People began to improve the breed of animals for a long time, and the first large-scale cattle breeding attempts were recorded in Switzerland, Great Britain, France, the Netherlands. Using local genetic material, the livestock breeders of these countries created cattle with traits useful for the population. As a result of artificial selection, now there are more than 1080 cattle species worldwide. Depending on the natural and social conditions, the priority development is received by meat or dairy varieties of cows.
The value of heredity for growing cattle
Cattle breeding is the main branch of modern animal husbandry. Its potential is constantly maintained and stimulated by means of genetics. Breeding bull significantly improves the gene pool of any herd. This animal is used as the main tool for optimizing and improving the breed of cows.
The karyotype (set of chromosomes) of cattle contains 60 genetic units that transmit hereditary information from parent to calf. It is on their individual combinations and structural changes depends on the breed and the state of the body of the cow.
Genetic anomalies of animals lead to the following consequences:
- oncological diseases;
- abnormalities of metabolism of born calves;
- violations of animal fertility;
- increased embryonic mortality;
- congenital deformities;
- reduced livestock productivity.
Such qualities as inheritance of cows, live muscle mass, peculiarities of udder morphology, resistance to infectious diseases are inherited. All the efforts of modern breeders are focused precisely on improving these indicators, since the productivity of cattle depends on them. Thus, the development of cattle breeding is directly related to an increase in the level of genetic potential of farm animals.
The concepts of genetics, heredity, variability
Genetics is a biological science that studies the hereditary characteristics of different organisms, transmitted from generation to generation. Also in cows. The property of offspring to reproduce the characteristics of parents, more distant ancestors is the basis for the preservation of behavioral, physiological and anatomical features. On the other hand, the improvement of the gene pool is due to variability, which is caused by both internal and external factors.
The genetic information of each animal is stored and transmitted to other generations by a set of gametes (gametes), which in the process of merging with an individual of the opposite sex form a zygote with a full set of chromosomes.
In the process of natural selection, the qualities of cows and bulls that were most useful for survival and evolution were established. Animals are characterized by stable heredity, forming breeds and species that persist over the centuries.
Signs that have arisen as a result of breeding cows during domestication, are characterized by increased variability. This enables a person to breed new livestock breeds, consolidating useful qualities for each new offspring.
Gene mutations and anomalies
Depending on how many chromosomes the cow has and on the state of the genetic material, pathological changes in the anatomy and physiology of the calves can occur at regular intervals. At the same time from the very birth of these individuals are not viable.
Such anomalies as hairlessness, partial congenital absence of extremities, paralysis of hind legs, fetal mummification, defects of the nasal mucosa, hard palate, tongue, underdevelopment of hoofs, change in the shape of the ears, dwarfism of cows are most common. Such mutations are transmitted by the genetic code (by recessive type), therefore, they do not appear immediately, but through a change of cow generation. Thus, livestock in the conditions of livestock farming requires increased attention.
The bull, which is used as a producer inside the pedigree herd, takes a significant part in the spread of chromosome abnormalities.
Therefore, on serious livestock farms it is necessary to make early detection of genetic abnormalities in cattle at the cellular (cytological) level.
Karyotype-impaired animals are rejected to prevent unwanted pathological situations.
Change of terms of pregnancy due to the characteristics of the karyotype
Manifestations of mutant genes often affect the duration of gestation of cows. Depending on the severity of the genetic abnormality, pregnancy may increase for a period of 20 to 100 days. At the same time, in cases of moderate deviations, calves outwardly look normal, but die at the hotel. And severe forms of animal genetic changes require veterinary surgery.
Different breeds of cattle manifest spastic paresis, syndactyly, congenital blindness, underdevelopment of internal genital organs in females, probatocephalus, porphyria. In addition, underdevelopment of the testes, ovaries in young bulls and heifers is often observed.
Such manifestations often lead to perinatal mortality. The viability and productivity of such animals in the future is also significantly reduced. Because of frequent diseases, they die.
Genetic resistance to mastitis
Mastitis - inflammation of the breast. Udder cows have an infectious nature. On the other hand, exacerbation of pathological processes may provoke other reasons. The frequency of this pathology is different within or between cattle breeds.
The number of diseased animals depends on the morphological features of the udder, which determines the corresponding karyotype. Structural and functional characteristics of the mammary gland of cows are inherited by the gametes of both sexes of cattle. Thus, the assessment and selection of bulls on the stability of their daughters to this pathology, which has a genetic origin, increases the efficiency of selection.
A uniform bowl-shaped udder, cylindrical nipples with convex tops are less susceptible to diseases, so such structural features are more desirable signs. In addition, susceptibility to mastitis can be determined by the rate of lactation. The best indicator can be considered the speed of 1.5-2 liters per minute. Such characteristics reduce the likelihood of this disease of livestock.
Chromosomal leukemia factors
Malignant changes in the blood-forming organs at the cellular level, which manifest as tumors, are called leukemias. One of the causes of these diseases in cows are hereditary genetic factors. Pathogens provoke the development of pathological processes mainly in a weakened animal organism, which has a certain tendency towards this. The karyotype of cattle contains chromosomes that reinforce the predisposition to this disease during transmission from ancestors to offspring.
The selection process, which aims to prevent oncology in cattle, is aimed at identifying hidden carriers of leukemia, culling sick individuals and their closest relatives. For this, the incidence rate in all related lines of cows is carefully analyzed. Particular attention is paid to the daughters of breeding bulls.
Belgian blue cow breed as a result of random mutation
Due to the long-term breeding of cattle and genetics, animals with high productivity have long appeared. In the second half of the 19th century in Belgium, a breed was created, the basis of which was muscular cows capable of producing good quality milk in the required amount. Because of its versatility, such cattle have become very popular in this part of Europe. Since 1960, it began to grow exclusively for meat, since the developed muscles were the hallmark of this herd.
With each generation, the fleshy qualities improved. Today, the typical representative of the Belgian blue breed is the bull, whose body is associated with an advertising picture of bodybuilding, depicting inflated bodybuilders. Because of the distinctly expressed muscular relief, such individuals have become called “bisexual”.
This phenomenon managed to explain genetics only in 1997. They discovered a gene responsible for a protein called "myostatin", which suppresses overgrowth of muscle tissue. Gametes of this breed are characterized by the suppression of this gene, which can be achieved by methods of genetics.
The main advantage of the Belgian cows is unusually tender juicy meat. The growth of such animals at the withers reaches 150 cm, and weight - 1400 kg. In this case, most of the weight is made up of muscles without fat and tendons.
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