Study On Breeding Of Specialized Line And Association Of Gene Polymorphisms With Egg Traits Of Dehua Black Chicken

Dehua black chicken is a rare breed in fujian province, and has many excellent characteristics, such as strong wildness, crude feed tolerance, good meat quality, rich nutrition and medicinal function. At the same time,it has the disadvantage of poor laying performance and small individuals. In order to make use of the excellent characteristics better, synthetic line combinations were used through specialized lines by selection and breeding to improve production performance based on conservation population; The relationship between genes and production traits of Dehua black chicken were analyzed at a molecular level to provide certain theoretical basis to genetic markers of economic traits of Dehua black chicken.In the reseach, specialized lines of Dehua black chicken was studied and production performance and breeding progress of specialized lines were analyzed, moreover, the association of the 5'region of IGF-Ⅰg ene, the exon2 and exon6 of VIPR-Ⅰgene polymorphism with egg traits in 500 Dehua black chickens were detected and analyzed by means of PCR-RFLP. The main results were showed as follows:1. The specialized strains of Dehua black chicken had obvious and tidy appearance characteristics by researching; At about 8 weeks of age the body was growth rapidly and it was in peak period of daily gain during 6 to 12 age.w, while the growth rate significantly decreased from 12 age.w on. Great improvement of laying performance for the specialized strains of Dehua black chicken had been made through selection and breeding, meanwhile, its egg quality was good. The carcass traits of cocks and hens was significant difference, shown as the live weight, carcass weight, half net thorax weight, whole net thorax weight, leg muscle weigh and leg muscle rate of cocks were extremely significantly higher than that of hens(P<0.05) and breast muscle weight of cocks was higher than that of hens although the difference was not significant(P>0.05), however, hens had significantly higher than cocks on abdominal fat weight and the percentage of abdominal fat(P<0.05). Effectiveness of mass selection was confirmed by the phenotypic results obtained in this experiment with body weight at 10 age.w for generation 3 increasing from 740.26 g(±127.95 g) to 808.35 g(±102.11 g) and coefficient of variation decreasing from 17.28% to 12.63% compared with generation 2 in sire line, meanwhile, the implementation heritability on body weight at 10 age.w was 0.3825; The egg number at 300 days of age for generation 3 was increased to 82.83 (±25.12) from 61.94 (±18.24) and increased by 33.73% compared with generation 1 in sire line, meanwhile, the implementation heritability on egg number at 300 days of age was 1.1938. Effectiveness of mass selection was also confirmed by the phenotypic results obtained in this experiment with egg number at 300 days of age for generation 3 increasing from 62.65 (±17.16) to 90.18 (±24.99) and increased by 43.94% compared with generation 1 in dam line, meanwhile, the implementation heritability on egg number at 300 days of age was 0.6858; The body weight at 10 age.w for generation 2 was increased to 735.46g (±85.28 g) from 729.35 g (±122.71 g) and coefficient of variation was decreased to 11.6% from 16.82% compared with generation 2 in dam line, meanwhile, the implementation heritability on body weight at 10 age.w was 0.8268.2. The PCR products of the 5'region of IGF-Ⅰgene, the exon2 and exon6 of VIPR-Ⅰgene were digested by PstⅠ, HpaⅡ, TaqⅠenzyme, and all arised 3 genotypes, one A-T mutation was at PstⅠsite, one A-G mutation was at HpaⅡsite, and one A-C mutation was at TaqⅠsite. Genotype frequency AA, AB, BB were 0.1937, 0.4867, 0.3196 and Allele frequencies A, B were 0.4370, 0.5630 at PstⅠsite, which were in Hardy-Weinberg equilibrium by chi square test; Genotype frequency CC, CD, DD were 0.3285, 0.4686, 0.2029, and allele frequencies C, D were 0.5628, 0.4372 at HpaⅡsite which were in Hardy-Weinberg equilibrium by chi square test; Genotype frequency EE, EF, FF were 0.0872, 0.3390, 0.5738, and Allele frequencies E, F were 0.2567, 0.7433 at TaqⅠsite which were not in Hardy-Weinberg equilibrium by chi square test. Dehua black chicken has moderate polymorphism(0.5>PIC>0.25) by analysis of genetic polymorphism at gene loci.3. In the age at first laying and body weight, genotypes of PstⅠsite had not significantly effect on the age at first laying, 160 days weight, 240days weigh and 300 days weigh(P>0.05), but the age at first laying and body weight of allele A had the lower trend than allele B; Genotypes of HpaⅡsite had significantly effect on 160 days weight, 240days weigh and 300 days weight (P<0.05) except the age at first laying, manifested as DD genotype had significantly higher body weight at 160 and 240 days of age than CC genotype(P<0.05), DD genotype had significantly higher body weight at 300 days of age than CD genotype(P<0.05), on the whole, allele C had lower than allele D on the body weight at laying period; Genotypes of TaqⅠs ite had not significantly effect on the age at first laying and body weigh each other(P>0.05).4. In laying traits and egg weight, genotypes of PstⅠsite had significant effect on the egg number at 240 and 300 days of age (P<0.05) except egg weight at 300 days of age, manifested as AA genotype had significantly higher egg number at 240 and 300 days of age than BB genotype(P<0.01), AA genotype had higher egg production at 300 days of age than BB genotype(P<0.05), on the whole, allele A had higher than allele B on laying traits; Genotypes of HpaⅡsite had significantly effect on the egg weight and egg production at 300 days of age (P<0.05) but not significantly effect on the egg number at 240 and 300 days of age (P>0.05), manifested as DD genotype had significantly higher egg weight at 300 days of age than CC genotype(P<0.05) and DD genotype had the trend of higher egg number, on the whole, allele D had higher than allele C on laying traits and egg weight; Genotypes of TaqⅠsite had the trend of FF genotype>EF genotype>EE genotype on egg number at 240 days of age, FF genotype had higher egg number than EF genotype (P<0.05), on the whole,allele F had higher than allele E on laying traits.