A second note arrived today from Dr. J.

I do think that grain fed cows could have a more harmful casein but I have never read that proven anywhere. It just makes sense to me for the same reason that you asked the question. But, I think the casein that grass fed cows produce in their milk is bad enough. Again, goat milk...the "universal foster milk" for millennia...had only 0-2% casein. Cow milk has a whopping 80-86% casein content. So, the jump from goats to cows as the source of milk was the single biggest mistake. Then, grain-feeding and pasteurization took things to a whole new level, with the latter actually denaturing casein and turning it into a super-glue.

Also, there are numerous other proteins/glycoproteins in cow's milk that we can react to, including alpha and beta lactalbumin.