Breeding of Agricultural Animals
Breeding of Agricultural Animals
(also, livestock breeding), the science of mating farm animals to improve their hereditary characteristics, to improve existing breeds, and to develop new breeds and highly productive herds; a division of zootechny.
The breeding of agricultural animals is concerned with developing theoretical principles and practical methods for pedigree work, a key element of which is the selection of the best animals based on an evaluation of the animals and their ancestors and progeny. Such an evaluation takes into account a number of traits, including constitution, conformation, and productivity. Also important in pedigree work is the purposeful selection of parents and the proper rearing of the young (under optimum conditions of feeding and care). Hence, livestock breeding involves not only the merit of individual animals but also the performance of entire groups—breeds, herds, and zonal types—regulated by pedigree work. The breeding of farm animals includes developing methods for guiding the evolution of breeds. Such methods are based on a deep understanding of animal biology, in particular the genetic processes characteristic of entire breeds and populations.
Livestock breeding began in early antiquity. Since the time of the primitive communal system, when the wild ancestors of many modern domestic animals were first domesticated, man has gradually altered and improved animals in various ways. Methods of improving domestic animals have been known for ages and have been handed down from generation to generation in the form of practical advice. Many valuable recommendations made thousands of years ago have reached us through ancient and medieval literature. The Roman scholar and writer Varro (second and first centuries B.C.) recommended selecting animals for breeding on the basis of an evaluation of their parentage, conformation, and offspring. The Greek writer and historian Xenophon and the Greek physician Hippocrates (fifth century B.C.) made reference to the constitution of animals. In the Middle Ages a concept of breeding similar to that which exists today developed.
In the 18th century, in connection with the intensive development of pedigree animal breeding, the principal breeding method—pure breeding—was established and put into general practice. The 18th-century French scientist G.-L. Buffon developed a theory of crossbreeding similar to the one known today. Charles Darwin’s On the Origin of Species (1859) greatly influenced the theoretical principles of livestock breeding by revealing the important role of artificial selection in the establishment and evolution of breeds. A number of works on livestock breeding published in the second half of the 19th century (for example, by the German scholars H. Nathusius and H. Settegast) owe much to Darwin’s studies in evolution.
In Russia in the late 19th and early 20th centuries zootechnical works appeared that laid the theoretical and practical foundations of modern livestock breeding. N. P. Chirvinskii uncovered the basic laws of growth and development of agricultural animals (seeONTOGENY) and P. N. Kuleshov studied the constitution of farm animals and methods of selection and matching. E. A. Bogdanov also studied animal constitution and matching, as well as linebreeding of purebred animals and the origin and domestication of animals. In addition, a great deal was contributed to the study of animal conformation by M. I. Pridorogin. Modern methods for pedigree work were developed by M. F. Ivanov, who also established a procedure for producing breeds that in a short time significantly improved existing breeds and led to the creation of approximately 60 new highly productive breeds of farm animals in the USSR.
Throughout the 20th century principles of livestock breeding have been developed by scientists from many countries. In the USSR, E. F. Liskun studied the conformation and constitution of animals, pedigree stockbreeding, and methods of increasing the productivity of dairy and beef cattle. D. A. Kislovskii devoted much work to the ontogeny, phylogeny, and evolution of domestic animals, as well as to the problems of inbreeding. N. A. Iurasov studied inbreeding and linebreeding and V. O. Vitt did work on the theory and practice of horse breeding. Important work has been done by the Swiss U. Duerst (cattle breeding) and by the British J. Hammond (the growth and development of agricultural animals and the biology of reproduction and lactation). In the United States, E. Davenport studied pedigree stock breeding, and S. Wright, J. Lush, and V. Rice were involved in animal genetics (primarily population genetics).
Livestock breeders have at their disposal an abundance of theoretical materials and effective methods, enabling them to use breeding systems with a high degree of scientific sophistication. The most important breeding methods are pure breeding, cross-breeding, and hybridization (with careful selection and matching of parents). The use of a variety of breeding methods has led to the creation of many different and highly productive breeds. The valuable traits of a breed and their hereditary stability are improved through the highest levels of pedigree work—linebreeding and family breeding.
The study of breeds in animal husbandry is developing. A breed classification has been established, and the structure of breeds and the factors influencing their formation and evolution are being studied. Research has intensified into such areas as the origin of farm animals and their alteration through domestication (seeDOMESTIC ANIMALS), individual development (ontogeny) and its control, conformation and constitution (the study of which is closely associated with the viability and productivity of animals), and production performance (its variability and heritability).
Genetics plays an important role in solving theoretical and practical problems in livestock breeding, making possible the discovery of methods for controlling heredity to obtain desired forms. The principles of genetics were first applied to the breeding of agricultural animals in the early 20th century. It was established that hereditary variety is a result of the combining of genes in crossbreeding or of alteration of the genes themselves, that is, mutation. However, genetics had no appreciable effect on livestock breeding at that time.
Modern genetics, especially population genetics, is developing on the basis of practical needs, and its influence on livestock breeding continues to grow. The discovery of phenotypes and genotypes required a more precise evaluation of hereditary traits as objects of selection, resulting in the evaluation of both the individuals selected for breeding and their progeny.
An analysis of the laws of inheritance of various traits in populations has made possible the development of genetic and mathematical methods for determining the heritability of almost any trait. Thus, a knowledge of the laws of inheritance of coat color in minks enabled many color variations to be produced in the fur of these animals. In sheep breeding, the many colors of astrakhan were produced by combining mutations. In sericulture, the application of genetic principles has successfully determined the sex of silkworms. Genetic methods are being developed for controlling heterosis in crossbred and hybrid animals. Immunogenetic methods are frequently applied to control the parentage of animals.
The genetic research of Soviet and foreign scientists in zootechny and animal husbandry is associated primarily with achievements in the biological sciences. The albumin in blood, chicken eggs, and milk are examined in reference to their hereditary conditionally and the productivity of animals, and methods of selection according to production and feed conversion are under study.
In the USSR and foreign countries, courses in livestock breeding are taught in the zootechnical departments of agricultural schools. Textbooks, reference books, and monographs on the subject are published.
REFERENCESIvanov, M. F. Izbrannye sochineniia, vols. 1–3. Moscow, 1949-50.
Hammond, J. Biologicheskie problemy zhivotnovodstva, Moscow. 1964. (Translated from English.)
Rukovodstvo po razvedeniiu zhivotnykh, vols. 1–3. Moscow, 1963-65. (Translated from German.)
Kislovskii, D. A. Izbrannye sochineniia. Moscow, 1965.
Borisenko, E. Ia. Razvedenie sel’skokhoziaistvennykh zhivolnykh, 4th ed. Moscow, 1967.
Johansson, I., J. Rendel, and O. Gravet. Genetika i razvedenie domashnikh zhivotnykh, Moscow, 1970. (Translated from German.)
E. IA. BORISENKO