In this March 3, 2014 photo sows at Fair Oaks Farms in Fair Oaks, Ind., lay in nesting boxes, left, inside a larger group pen, while another eats inside an electronic feeding stall, right. Animal rights activists have been pushing hog farmers to move pregnant pigs into group pens from individual gestation stalls often too narrow for the animals to turn around. (AP Photo/M.L.Johnson)
Read: Bigger Pig Crates Challenge Farmers 
In this March 3, 2014 photo sows at Fair Oaks Farms in Fair Oaks, Ind., are kept in large group pens with computer-controlled feeding systems. (AP Photo/M.L.Johnson)
In this March 3, 2014 photo two sows push up against another entering an electronic feeding stall, center, at Fair Oaks Farms in Fair Oaks, Ind. The electronic feeding system is aimed at preventing bigger sows from hogging all the food and lets each sow eat in peace. It is one of the tools farmers are using as they move pregnant pigs out of small, individual gestation stalls and into group pens. (AP Photo/M.L.Johnson)
Farmers under consumer pressure are spending millions of dollars to switch from gestation stalls to bigger pens and electronic feedings systems for pregnant pigs. But producers have no certainty that these changes are best for the animals.