Clint Lichty from Southwest Ontario Veterinary Services, “Masked Mycotoxins”: A Diagnostic Challenge!

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Some years are certainly worse than others for   mycotoxins.   When   mycotoxins   are expected to be the “tipping point” that sets off  a  health  issues  it  is  helpful  to  have  a laboratory  test  that  can  confirm  the  levels  of  the suspect   mycotoxin   in   the   feed.   Unfortunately, diagnosing mycotoxin levels is not usually a simple process.  High  positive  test  result  for  a  mycotoxin will  certainly  confirm  a  mycotoxin  problem.  The bigger problem is false negative results. Finding the right  subsample  can  be  hit  or  miss  when  there  are “pockets”  of  mycotoxin  in  feed.  Another  cause  of false negatives is the presence “masked mycotoxins” in feed.

Masked  or  modified  forms  of  Zearalenone  (ZEN) are  alternate  forms  of  ZEN.  After  ingestion,  they can  be  cleaved  by   gastric  acid,  small  intestinal enzymes  or  large  intestinal  microbial  activity  into the    parental    form.    Modified    mycotoxins    can themselves   possess   estrogenic   potential which sometimes  exceeds  even  that  of  the  parental  ZEN. They  are  not  routinely  monitored  nor  regulated. Biomonitoring of selected metabolites in body fluids can  be  used  as  quantitative  indicators  of  exposure. Rather than looking for a “needle in a haystack” in the feed  the  total  effect  of  exposure  to  both  the  parent mycotoxin   and   its   masked   modified   forms   is evaluated  by  measuring  them  in  bodily  fluid  after ingestion and absorption.EU  researchers  wanted  to  better  understand  the toxicity  and  bioavailability  of  Zearalenone  (ZEN) and   its   common   modified   forms   including   α-zearalenol (α-ZEL), β-zearalenol (β-ZEL), zearalenone-14-glucoside (ZEN14G) and zearalenone-14-sulfate  (ZEN14S).  After  pigs  were exposed    by    means    of    intravenous    and    oral administration  of  ZEN  and  its  modified  forms  the systemic  blood  plasma  concentrations  of  the  toxins and    their    metabolites    were    quantified.

The researchers found the following:

  • ZEN14G     and     ZEN14S     were     completely hydrolysed to ZEN.
  • All  administered  compounds  demonstrated  high oral bioavailability.

Take Home Message

Zearalenone and the modified Zearalenone forms such  as α-ZEL,  β-ZEL,  ZEN14G  and  ZEN14S work     together     to     contribute     to     overall Zearalenone systemic toxicity in pigs.

When faced with a lot of red swollen vulvas and teats  in  prepubertal  growing  pigs  in  the  face  of low   or   negative   Zearalenone   diagnostics   the problem  may  be  related  to  masked  or  modified forms.

Sometimes the pigs are better able to tell us what the problem is rather than the diagnostics.

Submitted by Clint Lichty, DVM

Ref:   Catteuw   A,   Broekaert   N,   De   Baere   S,   Lauwers   M,   Gasthuys   E, Huybrechts  B, Callebaut  A,  Ivanova  L,  Uhlig  S,  De  Boevre  M,  De  Saeger  S, Gehring  R,  Devreese  M,  Croubels  S.  Insights  into  in  vivo  absolute  oral bioavailability,   biotransformation   and   toxicokinetics   of   zearalenone,   α-zearalenol,  β-zearalenol,  zearalenone-14-glucoside  and  zearalenone-14-sulfate in  pigs.  J  Agric  Food  Chem.  2019  Feb  26.  doi:  10.1021/acs.jafc.8b05838. [Epub ahead of print]

 

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