Conditions and implementation of purebred breeding of Beef cattle

Beef cattle, that is, beef cattle, is a kind of cattle mainly producing beef. Beef cattle are characterized by plump body, fast weight gain, high feed utilization rate, good meat production performance and good meat taste. Beef cattle not only provide people with meat products, but also provide people with other non-staple food. The prospect of beef cattle breeding is broad. Especially on November 30, 2011, the Ministry of Agriculture issued the National Beef cattle genetic improvement Plan (2011-2025), which provides a broader space for promoting the herd genetic improvement process and improving the production level and economic benefits of beef cattle. The purebred breeding of beef cattle has greatly increased the production efficiency of beef cattle, so what conditions and how to implement the purebred breeding of beef cattle?

Purebred breeding is also known as this variety breeding. It refers to the method to continuously improve the quality and production performance of cattle through breeding, breeding and breeding in cattle breeds. Many foreign beef cattle breeds and many local yellow cattle crystal seeds in China are cultivated by this method, and the existing beef cattle breeds still need to continue to implement the purebred breeding system to increase the efficiency of beef cattle production. In the beef cattle industry, we still need to rely on purebred breeding to provide breeding cattle, as well as a large number of shelf cattle for fattening.

(1) the conditions of purebred breeding are generally carried out under the condition of pure breeding.

1. The meat local variety has the same body shape, appearance and high production performance, and has stable heredity. In order to further improve its production performance and promote its shape and appearance to be more consistent, it is necessary to adopt the method of purebred breeding to consolidate and improve the characteristics of some excellent characters. This method is also known as improved variety breeding. Such as China's excellent local breeds Qinchuan cattle, Nanyang cattle, Jinnan cattle, Luxi cattle, Yanbian cattle, Fuzhou cattle, Yixian Red Bull and Bohai Black cattle. Through purebred breeding, some shortcomings in appearance and structure can be gradually corrected and its production performance can be improved.

2. The excellent breed of beef cattle has been bred to become a specialized beef breed with high meat production performance and stable heredity. In order to increase the number of populations, maintain the characteristics of varieties, and constantly improve quality, it is necessary to carry out purebred breeding in a planned way. Such as foreign beef breeds Charlotte cattle, Limousin cattle, Angus cattle, Piedmont cattle, Simmental cattle, Highford cattle, short-horned cattle and other improved breeds. It is necessary to adopt the method of purebred breeding to maintain purebred and expand the population in order to meet the needs of popularization and cross breeding.

3. Although the local meat variety has low economic value and can not fully meet the needs of people, some characters and characteristics, such as adaptability to environment, disease resistance, rough feeding tolerance and production performance, have certain or outstanding advantages. It is necessary to retain its necessary quantity in a certain area as a gene bank for cross breeding. This method is also called species conservation and breeding.

4. Meat hybrids after entering the cross-crossing fixed stage, it is necessary to select and match purposefully, lie down and fix its excellent characters, so as to further improve the quality of the whole population and tend to be neat. Although the breeding work at this stage is not carried out within a variety, it is similar to the method of intra-variety breeding, which is also called self-group breeding.

(2) the mating mode of purebred breeding population mainly includes two aspects: kinship breeding (inbreeding) and crystal line breeding.

Kinship breeding: consanguineous breeding refers to the mating combination between related bulls and cows. Inbreeding is also called inbreeding. The parameters reflecting the degree of inbreeding are inbreeding coefficient and kinship coefficient. Inbreeding coefficient is a measure of the decrease in the proportion of heterozygous genes. Kinship breeding can not only purify some good genes, but also make some recessive unfavorable genes homozygous and exposed, showing bad traits and becoming bad individuals, such as smaller physique, weaker physique, lower production performance, abnormal development and so on. The methods to prevent the decline of inbreeding are as follows: first, inbreeding is used only once or twice, and then mating with middle or distant parents to maintain its good traits; second, strict selection to prevent mating between bulls and cows with common shortcomings; the third is to strictly eliminate the bad individuals of those mutants and recombined homozygous inferior genotypes.

(3) Crystal line breeding is an advanced stage of breeding, and it is a breeding method commonly used in purebred breeding. Its characteristic is to purposefully cultivate the difference in the type of cattle, so that the beneficial traits of the herd can be maintained and extended to the offspring. For the individuals or groups that have outstanding performance in a certain aspect, the excellent characters of the variety can be maintained by using the method of homogeneous selection. By using this method, several crystal systems are established in one breed, and each strain has its own characteristics, and then the whole herd can be improved in many aspects through the combination (hybridization) between crystal systems. Therefore, crystal line breeding can not only maintain and consolidate the excellent characteristics of varieties, but also combine these excellent characteristics in individuals.

1. Methods and steps of establishing strain

The main results are as follows: (1) the most important problem in creating and selecting pedigree is to cultivate pedigree. The ancestor must be an excellent breeding bull, which not only performs well, but also can pass on its own excellent characteristics to future generations. If the characteristics of lineage ancestors are not significant, especially hereditary instability, then, when matched with homogenous cows, the offspring may not necessarily have the characteristics of strains. Therefore, when the ideal ancestor has not been found in the herd, we should not rush to build the system, but should start with actively creating and cultivating the ancestor. When breeding ancestral ancestors, several cows that meet the requirements of the strain can be selected from the cow herd or core group and matched with the ideal breeding bull, and the male calf will be selected through breeding and progeny testing to establish the strain. In order to avoid the possible genetic instability in the progeny, inbreeding selection can be adopted to consolidate the heredity in the process of creating and cultivating lineage ancestors. However, in order to prevent genetic defects caused by the decrease in the vitality of offspring and the combination of some bad genes due to inbreeding, father-daughter or mother-child mating should be avoided, and the inbreeding coefficient should not exceed 12.5%.

(2) carefully selected basic cows with excellent ancestral bulls can be mated with homogenous cows, and homogenous cows must be carefully selected, and only cows that meet the requirements of the strain can mate with progenitor bulls. There must also be a considerable number of basic cows in this crystal system, generally speaking, when each crystal line is being established, there must be at least 100 150 adult cows available for the establishment of a line, because the more the number of basic cows available for the establishment of a line, the more it can play the role of breeding bulls, especially in the case of frozen semen breeding, the number of basic cows in a crystal line should be greatly increased.

(3) in order to maintain the established crystal system, the successors of the ancestral ancestors must be cultivated. Generally speaking, the son of the ancestral bull can be used as the heir of the strain. Breeding ancestor successors must also select outstanding breeding bulls through progeny identification in accordance with the requirements of breeding ancestral bulls. Because of the long generation interval of cattle, it is necessary to cultivate and select the successors of the bull strain as soon as possible after the establishment of the strain LK. In general, a crystal system lasts for three generations and gradually disappears. If there is no need for this crystal system to exist, there is no need to consider the continuation of the strain. If a particularly valuable strain needs to be retained, the following methods should be adopted: ① should continue to continue the established strain by selecting the offspring bull with more genetic relationship with the original ancestor as the successor of the crystal line. ② re-established the corresponding new strain, that is, re-cultivate the lineage ancestor.

2. The establishment of the binding crystal line of the strain is to increase the difference within the strain and maintain the rich heredity of the variety. The combination of Regent lines (that is, the hybridization between strains) is to increase the identity of varieties. Through the combination of crystal system, the excellent characteristics of the strains complement each other, so as to improve the quality of cattle.

3. The use of top crossing to prevent inbred degenerated crystal line breeding is an important means of seed selection. However, inbreeding often leads to the decline of offspring. In order to solve this problem, the methods that can be adopted are as follows: first, the degree of inbreeding reproduction should be controlled, and the inbreeding coefficient should not be too high; in addition, when inbreeding degeneration occurs, inbreeding bulls can mate with unrelated cows to achieve the effect of heterosis in the same breed, in order to enhance the physique of cattle and improve production performance, which is called "top crossing".

4. Several common strains developed from a high-performance breeding bull are also called single lines. In addition, due to the different emphasis of the method and purpose of establishing the line, there are several kinds of strains.

(1) the inbred line is a group of cattle developed from continuous sibling mating, and its inbreeding coefficient is often more than ten times of the average inbreeding coefficient of large herds, such as quotient of more than 20%.

(2) the formation consists of cattle with similar excellent traits to form the basic group, without considering whether they are siblings or close relatives. Then the closed breeding method within the group is implemented to consolidate and expand the population with the excellent characteristics. There are also those who call this method of line building as the method of population subculture, and the developed breeds of cattle are called formations.

(3) the specialized strain has special performance in a certain aspect, and it is called the specialized strain for crossing with other specific strains.

(4) among the varieties with wide distribution and large number of varieties, local strains often form different local groups within the varieties due to different physical and geographical conditions, feed types and management methods, as well as regional selection criteria, which are called local strains. For example, the Chinese yellow cattle breed Bashan beef, there are Xuanhan cattle, Xizhen cattle, Pingli cattle, Miaowu cattle and other local strains.