Michael Massey happened to call today and I learned a bit more.
 
Some things learned or once again repeated about cystine:
 
Birds can convert Methionine to cystine but he did NOT know if mammals
can.
 
When amino acids aren't in proportion there winds up being reduced
uptake of the some other amino acids (health consideration when weighing
modified diet against meds).
 
(BTW: earlier known: When there is a genetic aspect involved it doesn't
always involve just cystine.  Sometimes the COLA grouping of amino acids
is involved but cystine if the one that precips out even if the others
are too high, so it is getting very complex...)
 
Feathers are almost 100% cystine so when cystine needs to be supplemented
processed feather meal becomes a source of cystine.  (I guess that is a
really good reason to need to be able to convert another amino acid to
cystine.)
 
Someone asked me to let us all know if I run into anything on bowel
problems and any uroliths.  I don't know if this will help but
http://www.clevelandclinicmeded.com/diseasemanagement/nephrology/
nephrolithiasis/nephrolithiasis.htm
on humans contains
>In other cases, the hyperoxaluria occurs in the setting of
>gastrointestinal malabsorption, seen in patients with inflammatory bowel
>disease.  When patients malabsorb fat, dietary calcium binds to the fat
>rather than to dietary oxalate (which is the norm).  This results in a
>larger amount of unbound intestinal oxalate that passes into the colon,
>from which it is absorbed.  In patients with ileostomies (colon
>excluded) this enhanced oxalate absorption does not occur.  A rare
>cause of hyperoxaluria is the inherited condition known as primary
>hyperoxaluria.9 In this condition, the hepatic enzyme that converts
>glyoxalate to glycine is deficient.  As a result, there is increased
>production of oxalate from glyoxalate.
 
Anyway, I hope to get replies no matter what they say and if I do I'll
share any for which the author has given me permission to share.
[Posted in FML issue 4572]