Coat length and texture is inherited in a Swedish Vallhund’s DNA. The gene responsible for a long coat is called FGF5. It is an autosomal recessive gene.  This means that dogs with a short, correct length may still be a ‘carrier’ of the long coat and pass this to their puppies without having an incorrect long/fluffy coat.  This may happen over many, many, generations and it is not until two parents, each carrying the long coat gene are bred together than puppies with long fluffy fur may appear.
The below chart shows the statistical probability of long coated puppy occurrence in a litter when dogs that are clear of the long coat gene (they will have a short coated), those that carry the gene (they will have a short coated) and those that are affected (they will have a long coated) when bred together.

The official regard for the long coat is that is it’s a disqualifying fault. A dog known colloquially as a ‘Fluffy’ cannot enter the show ring, for these dogs are ‘outside of the standard’ and therefore cannot earn ‘challenge certificates’ which is the path to earning a championship title.  Fluffies are still purebred, and pedigreed and can be placed on the NZKC register.  They can also be bred, and looking at the chart above it can be seen that a long coated dog bred can have puppies on the first generation that have a short coat but are carriers, and these carriers when bred can on the first generation produce short coated dogs clear of the gene.  The only significant reason to breed from a long coated dog would have to be that they are the very last of an exceedingly rare breed line, when achieving a FGF5 free puppy in a breeding plan is easier from a carrier.  Therefore a breeder would opt to use a carrier sibling before they would use an affected long coated dog.

The breeder regard for long coated puppies in Sweden and Finland, (where the majority of the breed population exists) is one of calm tolerance. It so rarely occurs that no one over reacts or stresses when one puppy pops up in a litter. Even when siblings are selected to breed on with, no great concern  is held for producing more fluffies as the chances of using a mate that carries the long coated gene is remote.  The percentage of carriers in the general population is sufficiently low enough not to impact upon the breed and it must be stressed that while a correct short coat is desirable as a functional hallmark of the breed a long coat is not a health consideration. 

The issue for New Zealand  is when there is a smaller sub population of the Swedish Vallhunds being bred  there is a risk of increasing the percentage of carriers in that population.  It has been noted that in the last five years six litters of Swedish Vallhunds produced (across five NZKC registered kennels) have produced pups affected with the long coat gene.  The siblings of these fluffies have been retained and bred and a proportion of these siblings will be carriers. 
This becomes problematic because as a recessive gene that can remain hidden if left unidentified may lead to it becoming more normal than not to have fluffy puppies in any litter.  

 "The correct length, hard, double layer coat is regarded as a HALLMARK of the breed."

The coat of Vastgotaspets is called double layer.  It is a medium length over the whole of the body aside from slightly longer around the ruff, over the middle of the shoulder and also as the ‘pantaloons’ or the back parts of the rear legs.  The fur is quite short on the paws and fronts of the lower legs. The coat should be harsh, or hard  - and not at all soft. 

The double layer consists of a tight top coat made of ‘guard hairs’. The guard hairs are longer than the undercoat; the shaft of the guard hair carries the dark banding which creates the distinct harness markings and patterning.  The undercoat is finer, softer and paler in colour.  It is this undercoat that the Vallhund will spontaneously shed over a short period of weeks going from their winter coat into summer their coat, also by the bitch in the post whelping period, and occasionally a convalescing dog will shed their woolly undercoat.

The benefit of the double layer coat keeps the dog warm and dry in colder climates, it also serves well as an protection against heat.  While all dogs require shade, water and protection from excessive heat, it is a mistake to cut, clip or shave a Vallhund in the belief it will help cool the dog. The guard hairs helps keep the dog dry, and the soft insulating undercoat keep the dog warm. The correct Swedish Vallhund coat has a functional and well being purpose and protection from weather and temperature. For the enthusiast is also has an aesthetic appeal.  A Swedish Vallhund with the correct length and double layer coat can remain active for hours in the snow of Sweden, and when they come indoors can shake off the moisture on the top of the coat and be quite dry next to their skin.  This fur has a ‘teflon’ quality, meaning that mud and dirt will dry and fall easily from the coat.  The Swedish Vallhund does not require bathing, blow-drying and grooming in the way in which a soft open dog coat does.