Study On Breeding Effect Of Hebei Domestic Chicken

As one excellent indigenous breed from Hebei province, Hebei Domestic chicken has many good characteristics, such as small size, remarkable adaptability to rearing under rudimentary conditions, stable heredity, excellent meat flavor, high nutritional value, and especially robust resistance to disease. In order to inspect the selection effect on Hebei Domestic chicken, SPASS15.0 was used to do multi-comparison and association analysis on its laying performance, slaughter performance and egg quality. Meanwhile, as a candidate gene affecting poultry production performance, MHC B-G gene was analyzed in this study. With the method of PCR amplification and directly sequencing, screening of Single Nucleotide Polymorphism (SNP), genetic diversity analysis and amino acid polymorphism analysis were done in exon 2 and partial intron 1 of MHC B-G gene of Hebei Domestic chicken with four plumage color strain (black, gray plumage color with black spots, yellow plumage color with black spots and white) and two red plumage color commercial chicken (Hy-Line Variety Brown and Lohmann Brown), so the variation of B-G gene in Hebei Domestic chicken could be enunciated as one reference for breeding of Hebei Domestic chicken new strain.Study on egg production heritability and combined selection index for forty-three week-old egg number of Hebei Domestic Chicken showed that that the egg production heritability of forty—three week—old of Hebei domestic chicken was 0.1323, without significant difference. The formula of combined selection index of the first generation was I=P+7.44Pf. And the combined selection index of each chicken was ranged from 50.314 to 105.857, providing the basis for selection and mating of Hebei domestic chicken.Comparison of laying performance showed that after selection of three generations, Hebei domestic chicken presented significant difference in laying performance:obvious extension of laying peak duration, more uniform production performance among different plumage color strain, significant increase of egg production at day 300 (P<0.01).In factor analysis for body size and slaughter production, a total of 5 common factors were extracted via comparison of characteristic roots of correlation coefficient matrix or covariance matrix. Factor-1 included carcass weight, live weight, chest depth, shank girth, body steep length, keel length and chest width; factor-2 included whole net carcass rate and semi net carcass rate; factor-3 included width of pelvis, wing percentage, fat ratio and shank length; factor-4 was chest angle; factor-5 included leg muscle rate and breast muscle rate. These five factors accounted for 87% of primitive variance. With the help of least square method, we analyzed the fixed effects on each of the aforementioned factor, which showed that plumage color had no significant effect on slaughter production (P>0.05), but there was extremely significant difference between cocks and hens (P<0.01). After artificial selection, each index for body size and slaughter production got one extremely significant improvement, providing reliable theoretical basis for future breeding of Hebei domestic chickens.Comparison and correlation analysis of the egg quality showed that flesh and blood spots had extremely significant positive correlation with eggshell strength and eggshell thickness, and had extremely significant negative correlation with haugh unit and eggshell ratio; yolk color had extremely significant negative correlation with eggshell thickness and eggshell strength (P<0.01), but had significant positive correlation with haugh unit (P< 0.05). Eggshell ratio had significant negative correlation with egg weight and egg shape index (P<0.05), had extremely significant positive correlation with egg ratio (P<0.01). Comparison of the egg quality showed that after artificial selection, the third Hebei domestic chicken generation got an extremely significant improvement (P<0.01) in eggshell strength and haugh unit, and a significant decrease in flesh and blood spots, bringing them tremendous competitiveness in domestic egg market.36 SNPs were detected within the partial B-G gene (encompassing exon2 and partial intron 1) in all analyzed populations by direct sequencing of PCR amplification product, and only 2 novel SNPs (g.863C>A and g.957C>A, based on NC₀06103) were found in Hebei Domestic Chicken. The genetic diversity analysis indicated that the haplotype diversity (0.963～0.995), the nucleotide diversity (0.024～0.027) and the average number of nucleotide differences (10.716～13.061) within each color strain of Hebei Domestic Chicken were all significantly greater than that of Hy-Line Variety Brown (0.942,0.022,10.345) and Lohmann Brown (0.873,0.024,10.947), indicating their rich genetic diversity.Alignment of the amino acid sequences form 210 individuals detected 20 nonsynonymous substitutions in total (site 36,37,48,59,61,65,68,69,75,76,78,81,89,92,95,96,106,109,116 and 122, based on NP₀01025844.1). Among the 20 substitutions mentioned above, eight (Iie48Asn,Arg68Ser,Leu69Ser,Leu75Gln,Va189Glu,Gly92Glu,Gly96Glu,Tyr109Ser) existed in each of the six analyzed populations. Except for substitutions at site 36,81,106 and 116, which only existed in Hebei Domestic chicken, the rest ones were found in all the analyzed populations. Meanwhile, variation rate of site 78 in Hebei Domestic chicken was higher than that in the two commercial chickens, with significant difference under chi-square test (P<0.05).