Genetic defects in domestic animals
Ratification Date: 20 Jul 2023
Animals with known genetic defects that have the potential to adversely affect their welfare or that of their progeny must not be used for breeding, other than in exceptional circumstances. Genetic testing and counselling should be part of any breeding program.
A genetic defect is a heritable trait that adversely affects an animal’s phenotype, physiology or function.
For many years people have selected for traits that enhance either the functional value or the aesthetic appeal of specific animal breeds. Specific genetic defects are also selected for and maintained in animal populations as models for further research on diseases of importance in animals (including humans). The ability to select for a specific genetic trait through controlled breeding has resulted in a remarkable variety of animal breeds that are both physically and functionally unique.
In all cases, whether genetic selection is intended to enhance production or aesthetic appeal, or to benefit biomedical or veterinary science, it is important that any associated welfare issues are recognised and managed.
For example, in some species, particularly companion animals, many genetic defects have become prevalent due to selection for particular physical traits. A few of these have even been included in breed standards. Brachycephaly (a short or flattened face) and chondrodystrophy (dwarfism) in dogs are examples of this active selection for a particular phenotype. Examples in cats include “Munchkin” dwarf cats and the Scottish Fold breed.
Some defects have arisen as the unintended consequences of selection for other traits; examples include atopic skin disease, predisposition to neoplasia and inherited anxiety in dogs. Examples in other species include Jaguar (JAG) carpet pythons with neurological abnormalities, satin guinea pigs with osteodystrophy, and “fainting” goats (congenital myotonia).
With advances in the understanding of the genome and the specific causes of genetic defects, there is an increasing awareness of the need to work with veterinary geneticists to reduce the impact of deleterious genes and, where appropriate, eliminate them from affected breeds.
The AVA makes the following recommendations with regard to genetic defects in domestic animals:
- Awareness of genetic diseases should be encouraged, as should practices that minimise their incidence and effects in populations of animals.
- Animal breed societies and controlling bodies must be encouraged to instigate, support and recommend procedures to identify affected and carrier animals. Individual owners should not be targeted; instead, breed societies must demonstrate a commitment to reduce the incidence of genetic defects. This should include active monitoring and selection against genetic disease where screening or testing is available.
- Breeders must adopt strategies for minimisation of the breeding and dissemination of animals displaying or carrying genetic defects.
- Individual animals affected by a genetic defect must be desexed or not bred. Some controlled breeding of affected animals under a recognised breeding program may be necessary to ensure genetic diversity in that breed in the short term, provided the welfare of individual animals is not compromised, and that the longer-term goal is to eliminate the defect from the breed. In these situations, every mating should be used as an opportunity to take tangible steps to improve the genetics of the group and reduce the chances of the defect persisting.
- Potential owners of animals should be advised of the problem and information provided to purchasers prior to sale.
- Where a genetic test is available for carriers of an inherited defect, two recognised carriers must not be bred.
- Animals (or their genetic material) should only be imported from other countries for breeding if they are certified by the breed society as free from known genetic defects.
- Veterinarians should play an active role in identifying and monitoring genetic diseases and assisting breed societies and breeders with advice. They should also assist in the education of owners managing animals displaying inherited defects.
- Artificial breeding techniques, such as embryo transfer and artificial insemination, have the potential to inadvertently accelerate the dissemination of genetic defects. Care must be taken to minimise this risk.
- Ongoing research should be carried out to determine the mode of inheritance and expression of particular defects, and to develop tests so that carriers can be identified and removed from the breeding pool.
- The development of practical and enforceable government legislation is encouraged to minimise promulgation and dissemination of genetic defects in domestic animals, with the onus of responsibility being placed on the breeder or vendor of animals displaying or carrying the genetic defect. In jurisdictions which already have this type of legislation, such as Victoria, the ACT and Queensland, the active enforcement of these provisions is strongly encouraged.
References and further reading:
Canine Inherited Disorders Database (Sir James Dunn Animal Welfare Centre, Atlantic Veterinary College, Univ of Prince Edward Island, and Canadian Veterinary Medical Association)
Genetic Welfare Problems of Companion Animals: Dogs (Universities Federation for Animal Welfare) - Information is listed by breed, with information about each disorder.
Online Mendelian Inheritance in Animals: Dogs (OMIA) (University of Sydney)
Other relevant policies:
Date of first ratification by AVA Board February 2009
Updated and re-ratified 20 July 2023