisms are still not clear. The objective of this study was to assess the effects of ZEA on the localization and expression of growth hormone (GH), growth hormone receptor (GHR), and heat shock protein 70 (Hsp70) in the ovaries of post-weaning gilts. Forty healthy post-weaning gilts were randomly provided one of four diets: normal basal diet supplemented with 0 (control), 0.5 (ZEA0.5), 1.0 (ZEA1.0), and 1.5 (ZEA1.5) mg ZEA/kg. Gilts were housed and fed individually for 35 days; the ovaries were collected after euthanasia for antioxidant index, relative mRNA and protein expression, and immunohistochemical analyses of GH, GHR, and Hsp70. The results revealed that the glutathione peroxidase and total superoxide dismutase levels decreased (p < 0.05), whereas the malondialdehyde level increased (p < 0.05) with increasing ZEA content. The localization pattern of GH, GHR, and Hsp70 in ZEA-treated gilts was the same as that in the control; however, the localization of yellow and brown immunoreactive substances of GH, GHR, and Hsp70 was stronger in the ZEA groups than in the control. The relative mRNA and protein expression of GHR and Hsp70 was the highest in the ZEA1.0 group (p < 0.05), whereas that of GH was the highest in the ZEA0.5 group (p < 0.05). The mRNA and protein expression of GH was lower in the ZEA1.5 group than in the control (p < 0.05). Hsp70 results showed adverse responses to increasing ZEA levels in gilt ovaries, suggesting that Hsp70 played an important role in alleviating ZEA-induced oxidative stress.

Zearalenone and Metabolites in Livers of Turkey Poults and Broiler Chickens Fed with Diets Containing Fusariotoxins

Zearalenone (ZEN) and metabolites were measured in livers of turkeys and broilers fed a control diet free of mycotoxins, a diet that contained 0.5 mg/kg ZEN (ZEN diet), and a diet that contained 0.5, 5, and 20 mg/kg of ZEN, fumonisins, and deoxynivalenol, respectively (ZENDONFB diet). The feed was individually distributed to male Grade Maker turkeys from the 55th to the 70th day of age and to male Ross chickens from the 1st to the 35th day of age, without any signs of toxicity. Together, the free and conjugated forms of ZEN, α- and β-zearalenols (ZOLs), zearalanone (ZAN), and α- and β-zearalanols (ZALs) were measured by UHPLC-MS/MS with [¹³C₁₈]-ZEN as an internal standard and immunoaffinity clean-up of samples. ZAN and ZALs were not detected. ZEN and ZOLs were mainly found in their conjugated forms. α-ZOL was the most abundant and was found at a mean concentration of 2.23 and 1.56 ng/g in turkeys and chickens, respectively. Consuming the ZENDONFB diet significantly increased the level of total metabolites in the livers of chickens. Furthermore, this increase was more pronounced for the free forms of α-ZOL than for the conjugated forms. An investigation of the presence of ZEN and metabolites in muscle with the methods validated for the liver failed to reveal any traces of these contaminants in this tissue. These results suggest that concomitant dietary exposure to deoxynivalenol (DON) and fumonisins (FB) may alter the metabolism and persistence of ZEN and its metabolites in the liver.

Toxicity of Fumonisins, Deoxynivalenol, and Zearalenone Alone and in Combination in Turkeys Fed with the Maximum European Union-Tolerated Level

Surveys of mycotoxins worldwide have shown that deoxynivalenol (DON), fumonisins (FB), and zearalenone (ZON) are the most abundant Fusarium mycotoxins (FUS) in European poultry feed, in both the level and the frequency of contamination. Previous studies reported that a combination of FUS at concentrations that individually are not toxic may negatively affect animals. However, although toxic thresholds and regulatory guidelines exist for FUS, none account for the risk of multiple contamination, which is the most frequent. The aim of this study was to compare DON, FB, and ZON toxicity, alone and in combination, in male turkey poults. Ground cultured toxigenic Fusarium strains were incorporated in corn-soybean-based feed in five experimental diets: control diet, containing no mycotoxins, DON diet (5 mg DON/kg), FB diet (20 mg FB1 + FB2/ kg), ZON diet (0.5 mg ZON/kg), and DONFBZON diet (5, 20, and 0.5 mg/kg of DON, FB1 + FB2, and ZON, respectively). Seventy male Grade Maker turkeys were reared in individual cages on mycotoxin-free diets from 0 to 55 days of age. On the 55th day, the turkeys were weighed and divided into five groups each comprising 14 birds. Each group was fed one of the five experimental diets for a period of 14 days. On the 70th day of age, feed was withheld for 8 hr, at which time a blood sample was collected, and then all the turkeys were killed, autopsied, and different tissues sampled. The weight of the different organs, analyses of performance, biochemistry, histopathology, oxidative damage, and testis toxicity revealed no significant effects attributable to FUS. Measurement of sphingolipids in the liver revealed an increase in the sphinganine to sphingosine ratio in turkeys fed diets containing FB, but had no apparent consequences in terms of toxicity. Finally, only slight differences were found in some variables and the results of this study showed no interactions between DON, FB, and ZON. Taken together, results thus suggest that the maximum tolerated levels established for individual contamination by DON, FB, and ZON can also be considered safe in turkeys fed with combinations of these FUS for a period of 14 days.

The protective effects of modified palygorskite on the broilers fed a purified zearalenone-contaminated diet

This study was conducted to evaluate the protective effects of dietary modified palygorskite (Pal) supplementation on broiler chickens fed a purified zearalenone (ZEN)-contaminated diet. A total of 144 1-day-old male chicks were allocated to one of the 3 treatments, with each treatment being composed of 6 replicates of 8 birds each. The birds were fed with a control diet (Control group), the ZEN-contaminated diet (2.0 mg ZEN/kg diet), and the ZEN-contaminated diet supplemented with 1.0 g/kg diet of modified Pal for 42 d, respectively. Compared with control group, feeding ZEN-contaminated diet reduced weight gain and feed conversion efficiency of broilers during the finisher and overall experimental period (P < 0.05), while the values of these parameters in broilers fed the diet contaminated with ZEN increased after modified Pal administration (P < 0.05). ZEN challenge increased the 21-d serum aspartate aminotransferase and 42-d serum alanine aminotransferase activities, 42-d relative liver weight, and ZEN residues in the liver at both 21 and 42 d and kidney at 42 d (P < 0.05). In contrast, birds fed the ZEN-contaminated diet that was supplemented with modified Pal exhibited lower serum alanine aminotransferase activity at 42 d, relative liver weight at 42 d, and hepatic and renal ZEN accumulation at both 21 and 42 d (P < 0.05), when compared with their counterparts fed the contaminated diet. ZEN contamination decreased superoxide dismutase activity in the serum at 21 d, kidney at 42 d, and liver at both 21 and 42 d, respectively (P < 0.05). The hepatic and renal malondialdehyde accumulation at 42 d increased, while renal glutathione level at 42 d decreased, when feeding broilers with the ZEN-contaminated diet (P < 0.05). Dietary modified Pal supplementation reduced hepatic malondialdehyde accumulation, whereas increased renal superoxide dismutase activity in broilers fed a ZEN-contaminated diet at 42 d (P < 0.05). This finding suggested that dietary modified Pal administration could promote growth performance, reduce hepatonephric ZEN residues, and improve liver function and antioxidant status of broiler chickens receiving a ZEN-contaminated diet.

Fumonisin B1, B2 and B3 in Muscle and Liver of Broiler Chickens and Turkey Poults Fed with Diets Containing Fusariotoxins at the EU Maximum Tolerable Level

Although provisional maximum tolerable daily intake and recommended guidelines have been established for fumonisins (FB) in food, few data are available concerning levels of FB in edible animal tissues. Such data are of particular interest in avian species that can tolerate relatively high levels of fumonisins in their feed. Also, even if multiple contamination of animal feed by toxins produced by Fusarium is very frequent, little is known about the consequences of multiple contamination for FB levels in tissues. The aim of this study was to analyze the concentrations of FB in the muscle and liver of chickens and turkeys fed with FB alone and with FB combined with deoxynivalenol (DON), and with zearalenone (ZEN). Experimental diets were formulated by incorporating ground cultured toxigenic Fusarium strains in corn-soybean based feeds. Control diets were free of mycotoxins, FB diets contained 20 mg FB1+FB2/kg, and FBDONZEN diets contained 20, 5, and 0.5 mg/kg of FB1+FB2, DON, and ZEN, respectively. Animals were reared in individual cages with free access to water and feed. The feed was distributed to male Ross chickens from the 1st to the 35th day of age and to male Grade Maker turkeys from the 55th to the 70th day of age. On the last day of the study, the birds were starved for eight hours, killed, and autopsied for tissues sampling. No sign of toxicity was observed. A UHPLC-MS/MS method with isotopic dilution and immunoaffinity clean-up of samples has been developed for analysis of FB in muscle (n = 8 per diet) and liver (n = 8 per diet). Only traces of FB that were below the LOQ of 0.25 µg/kg were found in most of the samples of animals fed with the control diets. Mean concentrations of FB1, FB2, and FB3 in muscle were 17.5, 3.39, and 1.26 µg/kg, respectively, in chickens, and 5.77, 1.52, and 0.54 µg/kg in turkeys, respectively. In the liver, the respective FB1, FB2, and FB3 concentrations were 44.7, 2.61, and 0.79 µg/kg in chickens, and 41.47, 4.23, and 1.41 µg/kg, in turkeys. Cumulated level of FB1+FB2+FB3 in the highly contaminated samples were above 60 and 100 µg/kg in muscle and liver, respectively. The concentrations of FB in the tissues of animals fed the FBDONZEN diet did not greatly differ from the concentrations measured in animals fed the diet containing only FB.

Lack of Toxic Interaction Between Fusariotoxins in Broiler Chickens Fed throughout Their Life at the Highest Level Tolerated in the European Union

Fusarium mycotoxins (FUS) occur frequently in poultry diets, and regulatory limits are laid down in several countries. However, the limits were established for exposure to a single mycotoxin, whereas multiple contamination is more realistic, and different studies have demonstrated that it is not possible to predict interactions between mycotoxins. The purpose of this study was thus to compare the toxic effect of deoxynivalenol (DON), fumonisins (FB) and zearalenone (ZON), alone and in combination on broiler chickens, at the maximum tolerated level established by the EU for poultry feed. Experimental corn-soybean diets incorporated ground cultured toxigenic Fusarium strains. One feed was formulated for chickens 0 to 10 days old and another for chickens 11 to 35 days old. The control diets were mycotoxin free, the DON diets contained 5 mg DON/kg, the FB diet contained 20 mg FB1 + FB2/kg, and the ZON diet contained 0.5 mg ZON/kg. The DONFBZON diet contained 5, 20, and 0.5 mg/kg of DON, FB1 + FB2, and ZON, respectively. Diets were distributed ad libitum to 70 broilers (male Ross PM3) separated into five groups of 14 chickens each reared in individual cages from one to 35 days of age. On day 35, after a starvation period of 8 h, a blood sample was collected, and all the animals were killed and autopsied. No difference between groups that could be attributed to FUS was observed in performances, the relative weight of organs, biochemistry, histopathology, intestinal morphometry, variables of oxidative damage, and markers of testicle toxicity. A significant increase in sphinganine and in the sphinganine to sphingosine ratio was observed in broilers fed FB. Taken together, these results suggest that the regulatory guidelines established for single contamination of broiler chickens fed with DON, FB, and ZON can also be used in the case of multiple contamination with these toxins.

Effects of zearalenone on the localization and expression of the growth hormone receptor gene in the uteri of post-weaning piglets

OBJECTIVE

In this study, we investigated the adverse effects of dietary zearalenone (ZEA) (0.5 to 1.5 mg/kg diet) on the localization and expression of the growth hormone receptor (GHR) in the uteri of post-weaning gilts and explored alternative mechanism of the reproductive toxicity of ZEA on piglets.

METHODS

A total of forty healthy piglets (Duroc×Landrace×Large White) aged 28 d were selected for study. Piglets were transferred to single cages after 10 days' adaptation on an obstetric table. The animals were allocated to one of four treatments: a normal basal diet supplemented with 0 (Control), 0.5 (ZEA0.5), 1.0 (ZEA1.0), or 1.5 (ZEA1.5) mg/kg purified ZEA, and fed for 35 d after the 10-d adaptation. Analyzed ZEA concentrations in the diets were 0, 0.52±0.07, 1.04±0.03, and 1.51±0.13 mg/kg, respectively. At the end of the feeding trial, piglets were euthanized after being fasted for 12 h. Two samples of uterine tissue from each pig were rapidly collected, one of which was stored at -80°C for analysis of the relative mRNA and protein expression of GHR, and the second was promptly fixed in Bouin's solution for immunohistochemical analysis.

RESULTS

The relative weight of the uteri and thickness of the myometrium and endometrium increased linearly (p<0.001) and quadratically (p<0.001) with an increasing level of ZEA. The results of immunohistochemical analysis indicated that GHR immunoreactive substance was mainly localizated in the cytoplasm of uterine smooth muscle, glandular epithelial, luminal epithelial, stromal, and vascular endothelial cells. In contrast, nuclear staining was rarely observed. The immunoreactive integrated optic density of GHR in the myometrium, luminal epithelium, glandular epithelium, and whole uteri of weaning gilts increased linearly (p<0.001) and quadratically (p<0.05) with an increasing level of ZEA. The mRNA and protein expression of GHR in the uteri of weaning gilts increased linearly (p<0.001) and quadratically (p<0.05) with an increasing level of ZEA.

CONCLUSION

In conclusion, ZEA at a concentration of 0.5 mg/kg was sufficient to significantly thicken the myometrium and endometrium, and at a concentration of 1.0 mg/kg induced a high level of GHR expression to promote growth and development of the uteri. This revealed an alternative molecular mechanism whereby ZEA induces growth and development of the uteri and provides a theoretical basis for the revision of Chinese feed hygiene standards.

Effects of naturally mycotoxin-contaminated corn on nutrient and energy utilization of ducks fed diets with or without Calibrin-A

One hundred sixty-two 21-d-old ducks were randomly allotted to 6 treatments with 3 levels of mycotoxin-contaminated corn (0, 50, and 100% M) and 2 levels of Calibrin-A (CA, a clay mycotoxin adsorbent, 0 and 0.1%) to evaluate the effects of increasing levels of mycotoxin-contaminated corn on nutrient utilization in ducks fed diets with or without CA. Endogenous losses were obtained from another 27 ducks. Excreta samples were collected to determine DM, OM, CP, amino acids, and gross energy. Gross energy was analyzed for computation of AME and TME. The apparent digestibility (AD) and true digestibility (TD) of the nutrients in all treatments with and without CA had common (P > 0.05) intercepts and slopes except Pro (P < 0.05). The AME, TME, AD, and TD of DM, OM, Phe, and Gly were linearly (P < 0.05) decreased as the concentration of contaminated corn in the diet increased. Ducks fed the 100% M diet supplemented with 0.1% CA increased AD and TD of Gly compared with the 100% M diet, and ducks fed 50 and 100% M diet supplemented with 0.1% CA increased AD and TD of Pro compared with 50% M and 100% M diet, respectively. In the present study, ducks fed mycotoxin-contaminated corn decreased nutrient digestibility in dose-dependent manner, and 0.1% CA supplementation improved AD and TD of Gly and Pro.

Toxicity of increasing aflatoxin B1 concentrations from contaminated corn with or without clay adsorbent supplementation in ducklings

A total of 1,280 1-d-old ducks were used in a study to investigate the effects of increasing aflatoxin B1 (AFB1) concentrations from naturally contaminated corn on young ducklings, and the effectiveness of a clay adsorbent (CA) to protect against those effects. Ducks were randomly allotted to 8 treatments (TRT) in a 4 × 2 factorial arrangement with 4 levels of AFB1 (0, 25, 50, and 100 μg/kg) and 2 levels of CA (0 and 0.1%) with 8 pens per TRT and 20 ducks per pen. All ducks were allowed ad libitum access to feed and water during the 21-d experiment. The ADG, ADFI, feed conversion rate, mortality, bill color, and CV of BW of each replicate were measured at the end of the study. Blood and tissue samples from 8 ducks per TRT were obtained on d 21 of the experiment to determine the serum immunoglobulin and protein concentrations, relative organ weights, and intestinal morphology. Average daily gain and relative weights of the liver, spleen, thymus, and bursa of Fabricius decreased linearly (P < 0.05) as dietary AFB1 increased. Serum proteins and intestinal villi heights and villus/crypt ratio followed the same pattern. Bill decolorization ratio, CV of BW, and mortality increased linearly (P < 0.05) as dietary AFB1 increased. Adding 0.1% CA to the diet improved (P < 0.05) the relative weights of the small intestine, spleen, and thymus, and the villus height and villus/crypt ratio of the duodenum and jejunum, as well as the serum IgG and IgM concentrations. Adding CA also reduced (P < 0.05) bill decolorization ratio, CV of BW, mortality, and serum IgA concentration. Therefore, duck performance was negatively affected by increasing AFB1 concentrations in diets. But the addition of 0.1% CA can protect against the detrimental effects caused by AFB1-contaminated corn in diets for ducks.