Casein A-2 vs. A-1?

A book I am reading mentioned that some breeds of cows produce different casein types. This book mentions Holsteins produce a casein referred to as A-1 while Guernseys  produce A-2. Supposedly the A-2 is better, more digestible and less likely to make a body react to it.

Has anyone heard of or had any experience with this? I've also heard, but without verification, that pasteurizing alters the casein in milk to where it 'sticks' to artery walls whereas raw milk's casein doesn't do that. Any feedback on that?  

Hi Jain;
Yes, A-2 A-2 milk is a very real thing.  Guernseys, Jerseys, brown Swiss,   They can be A-2 A-2 but can be A-1 A-2 as well.  
Even Holsteins could be bred to ultimately be A-2 A-2.

For years my wife could not eat any dairy products (milk , cream, cheese, butter ) you know all the good stuff.
When she did ingest any of the A-1 products, her voice went scratchy, nose and throat flemmy and her belly would be off.
Every time we ate out ... restaurants other people's cooking it all caused a reaction.

Then one day we heard about A-2 A-2 cow milk. Seems all goat / sheep products (milk ,butter cheese) are A-2 A-2  as well.
It took several months before we could find any Cow A-2 A-2 milk.
I remember the day. We had a frosty cold 1/2 gallon of A-2 A-2 milk... several inches of heavy cream floating on top... With a hopeful look on her face , she shook in the cream , popped the top and took a good long drink.... She was awful cute with her milk mustache and a growing grin on her face as she realized there was NO REACTION !!!
OMG our lives changed back for the better that day!  With goat butter and cheese and super awesome A-2 A-2 milk, Liz can cook and we can eat good again!  

I'm not sure about raw versus pasteurized , other than I've always heard the raw milk was much better for you.

EDIT)    Check out this post https://permies.com/t/55943

Thanks Thomas for steering me towards this information. Seems information will be he 'easy' part, locating A-2 milk will be the real challenge. The irony is that I live not far from a couple of dairies, but this being California, every one is quaking in their boots about laws and regulations.

Hi Jain;
The A-2 corporation, out of I believe New Zealand has started selling cartons of whole / 2% A-2 milk in America.
We first heard this from a friend in (of all places) South Dakota. They had it at Safeway.  We checked and checked at all the big grocery stores all around the inland north west  ... nothing :)
Then we found it Raw at a health food store in Sandpoint, Idaho that was where Liz got to try it for the first time.
Since then it has expanded to the large grocery chains in Sandpoint.  Safeway , Yokes and others all carry it now.
You have to check the milk cooler. They are very innocuous , look just like all the others .  
The whole milk is in a red and white container.
A-2 Corp. is advertising on national TV now, I suspect that it may be available near you.