Recessive Coats
Update - December 2016: KC announcement on registering recessive coats.
• Dachshunds in the UK normally have 2 copies of their own coat type gene (WW, SS or LL) because we do not, as a rule, currently perform cross-coat matings. However, these were allowed until 1977 and there are still Wires and Smooths that “carry” the genes for different coat types.
• Imported dogs from countries where cross-coat (and cross-size) matings are more common may have combinations of the coat type genes. Wires may carry the gene for Smooth or Long and Smooths may carry the gene for Long.
• Wire is dominant to all other coat types; if a dog has just one W gene it will be a Wire, if it has one of the other coat-type genes it can pass that gene on to its progeny and produce “recessive Smooths” or “recessive Longs”.
• Smooth is dominant to Longs, if a dog has one S and one L gene it will be a Smooth, but if it carries the Long gene it can therefore pass it on to its progeny and produce “recessive Longs”.
• Long is recessive to both Wire and Smooth, therefore if a dog has a Longhaired Coat it has to have 2 copies of the Longhaired gene (LL); two Longhaired parents can only produce Longhaired puppies.
• Recessive coats will inevitably occur occasionally in UK litters of Wires and Smooths (of both sizes). These can now be registered in the UK according to their coat. Recessive coats born in litters outside the UK can be registered overseas according to their coat and then imported to the UK.
What are the health risks?
• Cord1 PRA exists in all three miniature varieties and there is a requirement for breeders to use the DNA test to avoid producing Affected puppies. Allowing the registration of recessive coats would have no impact on the presence of cord1 PRA in any of the 3 miniature varieties.
• Lafora Disease exists in Mini Wires and there is a requirement for breeders to use the DNA test to avoid producing Affected puppies. The Lafora mutation could be introduced to the Mini Smooth or Mini Long gene pool if an untested recessive Mini Smooth or Mini Long was allowed to be registered. A policy of only allowing DNA tested Lafora Clear recessive Mini Smooth or Mini Long dogs to be registered would prevent this risk.
• Idiopathic epilepsy occurs in Mini Longs with 4 times the prevalence of the other 2 Mini varieties. Since the gene for the Long coat is recessive to both Wire and Smooth, it is not possible for any genetic mutations associated with idiopathic epilepsy to be transferred into the other 2 varieties. The same applies to Distichiasis which is 4 times more prevalent and Patellar Luxation which is 3 times more prevalent in Mini Longs than the other 2 Mini varieties. Allowing the registration of recessive Mini Longs from Smooth or Wire parents may have the potential to lower the risk of these three conditions in Mini Longs, assuming they are heritable.
• IVDD is most prevalent in Smooths. Allowing the registration of recessive Smooths from Wire parents may have the potential to lower the risk of IVDD in Smooths. The prevalence of IVDD is very similar in all 3 Mini varieties and therefore the registration of recessive coats would have little impact on overall IVDD risk.
What about coat colours and patterns?
· In theory, all 6 varieties could exhibit any of the wide range of possible Dachshund coat colours and patterns. The registration of recessive coats does not change this fact, but highlights the importance of knowing the colours and patterns that exist in any given pedigree.
· DNA tests for dog coat, colour and pattern are available (e.g. laboklin.co.uk) and these could be used to confirm:
o A recessive Smooth coat from Wire parents
o A recessive Long coat from Wire or Smooth parents
o Dapple (Merle) or Piebald in any variety
o Blue or Isabella (the dilute versions of Black and Chocolate)
· It is unhelpful that some colours and patterns which exist in Dachshunds can currently only be registered in the UK as “Colour not recognised”. This has potential adverse consequences for future breeding decisions and pedigree research.
Genetic Diversity: the bigger picture
· According to the KC’s 2015 analysis, Smooth, Long and Mini Long varieties are most at risk because of historic breeding practices that have resulted in low genetic diversity. The registration of recessive coats from other varieties would be a positive step to help address the problem.
· The KC has previously given permission for a cross-variety mating (MW – MS) and the offspring from these would have to be registered according to their coat. The option to carry out cross-variety matings is open to any breeder, subject to KC permission and represents another potential approach to address issues of low genetic diversity, or to introduce specific traits.
· Cross-coat and cross-variety matings will continue to be done outside the UK and puppies with these pedigrees will continue to be imported and registered in the UK according to their coat and size. The use of imported dogs is a matter of individual breeders’ choice, but also has the potential to improve genetic diversity. It also highlights the importance of knowing their pedigrees and ensuring all relevant health tests are carried out in order to avoid importing unexpected health problems or undesirable coat colours/patterns.