
Description:
This gene causes black skin, eyes, organs, and some plumage colors in chickens. Contrary to some media, the fibro gene in chickens does not cause the chicken to also lay black eggs. It is most commonly seen in the Ayam Cemani and Silkie breeds, though it can be introduced into other crosses and has been recently seen in the Zombie Cross (Leghorn x Cemani).
Fibro is not sexlinked, though it can have more of a prominent affect on females over males in some breeds (like leghorn and white rocks) due to a separate sex-linked gene that enhances the affect.
It is considered an almost completely dominant gene in cemanis, meaning that it is very hard to tell if a bird has only one copy or two copies of the gene in cemanis, and all crosses will share similar characteristics (black skin, organs, eyes, etc.) It has been found that in heterozygous form, the bird will often have reddish black leadage in the comb (2), and it is uncertain if other slight leakage (pink leakage on the tongue, white toenails, etc) is also due to the gene being heterozygous or if it is just natural variance. Fibromelanosis does not affect the plumage color at all, as seen in buff, white, and other varieties of Silkie.
The APA only recognizes Silkies with black skin and fibro gene, though the Ayam Cemani Breeders Association is working to get APA recognition as well.
Breeding with Fibro:
Fibro x Fibro = 100% Complete fibro
Fibro bird x Non-fibro = 100% fibro chicks with red leakage
Fibro x Leakage = 50% chicks with leakage, 50% complete fibro
Leakage x non-fibro = 50% leakage, 50% non-fibro
Leakage x leakage = 25% non-fibro, 50% leakage, 25% complete fibro
References & Further Reading
Lukanov, H., & Genchev, A. (2013). Fibromelanosis in domestic chickens. Agricultural Science and Technology, 5, 239-246.
Identification of variation in Fibromelanosis region on chromosome 20 for determining the purity of Indonesian Cemani chicken.
Anik Budhi Dharmayanthi, Keiji Kinoshita, Isyana Khaerunnisa, Rona Saumy Safitry, Syam Budi Iryanto, Yohanna, Sutikno, Andi Baso Lompengeng Ishak, M Syamsul Arifin Zein, Yoko Satta, Toyoko Akiyama, Cece Sumantri
bioRxiv 2022.11.13.516295; doi: https://doi.org/10.1101/2022.11.13.516295
Zhang, X., Wang, H., Lou, L., Li, Q., Zhang, L., & Ge, Y. (2022). Transcript expression profiling of fibromelanosis-related genes in black-bone chickens. British Poultry Science, 63(2), 133–141. https://doi.org/10.1080/00071668.2021.1966750
Mishra, S. K., Arora, G., Pratap, S. O., Singh, D. P., Narayan, R., & Beura, C. K. (2008). Interaction of fibromelanosis gene with various genetic backgrounds affecting carcass pigmentation in crossbred Kadakanath chicken. Indian Journal of Poultry Science, 43(3), 267-271.
Ai Shinomiya, Yasunari Kayashima, Keiji Kinoshita, Makoto Mizutani, Takao Namikawa, Yoichi Matsuda, Toyoko Akiyama, Gene Duplication of endothelin 3 Is Closely Correlated with the Hyperpigmentation of the Internal Organs (Fibromelanosis) in Silky Chickens, Genetics, Volume 190, Issue 2, 1 February 2012, Pages 627–638, https://doi.org/10.1534/genetics.111.136705
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