THE AUSTRALIAN SHEPHERD
The Australian Shepherd has always been a breed known for its bobbed tail. The breed has always carried the gene for a naturally bobbed tail, however traditionally the tails have been docked to provide a uniformed tail length under 4 inches long. Docking was banned in the UK in April 2007.
A naturally short tail is often referred to as 'NBT' or natural bob tail.
The gene for shortening tails in the Australian Shepherd, is a dominant trait, which means a dog only needs to have 1 copy of the gene to have a shortened tail. However the gene does not shorten the tail at a specific point. This means a dog could be 1 vertebrae short of a full tail, down to having no obvious tail at all. Where shortened tails appear in a litter you will get a wide variety of tail lengths within the litter. It is rare for a litter of bobbed tails to be all the same length.
Where both parents are genetically a full tail all puppies in a litter will have full tails.
Where 1 or both parents carry the NBT gene you will have a mixture of various length bobbed tails and full tails. This can vary from the majority (or all)of pups having a bobbed tail, with only the odd tail. To the majority of the pups having full tails with only the odd bobbed tail.
Because Docking in the UK is banned, all tail lengths are acceptable in the breed. And when showing in the UK a dog should not be penalised for having a tail or longer NBT. Breeders should not be inflating their prices for dogs who have a naturally very short tail.
If you aren't sure whether your dog has the NBT gene, there is a DNA test available which will identify the gene, although it cant give the length of the bobbed tail. Most labs in the UK are able to test for the gene.