In gastronomy, red meat is darker-colored meat, as contrasted with white meat. The exact definition varies by time, place, and culture, but the meat of adult mammals such as cows, sheep, and horses is invariably considered red, while chicken and rabbit are invariably considered white. The meat of young mammals such as milk-fed veal calves and sheep, and pigs is traditionally considered white; while the meat of duck and goose is considered red. Game is sometimes put in a separate category altogether (French viandes noires 'black meats').
Red meat does not refer to how well a piece of meat is cooked. Nor does it refer to its coloration after cooking.
The main determinant of the nutritional definition of the color of meat is the concentration of myoglobin. The white meat of chicken has under 0.05%; chicken thigh has 0.18-0.20%; pork and veal have 0.1-0.3%; young beef has 0.4-1.0%; and old beef has 1.5-2.0%.
According to the USDA all meats obtained from livestock are red meats because they contain more myoglobin than chicken or fish.