It was still dark outside at four o’clock on a recent morning when a tanker truck poured 6,000 gallons of milk into a manure pit on Nancy Mueller’s Wisconsin dairy farm.

The milk, collected from Mueller Dairy Farm’s 1,000 cows, should have been hauled to dairy processors across the state for bottling or to be turned into cheese. But the coronavirus pandemic is disrupting all that, closing restaurants and schools that buy the nation’s dairy products—and forcing hard choices for farmers like Mrs. Mueller.

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