Today we continue the topic of breeding animals that we started in the previous article. As you know, most farm animals differ from each other even within the same species, where they can be represented by many breeds that differ in external features, productive direction and level. The same type of animal, depending on the direction of the productivity of the breed, can give a person different types of products.
But it was not always so. In the early period of the emergence of animal husbandry, wild species domesticated by people did not have such a variety. The first breeds were formed over a very long time, sometimes even centuries. They arose in the process of long-term economic use of these animals by humans. But most of the well-known and popular breeds today were nevertheless bred in a relatively short time, in a few decades. The source material was already existing at that time, previously recognized breeds.
To create a new breed, only a few basic methods are used: selection, crossbreeding, random mutation and genetic engineering.
Long-term selection of a outbred group of animals according to a trait of interest to a person is the most ancient of them. The whole process consists in the constant and very long culling of those animals from the herd that do not meet certain criteria that are important for humans. Simultaneously with the culling, the selection of the best representatives of the livestock and the compilation of the most successful pairs for further reproduction is carried out. Often such assessment is carried out intuitively and unconsciously.
So all the most ancient breeds of productive and working farm animals were created. In this way, the Flemish, Arden breeds of horses appeared; grey Ukrainian, Simmental, Limousin, Aberdeen Angus, Keane breeds of cattle; Merino, Romanov breed of sheep; Saanen goat breed; Chinese goose breed and many others. This method of breeding breeds is similar to natural selection, which constantly occurs in nature. But the directing and decisive driving factor of rock-forming microevolution is not the greater adaptability of animals to specific living conditions, but the greater correspondence of their properties to human needs.
At the first stages, artificial selection was carried out by man in most cases spontaneously and unconsciously. The owners left for the reproduction of the individuals they liked most on any basis from the animals they had. The determining qualities could be external signs, growth rate or developmental features, the fertility of animals, their temperament, milk production, wool quality, parental instinct, and much more.
Often the selection was carried out not by one, but by several economically valuable characteristics at once. After the first results are achieved, the formation of the desired type in a group of animals becomes more targeted. Individuals that differed from the main mass of animals were valued more than usual, therefore the economic factor came into force, and most livestock breeders sought to breed them, and not the usual livestock. This is how the tribal core of the breed was formed.
Do not forget that the selection method in creating a breed is used not only by scientists, but also by ordinary livestock owners, who, in the process of breeding animals, do not always have the opportunity to move the breed to the desired indicators. This circumstance greatly slows down the creation of the breed.
The history of animal husbandry is closely intertwined with the stages of development of human society. The process of creating a new breed with the help of selection is moving slowly also because a noticeable increase in productive characteristics occurs mainly only as a result of random mutations. And cases of the appearance in the herd of individual animals with outstanding qualities, for example, having greater productivity than all the others, do not occur as often as we would like.
Breeding with the help of artificial selection and simple selection is a very laborious, time-consuming and costly process, and, perhaps, the closest to natural. But now it is rarely used. One of the best modern dairy breeds, the Holstein, was obtained by selecting the livestock of the already existingDutch Black-and-White breed.
A more productive way to get the desired results much faster is to use the genetic potential of breeds created by crossing with other breeds or with local outbred animals that have the necessary, economically demanded characteristics (for example, good adaptation to climate or innate immunity to some then diseases, etc.).
Crossbreeding of breeds is quite justified, since it makes it possible to use the genetic material already accumulated over a long time, and not to start the process from scratch each time. This method is not so time-consuming, but requires the participation of highly qualified livestock specialists who deeply understand the laws of genetics and possess the necessary professional knowledge. A well-chosen combination of parent breeds often brings very good results in a short time.
Crossbreeding has been and is used to breed many modern breeds. There are several types of crossbreeding of the original breeds to obtain a new one.
Reproductive crossbreeding consists in creating a mixture of two or more breeds on a relatively small group of animals, after which the offspring are bred “in themselves” and selected from their total mass of animals with the necessary signs. Then increase the number of livestock with the desired properties. If the basis for rock formation is only two breeds, then the crossing is called simple, but if there are more than two original breeds, then it is complex.
Many breeds have been created this way. For example, the Lebedinskaya breed of cattle, which was formed in 1950, was bred by crossing cows of the gray Ukrainian breed with bulls Switzerland breed. The resulting cross between the second and third generations was bred under conditions of good feeding and maintenance, after which their best representatives were selected. As a result of painstaking work, after many generations, large, unpretentious animals with high productivity were obtained, which combined the best properties of both parent breeds.
Red Belted The breed of pigs was also bred by the method of complex reproductive crossing of breeds of Duroc, Landrace, Poltava Meat, Large White and Hampshire. It took Poltava scientists about 30 years to create red-nosed pigs. Kuchinsky Jubilee breed of chicken was bred on the basis of Liven calico, New Hampshire, Russian White, Australope, Plymouth Rock, Rhode Island. She inherited their productive characteristics and adaptive abilities. Horses of the Brabancon breed were bred by crossing Arden and Flemish breeds. It often happens that breeds obtained from reproductive crossing later become the basis for the creation of new ones. The Vladimir heavy truck was obtained by crossing the breeds Chair, Percheron, Brabancon, Arden, Clydesdale and local heavy draft mares.
Accumulation cross breeding is used to significantly increase the productivity of local livestock or create more productive animals based on a low-productive breed that is highly adaptable to the local climate. The aim of the method is to radically change the quality of an existing group of animals. First, a breed-improver is selected and the males of this breed inseminate the queens of the improved breed or outbred animals.
If thoroughbred producers inseminate local outbred livestock, and then their descendants in the next generations, then in five generations it is possible to obtain purebred animals of the original breed, with the help of which the low-productive livestock was improved. But if thoroughbred producers are not used for five generations in a row, but only at the initial stage, and then purposeful selection is applied according to the traits of interest, then the result will be a new breed of this species.
The duration of use of the improver breed (number of generations) depends on the tasks set by the breeders, the initial quality of the improved animals, and many other circumstances. Such crossbreeding can be practiced not with one improver breed, but with several at different stages. First, the desired trait of one breed is given to the livestock, then, after it is fixed in the crossbred offspring, another breed is used. Work is carried out until the task is completed as fully as possible.
So, for example, the Mirgorodskaya breed of pigs was created. Local low-producing sows were mated with thoroughbred boars Temvos and Berkshire. This breed was formed by the method of folk selection lasting about half a century. The Fleckfie breed has a similar history; to obtain it, local cows were crossed with bulls of the Simmental breed. Crossbreeding of local Kazakh cattle and bulls of the Herefordbred gave the Kazakh Whitehead breed. The world famous horses of the percheron breed obtained from crossing Arab stallions with local French workers harness-type mares.
Admixture of new blood is used when it is necessary to correct individual shortcomings of a generally satisfactory breed or to give it some new property that exists in representatives of other breeds, while maintaining, at the same time, all other characteristics inherent in it. These desirable changes, as it were, are added (introduced) into the future breed.
An introductory crossbreeding is also kbown as admixture of new blood. Success largely depends on the successful choice of breed-improver and is carried out in several stages. First, the producer of this breed inseminates the queens of the improved breed once, and the resulting crossbreeds are bred “in themselves”. The best crossbred females, who have inherited the desired trait from the improver breed, are mated with the producers of the improved breed, and the best crossbred males are mated with the queens of the improved breed.
Further, the offspring from this mating are again mated according to the same principle with the improved breed. And the generation already received from this breed is mated with each other and a strict rejection of all animals that have not inherited the desired property of the improver breed is carried out. Thus, an existing breed is improved, or a new one is created. This is how the Russian heavy truck was bred. Russian horse breeders, eliminating the shortcomings of the Arden horses with the help of Brabancons blood, bred this breed.
The Don breed of horses during its centuries-old history was constantly subjected to short-term infusion of blood of different breeds: Turkmen horses, Karabakh and at the end of the 19th century – thoroughbred breeds. Each breed added its own to the already established Don breed.
A good example of a successful introductory crossbreeding is the mating of fine-fleeced sheep with Australian Merinos. In a few years of such livestock-improving crosses, there has been a significant wool shearing increased (by 250 g) with a washed fiber yield of 47% (instead of 40%). Bulls shorthorns have also been successfully crossed with cows of some offspring of Dutch cattle to give them a wider pelvis and improve their propensity to young for fattening.
Nowadays, it is possible to create animals with desirable properties using genetic engineering. The use of genetic engineering in animal husbandry makes it possible to radically change the properties of the body, such as increasing resistance to diseases, increasing productivity, and improving the quality properties of products. So cows were created, in whose milk the substance erythropoietin is produced, which is used in the treatment of leukemia; transgenic chickens have been obtained that lay eggs, which have a therapeutic effect due to the medicinal components they contain.
Scientists are actively researching the production of drugs from the products of farm animals: hormones, interferon, insulin, essential amino acids. As a result of the transplantation of certain genes, new characteristics appear in the offspring, and further breeding work allows you to fix them and create whole transgenic lines. Transgenic fish have already been created that grow larger and faster than ordinary fish, but this direction is new and has not yet become widespread.
Sometimes breeds arise by chance. So unexpectedly, the first specimens of the rex breed were obtained from rabbits, many breeds of cats (for example, sphinxes), fish and decorative animals. Spontaneous mutation liked people and was fixed in the genes of animals through their purposeful further breeding.
This is how animal breeds are created and improved. About specific breeds and their characteristics will be my next articles.
