Silkie Chicken

posted in: birds, Blue, Color, ear lobes | 0

 

Silkie chicken

Gallus gallus domesticus Brisson is also known as Chinese Silky Chicken or Black bone chicken

 

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Silkie Chicken

Gallus gallus domesticus Brisson

Silkie chicken is also known as the Chinese silky chicken. It is a very old breed, originating in China and later spreading to Europe, then America, mainly as a novelty.

It is most popular as a pet because of its completely white fluffy plumage. Its hair-like feather feels silky soft, hence its name. Feathers also extend to its legs and feet. It is described as a very quiet, gentle, friendly, calm and docile bird. All  these make it very suitable as a pet. Life span is about 7 to 9 years.

For Birders, this is an example of a Leucistic bird. It has a completely white plumage and black eyes. However, no one is excited over it because it is not the odd one out, it is the norm, the whole flock is white.

In spite of the above, this is a good example of a Leucistic bird that is not caused by a lack of black melanin pigments. The feathers are white because of a defect in the transport of melanin from skin melanocytes to the feathers. In fact, it has so much melanin that it is called black chicken. Its whole skin beneath the white feathers is black, including its feet, beak and comb. The excess melanin has even gone inward, causing the bones and muscles to becomes black. All the internal organs like heart, intestines and connective tissues are also black.

The only part of its body that is not black is its ear lobe, which is curiously blue. So far no blue biological pigment has been found in the skin or feather of birds. It is also very rare amongst animals, only found in two species of fish. But there are no shortages of examples of blue colored birds, like the beautiful blue peacock. The reason for this contradiction is that the blue color in birds is a structural color. This means that the blue color is the result of light interacting with microscopic/nanoscopic physical structures in the feather (extra dermal) or in the skin (either within dermal cells, or in the extracellular space of the dermis e.g. hexagonally arranged collagen fibers). When the blue segment of visible white light hits the collagen bundles the blue light is reflected more intensely because of constructive wave interference. Light of other wavelengths (e.g. red, yellow) are reflected out of phase because their wavelengths do not fit the spacing within the collagen bundle. This destructive wave interference results in the annihilation of red, yellow etc. color, leaving only blue. Any light rays not hitting the collagen bundles pass through and is absorbed by the underlying black melanin layer. This makes the blue color more intense and prominent.

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Photo 4. Blue ear lobe is visible.

 

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Silkie’s feathers look and feel like soft fur. This is due to the absence or non-functioning of the barbules in its feathers. The vane feather has a central keratin shaft with a broad flat web on either side known as the vane. The vane is made up of paired keratin barbs growing out from the central shaft at an angle e.g. 45º, on a single plane. The barbs in turn have keratin branches (barbules) growing out from them in similar fashion. The opposing barbules then meet each other at an angle, producing a crisscross pattern. The barbules from the distal side of a barb usually have hook-lets along its length. Barbules from the proximal side of a barb usually have saw-tooth undersides.  Each upward pointing barbule will grip tightly onto several downward pointing saw-tooth barbules. Thus, each barb is securely bound to its two neighbors. This construction results in an effective flight feather. If the barbules and their hooks become defective then the whole fixture unravels. The feathers become hair-like silky feathers and are unable to support chicken flight. However, they provide good heat insulation.

feather-schematic

Silkie  has five toes on each foot, in contrast to four toes in most birds. The fifth toe is usually smaller and less functional. The wings are still in the standard tridactyly  (three digit) arrangement.

Silkie lays cream-colored eggs, about 100 per year. This is less than half what an average layer-hen does. The reason is because Silkie has a very strong mothering instinct. It gets broody frequently and then egg production is halted. This is also the reason why the Broody tendency is selectively bred out of egg production hens. Since Silkie hens accept eggs from other hens (even of other species), the farmers exploit the silkie to raise the offspring of other birds.

Another economic importance of Silkie is in Traditional Chinese Medicine (TCM). Silkie, a black bone chicken, is highly regarded in TCM for its potency in improving immunity and general wellbeing. This is especially so in China and South East Asia. Recently some western scientific studies have shown high levels of Carnosine in Silkie muscle cells. This is more than twice the level found in other breeds of chicken. Carnosine is an imidazole dipeptide with strong antioxidant ability. It scavenges oxygen-free radicals, thus protecting mitochondrial membranes from damage.

Nowadays, many colors have been bred into Silkie chickens: black, orange, lavender, red and cuckoo pattern.

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Photo 13. Also known as brown Silkie.

 

Article by Wong Kais

 

All Silkie chicken subjects were kindly provided by Thomas Hee (Singapore).

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