Haven’t a clue about cow blood types and whether they follow the same typing in humans (A, B, AB or O). However, in the US milk from a single dairy herd is mixed with other herd’s milk in the tanker that goes from farm to farm picking up milk. Some dairies do separate milk produced by cows that are not on rbST, a hormone to boost milk production. I would highly recommend contacting the Agriculture Department at your local university for research about blood groups of cows and whether that influences milk tolerance by humans.
Also, people can be allergic to milk protein or lactose intolerant to milk sugar. That said, I highly doubt that cow blood type would affect either milk allergy or lactose intolerance. On a practical thought, how would you purchase milk from these cows unless you are in the African country where the cows reside since milk is a fresh product?