Poultry
In some countries, geese and ducks are force-fed to produce livers with an exceptionally high fat content for the production of "foie gras". Over 75% of world production of this product occurs in France, with lesser industries in Hungary and Bulgaria and a growing production in China. "Foie gras" is considered a luxury in many parts of the world, but the process of feeding the birds in this way is banned in many countries on animal welfare grounds.
Foie gras
The ideology behind foie gras production is the ability that some waterfowl have to expand their esophagus and to gain weight, particularly in the liver, in preparation for migration. Unlike many birds, geese and ducks lack a crop. In the wild, esophageal dilation allows them to swallow large foodstuffs, such as a whole fish, for later digestion. Wild geese may consume 300 grams of protein and another 800 grams of grasses per day. Farmed geese allowed to graze on carrots adapt to eating 100 grams of protein, but may consume up to 2500 grams of the carrots per day. The increasing amount of feed given prior to force-feeding and during the force-feeding itself cause expansion of the lower part of the esophagus.