Studies On Egg-laying Performance And Polymorphism Of Relavent Candidate Genes (GnIH) In The Underlying Group Of New Local Hens

Chinese local chicken is rich genetic resources, has many characteristics, such as sweet-meated and hardiness. Its production performance is low, which affect the economic benefits of local chichen. In this study, the underlying group of new local hens is created by the hybridization of Er-lang mountainous chickens (S) and Hei-kang chickens (H). Then hybrid chickens of HS, HS1, underlying group was obtained using♂Hx♀S,♂HSx♀HS,♂Hx♀HS1, respectively. This research was conducted to analyze the laying performance and egg quality of underlying group, which provides the basic theory for breeding of local laying chicken. Meanwhile we analyzed the relationship between the polymorphism of underlying group GnIH gene and laying characters to explore candidate gene associated with high laying performance, which pave the way for effective breeding and shorten the generation gap using Marker-assisted selection (MAS) in the future.According to the laying performance, egg production within300days of underlying group was117.42, which is significantly higher than S, HS and HS1(P<0.01). HU of underlying group was80.776and Egg strength was5.221km/cm2. They were significantly higher (P＜0.05) than that of S, HS and HS1. The results indicated that laying performance of underlying group worked well.According to the egg laying curve fitting, the fitting degree of McMillan, Wood and Yang-Ning model:R2=0.995,R2=0.979and R2=0.852. The results indicated that we can use Yang-Ning model fit the curve of egg production in future breeding work.According to the correlative analysis of laying performance, age at first egg was highly significantly positive correlated to bodyweight at first egg (P＜0.01, r=0.21), highly significantly positive correlated to egg weight at first egg (P＜0.01, r=0.18), highly significantly negative correlated to egg weight at300days (P＜0.01, r=0.15), and highly significantly negative correlated to egg production within300days (P＜0.01, r=-0.42). Bodyweight at first egg was highly significantly positive correlated to egg weight at first egg (P＜0.01, r=-0.15), highly significantly negative correlated to egg production within 300days (P＜0.01, r=-0.19). Egg production within300days was significantly negative correlated to egg weight at first egg (P<0.05, r=-0.06), highly significantly negative correlated to egg weight at300days (P＜0.01, r=-0.11).According to the correlative analysis of egg quality, eggshell color was highly significantly negative correlated to HU (P＜0.01, r=-0.20), highly significantly positive correlated to egg shape index (P＜0.01, r=0.24). Egg strength was highly significantly positive correlated to eggshell thickness (P<0.01, r=0.46). Egg shape index was highly significantly negative correlated to HU(P<0.01, r=-0.19).A total of5SNPs was detected in GnIH gene sequence, including T3305C、 T3310C、G3403C、G3411A、T3591C (GeneBank NO:AB193126), in which located at3’-UTR. SNP1was completely linked to SNP3. Correlative analysis between SNPs and laying characters was conducted. It indicated that SNP1(SNP3) was highly significantly correlated with age at first egg (P<0.01) and significantly correlated with egg production within300days (P＜0.05). SNP2was significantly correlated with egg production within300days (P＜0.05).. SNP4was highly significantly correlated with age at first egg (P＜0.01). SNP5was highly significantly correlated with body weight at first egg (P<0.01). No significant correlated was detected between these5SNPs and egg weight at first egg and egg weight at300days.A total of6haplotypes and9haplotype combination was obtained. It indicated that haplotype combination was highly significantly correlated with age at first egg, egg weight at first egg, body weight at first egg, and egg production within300days (P＜0.01). H3H4was the dominate haplotype combination for age at first egg, body weight at first egg and egg weight at first egg. H4H5was recessive haplotype combination for egg weight at first egg and dominate haplotype combination for egg production within300days. Therefore H3H4was the best haplotype combination for egg production, which is the potential marker for laying performance.