Chicken is the largest meat production and consumption product in the world. About 70% of the global chicken comes from white feather broilers. Chicken is the second largest meat product in China. Chicken in China mainly comes from white feathered broilers and yellow feathered broilers. The contribution of white feathered broilers to chicken production in China is about 45%, and that of yellow feathered broilers is about 38%.

White feathered broiler is the one with the lowest ratio of feed to meat, the highest degree of large-scale breeding and the highest degree of external dependence. The Yellow feathered broiler breeds used in China's production are all self bred breeds, and the number of breeds cultivated is the largest among all livestock and poultry breeds, which is a successful example of transforming the resource advantage of local breeds into product advantage.

1、 Development history of chicken breeds

Domestic chicken was domesticated by Asian jungle pheasant 7000-10000 years ago, and its domestication history can be traced back to more than 1000 BC. Domestic chicken is similar to the original chicken in body shape, feather color, song and so on. Cytogenetic and morphological studies have proved that the original chicken is the direct ancestor of modern domestic chicken. There are four species of the genus Gallinula, which are red (Gallus gallus, Fig. 3), green collar (Gallus various), black tailed (Gallus lafayetii) and Gray Striped (Gallus sonnerati). There are two different views on the origin of domestic chicken from the original chicken: the single origin theory holds that the Red original chicken may be domesticated once or more; According to the theory of multiple origins, in addition to the red jungle fowl, other Jungle Fowls are also the ancestors of domestic chickens. At present, most studies support the single origin theory, that is, domestic chicken mainly originated from red jungle fowl.

 

（1） Breeding process of foreign broilers

Before 1930s, the group selection and pedigree free cultivation were carried out. The main selection characters were egg production performance, chicken was by-product, and chicken breeding was a small-scale courtyard economic model. With the invention of the self closing egg box in the 1930s, the egg production performance was selected according to the individual egg production record; In the 1930s-50, using maize double hybrid technology as reference, heterosis was introduced into chicken breeding, which quickly replaced pure line breeding, and became the mainstream of commercial chicken production. The matching methods of hybridization have gradually developed from the earliest binary hybridization to the matching of ternary and Quaternary. The selection efficiency of limited and low heritability characters was improved after pedigree recording was started in 1940s, and the inbreeding decline caused by close relatives could be avoided. After 1945, random sample tests was carried out by some third-party institutions or test stations in Europe and America. The purpose was to objectively evaluate the varieties participating in the evaluation under the same environmental conditions, and played an active role in improving the market share of the excellent varieties with excellent performance. Such performance measurement work was terminated in the 1970s. In the 1960s-1980s, the main selection of easy to measure traits, such as egg production, hatching rate, growth rate and feed conversion rate, was mainly made of bone chicken and household consumption. The single cage determination of feed conversion rate since 1980s has played a direct role in reducing the consumption of broiler feed and improving the utilization rate of feed. Since 1990s, processing characteristics have been paid attention to, such as net bore weight and boneless sternum weight. The application of genetic evaluation methods such as the best linear unbiased prediction (BLUP) and the progress of computer technology play an important role in breeding development. After entering the 21st century, broiler breeding began to consider the quality of products and animal welfare. At present, the molecular breeding technology of broiler represented by genome wide selection (GS) is changing from research and development to application.

（2） The breeding process of Broiler in China

In the middle of 19th century, local chickens in China had been the world leading in laying eggs and meat production. For example, the introduction of wolf mountain chicken and nine Jin yellow chicken from Jiangsu and Shanghai in China, then from the UK to the United States, after breeding, it has been recognized as standard varieties in both countries. Langshan Chicken is considered as a dual use variety, and nine Jin yellow chicken is regarded as meat variety. These breeds have an important influence on the formation of some world-famous livestock and poultry varieties, such as the British oppington and Australian Black Australia have introduced the blood relationship of wolf mountain chicken in China. Rockcock, Luodao red and other breeds also take nine Jin yellow chicken as breeding materials. From the end of 19th century to 1930s, eggs and chicken are important export products in China. But in the long time after that, the industry of chicken raising in China stays at the extensive level of raising, and the production level of chicken is far from the advanced level in the world. In the mid-1960s, three local varieties of Huiyang chicken, Qingyuan hemp chicken and Shiqi chicken were selected as the main improvement objects in Hong Kong. The hybrid was carried out by using new Han Xia, bailoc, baikonish and habad to breed Shiqi hybrid chicken, which played an important role in the production and consumption of Hong Kong broilers. From the 1970s to 1980s, Shiqi hybrid chicken was introduced to Guangdong and Guangxi, and was crossbred with recessive white chickens, forming a modified Shiqi hybrid chicken and widely spread in production. From 1960s to 1980s, we used hybrid breeding and family selection to cultivate new wolf mountain chicken, Xinpu East chicken and xinyangzhou chicken. From 1983 to 2015, yellow feather broilers adopted the mode of breeding in the north and south, and made full use of the differences in the climate environment, feed, manpower and breeding technology between the north and the south, and raised the parents' chickens in the northern areas of Henan, Shanxi and Shaanxi. The commercial eggs were transported back to the south for incubation and raising, which improved the production efficiency of yellow feather broilers. The systematic breeding of yellow feather broiler started in the late 1980s. The introduction of recessive advantageous genes such as low and small grain saving genes (DW gene) and recessive white feather gene played an important role in the breeding of yellow feather broilers in China. About one third of the Yellow Feather Broiler breeds in China have applied these techniques. In 1986, Guangzhou Baiyun poultry development company introduced recessive white and Shiqi hybrid chicken to breed 882 yellow feather broilers. In 1999, Shenzhen kangdal (Group) Co., Ltd. bred the first matching line of yellow feather broiler 128 (Fig. 4) approved by the state. After that, the new breed cultivation of Yellow Feather Broiler in China entered a rapid development period. In order to coordinate the variety examination and approval, the Poultry Quality Supervision and inspection and Testing Center (Yangzhou) of the Ministry of agriculture and rural areas (Beijing) was established in 1998 and 2003 respectively, and was responsible for the national poultry production performance measurement.

 

2、 Development of modern broiler breeding at home and abroad

（1） Foreign development

Since the late 1950s, the progress of genetic breeding has laid the foundation for modern chicken production, promoted the specialization of egg and chicken production, and broiler production has become an independent poultry industry. Over the past 80 years, North America and Western European countries have carried out systematic genetic breeding for growth rate, feed reward and carcass composition of chickens, forming today's white feathered broiler breeds and rapidly occupying the global market. The male line of modern white feathered broiler is white Cornish chicken, and the female line is white Plymouth Rock chicken. The heterosis is produced by systematic mating. At present, including China, the main varieties used in the production of white feathered broilers in the world are AA +, Ross, Cobb, Hubbard and a few other varieties, which are from aviagen and Cobb vantress respectively. White feathered broiler has a mature and perfect breeding system, forming a pyramid structure composed of breeding core group, great grandparents, grandparents, parents and commercial chickens. It takes 4-5 years for the genetic progress of core group to be transmitted to commercial chickens (Fig. 5). One core group hen can produce more than 3 million commercial broilers and more than 5000 tons of chicken. At present, the world produces about 11.6 million sets of white feathered broiler grandparent breeders, 600 million sets of parent breeders and 80 billion commercial chickens every year.

 

3、 Problems and gaps

（1） White feather broiler breeding

Compared with the international advanced level of white feathered broiler breeding, China's independent white feathered broiler breeding time is short, the foundation of high production performance genetic material accumulation is weak, the application of new technologies such as molecular breeding is not enough, and there is a large gap in the research and development of provenance disease purification technology and detection products. The details are as follows: 1. Multinational companies have a series of excellent strains with fast growth and high meat production rate, and through the merger and reorganization of breeding companies such as broilers and layers, the materials and genes are further enriched, which provides a guarantee for the breeding of new varieties; The breeding resources of white feathered broiler in China have a weak foundation and few excellent breeding materials.

2. Breeding technology. Compared with the international multinational companies with more than 100 years of breeding experience, the breeding of white feathered broiler in China started late, and there is a big gap between the research and application of balanced breeding technology between growth and reproduction and international advanced level. The application degree of new technologies such as genome breeding is not high; Lack of high-throughput phenotype intelligent accurate measurement technology, data automatic collection and transmission application degree is low.

3. Purification technology of provenance diseases. Large international poultry breeding companies have taken effective purification measures for vertical transmission diseases of avian leukemia, pullorum and other provenances, significantly improving the competitiveness of products. The purification of avian leukemia and pullorum is a short board that hinders the development of China's breeding poultry industry, and the detection kits are heavily dependent on imports.

（2） Yellow feather broiler breeding

The breeding and production of yellow feathered broiler in China is at the leading level in the world. However, the number of breeding enterprises is large, the scale is uneven, the overall technical strength is weak, the application of advanced breeding technology is not enough, and the breeding facilities and equipment are relatively backward; There is a certain degree of repeat breeding phenomenon, and there are few core varieties with obvious characteristics, excellent performance and large market share; For a long time, the breeding goal is to adapt to the correlation of live poultry sales, such as feather color, body shape and appearance, which can not meet the market demand of centralized slaughtering and chilled products under the new situation.

There are abundant local chicken breeds in China, which have formed many excellent genetic characteristics under long-term and complex ecological and socio-economic conditions. However, for a long time, there is a lack of in-depth research on the characteristics of germplasm resources, the investigation and evaluation of variety resources are insufficient, and the analysis and evaluation are lack of sufficient information support. In addition, the construction of dynamic monitoring system of variety resources is insufficient, and the evaluation of resource characteristics with strong adaptability, high yield and high quality in genetic resources is not comprehensive and systematic, which leads to the serious shortage of mining and utilizing the excellent characteristics of local varieties, hinders the process of protection, development and utilization of local genetic resources, and affects the production level of poultry industry in China Market competitiveness of poultry products and sustainable development of poultry industry.