Nearly 20 million egg-laying hens live on large-scale farms in California, making the state a target for animal rights activists who say factory farming practices are cruel. Backed by the Humane Society, this proposal would require farmers to provide every farm animal enough space to stand, lay down and turn around. (Under current standards, egg-laying hens and calves raised for veal are kept in cages so small they can barely move.) The measure looks likely to pass, based on recent polls, meaning major operational changes at scores of California farms could be on the way.