I have had similar problems with hogs - all sizes - especially over 200 pounds. One possibility is arthritis due to inflammation or injury - i run several sizes together. Ive had three large sows (600+ lbs) whose feet broke down with the body weight when my feed was deficient. In sows this could be a calcium or phosphorous related deficiency. brooding and lactating sows need a lot of both. I custom mix my own feed to make sure diet is sufficient in both. Found good information at University of Oklahoma that gives the composition of feeds. With a spreadsheet you can make a formula for a balanced ration.(can email this to you).(posted 9290 days ago)Limping hogs generally end up in my freezer too.