Red meat vs white meat
The skeletal muscles of large mammals, such as cow and deer, contain high concentrations of myoglobin. These muscles are also called ‘slow twitch’ as they are used for extended periods of time, for example when standing and walking, therefore needing a consistent oxygen and energy source. The high myoglobin levels are what make the meat appear red, hence the term ‘red meat’.
The ‘fast twitch’ muscles (used in quick bursts for example when fleeing danger) of animals such as chickens, get most of their energy from glycogen, and therefore there is less myoglobin and less of a red appearance, hence the term ‘white meat’.