Which Cows Produce A2 Milk in the USA?
                                
                                
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                                    4 min read                                
                            
                                While standard milk contains a mix of A1 and A2 beta-casein proteins, a 2019 study at the University of Minnesota found that over 50% of its Holstein herd were A2/A2, a trait not actively selected for. In the USA, A2 milk comes from specific breeds and genetically tested herds, not just any cow.