Effect Analysis On The Selection Of Pengxian Yellow Chicken And Its Hybridization With Recessive White Feather Broilers

Pengxian yellow chicken is one of the excellent local breeds of chicken in China.It has good adaptability,delicate meat quality and delicious taste.It is a representative type of yellow chicken widely distributed in Chengdu plain and hilly areas.From 1980 s to 1990 s,the introduction of high-yielding chicken breeds abroad led to the rapid decline of germplasm resources and on the verge of extinction.In view of this,Chengdu government carried out a survey of its germplasm resources and planned to protect and develop this precious breed.However,due to the lack of systematic and scientific breeding and selection methods,the appearance of Pengxian yellow chicken appeared to be separated and its production performance deteriorated continuously.In order to promote the industrialization of Pengxian yellow chicken,the research group on poultry breeding of Sichuan Agricultural University and Tianhua Poultry Industry Co.,Ltd carried out systematic conservation,purification and rejuvenation of Pengxian yellow chicken,and introduced the female parent of recessive white feather broiler for hybridization.This experiment measured the appearance characteristics,production performance and positive rates on diseases of Pengxian yellow chickens for different generations in order to explore the breeding progress of Pengxian yellow chickens,and compared the production performance of the second generation of pure lines and hybrid combinations to explore the hybridization effect.At the same time,the growth and laying rate of the two kinds of chicken were fitted to provide reference for the breeding and cross utilization of Pengxian yellow chicken.The main results were as follows:(1)After the purification and selection for 2 generations,the proportion of the variegated feathers of Pengxian yellow chickens decreased from 25.63% in the 0th generation to 9.60% in the 2nd generation,and the flesh-colored shank of the 2nd generation increased from 79.86% in the 0th generation to 96.40% in the 2nd generation,the appearance characteristics tend to be consistent.(2)The live-weight,slaughter weight,half-eviscerated weight,eviscerated weight,breast muscle weight and leg muscle weight of the cocks of the 2nd generation at 180 days old were significantly higher than those of the 0th generation(P < 0.05).The age at first egg of Pengxian yellow chickens decreased from 181.2 days in 0th generation to 166.8 days in 2nd generation and shortened by 14.4 days,shortened by 7.2 days averagely in each generation.The egg production for 300 days improved from 72.8 eggs in 0th generation to 84.7 eggs in 2nd generation and the laying performance improved significantly.(3)The hybrid offspring basically retained the feather color of Pengxian yellow chicken,and the weight of each week was significantly higher than that of the pure line(P < 0.05).The live weight of 150-day-old hybrid cocks was 311 g larger than that of the pure line,and the slaughter weight,half-eviscerated weight,eviscerated weight,breast muscle weight and leg muscle weight were also significantly larger than those of pure line(P < 0.05),the meat performance improved greatly.The body weight at first laying,the egg weight at first laying,the egg production for 300 days and the egg weight at 300 days were significantly better than those of Pengxian yellow chickens(P < 0.05)and there were no significant differences in egg quality traits such as eggshell color,index of egg shape,eggshell strength and haugh unit(P > 0.05).(4)After two generations of disease purification,the positive rate of pullorum for Pengxian yellow chickens(male)decreased from 3.96% in the 0th generation to 0.25% in the 2th generation and from 3.78% to 0.11% for hens.The positive rate of leucosis decreased from 5.31% in the 0th generation to 0.73% in the 2th generation and from 4.94% to 0.53% for hens.The obvious effect had been achieved in disease purification.(5)The curve models of growth(Gompertz,Logistic,Von Bertalanffy)and laying rate(Wood,McMillan,Yang-Ning)were utilized to fit the rules of growth and laying rate on Pengxian yellow chickens in 2nd generation and cross combinations.The results showed that the best fitting models of growth curve for Pengxian yellow chicken and cross combination were Von Bertalanffy model while the best fitting models of laying rate curve for Pengxian yellow chicken and cross combination were Yang-Ning model model,which could predict the rules of growth and laying rate of Pengxian yellow chicken and its cross combination respectively,and provide basis for further breeding and feeding management.In conclusion,after systematic breeding for two generations,Pengxian yellow chicken had made remarkable progress on appearance characteristics,growth performance,body size and slaughter performance,egg production performance,disease purification and so on,basically realizing the original intention of protection and purification on Pengxian yellow chickens.The hybridization of recessive white feather broiler and Pengxian yellow chicken had significant heterosis.The cross combinations inherited some advantages of recessive white feather broilers such as fast growth,good meat performance and high egg laying performance etc.While most of the egg and meat quality traits did not show significant decline,in addition,the appearance characteristics of cross combinations retained the features of Pengxian yellow chickens.