Toxicity of different Fusarium mycotoxins on growth performance, immune responses and efficacy of a mycotoxin degrading enzyme in pigs (Extract)

Deoxynivalenol and fusaric acid have been shown to sequentially elevate brain tryptophan, serotonin (5-hydroxytryptamine, 5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) concentrations, and these neurotransmitters can lead to a decrease in feed intake.

Zearalenone (ZON) and its metabolites (α- and β-zearalenol), α-zearalenol is the predominant metabolite of ZON in pigs. The ZON and its metabolites disrupt reproductive processes via mimicking of the action of estradiol-17β depending on the reproductive status (pre-pubertal, cycling or pregnant) of the affected animal.

This study was aimed at investigating the effects of a defined concentration of Fusarium mycotoxins, deoxynivalenol (DON) and zearalenone (ZON) incorporated into feeds on growth performance, blood biochemistry, and immune response of pigs and the alleviating effects of a mycotoxin degrading enzyme (MDE) on the toxicity of Fusarium mycotoxins.

1. A total of 48 weaning pigs was randomly allotted to four treatments (two replicates per treatment) including a control, Toxins (1 ppm DON and 250 ppb ZON), Toxin+MDE (1 ppm DON, 250 ppb ZON and 1.5 kg MDE per ton of feed), and MDE alone (1.5 kg per ton of feed) for a 6 week challenged trial.

2. The MDE product was a kind of mycotoxin degradation enzyme with esterase, epoxidase and peptidase activity.

3. Zootechnical parameters: the body weights and feed intakes of the pigs were measured at the 16th, 28th day and the end of the experiment. Three pigs were sacrificed per pen for the determinations.

The results of DON and ZON on growth performance in pigs are summarized in Table I. There were significantly lower (P < 0.05) body weight gains at the 16th day and final day of the experimental period in the Toxins group compared to the other treatments. The results in the growth performance revealed that DON and ZON hampered growth response in pigs as early as the 16th day of the experiment. This could be due to feed refusal behavior caused by DON toxicity. The worst feed efficiency in group Toxins also reflects the toxicity of DON and ZON mycotoxins. The MDE incorporated in the feed with mycotoxins (Toxins+MDE) counteracted the negative effects from mycotoxins, there was no negative effect on growth performance in the MDE alone. Observations on the 7th day of the experiment were obvious vulva swelling seen in female pigs lasting until the end of the experiment in the Toxins group, however, no similar symptoms were observed in the other groups.

Table II summarizes the effect of DON and ZON on some serum biochemistry in pigs. Group Toxins had the lowest level of total protein, albumin and globulin among the treatments. However, in the γ-glutamyltransferase (GGT), AST and ALT assay, the DON and ZON challenged (Toxins) group, show the highest enzyme activity in the serum, increased 2.3–2.6 fold compared to the control group. Even though MDE was incorporated in the diets (Toxins+MDE) at 1.5 kg per ton, the addition of MDE could not counteract the detrimental effect in GGT and AST, except in ALT.

The results of alveolar macrophage activity in pigs are shown in Table III. In evaluation of chemotaxic ability, DON and ZON (Toxins) significantly impaired the ability of chemotaxis and showed only 49% in comparison with the control group. However, MDE incorporated in mycotoxin groups obviously alleviated the abilities of chemotaxis and phagocytosis, similar to the control group. A similar trend was also found in the percentage of phagocytic macrophages; for the Toxins group a significantly lower level was recorded than that of the control, indicating that these phenomena might be due to the inhibition of phagocytic ability and lower numbers of functional intact cells.

PR Vaccine was challenged on day 7 and 14 of the experiment, and serum was collected on the 14th and 28th day after vaccine inoculation. The effects of DON and ZON on anti-pseudorabies titer production of pigs are shown in Table IV. Generally, PR antibody titers were significantly decreased on day 28 and overall means in the Toxins group compared to that of the control. Some improvement was also noted when MDE was incorporated in the Toxins+MDE group, however, no significant difference in comparison with the Toxins group was found.

Table I. Effects of DON and ZON on growth performance in pigs.

Table II. Effects of DON and ZON on some serum biochemistry parameters in pigs.

Table III. Effects of DON and ZON on alveolar macrophage activities in pigs.

Table IV. Effects of DON and ZON on anti-pseudorabies titer production of pigs.

The results of tested cytokine gene expression in the spleen of pigs are illustrated in Figure 1. All data are expressed as relative intensities of beta-actin, a housekeeping gene. DON and ZON challenged groups almost decreased the expression levels of all cytokines in this study, especially IFN-γ, TNF-α, IL-1β, IL-2 and IL-6 had a much lower level. Interestingly, IFN- γ, IL-1β, and iNOS cytokine expressions were elevated by MDE alone and were even higher than the control group. An improvement of mRNA in different cytokines was observed in the Toxins+MDE group, this implies that MDE could alleviate the impairment effect in cytokine expression from toxins.

Figure 1. Quantification of regulatory and inflammatory cytokine mRNA levels in the spleen of pigs.

Error bars represent the mean ± SD of these results for different treatment (n = 4).

The results in different criteria including growth performance, serum biochemistry parameters, alveolar macrophage activity, antibody titers of pseudorabies (PR) vaccine and cytokine secretion profile showed that DON and ZON consistently impaired pigs after 6-week exposure. Based on these findings, we suggest that the combination of DON and ZON confers a chemical multi-organ toxicity in pigs and MDE provides a partial or complete toxic sparing effect of mycotoxins.