Wikipedia
Schweinemord
In 1915, due to World War I food restrictions and rationing, the German bureaucracy decided to regard pigs as co-eaters with humans and tried to preserve supplies. As a result, five million pigs were massacred in the so-called Schweinemord (German: pig massacre) to both make food and preserve grain. However it did little to increase the supply of grain, as officials did not take into account the use of pig manure as fertilizer on small farms. Because of this, killing the pigs actually decreased crop yields in the region.