Interaction of fibromelanosis gene with various genetic backgrounds affecting carcass pigmentation in crossbred Kadakanath chicken

Kadakanath is an important indigenous breed of India, which is locally known as “Kalamassi” meaning the fowl having black flesh, caused due to a genetic condition called “fibromelanosis”. To study the inheritance of the skin-colour pigmentation, Kadakanath (KN) was crossed individually with four other chicken breeds with known background for skin colour genes. Breed-crosses along with reciprocals were produced by crossing KN separately with White Leghorns (KWL), White Plymouth Rock (KWR), Rhode Island Red (KR), Aseel Peela (KAP) and Aseel Kagar (KAK) and were compared to a pure KN group. All experimental chickens were slaughtered at 12 weeks of age to visually evaluate the skin-pigmentation across comb, wattle, breast, thigh, shanks and visceral organs. The analysis revealed that KWL and KWR backgrounds imparted a masking effect on melanin deposition in the males, while KWL and KWR females exhibited intermediate melanin deposition. The reciprocal crosses (WLK and WRK) were totally devoid of pigmentation not only in the skin but also in the visceral organs. The KR, KAK, KAP were intermediate in skin melanosis in both straight and reverse crosses, ruling out presence of any sexual dimorphism in melanosis. It was concluded that fibromelanosis was primarily caused due to a single autosomal gene (Fm) that exhibited incomplete dominance. The study also highlighted the epistatic effect of the dominant sex-linked ‘Id’ gene in White Leghorns and White Plymouth Rock crosses on ‘Fm’ induced melanin deposition. Further studies on elaborating on the interaction of Id and Fm are necessary to understand the physiological basis of fibromelanosis.