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.
Mulard
Traditionally, foie gras was primarily produced with geese, but in the 1960s the majority of farmers began to use mulards. Geese are more expensive to maintain than ducks (they are larger and more aggressive), and the more temperamental muscovies did not accept the process of gavage (force feeding) as readily as Pekins, causing the quality of the foie gras to suffer. This problem was avoided by the introduction of mulards. These hybrids have also become extremely common in countries where foie gras is not produced.