Video: Breeding Against Anomalies In The Exterior Of Dogs
One of the most important tasks of dog breeding, like all modern animal husbandry, is to strengthen the constitution of animals in the process of improving breeds. The strength of the constitution, as a reflection and guarantee of health and adaptive ability, together with the expressed breed characteristics, is the basis of the desired performance of dogs.
These parameters, which are formed in the process of ontogeny (development of the organism) in the interaction of heredity and environmental conditions, must be taken into account in breeding work. This is all the more important because dog breeders have to note cases of birth from outwardly normal producers of so-called abnormal offspring - animals with disorders in the structure and functioning of organs and body systems. With insufficient attention to the selection (culling) of such animals, the frequency of deviations from normal development sometimes sharply increases, which significantly complicates the improvement of the breed.
Anomalies can be of different nature, depending on whether they are inherited or not. Genetic (hereditary) are those that are determined by heredity, genotype. Such deviations appear and spread in breeds as a result of the use of producers of carriers of harmful genes. Most often, this is facilitated by the use of closely related mating, inbreeding.
The success of modern genetics determines the development of private animal genetics, including the genetics of dogs, and the development of selection on a scientific basis. Knowledge of the laws of genetics allows livestock breeders to successfully improve breeds and eliminate hereditary anomalies.
It is possible to establish whether this or that anomaly is hereditary if the abnormal puppies are found in litters from sires of related origin or in different litters of the same sire or sire. However, this in itself is not yet complete proof of the genetic nature of the anomaly: after all, a group of related animals is usually kept and bred in similar conditions, is exposed to the same environmental influences, which can cause the manifestation of two types of anomalies.
1. Hereditary-environmental. Their manifestation depends both on the genotype and on the action of the external environment.
2. Exogenous, arising under the influence of special external factors - teratogens.
Teratogens are of chemical, physical, biological nature (ultraviolet radiation, some chemical preparations, pathogens, etc.). It is known, for example, that in females who had recovered from parvovirus enteritis during the period of gestation, puppies with various deformities were repeatedly born. In this regard, the requirements of correct breeding and keeping of animals to obtain full-fledged healthy offspring remain relevant.
The breeder's particular attention should be drawn to genetic abnormalities for which a specific type of inheritance can be established. This makes it possible to take measures to eliminate or at least initially reduce the frequency of congenital malformations.
Each individual anomaly is relatively rare, but the total effect of the "hereditary burden" of all congenital malformations can be quite noticeable in the breed. Its degree depends on many reasons, including the completeness of the study of the issue. For example, R. Robinson (1982) notes that individual anomalies can sometimes become a scourge for the breed, as happened with the so-called collie eye disease; in cynological associations where selection and screening for the disease is not well established, it affects more than 80 percent of the total Scottish Shepherd Dog (collie) population.
In addition, as clearly shown in the new textbook on veterinary genetics by V.L. Petukhova et al. (1985), the frequency of anomalies encountered depends on the accuracy of registration of the birth of abnormal animals. There are two aspects here. The first is that many abnormal animals are difficult or even impossible to identify at an early age without special diagnostic tests. The basis of the second, especially characteristic of dog breeding, is that the breeding stock is owned by amateurs. And breeders are often inclined to hide the case of the birth of puppies with deformities to preserve the reputation of the plant. Apparently, all these reasons explain the relatively high frequency and even an increase in the prevalence of such anomalies in dogs in recent years as hip dysplasia, umbilical and inguinal hernia, various types of incomplete teeth,cryptorchidism and some others.
The frequency of hereditary anomalies usually differs between breeds and lines; this, by the way, is one of the confirmations of the genetic nature of such deviations. ".
The famous American geneticist F. Hutt (1979) published a list of dog breeds in which anomalies known at that time were found with different frequencies. Such a list allows with a certain probability to assume the presence of a specific anomaly in a given breed of dog. Discovered and identified, it can be eliminated during planned breeding, and for this it is not at all necessary to transfer the entire breed as a whole. A similar list of all known canine anomalies, classified by organ systems, with an indication of the breeds in which they were found (cited by the famous Swedish specialist A. Hedhammar (1986), The message was published in the proceedings of the Symposium on hereditary diseases of dogs, organized by the Kennel Club and the University of Agricultural Sciences in Sweden in 1984.