A small group of animal welfare scientists is seeking answers to that question. Facing a growing anti-dairy movement, many farmers are altering their practices.

The 1,500 Jersey cows that Nathan Chittenden and his family raise in upstate New York seem to lead carefree lives. They spend their days lolling around inside well-ventilated barns and eating their fill from troughs. Three times a day, they file into the milking parlor, where computer-calibrated vacuums drain several gallons of warm milk from their udders, a process that lasts about as long as a recitation of “The Farmer in the Dell.”

Mr. Chittenden, 42, a third-generation dairy farmer whose family bottle-feeds each newborn calf, expresses affection for his animals. It’s a sentiment they appeared to return one recent afternoon as pregnant cows poked their heads through the enclosure to lick his hand.

“I’m in charge of this entire life from cradle to grave, and it’s important for me to know this animal went through its life without suffering,” he said, stroking the head of one especially insistent cow. “I’m a bad person if I let it suffer.”