Abstract
Deoxynivalenol (DON) and fumonisins (FB) are the most frequently encountered mycotoxins produced by Fusarium species in livestock diets. The effect of subclinical doses of mycotoxins in chickens is largely unknown, and in particular the susceptibility of birds to pathogenic challenge when fed these fungal metabolites. Therefore, the present study reports the effects of DON and FB on chickens challenged with Eimeria spp, responsible for coccidiosis. Broilers were fed diets from hatch to day 20, containing no mycotoxins, 1.5 mg DON/kg, 20 mg FB/kg, or both toxins (12 pens/diet; 7 birds/pen). At day 14, six pens of birds per diet (half of the birds) were challenged with a 25×-recommended dose of coccidial vaccine, and all birds (challenged and unchallenged) were sampled 6 days later. As expected, performance of birds was strongly affected by the coccidial challenge. Ingestion of mycotoxins did not further affect the growth but repartitioned the rate of reduction (between the fraction due to the change in maintenance and feed efficiency), and reduced apparent nitrogen digestibility. Intestinal lesions and number of oocysts in the jejunal mucosa and feces of challenged birds were more frequent and intense in the birds fed mycotoxins than in birds fed control feed. The upregulation of cytokines (interleukin (IL) IL-1β, IL-6, IL-8 and IL-10) following coccidial infection was higher in the jejunum of birds fed mycotoxins. Further, the higher intestinal immune response was associated with a higher percentage of T lymphocytes CD4+CD25+, also called Tregs, observed in the cecal tonsils of challenged birds fed mycotoxins. Interestingly, the increase in FB biomarker of exposure (sphinganine/sphingosine ratio in serum and liver) suggested a higher absorption and bioavailability of FB in challenged birds. The interaction of DON and FB was very dependent on the endpoint assessed, with three endpoints reporting antagonism, nine additivity, and two synergism. In conclusion, subclinical doses of DON and FB showed little effects in unchallenged chickens, but seem to result in metabolic and immunologic disturbances that amplify the severity of coccidiosis.
Highlights
Mycotoxins are structurally diverse low-molecular weight metabolites produced by various molds belonging to the Aspergillus, Penicillium, or Fusarium species
Investigations are growing in the field of gut health, and recent reports on mycotoxins have primarily focused on their effects in the gastro-intestinal tract (GIT)
There was no significant difference between the diets, the relationship between the change in growth and feed intake of birds challenged with the coccidial vaccine was different between diets (Figure 1)
Summary
Mycotoxins are structurally diverse low-molecular weight metabolites produced by various molds belonging to the Aspergillus, Penicillium, or Fusarium species. Feeding trials conducted prior to the 1990s have used different strains of birds, and it has been noted a differential sensitivity to mycotoxins, especially aflatoxins, between traditional and modern poultry production [11]. This might be a consequence of genetic selection for rapid growth which may have altered metabolic and nutrient partitioning, and has long-been criticized in reducing immunity [12]. DON and FB are very poorly absorbed (approximately 10% and 1%, respectively), inferring that a substantial part of mycotoxins remains in the GIT and expose the intestinal cells to high concentrations of toxins. This might result in the impairment of intestinal functions, and favor the growth and colonization of digestive pathogens in poultry
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