This Post article quotes these two paragraphs from NPR:
"Since dairy cows were first brought to the United States, their owners have been trying to coax more and more milk out of them. They've done that through dairy parlor design, barn layout, feed rations, milk scheduling and hormone treatments.
Now the focus is on genetics: Cows are being bred to be larger, hungrier, and more productive. But this drive to raise ever-larger, hulking Holsteins has some prominent livestock advocates ringing alarm bells."That's misleading, if not wrong. Farmers have been breeding cows for greater milk production ever since humans domesticated them. That's what we do, not only with cows but all our grains, fruits, and vegetables. We had registered Holsteins on the farm, meaning we submitted pictures or drawings of each cow added to the herd to the central registry, along with data on their dam and sire. When the inseminator came, he and dad consulted over which bull to choose (he carried vials of semen from 3 or 4 bulls with him). That was one of the big advantages of artificial insemination, the choice of bulls, by looking at the production of the bull's offspring.
Since the Derby is coming along, I can't resist noting that similar efforts have been going on in racing for years, probably earlier than dairy because the potential payout for a great foal is so much greater than a great calf.
So the reality is: breeding has always been there. In the last half of the twentieth century we also started to pay attention to dairy rations,barn/parlor design, etc. Grandin would know this, so the writer has misled by using NPR to lead into her position, which is "[good dairymen] raise smaller cows that tend to be healthier, as well as productive over a longer period, and opting to feed their herds grass as often as possible. The latter [bad dairymen], meanwhile, are driving up the efficiency numbers you see in the chart above, selecting for cows that tend to suffer from a number of adverse health outcomes."
Here I feel only qualified to say:if dairymen have overbred, it's little different than turkey growers raising turkeys which can't reproduce because their breasts are too big or Great Dane breeders raising dogs doomed to hip displasia.