Conditions and implementation of purebred breeding of Yellow cattle

Yellow cattle is a common breed of cattle native to China. The number of its reared head in China ranks first among large livestock or cattle, and its breeding areas are almost all over the country. In agricultural areas, it is mainly used for service, semi-agricultural and semi-pastoral areas for both service and milk, and pastoral areas for both milk and meat. There are differences in body shape and performance between yellow cattle in different natural environment and feeding conditions, which can be divided into three types: northern yellow cattle, central plains yellow cattle and southern yellow cattle. Yellow coat is the most common color in cattle, which may be the reason for the breed name, but there are also reddish brown and black. The head is slightly heavier, the angles are not uniform, and the angle roots are round. Strong physique, compact structure, muscular, strong limbs, solid hoof. There are about 25 kinds of yellow cattle in China. The top five are Nanyang cattle, Qinchuan cattle, Luxi cattle, Yanbian cattle and Jinnan cattle, which are collectively called the five improved yellow cattle in China.

Purebred breeding is also called breeding of this variety. It refers to the method of continuously improving herd quality and production performance through seed selection, selection and breeding within cattle breeds. Many foreign yellow cattle breeds and many local yellow cattle seed crystals in China were bred by this method, and the existing yellow cattle breeds still need to continue to carry out pure breeding system to increase the production efficiency of yellow cattle. The cattle industry still relies on pure breeding to provide breeding cattle and a large number of rack cattle for finishing.

(1) The conditions for purebred breeding are generally carried out under the circumstances of purebred breeding.

1. The meat landrace has more consistent body shape appearance and higher production performance, and has stable heredity. In order to further improve its production performance and make its body shape more consistent, it is necessary to adopt purebred breeding methods to consolidate and improve some excellent traits. This method is also known as seed selection. Such as Qinchuan cattle, Nanyang cattle, Jinnan cattle, Luxi cattle, Yanbian cattle, Fuzhou cattle, Jia County red cattle and Bohai black cattle. Through purebred breeding, to gradually correct some of the shortcomings in the appearance of the structure, improve its production performance.

2. Yellow cattle fine breed This breed has become a specialized yellow cattle breed after people's breeding. It has high meat production performance and stable heredity. In order to increase the population number, maintain the variety characteristics and continuously improve the quality, it is necessary to carry out purebred breeding in a planned way. Such as foreign cattle breeds Charolais cattle, Limousin cattle, Angus cattle, Piedmont cattle, Simmental cattle, Hereford cattle, short-horned cattle and other improved varieties. All need to adopt purebred breeding method, keep purebred, expand population, in order to meet the needs of popularization and crossbreeding.

3. Although the economic value of this variety is not high, it can not fully meet the needs of people, but some traits and characteristics, such as environmental adaptation ability, disease resistance, coarse feeding tolerance, production performance, have certain or more outstanding advantages, which requires the necessary quantity to be retained in a certain region as a gene bank for cross breeding. This method is also called conservation breeding.

4. Meat hybrids After the hybrids enter the stage of cross-fixation, it is necessary to select and match them with purpose, and fix their excellent traits horizontally, so that the quality of the whole population is further improved and tends to be neat. This stage of breeding work, although not within a variety of breeding, but it is similar to the method of intra-variety breeding, this method of breeding is also called self-group breeding.

(2) Purebred breeding group rhyme mating mode It mainly includes two aspects of genetic breeding (inbreeding) and system breeding.

Inbreeding: Inbreeding is the mating of related males and females. Inbreeding is also called inbreeding. Inbreeding coefficient and kinship coefficient are the parameters reflecting the degree of consanguinity. The inbreeding coefficient is a measure that indicates a reduction in the proportion of heterozygous genes. Genetic breeding can purify some good genes and expose some recessive unfavorable genes homozygous, which can be manifested as bad characters and become bad individuals, such as small physique, weak physique, reduced production performance, abnormal development, etc. The methods to prevent inbreeding depression are: first, inbreeding only once or twice, and then mating with middle or distant relatives to maintain their good traits; second, strict selection to prevent male and female mating with common defects; and third, strict elimination of those mutant and recombined homozygous poor genotype bad individuals.

(3) System breeding line breeding is the advanced stage of breeding work, and it is a breeding method commonly used in purebred breeding. It is characterized by purposeful breeding of herd differences in type so that beneficial traits of the herd are maintained and extended to future generations. The individuals or groups with outstanding performance in one aspect can continue to maintain the excellent characters of this variety by using the method of homogeneous selection. By this method, several crystal systems are established within a breed, each strain has its own characteristics, and then through the combination of crystal systems (hybridization), the whole herd can be improved in many ways. Therefore, crystal system breeding can not only maintain and consolidate the excellent characteristics and characteristics of varieties, but also combine these excellent characteristics in individuals.

1. Methods and procedures for establishing strains

(1)The primary problem in creating and selecting lineages to establish a line is to cultivate lineages, which can only be established when lineages are available. The sire must be a superior bull, not only performing well in itself, but also capable of passing on its own fine traits to offspring. If the traits of the lineages are not significant, especially if they are genetically unstable, then the offspring produced when mated with homogeneous cows may not all have the traits of the line. Therefore, when ideal lineages have not been found in herds, we should not rush to establish lineages, but should actively create and cultivate lineages. When breeding line ancestors, several cows meeting the line requirements can be selected from the cow herd or core herd, matched with more ideal breeding bulls, and the male calves born are selected from five through breeding and progeny determination to establish the line. In order to avoid the genetic instability that may occur in the progeny of line ancestors, inbreeding selection can be appropriately adopted in the process of creating and cultivating line ancestors to consolidate heritability. However, in order to prevent the decline of offspring viability due to inbreeding and genetic defects caused by some bad gene combinations, father-daughter or mother-child mating should be avoided, and the inbreeding coefficient should generally not exceed 12.5%.

(2)Carefully selected line base cows with excellent sire bulls can be individually mated with homogeneous cows, which must be carefully selected to meet the requirements of the line before mating with sire bulls. The crystal line of the base cow must also have a considerable number, generally each system when the establishment of the line, at least 100-150 adult cows for the establishment of the line, because the more the number of basic cows for the establishment of the line, the more can play the role of breeding bulls, especially in the case of the use of frozen semen breeding, the number of basic cows of a system should be greatly increased.

(3)In order to maintain the established system, it is necessary to cultivate successors of lineages. In general, the sons of sired bulls are considered heirs to the line. Breed sire heirs must also select superior sire bulls through progeny identification in accordance with the requirements for breeding sire bulls. Due to the long generation interval of cattle, early attention should be paid to the cultivation and selection of line bull successors after the establishment of line LK. Generally, a crystal system lasts for three generations and gradually disappears. If this system is not necessary, 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 Continue to continue the established strain by selecting offspring bulls with more kinship with the original line as successors to the system. (2) Re-establish corresponding new lines, i.e., re-cultivate line ancestors.

2. The establishment of the associative system of the strain increases the diversity within the strain and maintains the rich heritability of the variety. Combination of Regent lines (i.e. crossing between lines) increases variety identity. Through the combination of crystal systems, the excellent characteristics of strains can be supplemented to improve the quality of cattle.

3. It is an important method of seed selection to adopt top cross to prevent inbreeding degeneration. However, inbreeding often results in offspring decline. In order to solve this problem, the methods that can be used are: first, control the degree of inbreeding reproduction, and the inbreeding coefficient should not be too high; in addition, when inbreeding degradation occurs, inbred bulls can be mated with unrelated cows to obtain heterosis in the same breed, so as to enhance the herd constitution and improve production performance. This is called "top crossing".

4. A line developed from a single bull with outstanding performance is also called a monobloc. In addition, due to the different emphasis of line establishment methods and objectives, several strains were issued.

(1)Inbred line is a group of cattle developed by mating between successive siblings. Its inbreeding coefficient is often dozens of times higher than that of large herds, such as more than 20%.

(2)A herd consists of cattle with similar good traits, regardless of sib or relative status. Then, the closed breeding mode within the group is implemented to consolidate and expand the group with the excellent characteristic. This method is also known as group succession method, and the developed breed cattle population is called herd.

(3)A specialized strain is a strain that has special properties in one respect and is specifically bred with other strains.

(4)Local strains are widely distributed and have a large number of varieties, often due to different natural geographical conditions, feed types and management methods, as well as regional differences in selection standards and the formation of different local groups within the variety, called local strains. For example, there are Xuanhan cattle, Xizhen cattle, Pingli cattle, Miaoya cattle and other local strains.