Analysis On The Growth Rule Of Breeding Population Of Lueyang Black-Bone Chickens And The Correlation Between Body Weight And SNP Of Candidate Genes

Lueyang black-bone chickens,which are the endemic breed of large black-bone chickens in China,are native to the Heihe area between Shannxi and Sichuan provinces.Lueyang black-bone chickens are also called Heihe black-bone chicken,which is the largest black-bone breed among the China’s four black-bone chickens.The other breeds are Taihe black-bone chickens,Yunyang black-bone chickens and Jiangshan black-bone chickens.The features that define the Lueyang black-bone chicken breed are strong disease resistance,better meat quality and high medicinal value.However,due to the depression of inbreeding,the population of Lueyang black-bone chickens has a relatively low genetic diversity,slow growing and production performance degradation.The increased costs are the bottleneck to the development of the Lueyang black-bone chickens industry.China is one of the countries with the largest amount of chicken breeding and the highest consumption level in the world.For decades,Chinese breeder flocks mainly rely on foreign imports,resulting in the variety and number of breeder flock continue to decrease.After a long period of mergers and integration,international breeding companies have formed a relatively stable technology monopoly group.Recently,frequent outbreaks of both domestic and foreign bird flu lead to the restriction of imports and exports.Therefore,the domestic breeding of local chicken breed is imperative.In order to investigate the growth curve of Lueyang black-bone chickens P1 and P2 population during the 1-10 weeks growth period,three nonlinear models which included Logistic,Gompertz and Bertalanffy models are chosen.PCR-SSCP and DNA sequencing method were used to study genetic variations of five growth-related genes,which included MSTN,KLF7,Smad3,FOXO1 and KPNA3 genes.The association between the growth performance of P1 population and genotypes were analyzed and verified in the P2 population.The results of experiments were as follow:(1)The growth curve fitting of early body weight was studied in Lueyang black-bone chickens P1,P2 and P3 populations.The results indicated that the Gompertz model was the best choice to estimate the Lueyang black-bone chickens` weight in the early period.The growth inflexion is 7-8 weeks old.(2)With the comparison of P1 and P2 populations’ growth curve,the significant differentiation between rooster and hen was observed at 5-6 weeks.(3)After the comparison of the weekly weight observation values and weekly gain curve,the results indicated that with the continuous generations of selection,the weight and weekly gain of Lueyang black-bone chickens were prompted significantly by animal breeding.(4)AA type of MSTN gene had high 8-weeks-old weight than GA and GG type(P<0.05).(5)TA type of KLF7 gene had high 8-weeks-old weight than AA type(P<0.01).(6)Genotypes among Smad3,FOXO1 and KPNA3 genes showed no significant diversity.Above all,the Gompertz model was the best choice to estimate the Lueyang black-bone chickens` weight in the early period Gompertz.The growth inflexion is 7-8 weeks old.Growth rate and uniformity of P3 population is the best,followed by P2 and P1 populations.The SNPs of MSTN and KLF7 genes can be used as the candidate genes of marker assisted selection.All the results provide a scientific theoretical basis for the formulation of high efficiency breeding standards and the early and accurate selection of chickens.