Comparative analysis of melanin deposition between Chishui silky fowl and Taihe silky fowl

Investigating the impact of pigmentation variation of breast muscle on growth traits, melanin deposition, and gene expression in Xuefeng black-bone chickens

The blackness traits, considered an important economic factor in the black-bone chicken industry, still exhibits a common phenomenon of significant difference in blackness of breast muscle. To improve this phenomenon, this study compared growth traits, blackness traits, and transcriptome of breast muscles between the High Blackness Group (H group) and Low Blackness Group (L group) in the Xuefeng black-bone chickens. The results are as follows: 1) There was no significant difference in growth traits between the H group and the L group (P > 0.05). 2) The skin/breast muscle L values in the H group were significantly lower than those in the L group, while the breast muscle melanin content exhibited the opposite trend (P < 0.05). 3) A significant negative correlation was observed between breast muscle melanin content and skin/breast muscle L value (P < 0.05), and skin L value exhibiting a significant positive correlation with breast muscle L value (P < 0.05). 4) The breast muscle transcriptome comparison between the H group and L group revealed 831 and 405 DEGs in female and male chickens, respectively. This included 37 shared DEGs significantly enriched in melanosome, pigment granule, and the melanogenesis pathway. Seven candidate genes (DCT, PMEL, MLANA, TYRP1, OCA2, EDNRB2, and CALML4) may play a crucial role in the melanin production of breast muscle in Xuefeng black-bone chicken. The findings could accelerate the breeding process for achieving desired levels of breast muscle blackness and contribute to the exploration of the mechanisms underlying melanin production in black-bone chickens.

Transcriptome Profile Analysis Identifies Candidate Genes for the Melanin Pigmentation of Skin in Tengchong Snow Chickens

Tengchong Snow chickens are one of the most precious, black-boned chickens in Yunnan province and usually produce black meat. However, we found a small number of white meat traits in the chicken population during feeding. In order to determine the pattern of melanin deposition and the molecular mechanism of formation in the Tengchong Snow chicken, we measured the luminance value (L value) and melanin content in the skin of black meat chickens (Bc) and white meat chickens (Wc) using a color colorimeter, ELISA kit, and enzyme marker. The results showed that the L value of skin tissues in black meat chickens was significantly lower than that of white meat chickens, and the L value of skin tissues gradually increased with an increase in age. The melanin content of skin tissues in black meat chickens was higher than that of white meat chickens, and melanin content in the skin tissues gradually decreased with an increase in age, but this difference was not significant (p > 0.05); the L value of skin tissues in black meat chickens was negatively correlated with melanin content, and the correlation coefficient was mostly above -0.6. In addition, based on the phenotypic results, we chose to perform the comparative transcriptome profiling of skin tissues at 90 days of age. We screened a total of 44 differential genes, of which 32 were upregulated and 12 were downregulated. These DEGs were mainly involved in melanogenesis, tyrosine metabolism and RNA transport. We identified TYR, DCT, and EDNRB2 as possible master effector genes for skin pigmentation in Tengchong Snow black meat chickens through DEGs analysis. Finally, we measured the mRNA of TYR, DCT, MC1R, EDNRB2, GPR143, MITF, and TYRP1 genes through a quantitative real-time polymerase chain reaction (qPCR) and found that the mRNA of all the above seven genes decreased with increasing age. In conclusion, our study initially constructed an evaluation system for the black-boned traits of Tengchong Snow chickens and found key candidate genes regulating melanin deposition, which could provide an important theoretical basis for the selection and breeding of black-boned chickens.

The Effects of Purple Corn Pigment on Growth Performance, Blood Biochemical Indices, Meat Quality, Muscle Amino Acids, and Fatty Acids of Growing Chickens

This study investigated the effects of dietary supplementation with different levels of purple corn pigment (PCP) on the growth performance, blood biochemical indices, meat quality, muscle amino acids, and fatty acids of growing chickens. A total of 288 (8 weeks of age) growing Chishui black-bone chickens (body weight, 940 ± 80 g; mean ± standard deviation) were randomly divided into 4 groups using a completely randomized design. The four diet groups were as follows: (1) control, basal diet; (2) treatment 1, treatment 2, and treatment 3, which were basal diet with 80, 160, and 240 mg/kg PCP, respectively. The results showed that compared with the control group, the feeding of anthocyanins significantly (p < 0.05) increased the average daily feed intake and average daily gain in chickens. Moreover, chickens receiving 80 mg/kg PCP significantly increased (p < 0.05) plasma total antioxidant capacity, superoxide dismutase, glutathione peroxidase, catalase, high-density lipoprotein cholesterol, and albumin concentrations relative to the control group. For meat quality, dietary supplementation with PCP significantly (p < 0.05) reduced the drip loss and water loss rate in breast muscle. Additionally, chickens receiving PCP tended to increase (p < 0.05) the levels of most individual amino acids, essential amino acids, and umami amino acids in the muscle. Specifically, the addition of 80 mg/kg PCP significantly improved (p < 0.05) total polyunsaturated fatty acids in chicken muscle. Accordingly, the consumption of anthocyanin-rich PCP by the growing chickens had the potential to increase the growth performance, enhance antioxidant and immune capacities, increase meat quality, and improve essential and umami amino acids as well as unsaturated fatty acids in the muscle.