Влияние общества на человека
Приготовление дезинфицирующих растворов различной концентрации
Практические работы по географии для 6 класса
Организация работы процедурного кабинета
Обработка изделий медицинского назначения многократного применения
Изменения в неживой природе осенью
Уборка процедурного кабинета
Сольфеджио. Все правила по сольфеджио
Балочные системы. Определение реакций опор и моментов защемления
Text 2 Contemporary methods of animal breeding.
Darwin explained the history of domestic animals’ and cultivated plants’ origin. He summarized the results, which were reached by the humanity with the help of firstly unconscious and then conscious artificial selection.
These works of his gave a strong impetus for a new achievements in breeding and plant growing. Indeed, after the publication of Darwin's works many new highly productive breeds of cattle, sheep, pigs, horses, chickens and other animals were graded up; a great success in the high milk producing ability of cows, egg-laying ability of hens and horses’ run agility were achieved.
The greatest success was achieved in the USSR. Works of the Soviet scientists and the best specialists in the area of animal husbandry allowed to change the quality of a farm animals's livestock in our country radically. For this purpose, the great scientific generalizations and conclusions, which were described in Darwin's teachings were used.
What are the contemporary methods of domestic animals breeding and improving their productivity, according to which our planned economy is working?
First of all, it is the method of selection, which is about choosing the best herds for a new breed: selectors here are primarily interested in economically valuable traits: meat, milk and egg-laying qualities, agility of run, greasiness, maturity speed, prolificacy and others. At the same time they pay attention to outward signs or physique of the animals: a deep chest, strong build, a good development of certain parts of the body. It is clear that each of these features needs to properly measured, depending on the direction of the farming, problems and needs of each region and many other problems breeders are challenged with.
For a good selection a lot of knowledge is needed. Both regional economy features and biological abilities of each breed are important. Moreover, breeders should know the history of biological science and be familiar with the works of the best stockbreeder. It takes even more skills to be able to choose the best animal according to the laws of heredity (according to which such features as meat, milk and egg-laying qualities or shearing of wool are inherited).
So-called cross-breeding (interbreeding of animals of different species) plays a great role in breeding. As a rule unproductive females of local breeds are being cross-breeded with high-valued thoroughbred stallions.
During the years of Soviet power the best manufacturers of the most valuable and productive foreign breeds were purchased abroad and imported into our country: bulls Shorthorn, Hereford, Simmentals, East Frisians, sheep Rambouillet and prekos, boars of Large White English breed, egg-laying breed chickens - white leghorn, yellow Rhode-Islands and others. The use of stallions to improve local unproductive females significantly improved the breed and productivity of our livestock. The cross-breeding of sheep were particularly successful thank to the use of artificial insemination allowing to fertilize several thousands of females per season with the sperm of one and the same sheep outstanding in quality.
But we should mention that along with the great achievements there were a plenty of errors in this sphere. Some selectors, using cross-breeding, forget about a very important indication of Darwin. Darwin always pointed out that every breed of an animal should be well adapted to the local climatic conditions, as well as to the needs of local communities.
For example, coarse fat-tailed sheep which are widespread in the steppes of Kazakhstan and Western Siberia. This sheep gives a little wool of low quality, but it has a large rump rich in fat. This sheep is really unpretentious so it managed to adapt to the local climatic and feeding conditions perfectly.
Some of our livestock breeders, not taking into account all this factors, began to breed coarse fat-tailed sheep with fine-wool prekos sheep or Rambouillet. However, they forgot to take into consideration their adaptability to the local conditions. As a result, although it has improved the quality of wool, some sheep lost their rumps and were less adapted to the local conditions.
Breeders working on the creation of a new breed are obliged to clearly imagine what qualities these animals should have, and strictly follow the selection plan. In the case above, livestock breeders planned to improve the quality of wool, while maintaining the animal’s ability to adapt to the local climatic and feeding conditions and build up the rump.
Similar errors were made while improving stunted Siberian cow. The breeders wanted to increase the weight and milk quality of this cow, but forgot about the importance of an extremely high fat content of the milk this breed has, which distinguishes Siberian cows from all other species in the world. In addition, crossing West Siberian and Kazakh stunted little cows with large, but more pampered bulls of foreign breeds such as the East Frisians or Simmentals, we get pampered offspring, not adapted to the scarce natural pastures of Western Siberia and Kazakhstan, to their severe frost and cold winds.
In general,while conducting cross-breeding, we should never forget about the improvement of animal welfare. It is necessary to create an improved forage, increasing the amount of legume forage grasses and root crops; it is important to build a good space for cattle and so on. Without these conditions, cross-breeding will not bring much benefit. At the same time, we should never try to improve via the cross-breeding these local breeds, which themselves possess many valuable economic traits.
Such as, for example, Yaroslavskaya and Kholmogorskaya breeds of cattle. These breeds should be improved not via the cross-breeding but via the selection inside the breed.
Последнее изменение этой страницы: 2017-01-20; Нарушение авторского права страницы
infopedia.su Все материалы представленные на сайте исключительно с целью ознакомления читателями и не преследуют коммерческих целей или нарушение авторских прав. Обратная связь - 184.108.40.206 (0.003 с.)