Piglets posed a particular problem. Baby pigs must suckle at their mother's teats and it takes weeks for a wobbly piglet to be strong enough to be shipped anywhere. And like other mammals, pigs evolved over the eons to protect their young. The animals have strong, innately bred social instincts that made it all but impossible to raise them in close quarters. Packing hundreds of female sows into a barn means some of them are going to kill the others. Crowded hog barns could easily turn into a big, messy carnival of violence. And that's not good for business. Stressed out animals don't yield good meat.
One of the most important innovations that led to the factory hog farm dealt with the problem of suckling pigs. Tyson Foods and other hog researchers broke hog production into two, distinct stages. In stage one, female pigs gave birth to piglets in special barns. In stage two, those piglets were fattened to slaughter weight.
During stage one, pregnant sows were confined in special pens, called "farrowing crates." These crates are narrow metal cages, no wider than the sow's body, which kept the mother pig immobilized, unable to turn right or left. On each side of the sow, there are smaller cages where the piglets resided and where they could suckle from their mother through metal slats. By keeping the mother pigs penned, there was no chance that the piglets might be crushed in the melee of a crowded barn. Workers walked up and down the gangway between rows of crated sows and easily plucked squealing piglets from their pens when they were old enough to be shipped away.