OGDENSBURG, Wis. — Cullen Schachtschneider, 6 years old, lay bleeding beside the barn, tangled up in a 4,600-pound farm machine that had ripped his left leg apart.

Like children across America’s two million family-run farms, Cullen had grown up around farm equipment, including the yellow loader now covered in his blood. He rode along as his father hauled calves. He watched his grade-school-age brothers drive the diesel-powered loader, carrying corn and doing chores to help keep their family’s struggling Wisconsin dairy afloat. The work was woven into their childhood.

But one evening last October, as Cullen’s father was using the loader — called a skid steer — to feed the cows, Cullen clambered aboard, and his foot slipped. The machine’s hydraulic bucket bit into Cullen’s left leg and tore it from knee to ankle, ripping off his tissue as easily as someone slipping off a glove.

The boy’s father, Caleb, jumped off the machine and frantically called 911. Two years earlier, Cullen’s brother Kholer, 8, had driven the steer into his older brother, Maric, sending him to the hospital. Now another child was hurt.