Litter Registration Limitations

ANKC Ltd is seeking the views of Golden Retriever owners if they wish to have Litter Registration Limitations in respect to Elbow Dysplasia, Progressive Retinal Atrophy and Hereditary Cataracts.

Rationale

Elbow Dysplasia:

Heritable elbow dysplasia is an orthopaedic disorder that results in the abnormal development of the elbow joint. These developmental anomalies can be associated with pain, forelimb lameness, and reluctance to extend or flex the elbow joint.

Several large studies have examined the genetic basis of elbow dysplasia, which appears to be inherited differently in different breeds. To complicate matters further, there is evidence that the different diseases of elbow dysplasia could be inherited independently. The differences in inheritance suggest that elbow dysplasia is a common end point for a variety of genetic disorders which disturb elbow development through various mechanisms.

Because of the complexity of inheritance and the effects of environmental variables in disease expression, it is unlikely that genetic testing for elbow dysplasia will be possible in the foreseeable future. Despite the ability to treat affected dogs, there is no satisfactory medical protocol or surgical procedure to significantly alter the progression or cure the disorder. This makes it increasingly important to reduce the incidence of the disease through selective breeding. Selectively breeding phenotypically normal individuals has been shown to reduce the incidence of the disorder.

Progressive retinal atrophy (PRA) is a group of inherited eye disorders that is characterised by vision loss due to degeneration of the photoreceptor cells in the retina, eventually leading to complete blindness. The mode of inheritance appears to be consistent with autosomal recessive and the age of diagnosis is most commonly at approximately 5 years of age. The Golden Retriever is on Schedule 1 of ACES and has more than one genetic form of PRA and it is thought that PRA can be caused by at least four different mutations three of which have been reported and account for approximately 91% of the cases in the breed (prcd-PRA (<1% of cases), GR_PRA1 (61% of cases) and GR_PRA2 (30% of cases) The genetic explanation for approximately 9% of cases remains to be identified. Patented commercial genetic tests are available for prcd-PRA, GR_PRA1 and GR_PRA2 forms of PRA. These tests identify those dogs with one copy of the mutation (carrier) and dogs with two copies of the mutation (affected). By ensuring that at least one parent is Normal/Clear of GR_PRA1, GR_PRA2 or pcrd-PRA then no GR_PRA1/pcrd-PRA/GR_PRA2 affected offspring will be produced in a mating. Because genetic tests are not available for approximately 9% of PRA cases in the Golden Retriever a yearly eye examination by a veterinary ophthalmologist is important to reduce the incidence of the disease through selective breeding.

Cataract is defined as any opacity of the lens or its capsule. There are many reasons for cataract formation, fortunately, the age of onset, appearance and evolution of hereditary cataracts are quite specific, enabling inherited cataracts to be distinguished from other non-inherited types of cataract.

Hereditary cataracts are a Schedule 1 disease for the Golden Retriever. Studies suggest that hereditary cataracts might be a complex disease, possibly involving several genes that might act independently or together with the environment to influence the development of hereditary cataracts. Since non-hereditary cataracts also occur, an examination by a board-certified veterinary ophthalmologist is necessary to determine if the cataract is suspected to be hereditary.

Quite apart from the undesirable perpetuation of abnormality within breeding lines, a proportion of inherited cataracts progress to produce visual impairment and blindness. Selective breeding of clear stock is important to lower the incidence of hereditary cataracts in the golden retriever.