White meat refers to any lighter-colored meat, often contrasted with red meat. White meat or light meat also refers to the lighter-colored meat of poultry as contrasted with "dark meat".The exact definition of white meat varies by time, place, and culture, but domestic chicken and rabbit are invariably considered "white", while the meat of adult mammals, such as beef, mutton, and horse is invariably considered "red". The meat of young mammals such as veal and milk-fed lamb, and that of pork is traditionally considered "white"; while the meat of duck and goose is considered "red", though the demarcation line may be changing. Game is sometimes put in a separate category altogether (French viandes noires 'black meats').A newer definition in the United States emphasizes not the appearance and strength of taste, but the fat content, making "white meat" synonymous with "lean meat"; traditionally "white" meats such as lamb and veal are reclassified as "red". Sometimes, even fish and seafood, including fatty and dark-fleshed fishes such as salmon, mackerel, and tuna, may be considered "white meat".Given nutritional concerns, meat producers are eager to have their products considered as "white", and the United States National Pork Board has positioned pork as "the other white meat", alongside poultry; however, meats which are red when raw and turn white on cooking, like pork, are categorized by the United States Department of Agriculture as red meats. White and dark poultry meatWithin poultry, there are two types of meats – white and dark. The different colors are based on the different locations and uses of the muscles. Dark meats occur in the legs, which are used to support the weight of the animals while they move. These muscles are designed to develop endurance for long-term use and contains a large amount of myoglobin, allowing the muscle to use oxygen more efficiently for aerobic respiration. In contrast the white meat, generally found within the breasts of the birds, are used for quick bursts of power which requires little of the meat-darkening myoglobin. Note that this holds for ground-based bird like chickens and turkeys – birds which use their chest muscles for sustained flight (such as geese and ducks) have dark meat throughout their bodies.