Реферат: Thoroughbred History Essay Research Paper Abstract
Thoroughbred History Essay, Research Paper
Abstract Selective breeding of English ponies with the Arabian, Turk and Barb stallions produced the modern Thoroughbreds, known for their high speed and stamina. The Thoroughbred horse can run faster than any other animal in the world, for any reasonable distance. The near optimal levels are established firstly by outcrossing the English ponies, with the three specified classes, to obtain the most desirable traits. Once the characteristics that produce a top line Thoroughbred have been established, they can be maintained, or raised to a new plateau, through the practices of nicking and linebreeding and the concept of additive genes. The History of Thoroughbreds The Thoroughbred was first established through the selective breeding of English ponies with the Arabian, Turk and Barb stallions during the 16th century. The first three know stallions that were bred to the developing breed were the Godophin Barb (1689), the Darley Arabian (1706), and the Byerly Turk (1724). Perhaps the most important three Thoroughbreds who contributed a high proportion of their genes to the modern American Thoroughbreds of today were: Matchum (1748), the grandson of Godophin Barb, Herold (1758), the great grandson of Darley Arabian, and Eclipse (1764), the great, great grandson of Byerly Turk. Matchum passed on approximately 5-6 percent of his genes, Herold contributed 17-18 percent and Eclipse passed on about 11-12 percent. The developing Thoroughbreds were bred with the three specific types of stallions to increase the probability of the traits influencing speed and stamina. Some promiscuous mating of the Thoroughbreds also occurred with the horses of Germany, Normandy, Flanders and Spain, establishing more desirable traits in their offspring. (Jones, 1982) Phenotypes In order to understand the features of Thoroughbreds which highly contributed to their amazing speed and stamina, a description of their early ancestors is necessary. The English ponies are of very short nature, consisting of very short legs and small bodies. Their deficiency in size is most likely due to natural selection in the severe environment of early Northern and Western Europe. Size, speed, stamina and form were improved upon by the introduction of Oriental blood, that of the Barb, Turk and Arabian (Sanders 1893). The Barb horses are tall, speedy and possess long legs and short, light bodies. The Turks consist of heavier bodies and shorter legs for fair endurance. The Arabians, of great endurance, display beauty of form and grace of motion. Some of the heavier horses from Normandy, Flanders and Germany may have played a role in the early breeding of the English ponies in an effort to increase their size (Sanders 1893). It is also possible that the Andalusians contributed their height somewhat down the line. (Jones, 1982) Linebreeding improved upon other characteristics important for Thoroughbred speed and stamina. Larger lung capacity and larger nose and throat air passages are important for the intake of vast amounts of oxygen and expulsion of great quantities of carbon dioxide. A large heart and a high concentration of hemoglobin in red blood cells is also important for sending the hard working leg muscles the oxygen needed for cellular respiration. Another important trait is the strength of tendons, ligaments and bone structures. This decreases the amount of injuries and therefore increases the career expectancy. (Jones, 1982) Inheritance Factors and Genetic Concepts Before domestication, speed and stamina was naturally selected. For example, the main “defense mechanism” used by horses to preserve their gene line was to simply outrun their competitors. Thus the slower horses were bred out. The switch from natural selection to selective breeding changed the modes of inheritance, yet kept the same desirable characteristics for speed and stamina.
Four significant factors that are involved in the selective breeding of Thoroughbreds are: outcrossing, nicking, additive genes and linebreeding. Outcrossing was the crossing of horses in unrelated families. This brought about the breed of Thoroughbreds. The English ponies were bred with the Arabian, Turk and Barb stallions. The genetic principle of the outcrossing was to produce hybrids whose genes would act complimentary to each other and consist of more desirable traits. Outcrossing is no longer used because any further outcrosses would only pollute the Thoroughbred gene pool. (Kieffer 1976) Once the breed of Thoroughbreds was established the practice of nicking occurred within the species. Nicking involves the breeding of Thoroughbreds to produce offspring with more desirable traits. This is done by using strong and weak points of different Thoroughbreds to complement each other. The resulting progeny having better qualities than their parents. (Jones, 1982) Another practice that arose in the breeding of Thoroughbreds was the concept of mating the best of one generation with each other. This emphasizes the additive gene concept. The additive gene principle consists of breeding two of the top line Thoroughbreds together in order to produce the best possible offspring. The concept of the additive gene implies that there is a base gene, which for instance is the lowest level at which a Thoroughbred can run. This speed level is increased with every additive gene. When breeding the “best” with the “best” you are accumulating more and more additive genes, resulting in faster and faster Thoroughbreds. A horses racing capacity has two main factors: the amount of inherited racing genes and the ability of a breeder to accurately identify the individuals that are truly genetically superior. (Kieffer, 1976) Lastly, linebreeding is practiced in Thoroughbreds. Thorough linebreeding causes Thoroughbreds to become more and more homozygotic, resulting in preservation of their more desirable characteristics. Continuous breeding of these horses produces higher endurance levels that are passed down to the upcoming generations. (Jones, 1982) Using these principles, the more desirable traits of Thoroughbreds are obtained. This establishes a higher, yet not optimal, level of speed and stamina. Continuous breeding, using these concepts, will bring one closer and closer to the “perfect” race horse. However, a breeder must remember that environmental factors effect the capability of a racehorse. The goal of selective breeding, in the Thoroughbreds, is to reach an optimal level of speed and stamina, but in order to do so, one must chose the most desirable traits according to the environmental factors. Conclusion The development of the Thoroughbred is due to a variety of fathering horses and genetic procedures. The English pony, Arabian, Turk and Barb blood all contributed to the overabundance of genes determining speed and stamina. This was achieved due to knowledge of the additive gene concept and through the processes of outcrossing, nicking and linebreeding. While evolution of the Thoroughbred has been greatly influenced by genetics, we must keep in mind that genes provide only potential for greatness, but the optimal environmental factors (nutrition, care, training, climate, etc.) is necessary for full realization of that potential. Bibliography Jones, W.E. (1982) Genetics and Horse Breeding. Lea and Febiger, Philadelphia. Osborne, Walker D. (1971) The Thoroughbred World. Leon Amiel Publisher, Israel. Sanders, J. H. (1873) Horse-Breeding. J. H. Harris Publishing Co., Chicago. Proceedings of the International Symposium on Genetics and Horse-Breeding. Royal Dublin Society, Ballsbridge, (1976)