Meat, the flesh or other edible parts of animals (usually domesticated cattle and sheep) used for food, including not only the muscles and fat but also the tendons and ligaments. Meat is valued as a complete protein food containing all the amino acids necessary for the human body. The fat of meat, which varies widely with the species, quality, and cut, is a valuable source of energy and also influences the flavour, juiciness, and tenderness of the lean. Parts such as livers, kidneys, hearts, and other portions are excellent sources of vitamins and of essential minerals, easily assimilated by the human system. Meat digests somewhat slowly, but 95 percent of meat protein and 96 percent of the fat are digested. Fats tend to retard the digestion of other foods; thus, meat with a reasonable proportion of fat remains longer in the stomach, delaying hunger and giving “staying power.” Extractives in meat cause a flow of saliva and gastric juices, creating the desire to eat and ensuring ease of digestion. The most widely consumed meat is beef, the flesh of mature cattle that normally weigh from 450 to 540 kg (1,000 to 1,200 pounds) and yield between 55 and 60 percent of their weight in meat. Veal, the flesh of calves of cattle, is much less fatty than beef.