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(agricultural Wealth net) the role and application of pig breeds in pig production I urgently need this manuscript, who can contribute? In a hurry! -- , no one gave it to you.-- Why are you so gloating upstairs? China is very rich in genetic resources of local pig breeds, which has not only attracted the attention of the Chinese people, but also made a great contribution to the improvement of pig breeds in the world. As early as two thousand years ago, the Roman Empire introduced Chinese pig breeds. at the beginning of the 19th century, the United States, Britain and other countries introduced Panyu pigs from Guangdong, and then spread to Germany, France, Japan and other countries, and participated in the breeding of Yorkshire pigs, Baksha pigs, Bozhong pigs and other breeds. In recent years, France, Japan, Britain, the United States, Canada and other countries have made use of China's excellent local breeds to cultivate some excellent lean pig breeds. According to the investigation of breed resources and the status of Livestock and Poultry genetic Resources in China (2004), there are 99 pig genetic resources in China, including 72 local breeds, 19 cultivated breeds and 8 introduced breeds. The main results are as follows: 1 the classification of local pig breeds in China can be divided into North China type according to the feeding and management methods, physical appearance and production performance of local pig breeds, as well as natural conditions such as climate, agricultural production, social economy and other factors. Medium-sized China, South China type, southwest type, Jiangnan type and plateau. 1.1 North China type (5) is mainly distributed in the north of Huaihe River and Qinling Mountains. Main pig breeds: northeast Min pig (northeast), Huang Huai Hai black pig (Hebei, etc.), Hanjiang black pig (Shaanxi), Yimeng black pig (Shandong), Bamei pig (Gansu) and so on. 1.2 South China type (9) are mainly distributed in the south of Nanling and Pearl River basins. Main pig breeds: Xiang Pig (Yunnan-Guizhou Plateau), Luchuan Pig (Guangxi), Taoyuan Pig (Taiwan), Wuzhishan Pig (Hainan), Guangdong Xiaoer Black back Pig (Guangdong) and so on. 1.3 Jianghai type (7) are mainly distributed between the Huaihe River and the Yangtze River. Main pig breeds: Taihu pig (Shanghai, etc.), Jiang Quhai pig (Jiangsu), Hongqiao pig (Zhejiang), Yangxin pig (Hubei), Wei pig (Anhui) and so on. 1.4 medium-sized China (19) are mainly distributed between the Yangtze River and the Pearl River. Main pig breeds: Jinhua pig (Zhejiang), Dahuabai pig (Guangdong), Ningxiang pig (Hunan), Wannan Hua pig (Anhui) and so on. 1.5 Southwest type (7) are mainly distributed in Yunnan-Guizhou Plateau and Sichuan Basin. Main pig breeds: Neijiang pig, Rongchang pig, Wujin pig (the only red-haired pig in China) and so on. 1.6 the plateau (1) is distributed in the Qinghai-Xizang Plateau. Main pig breed: Tibetan pig. 2 the genetic diversity of local pig breeds in China, especially the excellent germplasm characteristics of local pig breeds have long been famous all over the world, such as early sexual maturity, high fecundity, strong stress resistance, large litter size, strong adaptability, rough feeding resistance, cold resistance and so on. 2.1 High fecundity Chinese local pig breeds have excellent reproductive characteristics, such as early sexual maturity, more ovulation, high conception rate, large litter size, less postpartum diseases, strong ability to care for piglets and high breeding rate of piglets. In terms of litter size and ovulation, local pig breeds in China can be divided into multiple types, such as Taihu pig, Jinhua pig, Min pig and so on, and common types, such as Jiang Quhai pig, Daweizi pig, Neikuo pig, Dahua white pig and so on. The representative pig breeds are Jiaxing Black Pig, Erhualian Pig, Northeast Min Pig, Jinhua Pig, Dahua White Pig, Neijiang Pig, Jiang Quhai Pig, Daweizi Pig and Hetao Big ear Pig. The average time of sexual maturity is 130 days, the average number of ovulation is 7.21, and the number of postpartum pigs is 21.58. The average number of newborn pigs was 10.54 and that of post-parturient pigs was 13.64. The first litter size of Northeast Min pigs reached 12.70, and the litter size of pigs after giving birth reached 15.50. The first birth number of Taihu pigs reached 13.48, and the number of post-parturition pigs was 16.65. 2.2 the meat quality of local pig breeds in China is excellent, and it is famous for its good taste, fragrance, tenderness and juiciness, which may be related to the long feeding cycle and diverse feed intake of local pig breeds in China. The meat quality of local pig breeds in China has remarkable characteristics, such as bright red meat color, no PSE meat and DFD meat. 45 minutes after slaughtering, muscle pH is normal (> 6.2min). Muscle marbling is suitable, muscle water is strong, muscle tissue structure is reasonable, muscle fiber diameter is fine, unit area density is high, water content is low. In the study of meat quality traits of 10 local pig breeds in China, Chen Runsheng did not find PSE meat, with tender and juicy muscle, fine muscle fiber, high density, moderate distribution of muscle marbling and fat particles between muscle fibers, which produced special flavor during cooking. 2.3 strong stress resistance mainly refers to the ability of the body to adjust and adapt to adverse environment. In the process of long-term natural and artificial selection, local pig breeds in China have good adaptability to adverse environment, such as climate, humidity, altitude, tolerance to rough feeding, hunger, disease invasion and so on. For example, the temperature regulation ability of Min pig is very strong. Under the cold temperature of-28 ℃, there is no shiver within 12 minutes, but when the temperature rises from 22.5 ℃ to 32 ℃, the respiration times of min pig and Harbin white pig increase by 31.87 times per minute and 47.94 times per minute, respectively. It is obvious that Chinese local pig breeds are better than foreign pig breeds in cold and heat resistance. 3 the role of local pig breeds 3.1 crossbreeding utilization of local pig breeds in China can not adapt to the industrial development of pig industry because of their slow growth rate, low production rate, low slaughtering rate, low lean meat percentage and low feed conversion rate. nor can it meet the growing demand for lean pork in the market. Since the reform and opening up, China has introduced a large number of lean pig breeds from abroad. There are great genetic differences between Chinese local pig breeds and foreign pig breeds, which can produce greater heterosis and genetic complementarity when crossing with foreign pig breeds. and Chinese local pig breeds have rich genetic characteristics, so they can achieve good hybridization results. At present, Chinese local pig breeds are often used as female parents to produce commercial pigs, or directly used to produce foreign commercial pigs. The binary hybrid of "one ocean, one soil", the three-way hybrid of "two ocean and one soil" and the "foreign three-yuan" hybrid model are the most representative. At present, such crossbred pigs are most widely raised in China, and they have the advantages of both local pig breeds and "foreign" pig breeds. they not only have high fecundity and good meat quality, but also grow fast, have high lean meat rate, tolerate extensive, and have low requirements for breeding environment and breeding technology. 3.2 the role of local pig breeds in meat quality improvement after entering the 21st century, with the change of supply and demand in the domestic market and the diversification of market demand, the requirements for product quality are very prominent. In the process of breeding, due to excessive emphasis on improving lean meat rate, one of the adverse consequences caused by the long-term development of "foreign three-way" hybrid breeding system is the obvious decline of meat quality, that is, rough muscle fiber, lack of intramuscular fat and lack of pork flavor. However, the long-term breeding of local pig breeds in China has made their meat delicious. First, the muscle fiber of Chinese local pig breeds is delicate and refreshing. The muscle fiber of Chinese local pig breeds is small in diameter, and the marbling is obvious and elegant after the carcass is mature. The beautiful frost flower pattern characterized by fine, dense and uniform is the key to high quality meat. The second is fat and juicy. For most domestic consumers, there is a demand for high-quality pork (high intramuscular fat), and people turn to high-intramuscular fat pork produced by local pig breeds. The meat quality parameters measured in recent years are shown in Table 1. Table 1 comparison of meat quality performance of consanguinity ratio of different local pig breeds item 100% 50% 25% 0% (local pig) (one foreign pig) (two foreign one) (foreign three yuan) 36527496pH245.925.935.855.85 storage loss (%) 0.833.464.916.29 Napoleon rate (%) 83.6077.6475.4862.28 luminance (L*) 47.7048.2350.0552.08 redness ( A *) 13.6410.4610.399.80 yellowness (b *) 1.121.842.372.22 Eye muscle fiber diameter (micron) 51.2660.4062.9768.12 Note: slaughtering weight is specific according to local varieties or hybrids. It can be seen from Table 1 that the pork indexes of Chinese local pig breeds are higher than those of hybrid breeds, indicating that the pork quality of Chinese local pig breeds has strong advantages in pH, water holding capacity, meat color, texture and so on. However, the pork quality decreased with the decrease of consanguinity proportion of local pigs. 3.3 the role of local pig breeds in the cultivation of new strains with the change of people's concept and the development of animal husbandry science and technology, the way of cross utilization of pigs in China is also constantly changing. Local pig breeds have made great contributions to the cultivation of new strains and played an important role in improving the production level of China's pig industry. Making use of the advantages of local pig breeds in China to cultivate new high-quality pig breeds, during the "Seventh five-year Plan" and "eighth five-year Plan", the State Science and Technology Commission organized the selection and research of national lean pig specialized strains, and 25 new pig lines were bred, of which 21 were matrilineal. In the scientific and technological research project of "breeding and industrialization of High-grade and High-quality Lean Meat Pig" in Yunnan Province in 2005, after 13 years of breeding, Saba Pig matching Line, the first pig matching line based on local pig breeds in China, was successfully cultivated. Saba pig matching lines made full use of the complementary and interaction effects of local pig breeds and imported pig breeds. The experiment adopted the combination of locking and regular opening, and individual and family selection to cultivate specialized lines. As a result, the main production performance of the matching lines reached a high level, and the inheritance was stable. The matching system has been approved by the National Professional Committee for Pig breed approval. At the same time, driven by the national key project, after years of breeding, China has successively cultivated new Taihu pig, six lines, Suzhong pig strain and new breed Rongchang No.1, New Dahe pig, New Laiwu pig and so on. The new female parent strain is composed of Chinese excellent local pig breeds and imported foreign lean meat breeds according to different proportions. According to the consanguinity ratio of Chinese and foreign pig breeds, the new pig strains are divided into 5 types. The consanguinity composition proportion of the parent breeds of each pig strain is shown in Table 2. Table 2 consanguinity proportion of new pig parent breeds (%) Type name consanguinity proportion of foreign lean pig breeds introduced Chinese local pig breed consanguinity Ⅰ Rongchang pig lean type strain 2575 Ⅱ Chinese lean pig D Ⅵ line Suzhong pig Ⅰ line Suzhong pig line 505050505050 Ⅲ Jiaxing black pig line 62.562.537.537.5 Ⅳ Xiang white pig line Songliao Black pig mother line 73757375737527252725272527252725 Ⅴ Chinese lean pig D line Xiangbai pig line 80.5 "87.580.5" 87.580.5 "87.519.5" 12.519.5 "12.519.5" 12.519.5 12.5 can be seen from Table 2 Local pig breeds in China play an important role in the cultivation of new strains, which retain the excellent traits of local pig breeds and reach a new level. 4 summary according to the current development trend of pig industry, the development and utilization of local improved pigs in China is not enough, and it is difficult to meet the needs of the current pig industry. Therefore, we must cultivate new strains according to the local economic development, market demand and the reality of pig industry, making use of the advantages of resources and with the help of science and technology such as molecular biotechnology, computer information technology and the application of system engineering theory. Formulate the goal of selection and breeding, constantly improve the construction of pig breed breeding system, determine the trend of pig breeds, and realize the development road of pig industry industrialization in China. Is the landlord satisfied?