Study On Breed Characteristies And Production Performances Of Pengxian Yellow Chicken

Pengxian yellow chicken is one of the outstanding local chicken breeds in China.It has good adaptability,tender meat,and delicious taste,it is representative of yellow chickens widely distributed in Chengdu plains and hilly regions.In the 1980 s and 1990 s,duing to the introduction of large numbers of foreign chicken breeds,the quantity of yellow chickens in Pengxian County town plummeted,and the only part of the breeds appeared mixed.The germplasm resources quickly shrank and were on the verge of extinction.With the constant attention of the country to the genetic resources of livestock and poultry,the City of Chengdu conducted a survey of Pengxian yellow chicken germplasm resources in 2008 and collected live animals from Tianhua Poultry for conservation and utilization.For a comprehensive understanding of the germplasm resources characteristics and basic production performance of Pengxian yellow chicken,the first study analyzed the mtDNA D-loop region sequence of Pengxian yellow chicken preserving population,combined with the existing data of GenBank,analyse the genetic diversity and origin of Pengxian chicken;Comparing the growth performance and meat quality of different Shank color in Pengxian Yellow Chicken,clear the development direction of breeding;Using growth curve fitting to develop a rational breeding program and scientific management model for Pengxian Yellow Chicken;Analysis of the correlation between body size and slaughter performance of 180-day-old Pengxian yellow chicken,comparison of the egg quality of different egg-laying ages.The main results are as follows:1.The mitochondrial D-loop region sequence of mitochondrial DNA in Pengxian yellow chicken was measured to be 504 bp to 506 bp in length.A total of 15 polymorphic sites were detected and divided into 7 haplotypes with a nucleotide diversity(Pi)of 0.00694± 0.000758,the haplotype diversity(Hd)was 0.713±0.041.The NJ method was used to construct the phylogenetic tree,it was found that the Pengxian yellow chicken had three branches,probably from three maternal origins.2.Both shank color of the Pengxian Yellow Chicken group slaughter rate reached 85%,the half net thorax weight ratio 75%,the rate of total net thorax was higher than 60%,the chest muscle rate was 11.54% to 12.28%,and the leg muscle rate was 19.28%~24.54%,indicating that Pengxian yellow chicken has good meat production performance.In addition to the abdomen index ratio of white shank color cock significantly higher than the yellow shank color cock(P <0.05),the remaining slaughter indicators were not significant.There were no significant differences in flesh color,drip loss,moisture,dry matter,crude fat,intramuscular fat and crude protein among different shank color of populations.The total amino acid content,essential amino acids and umami amino acids of white shank color hens were significantly higher than those of yellow hens(P<0.05),but there was no significant difference between cocks.In addition,the fatty acid content was not significantly different between different shank color,and the content of inosinic acid in yellow chicken was significantly higher than that of white chicken(P<0.05).3.Gompertz,Logistic and Bertalanffy three models on the growth curve of Pengxian yellow chicken fitting(R2)are more than 0.995,and can be used for the fitting growth curve of Pengxian yellow chicken,among which Gompertz model can well fit each week-old weight,indicating that the Gompertz model has the best fitting effect on the growth curve of Pengxian yellow chicken.4.There was a significant or extremely significant positive correlation between body size and slaughter performance of the Pengxian yellow chicken for 180 days(P<0.05 or P<0.01);The first pair of canonical correlation coefficients between body traits and slaughter performance of male and female chickens were 0.971 and 0.927,respectively,and their contribution rates were 0.974 and 0.817,both of which were extremely significant.The indicators that play a major role in both traits are body mass.The indicators that play a major role in the two groups of traits are body length,half net sucking rate,and total net sucking rate.The results of the study indicate that the selection and breeding of Pengxian yellow chicken slaughter performance can use Body length as the main reference index for indirect selection.5.The egg quality and egg weight,yolk weight and egg ratio of Pengxian yellow chicken increase with age,the three indexes at 155 days were significantly lower than the other three time points(P<0.05);The egg shell strength and shell thickness at 155 days and 400 days were significantly lower than 240 days(P<0.05),but there was no difference with 300 days old(P>0.05);The protein height and Harbin's unit were better at 240 days and 300 days,which were significantly higher than those at 155 days(P<0.05),but not at 400 days(P>0.05).The results showed that Pengxian yellow chicken had the best mid-stage egg production(240-300 days old),and the egg quality gradually decreased as the age increased.In summary,this study shows that the mtDNA D-loop region of Pengxian yellow chicken is not rich in polymorphism and has three maternal origins.During the breeding of Pengxian yellow chicken,the Gompertz model can be used to fit the growth curve,and the length of body is used as the main reference to indirectly select the growth performance,and try to select the mid-spring egg laying(240-300 days old)for early seeding,and provide scientific guidance for the development of the breeding scheme of Pengxian yellow chicken and early breeding selection.