Natural Bobtail

Introduction

Natural bobtail (NBT) is a naturally occurring mutation in the T-box gene resulting in a shortened tail. The mutation is inherited in an autosomal dominant fashion with both sexes being equally affected.  This mode of inheritance means that presence of one copy of the mutant gene will produce the bobbed tail phenotype in males and females. The length of the bobbed tail is variable and under the influence of other as yet undetermined genetic factors that cause some NBT individuals to have nearly full-length tails while others may have virtually no tail.  While heterozygous individuals (possessing one normal and one affected T gene) have shortened tails, data suggest that the homozygous condition (possessing two copies of the affected gene) is lethal in utero. Breeding of two carriers is predicted to produce 25% homozygous affected offspring thus a 25% reduction in litter size.

Genetic testing is recommended to verify and validate the natural bobtail status of dogs, especially if docking is allowed, and to help with breeding pair selection to eliminate the risk of reduced litter size. Testing is recommended for: Australian Shepherd, Austrian Pinscher, Australian Cattle Dog, Bourbonnais Pointer, Brazilian Terrier, Brittany Spaniel, Catahoula Leopard Dog, Croatian Sheepdog, Danish/Swedish Farmdog, Jack Russell Terrier, Karelian Bear Dog, McNab, Mudi, Pembroke Welsh Corgi, Polish Lowland Sheepdog, Pyrenean Shepherd, Savoy Sheepdog, Schipperke, Spanish Waterdog, Swedish Vallhund.

The VGL offers a test for Natural Bobtail to assist owners and breeders in identifying dogs that have this trait. The test uses DNA collected from buccal (cheek) swabs, thus avoiding blood sample collection.

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Allow 2-6 business days for results.

Results reported as:

Test Result Natural Bobtail
N/N Normal - no copies of the NBT mutation
N/BT Natural bobtail - 1 copy of the NBT mutation
BT/BT Natural bobtail - 2 copies of the NBT mutation*

* Result unlikely to occur for live dogs; NBT is considered a homozygous lethal in utero.


Reference:
Haworth K, Putt W, Cattanach B, Breen M, Binns M, Lingaas F, Edwards YH. 2001 Canine homolog of the T-box transcription factor T; failure of the protein to bind to its DNA target leads to a short-tail phenotype. Mamm Genome. 12:212-218.

Hytönen MK1, Grall A, Hédan B, Dréano S, Seguin SJ, Delattre D, Thomas A, Galibert F, Paulin L, Lohi H, Sainio K, André C. 2009. Ancestral T-box mutation is present in many, but not all, short-tailed dog breeds. J Hered. Mar-Apr;100(2):236-40.

Veterinary Genetics Laboratory, Tel 530-752-2211, Email VGL