Hi! This is what is known as a scrape through system, pigs are naturally very clean animals so they have specific areas for dunging. In this system they use the ends of the pens which are on a lightly lower level and this is then scraped away and the manure is cleared from the pen. The central area of the pen is replenished with fresh straw periodically, so this part of the pen stays clean and dry for the pigs to root around and sleep in.