Two types of hybridization are used in animal breeding: related (inbreeding) and unrelated (outbreeding).
Crossbreeding between brothers and sisters or between parents and offspring leads to homozygosity and is often accompanied by a weakening of animals, a decrease in their resistance to adverse environmental factors, a decrease in fertility, etc. Nevertheless, inbreeding is used in animal breeding in order to fix characteristic economic valuable signs. As a rule, closely related crossing is carried out in several lines inside the breed. To eliminate the adverse effects of inbreeding, unrelated crossing of different lines or even different breeds is used. This crossing is accompanied by strict selection, which allows to strengthen and maintain the valuable qualities of the breed.
The combination of closely related crossbreeding with unrelated crossbreeding is widely used by breeders to breed new breeds of animals. So, the famous breeder M.F. Ivanov, using this technique, created a highly productive breed of Ukrainian white steppe pigs, Askaniy ramambuly sheep breed, etc.
Interspecific hybrids of horses with a donkey (mule), one-humped and two-humped camels (bunks), a yak with cattle and others have been used by humans since ancient times. These hybrids have increased endurance compared to parents.
In some cases, the distant hybridization of domestic animals with wild ancestors gives rise to prolific offspring and can be used in breeding. Thus, as a result of the crossing of fine-fleeced merino sheep with wild sheep argali, fine-fleeced archaromerinos were obtained that can graze year-round on high mountain pastures. As a result of crossing cattle with humpback zebu, valuable groups of dairy cattle were obtained.
In addition to the methods described above, animal breeding uses artificial insemination (introducing sperm obtained from high-value males into the female genital tract for the purpose of fertilization) and polyembryony (the artificial formation of several embryos from one zygote of valuable breeds, followed by their introduction into the uterus of outbred animals). These methods allow several times to increase the rate of procreation from valuable producers.
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