New Delhi, Sept. 10 -- Dairy farming never stops, according to Bobbi Frost of Harrold's Dairy.

"You can't ask the cows to take a break," she said.

Frost, 30, is the fourth generation of her family to operate Harrold's Dairy, which was founded by her great-grandfather in 1946. The dairy milks 375-400 cows on 1,000 acres and grows its own feed for the cows.

About 36% of farms are run by female producers, according to the USDA's 2017 Census of Agriculture. "I always loved growing up on the farm," she said. "My parents wanted me to be in ruminant nutrition so I could see cows every day but not be at the mercy of farm life."

It was her junior year of college when she spoke with a salesman who had grown up on a farm but his family had sold i...