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Deoxynivalenol as a Contaminant of Broiler Feed

28 May 2012, at 12:00am

The performance and vaccine response of broilers were found by a multinational group of researchers to be modulated at concentrations of the mycotoxin, deoxynivalenol (DON), lower than previously thought to cause problems in these birds. In related work, scientists at the same institutes found evidence that the intestines of chickens may adapt to a chronic DON challenge with morphological and functional modifications.

Two papers have been published recently in the journal, Poultry Science, investigating the effects of the mycotoxin, deoxynivalenol (DON), in the feed on broilers.

In the first paper1, A.W. Yunus of the University of Veterinary Medicine in Vienna, Austria and co–authors there and at the National Agricultural Research Centre in Islamabad, Pakistan and at Kazimierz Wielki University in Bydgoszcz, Poland, examined the effects of DON on bird performance and the response to common vaccines.

The researchers explained that recent data suggest Fusarium trichothecenes may reduce broiler performance at levels previously thought not to affect this variable in chickens. In their present study, they investigated the effects of deoxynivalenol (DON), a type-B trichothecene, on broilers.

Male broilers at seven days of age were fed either a basal diet (0.265 ± 0.048mg of DON; 0.013 ± 0.001mg of zearalenone per kg), a low–DON diet (1.68mg of DON per kg; 0.145 ± 0.007mg of zearalenone per kg) or a high–DON diet (12.209 ± 1.149mg of DON per kg; 1.094 ± 0.244mg of zearalenone per kg).

Increasing levels of DON decreased the weekly weight gain linearly (P=0.041) during the first three weeks of exposure. There were no significant differences in the weight gain of the birds after week 3.

With increasing levels of DON, the titres against Newcastle disease virus increased linearly during week 2 (P=0.022) and week 4 (P=0.033) of exposure. Titres against infectious bronchitis virus, however, decreased linearly (P=0.006) during week 5 of exposure.

Serum protein concentration increased linearly (P=0.017) during week 2 and quadratically (P=0.002) during week 4 of exposure.

Yunus and co–authors concluded that, under these experimental conditions, the performance and vaccine response of the broilers were modulated to varying degrees at concentrations of DON that are currently permitted (up to 5mg per kg of diet) in many countries. Further studies are therefore required to clarify the implications of these results on the welfare of chickens, they added.

In the second paper2, the same first and last authors, together with co-workers from the same institutions and the University of Agriculture in Faisalabad and the University of Veterinary and Animal Sciences in Lahore, Pakistan, examined the effects of DON on broiler intestinal development, absorptive functionality and the metabolism of the mycotoxin.

Deoxynivalenol (DON) has been recently documented to deteriorate intestinal morphology in chickens at dietary doses that are regarded as safe for this species, they reported and so they conducted a trial to explore the significance of these morphological changes in relation to intestinal absorptive functionality and DON metabolism.

From seven days of age, Ross broilers were fed a basal diet or one with low– or high–DON, as in the first trial.

The DON diets (to variable degrees) progressively decreased the relative density (weight:length) of the small intestine with increasing exposure length, which could be correlated with a decrease in villus height in the small intestine.

Short circuit current of the jejunal epithelium, reflecting transport function of the epithelium per unit area, was reduced (P=0.001) in the birds fed the high DON diet. The increasing dietary level of DON linearly (P=0.035) increased the length of the jejunum in week 4 of exposure, resulting in conservation of macronutrient retention.

Upon challenging the birds with a fixed amount of DON after week 5 of exposure, higher (P=0.033) amounts of DON and the detoxification metabolite (de-epoxy-DON) were found at five hours post–challenge in the guts of birds raised on the DON diets. The increasing level of previous exposure to DON linearly (P=0.040) decreased the plasma level of DON in the birds at one hour post–challenge.

The amounts of zearalenone and its analogues in the gut and plasma followed a trend similar to that for DON.

From these results, Yunus and co–authors conclude the data suggest that intestines in chickens may adapt to a chronic DON challenge by morphological and functional modifications. Birds that had previous exposure to Fusarium mycotoxins showed moderate detoxification, coupled with reduced transfer of the mycotoxins to systemic circulation. Some metabolites of zearalenone found in this study were previously unknown for chickens, added the researchers.

References

1. Yunus A.W., K. Ghareeb, M. Twaruzek, J. Grajewski and J. Böhm. 2012. Deoxynivalenol as a contaminant of broiler feed: Effects on bird performance and response to common vaccines. Poult. Sci. 91(4):844-851. doi: 10.3382/ps.2011-01873. For the full paper (fee payable), click here.
2. Yunus A.W., A. Blajet-Kosicka, R. Kosicki, M.Z. Khan, H. Rehman and J. Böhm. 2012. Deoxynivalenol as a contaminant of broiler feed: Intestinal development, absorptive functionality, and metabolism of the mycotoxin. Poult. Sci. 91(4):852-861. doi: 10.3382/ps.2011-01903. For the full paper (fee payable), click here.



May 2012