I grew up drinking unpasteurized milk. There is quite a bit of difference in milk just in this last generation. Antibiotic "contamination", for one example. Another would be the breed of milk cow. Dairy farms are much rarer now. When you see one, you'll likely see "Holsteins". {colored like a Dalmatian} Not long ago, you would see Jerseys, Guernseys, Milking Shorthorns, and maybe others. The difference in the milk was very noticeable, even though the lactose couldn't be that much different.
I'm fascinated by some old recorded accounts from the Ozarks of an illness called "milk sick". They believed it was caused by the cow eating some type of plant and contaminating the milk. These old doctors could diagnose this condition from the odor when entering the home.
"They believed it was caused by the cow eating some type of plant and contaminating the milk."
Wasn't it Jimsonweed?
Abraham Lincoln's mother supposedly died of "milk sick." I wondered later if it were salmonella.
It was "snake root" and was responsible for the death of many of the early settlers in the Midwest including Abe Lincoln's mother.