The selection of cattle means that within the herd, the most suitable bull is selected for the cows systematically according to the breeding goal of the cattle, or the bull is selected for the best mating of the cows, so as to produce offspring with excellent genotypes. Different options have different effects.
First, quality matching
Quality matching is the consideration of matching the quality of the mating partner. According to the similarities and differences between the quality of the selected parties, the quality selection can be divided into homogenous and heterogeneous options.
1. Homogeneous matching: It is to select excellent male and female mating that are similar in appearance, production performance, or other economic traits. The goal is to obtain offspring that are similar in quality to both parents in order to consolidate and strengthen their good traits. The role of homogenous selection is mainly to stabilize the good traits of cattle and increase the number of homozygous genotypes, but at the same time it is also possible to increase the frequency of homozygous binding of harmful genes and fix the disadvantages of both parents, resulting in adaptation and life. The force drops. Therefore, we must strengthen the selection of species, strict elimination of adverse individuals, improve feeding management, in order to improve the effect of homogeneous selection.
2. Heterogeneous Matching: It is the selection of excellent male and female matings that differ in appearance, productivity, or other economic traits. The purpose is to select mating cows with different good traits, and combine different advantages to obtain offspring with good quality of both parents. The role of heterogenous selection is to enrich the genetic variation of selected elite traits in herds by combining the advantages of both parents or improving the quality of certain individuals' offspring. In the practice of breeding, as long as there are some differences in the herd, heterogenous matching methods can be used to improve the quality and be transferred to the homogenous matching and fixed in time.
Second, affinity selection
Affinity matching is based on the kinship between the mates. According to the degree of affinity between the two parties, they are divided into inbreeding (short-term indirect) and non-inbreeding (non-inferior). It is generally believed that mating of males within 5 generations is called inbreeding, otherwise it is called non-inbreeding. From the point of view of population genetics, under a certain condition, a large population should maintain relative balance between the frequency of the gene and the frequency of the genotype in the intergenerational transmission. If the environmental conditions of the upper and lower generations are the same, the population is expressed in terms of quantitative average. The number and standard deviation are roughly the same. However, if it is not random mating, instead of matching, it will break this balance. When the kinship between the selected individuals is higher than that of the random mating, it is inbreeding, and when the degree of mating is lower than the degree of random mating.
Third, the matching work should pay attention to several points
1. Each cattle farm must regularly develop a matching plan that meets her breeding objectives. Special attention should be paid to preventing inbreeding recession.
2. On the basis of investigation and analysis, select excellent and matching bulls for each cow's own characteristics. That is to say, matching bulls must pass the test of descendants, and the breeding value of milk production, milk fat percentage, appearance, or The choice index is higher than the cow
3. The effect of each matching should be analyzed and summarized in a timely manner to continuously improve the effectiveness of the matching work.
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