I can only answer Pam Morrison's question from personal experience, and that was years after my last baby weaned herself.
In 1996 I was put on an elimination diet for allergies identified in testing.  For some time I'd felt vaguely queasy after eating a delicious veal or beef casserole, however much I'd looked forward to it.  As a busy person, I hadn't made the connection to allergy.  I already knew about my dairy and soy allergies and had needed to avoid those foods already, but the doctor also took me off beef and veal (young beef), as well as some other foods that showed up in the tests.  I avoided beef and veal for years  Instead I ate lamb or, occasionally, venison (when I could get it).   In the last two years or so I  have been able to reintroduce this food without any symptoms.  I still don't have it every day, but so far I have had no ill effects.
Rather than thinking of just one bovine protein as potentially allergenic, we need to recognise that it could be others.  If adults can react to the foreign proteins in bovine meat (beef or veal), it makes sense that a breastfeeding baby susceptible to these allergies can, too.
I look forward to seeing more comments on this by Lactnetters.
Virginia
in Brisbane, Queensland, Australia
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On Tue, 14 Oct 2008, Pamela Morrison wrote:
I've had a question about infant sensitivity to bovine proteins 
coming through the mother's milk, and specifically querying whether 
beef as well as dairy products can cause problems.   My experience is 
that it definitely can, and that a total elimination of both dairy 
products _and_ beef from the mother's diet can result in complete 
resolution of "colic", eczema, reflux, extreme wakefulness, and 
general irritability in the exclusively breastfed baby.  The enquirer 
suggests that the allergic protein in cow's milk isn't present in 
cow's meat - beef.  ....   Does anyone have any more information, or a more up to date reference 
to share that confirms what we intuitively know - ie that the more 
concentrated form of bovine protein in the meat is likely to also be 
a problem for some EBF babies who are sensitive to cow's milk 
proteins ingested by the mother?
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