Animal Breeding Selection
A number of factors have a certain influence on the selection efficiency, for example, the external environment, feeding and keeping conditions, and technological processes. This is primarily due to the various manifestations of hereditary properties and the implementation of the genotype in certain conditions. Consequently, the assessment of productivity and breeding value will be biased. A sharp change in the climatic and technological conditions causes a change in the assessment of animals and affects the efficiency of selection. The number of signs by which selection is conducted also affects its effectiveness. For example, if the selection is carried out on one basis, then its effectiveness is 100%, and if on four – 1 only 50%:
The efficiency of selection is affected by the size of the animal population. In a large group of animals, it is easier to identify the best, since there is a large variability of characters, a greater deviation from x- in the group. At a critical level of population size (for example, in native breeds: Yakut horse, Yakut cattle), inbreeding increases and the effect of stabilizing selection makes it difficult to conduct targeted selection and reduces its effectiveness. The higher the selection requirements, the more intense it is, the better the quality of the animals we leave on tribe. The selection intensity is expressed in fractions or percentages of culled animals. For example, if you have 10 breeding cocks, 10 cocks are needed for reproduction. The intensity of selection in this case is equal to zero. If 1 rooster is left for reproduction, the selection intensity will be 0, 9, or 90%. The proportion of rejected individuals is called selective pressure. The selection efficiency depends on the generational interval (i). The smaller the interval between generations, the higher the fecundity of animals, the more effective the selection. And this, in turn, depends on the duration of pregnancy of animals of different species. The intergenerational interval for horses is 10 years, for dairy and meat cattle – 4-5, sheep – 4, pigs – 2.5, chickens – 1, 5 years. The earlier the animals are evaluated and selected, the more effective the selection.