Why Do Birds Have Light and Dark Meat?
Why Do Birds Have Light and Dark Meat? Birds have light and dark meat because of the way their muscles are used. The muscles that are used the most, like the powerful flight muscles in the breast and wings of the flying bird, need lots of energy.
So wing and breast muscles in flying birds have more blood vessels than the legs do. The extra blood makes the wings and breast muscles darker in color. Chickens and domestic turkeys spend most of their time on the ground.
They use their leg muscles more than their wings. The active muscles, such as the legs and thighs, are full of blood vessels. These blood vessels contain myoglobin, which delivers oxygen to the muscles. The more myoglobin the muscles contain, the darker the muscle. That’s why they have dark meat on their legs and white meat on their wings and breasts.
Scientists often refer to these active muscles as slow-twitch fibers. Slow-twitch fibers are built for endurance, which allows the muscles to work for long periods of time. Thus the turkey can run around all day without getting tired.
On the other hand, white meat is the result of well-rested muscles. The breast muscles, which are used for flying, are hardly used by turkeys. There is no need to have a rich supply of oxygen delivered to these muscles.
Scientists refer to these types of muscles as fast-twitch fibers. Fast-twitch fibers are designed for quick bursts of energy, but they fatigue quickly. In addition, fast twitch muscles are fueled by glycogen giving the muscles that immediate explosion of energy needed to move rapidly.