A significant quantitative trait locus on chromosome Z and its impact on egg production traits in seven maternal lines of meat-type chicken

Background:Egg production is economically important in the meat-type chicken industry.To better understand the molecular genetic mechanism of egg production in meat-type chicken,genetic parameter estimation,genome-wide association analyses combined with meta-analyses,Bayesian analyses,and selective sweep analyses were performed to screen single nucleotide polymorphisms(SNPs)and other genetic loci that were significantly associated with egg number traits in 11,279 chickens from seven material lines.Results:Yellow-feathered meat-type chickens laid 115 eggs at 43 weeks of age and white-feathered chickens laid 143 eggs at 60 weeks of age,with heritability ranging from 0.034–0.258.Based on meta-analyses and selective sweep analyses,one region(10.81–13.05 Mb)on chromosome Z was associated with egg number in all lines.Further analyses using the W2 line was also associated with the same region,and 29 SNPs were identified that significantly affected estimation of breeding value of egg numbers.The 29 SNPs were identified as having a significant effect on the egg number EBV in 3194 birds in line W2.There are 36 genes in the region,with glial cell derived neurotrophic factor,DAB adaptor protein 2,protein kinase AMP-activated catalytic subunit alpha 1,NAD kinase 2,mitochondrial,WD repeat domain 70,leukemia inhibitory factor receptor alpha,complement C6,and complement C7 identified as being potentially affecting to egg number.In addition,three SNPs(rs318154184,rs13769886,and rs313325646)associated with egg number were located on or near the prolactin receptor gene.Conclusion:Our study used genomic information from different chicken lines and populations to identify a genomic region(spanning 2.24 Mb)associated with egg number.Nine genes and 29 SNPs were identified as the most likely candidate genes and variations for egg production.These results contribute to the identification of candidate genes and variants for egg traits in poultry.

New insights into the associations among feed efficiency, metabolizable efficiency traits and related QTL regions in broiler chickens

Background: Improving the feed efficiency would increase profitability for producers while also reducing the environmental footprint of livestock production. This study was conducted to investigate the relationships among feed efficiency traits and metabolizable efficiency traits in 180 male broilers. Significant loci and genes affecting the metabolizable efficiency traits were explored with an imputation-based genome-wide association study. The traits measured or calculated comprised three growth traits, five feed efficiency related traits, and nine metabolizable efficiency traits.Results: The residual feed intake(RFI) showed moderate to high and positive phenotypic correlations with eight other traits measured, including average daily feed intake(ADFI), dry excreta weight(DEW), gross energy excretion(GEE), crude protein excretion(CPE), metabolizable dry matter(MDM), nitrogen corrected apparent metabolizable energy(AMEn), abdominal fat weight(Ab F), and percentage of abdominal fat(Ab P). Greater correlations were observed between growth traits and the feed conversion ratio(FCR) than RFI. In addition, the RFI, FCR, ADFI, DEW,GEE, CPE, MDM, AMEn, Ab F, and Ab P were lower in low-RFI birds than high-RFI birds(P < 0.01 or P < 0.05), whereas the coefficients of MDM and MCP of low-RFI birds were greater than those of high-RFI birds(P < 0.01). Five narrow QTLs for metabolizable efficiency traits were detected, including one 82.46-kb region for DEW and GEE on Gallus gallus chromosome(GGA) 26, one 120.13-kb region for MDM and AMEn on GGA1, one 691.25-kb region for the coefficients of MDM and AMEn on GGA5, one region for the coefficients of MDM and MCP on GGA2(103.45–103.53 Mb), and one 690.50-kb region for the coefficient of MCP on GGA14. Linkage disequilibrium(LD) analysis indicated that the five regions contained high LD blocks, as well as the genes chromosome 26 C6 orf106 homolog(C26 H6 orf106), LOC396098, SH3 and multiple ankyrin repeat domains 2(SHANK2), ETS homologous factor(EHF), and histamine receptor H3-like(HRH3 L), which are known to be involved in the regulation of neurodevelopment, cell proliferation and differentiation, and food intake.Conclusions: Selection for low RFI significantly decreased chicken feed intake, excreta output, and abdominal fat deposition, and increased nutrient digestibility without changing the weight gain. Five novel QTL regions involved in the control of metabolizable efficiency in chickens were identified. These results, combined through nutritional and genetic approaches, should facilitate novel insights into improving feed efficiency in poultry and other species.

The regulation of IMF deposition in pectoralis major of fast-and slow-growing chickens at hatching

Background： The lipid from egg yolk is largely consumed in supplying the energy for embryonic growth until hatching. The remaining lipid in the yolk sac is transported into the hatchling＇s tissues. The gene expression profiles of fast-and slow-growing chickens, Arbor Acres（AA） and Beijing-You（BJY）, were determined to identify global differentially expressed genes and enriched pathways related to lipid metabolism in the pectoralis major at hatching.Results： Between these two breeds, the absolute and weight-specific amounts of total yolk energy（TYE） and intramuscular fat（IMF） content in pectoralis major of fast-growing chickens were significantly higher（P 〈 0.01,P 〈 0.01, P 〈 0.05, respectively） than those of the slow-growing breed. IMF content and u-TYE were significantly related（r = 0.9047, P 〈 0.01）. Microarray analysis revealed that gene transcripts related to lipogenesis, including PPARG, RBP7, LPL, FABP4, THRSP, ACACA, ACSS1, DGAT2, and GK, were significantly more abundant in breast muscle of fast-growing chickens than in slow-growing chickens. Conversely, the abundance of transcripts of genes involved in fatty acid degradation and glycometabolism, including ACAT1, ACOX2, ACOX3, CPT1 A, CPT2, DAK, APOO, FUT9, GCNT1,and B4 GALT3, was significantly lower in fast-growing chickens. The results further indicated that the PPAR signaling pathway was directly involved in fat deposition in pectoralis major, and other upstream pathways（Hedgehog, TGFbeta, and cytokine–cytokine receptor interaction signaling pathways） play roles in its regulation of the expression of related genes.Conclusions： Additional energy from the yolk sac is transported and deposited as IMF in the pectoralis major of chickens at hatching. Genes and pathways related to lipid metabolism（such as PPAR, Hedgehog, TGF-beta, and cytokine–cytokine receptor interaction signaling pathways） promote the deposition of IMF in the pectoralis major of fast-growing chickens compared with those that grow more slowly. These findings provide new insights into the molecular mechanisms underlying lipid metabolism and deposition in hatchling chickens.

Chicken gga-miR-1306-5p targets Tollip and plays an important role in host response against Salmonella enteritidis infection

Background: Increasing evidence indicates that micro RNAs(mi RNAs) are involved in inflammatory response and immune regulation following pathogen invasion. The purpose of this study was to elucidate the roles played by Gallus gallus micro RNA-1306-5 p(gga-mi R-1306-5 p) in host responses against potential invasion by Salmonella enteritidis(SE) in chickens and the underlying mechanisms.Results: In present study, the expression levels of gga-mi R-1306-5 p were determined in both tissues and HD11 cells. The results showed that gga-mi R-1306-5 p was significantly increased following SE infection or lipopolysaccharide(LPS) stimulation. The dual luciferase reporter assay further validated that gga-mi R-1306-5 p targeted the Toll-interacting protein(Tollip), and thereby participated in the regulation of immune response against SE or LPS stimulation through binding with the 3′-untranslated region(3’UTR) of Tollip. Additionally, the expression of Tollip was significantly blocked by over-expressed gga-mi R-1306-5 p. The underlying mechanisms by which ggami R-1306-5 p modulated the production of pro-inflammatory cytokines were also investigated. Molecular biological assays demonstrated that overexpression of gga-mi R-1306-5 p promoted the production of pro-inflammatory mediators, including NF-κB, TNF-α, IL-6, and IL-1β, which produced effects similar to those of Tollip knockdown.Conclusions: Taken together, gga-mi R-1306-5 p induced by SE or LPS, regulates the immune response by inhibiting Tollip, which activates the production of inflammatory cytokines. This study has provided the first direct evidence that gga-mi R-1306-5 p targets Tollip, and is involved in the host response against SE.