Industry and Farming Terminology

• Gavage: The process of force-feeding ducks or geese by inserting a tube into the esophagus to deliver large quantities of feed. The term comes from French gaver (“to gorge”). Gavage is central to foie gras production and typically involves 2–3 feedings per day of energy-rich corn mash for 12–21 days[1][2]. This causes the birds’ livers to enlarge up to 10 times normal size (see hepatic steatosis). According to French law, foie gras is defined as the liver of a duck or goose “fattened by gavage”[3].
• Mulard (Moulard) Duck: A sterile hybrid duck produced by crossing a male Muscovy duck (Cairina moschata) with a female domestic duck (usually Pekin, Anas platyrhynchos). Mulard (or mule) ducks are the preferred breed for foie gras, as they readily undergo liver fattening (males for foie gras, females often for meat)[4][5]. They are hardy and calm, combining traits of Muscovy and Pekin ducks. By the 1960s, mulards largely replaced geese in foie gras farming due to their higher feed efficiency and docility during gavage[5][6].
• Brooder: A heated shelter or enclosure for raising young poultry. In foie gras farms, newly hatched ducklings or goslings spend their first weeks in a brooder house kept warm and safe, until they can regulate body temperature. A brooder provides warmth, bedding, food, and water for the hatchlings[7] before they transition to grow-out barns or pasture.
• Finishing Pen: A pen or enclosure where birds are placed during the final stage of the feeding cycle to be fattened for slaughter. In foie gras production, finishing pens (often small group pens or cages) confine ducks/geese and limit exercise in the 2–3 weeks of force-feeding. This confinement “finishes” the birds by promoting rapid weight gain[8][9]. Traditional advice is to keep finishing pens calm and free of disturbance, with just enough space for birds to remain clean but not enough to burn off the fat being added.
• Palmipeds: A term referring to web-footed birds (from Latin palmipes), i.e. waterfowl like ducks and geese. In French, palmipèdes is commonly used for species farmed for foie gras[10][11]. The foie gras industry often speaks of canards et oies palmipèdes (ducks and geese) and “fat palmipeds” for those being force-fed.
• Force-Feeding Period: The final fattening stage (typically 12–15 days for ducks, 15–21 days for geese) when birds are fed via gavage. During this period, ducks are usually 11–12 weeks old and kept in restrictive housing. They are fed a progressively increasing ration of corn boiled with fat, via tube, until their liver reaches the legally required minimum weight (≈300 g for duck, 400 g for goose)[12][13].
• Free-Range vs. Intensive Phase: Foie gras ducks often have an initial raising phase where they live in barns or pastures with ad libitum feeding until ~8–12 weeks of age. They may have outdoor access to build fitness and a dilated esophagus (“pre-fattening”). This is followed by the intensive gavage phase in confined pens[14][15]. Some farms market “free-range foie gras” where birds roam freely until the force-feeding begins, but French regulations still mandate gavage for authentic foie gras[16].

Duck and Goose Breeds & Anatomy

A Mulard (Moulard) duck, the hybrid of a Muscovy drake and Pekin duck, which is the primary breed used in foie gras production[17].

• Muscovy Duck: A large duck species (Cairina moschata) native to Central/South America, also called Barbary duck in France. Muscovy drakes are commonly used to sire hybrid mulards for foie gras. Pure Muscovies have lean meat and are less tolerant of force-feeding stress, so they are now usually crossed with Pekins[18][5]. Muscovies have claws on their feet and a caruncled face; they’re known for being less gregarious but their genes contribute to the mulard’s leaner meat.
• Pekin Duck: The common domestic duck (Anas platyrhynchos domesticus, usually the American or French Pekin) descended from mallards. Pekin ducks (often white-feathered) are the typical female parent for mulards[19]. They grow fast and have calm temperaments. Pekin traits in mulards make them more docile during gavage and improve foie gras quality[5]. (Note: “Pekin” is sometimes just called canard commun or common duck in French.)
• Landes Goose (Grey Goose): A traditional French breed of goose (Anser anser domesticus) renowned for foie gras. Often called the Oie grise des Landes, this grey goose has a natural ability to store fat in the liver, yielding high-quality foie gras[11][20]. Goose foie gras is rarer (about 5% of France’s foie gras[21]) due to higher cost, but is considered the “foie gras royalty” by some for its refined taste. Another heavy goose breed used is the Toulouse Goose, especially the dewlap Toulouse, bred for rapid weight gain and traditionally used for foie gras and fatty meat[22][23].
• Liver (Foie): The organ that is specially fattened to produce foie gras. Under force-feeding, a duck’s liver swells from a normal ~70–80 g to 550–900+ g with >50% fat[24]. This condition (hepatic steatosis) imparts a rich, buttery texture to the liver. In foie gras labels, foie means liver and gras means fatty – literally “fatty liver.” The liver’s two large lobes are used whole (foie gras entier) or ground into various products (mousses, pâtés, etc.).
• Esophagus: The gullet or food pipe of the bird. Ducks and geese lack a distinct crop, but have an expandable lower esophagus that serves as a food reservoir[25]. Farmers often “prepare” the esophagus by preliminary feeding (e.g. green grass or stretch feeds) to dilate it before gavage[26][27]. During gavage, a 15–30 cm tube is inserted into the esophagus to deliver feed; the esophagus can stretch to accommodate ~0.4–0.5 kg of mash per meal[28]. Care is taken to avoid injuring the esophagus with the tube or excessive volume.
• Crop (In Birds): A storage pouch in the esophagus of many birds. Geese have a small crop; ducks effectively do not have a true crop, but the lower esophagus expands similarly under repeated feeding[25]. In foie gras husbandry, the term “crop” may refer to that expanded portion (sometimes called a crop-like area[27]). During the pre-fattening phase, birds may be allowed to eat freely (ad libitum) to achieve a “half-fat” state that enlarges the esophagus/crop region in preparation for gavage[29].
• Magret: A French term for the breast fillet of a fattened duck (or goose) raised for foie gras. Magret (literally “lean piece”) specifically refers to the breast from a foie gras duck, which is particularly meaty and flavorful due to the bird’s fattening[30]. For example, magret de canard is a popular dish of seared duck breast from a gavage-fed duck. (By EU definition, “magret” must come from a foie gras animal[30].) The term distinguishes it from ordinary duck breast, as the foie gras duck’s breast is larger with a layer of fat.
• Hepatic Lobes: The two lobes of the liver. In foie gras production, the term lobes often appears in product descriptions (e.g. foie gras entier uses one or more whole intact lobes[31]). Producers carefully handle and devein the lobes after slaughter, as their delicate, fat-laden texture can easily bruise or tear.

Diseases and Veterinary Issues

• Hepatic Steatosis: The scientific term for fatty liver disease, which is intentionally induced in foie gras birds. Through overfeeding, large fat globules accumulate in the liver cells far beyond normal levels[32]. By the end of gavage, a duck’s liver may be 7–10 times its healthy size (averaging ~600–700 g with ~56% fat)[24]. This extreme steatosis impairs liver function (reduced blood flow, cellular damage)[33]. If force-feeding continued, the liver degeneration would likely progress to organ failure and death[34]. Notably, if gavage is stopped early, the condition is partly reversible as the liver can metabolize and reduce the fat over time[35]. In essence, foie gras is a pathologically fatty liver (a form of hepatic lipidosis), albeit a culinary delicacy created under controlled conditions.