[ SHOWGSD-L ] Re: "birth defects" [Pyometra, antibiotic use and cryptorchidism]

From: Donna Fefee <dlfefee@xxxxxxxxx>
To: "showgsd-l@xxxxxxxxxxxxx" <showgsd-l@xxxxxxxxxxxxx>
Date: Fri, 17 Sep 2010 09:02:24 -0400
> From: Katie Halfen <kthalfen@xxxxxxxxxxx>:
> As a side note, I just want to say that if you think a birth defect
> is caused by these antibiotics which are considered an "environmental
> influence" and not a genetic defect-then the ENTIRE litter will be
> affected because all the puppies are exposed to the same
> environment-blood supply, nutrition, etc. as the rest of the pups.

I'm sorry, but this is incorrect--sometimes an entire litter will be 
affected, but this is definitely not always the case.  After all, 
"individual variation" is one of the hallmarks of toxicology (and 
medicine).  While the entire litter may be exposed to a substantially 
similar environment, the puppies themselves are NOT identical.  There 
are subtle (and sometimes not so subtle) genetic differences, some of 
which influence susceptibility to damage related to chemical exposures.

When toxicity studies are carried out in pregnant laboratory animals 
(e.g. rabbits, mice, and rats), which are highly inbred and probably 
some of the most genetically and phenotypically uniform mammals in 
existence, you will often find only *some* litters are affected by the 
toxicant.  This is due to individual variation of the dams.  Then as 
regards the affected litters, any percentage of the offspring can be 
affected, and/or the severity of the effect can vary, as well.

Of course, in an experimental setting, one has the advantage of both 
numbers and untreated "control" groups, so the chemical or whatever is 
being tested can be identified as the actual cause of the effect(s), 
i.e. death/resorptions, malformation, delayed/altered growth, and/or 
functional deficits.  Unfortunately, real life often doesn't work this 
way.  You cannot run statistical analyses on your one beloved bitch and 
her litter.

Donna Fefee
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[ SHOWGSD-L ] Re: "birth defects" [Pyometra, antibiotic use and cryptorchidism]

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