The effects of feed-borne Fusarium mycotoxins and glucomannan in turkey poults based on specific and non-specific parameters

Highlights

• Effects of DON on unspecific and specific parameters in turkey poults was studied.

• The efficacy of a GMA mycotoxin binder on these parameters was evaluated.

• GMA could alleviate some negative effects of DON on unspecific parameters.

• GMA did not prevent intestinal absorption of DON or its metabolite DOM-1.

Abstract

An experiment was conducted to investigate the effects of feeding grains naturally contaminated with Fusarium mycotoxins and a yeast derived glucomannan mycotoxin adsorbent (GMA) on selected specific and non-specific parameters in turkey poults. Two hundred and forty 1-day-old male turkey poults were fed the experimental diets for twelve weeks. Experimental diets were formulated with control grains, control grains + 0.2% GMA, naturally-contaminated grains, or naturally-contaminated grains + 0.2% GMA. Deoxynivalenol (DON) was the major contaminant of the contaminated grains and concentrations varied from 4.0 to 6.5 mg/kg in the contaminated diets. Non-specific parameters measured included: performance parameters, plasma biochemistry profiles, morphometry and CD8⁺ T-lymphocyte counts in the duodenum. Plasma concentrations of DON and de-epoxydeoxynivalenol (DOM-1) were used as specific parameters. Performance parameters and plasma biochemistry were altered by the feeding of contaminated diets and GMA but this was not consistent throughout the trial. The feeding of contaminated diets reduced duodenal villus height and apparent villus surface area. This effect was prevented by GMA supplementation. The feeding of contaminated diets elevated total duodenal CD8⁺ T-lymphocyte counts but this effect was not prevented by GMA. No significant differences were seen in plasma concentrations of DON and DOM-1 comparing birds fed contaminated and contaminated + GMA diets suggesting that GMA did not prevent DON absorption under these conditions.

Introduction

Mycotoxins are secondary metabolites produced by toxigenic fungal species. Fusarium fungi frequently infest crops in temperate regions such as Western Europe and North America. The produced mycotoxins (mostly trichothecenes, zearalenone (ZON) and fumonisins (Fig. 1)) can cause deleterious effects on animal health after oral intake of these toxins. Symptoms can vary from vomiting and feed refusal, to estrogenic effects and reduced performance, depending on the toxin and sensitivity of the animal species. In general, feed contamination with mycotoxins leads to important economic losses in animal production (Wu, 2007). A variety of methods to prevent the adverse effects of mycotoxins have been developed. Mycotoxin detoxifying agents (mycotoxin detoxifiers) are the most commonly used preventative method (Jard et al., 2011, Kolosova and Stroka, 2011). These detoxifiers can be classified as mycotoxin binders and mycotoxin modifiers. Mycotoxin binders adsorb the toxin in the gut, resulting in the excretion of toxin-binder complex in faces, whereas mycotoxin modifiers transform the toxin into non-toxic metabolites (Kolosova and Stroka, 2011).

Mycotoxin detoxifiers should be tested for their mycotoxin binding or degrading ability in vitro as well as in vivo. In vitro models are a powerful tool to screen and select a large number of compounds (Devreese et al., 2013). Only in vivo trials, however, can fully proof the efficacy of mycotoxin detoxifiers as mycotoxin adsorbents or biotransforming agents as in vivo studies are influenced by physiological variables and the composition of feed (Lemke et al., 2001). Mycotoxin detoxifiers are currently evaluated in vivo by non-specific parameters. Those include animal performance (e.g. growth rate, feed intake and feed conversion rate), plasma biochemistry (e.g. concentrations of proteins and minerals and enzyme activities), effects on immune function and tissue histological changes. As the criteria are non-specific, differences obtained between treated and untreated animals cannot be solely attributed to the efficacy of the detoxifier. There may be confounding effects such as immuno-modulating activity of β-glucans and antioxidant action of other feed components. Due to the lack of specificity of these parameters, the European Food Safety Authority (EFSA) recently proposed other end-points based on specific toxicokinetic parameters (EFSA, 2010). As mycotoxin binders are deemed to adsorb mycotoxins in the gut, a lowered intestinal absorption is expected. According to the EFSA, the most relevant parameter to evaluate the efficacy of these products against mycotoxins is the plasma concentration of these toxins or their main metabolites (Devreese et al., 2012).

The goal of the present study was: (1) to determine the effects of diets naturally contaminated with Fusarium mycotoxins, mainly DON, on specific and non-specific parameters on turkey poults, and (2) to evaluate the efficacy of a yeast derived glucomannan mycotoxin binder (GMA). The selection of non-specific parameters for this trial was based on previous research (Girish and Smith, 2008, Girish et al., 2008, Girish et al., 2010, Yunus et al., 2012a, Yunus et al., 2012b). These included performance parameters, plasma biochemistry profile, intestinal morphometry and CD8⁺ cell population in the duodenum. Specific parameters, plasma concentrations of DON and its main metabolite de-epoxydeoxynivalenol (DOM-1), were selected as advised by the EFSA (EFSA, 2010).