To Tobiano Pattern
Test that shows if your horse carries Tobiano, big white patches that usually cross the back. Finds out whether your...
€43.05 Mat TVA
About
This test shows whether your horse carries Tobiano, the white spotting pattern with smooth, rounded patches that usually cross the back, and how many copies it has.
It is for breeders of spotted horses of many breeds and for anyone buying or selling one.
Why test?
Breeding. Knowing the result of both parents tells you the chance of a tobiano foal before the mating.
Registration and sale. The result is objective information you can show a studbook or a buyer.
Unclear coats. When the pattern is hard to read by eye, the result settles it.
Clinical signs
Tobiano is a coat pattern, present at birth. It is not linked to any disease.
Without Tobiano: no tobiano pattern. The horse can still have face and leg markings, or white from other genes.
With one or two copies: the same tobiano pattern. The eye cannot tell one copy from two.
- White patches with smooth, rounded, clear edges
- One or more white patches usually cross the back
- The lower legs are usually white
- The head is usually coloured, with ordinary face markings like a solid horse
- The tail is often two-coloured
- White covers roughly 20 to 80% of the body
What can fool the eye:
- A tobiano with very little white, read as a solid horse with big markings
- Tobiano and frame overo together, called tovero, where the patterns mix
Transmission
Tobiano is dominant. One copy is enough for the pattern to show. The gene is not on a sex chromosome, so colts and fillies are the same.
What each mating can produce:
- N/N x N/N gives 100% N/N: no tobiano foals
- N/N x To/N gives 50% N/N, 50% To/N: one foal in two tobiano
- N/N x To/To gives 100% To/N: every foal tobiano
- To/N x To/N gives 25% N/N, 50% To/N, 25% To/To: three foals in four tobiano
- To/N x To/To gives 50% To/N, 50% To/To: every foal tobiano
- To/To x To/To gives 100% To/To: every foal tobiano
Tobiano does not skip a generation. A solid foal from a tobiano parent cannot pass it on.
Prevention
To be sure of a tobiano foal, use a parent with two copies.
Check frame overo too. A tobiano horse can carry frame overo without showing it, and two frame overo carriers can produce a lethal white foal. Before mating two spotted horses, test both parents with the Overo test as well.
Colour should not be the only thing that decides a mating. This test says nothing about health, performance or temperament.
Results
N/N: no copy. Cannot pass Tobiano on.
To/N: one copy. Passes the pattern to about half of its foals.
To/To: two copies. Passes the pattern to every foal.
Sample
Hair roots: 20 to 40 hairs pulled (not cut) from the mane or tail, with the roots attached. White or coloured hair both work. Tape them inside the marked area of the printable sample submission form. Hairs without roots cannot be analysed.
Blood: 5 mL of whole blood in a K3-EDTA tube, collected by a veterinarian. Label the tube with the horse's name and send it with the submission form.
Keep samples dry and at room temperature, and do not freeze them. Do not send hair that is wet, mouldy or soiled with bedding or faeces.
Send your sample by regular mail or express delivery to:
Equigerminal Lab HIESE
Rua da Quinta do Sobreiro Nº25
3230-343 Penela, Portugal
Turnaround
Standard processing: results within 5 to 10 working days of the sample arriving at the laboratory. Shipping is arranged and paid for by the client, and transit time is not included in the 5 to 10 working days.
Samples that fail DNA extraction or amplification are repeated at no extra cost, which may add a few working days. We contact you if a new sample is required.
How it works
🛒 Purchase the test: select and buy the test online.
📧 Receive instructions: after payment confirmation you receive sample collection instructions by e-mail.
✨ Collect the sample yourself: pull 20 to 40 hair roots with the bulb attached, or ask your veterinarian to collect blood in a K3-EDTA tube.
📄 Complete the form: print and complete the submission form with the animal identification.
📮 Send it to the laboratory: Equigerminal, S.A., HIESE, Rua da Quinta do Sobreiro, 25, Quinta Vale do Espinhal, 3230-343 Penela, PORTUGAL.
📄 Receive your report: your certified report is issued as soon as the analysis is validated.
FAQs
Do small coloured spots inside the white mean two copies?
They are sometimes said to. We know of no study confirming it.
What does this test not detect?
Frame overo, splashed white, sabino, dominant white, leopard and the base colour. Each needs its own test.
At what age can a horse be tested?
Any age. The genotype is fixed at conception and never changes.
What should I order alongside it?
Extension and Agouti, to predict the colour of the foal.
For Professionals
Genetic and clinical detail for veterinarians, geneticists and laboratories.
- Gene / locus: Tobiano (TO) locus, ECA3; inversion breakpoint near KIT (KIT proto-oncogene, receptor tyrosine kinase), a gene involved in white spotting in horses. No gene is disrupted.
- Variant: chromosomal inversion of about 43 Mb on ECA3 (Brooks et al., 2007). No HGVS description is available in our sources.
- Variant classification: no OMIA variant entry for the tobiano inversion in the OMIA variant table (dump of 2026-09-19); no ISAG/AVCG classification available.
- Inheritance: autosomal dominant; To/N and To/To are phenotypically indistinguishable.
- Penetrance / expressivity: the inversion was present in every tobiano horse tested in German breeds (Haase et al., 2008).
- Breeds with documented carriers or cases: Brooks et al. (2007): American Miniature Horse, American Paint Horse, Arab and Pinto crosses, draft horses and draft crosses, Icelandic Horse, Missouri Fox Trotter, Pinto, Saddlebred, Shetland Pony, Spotted Saddle Horse, Tennessee Walking Horse, Welsh crosses. Haase et al. (2008): German breeds, including the Lewitzer, the Tinker, German ponies and Pinto horses and ponies. Absence from these lists means not reported, not proven absent.
- Allele / carrier frequencies: about 36% of horses registered with the American Paint Horse Association are reported to be tobiano (Magdesian et al., 2009). No breed-level allele or carrier frequency study identified in our sources; 0 of 58 Thoroughbreds carried the inversion (Brooks et al., 2007). Of 109 tobiano horses from white-patterned bloodlines (over 90% of the study samples were registered Paint horses), 11 (10%) also carried the EDNRB frame overo allele (Santschi et al., 2001), the variant associated with lethal white foal syndrome (Metallinos et al., 1998).
- Clinical / diagnostic notes for veterinarians: the main use is zygosity testing. Loci of the other white patterns: EDNRB (frame overo), KIT (dominant white, sabino), MITF/PAX3 (splashed white).
Key references:
- Brooks SA, Lear TL, Adelson DL, Bailey E (2007). A chromosome inversion near the KIT gene and the Tobiano spotting pattern in horses. Cytogenet Genome Res 119:225-230.
- Haase B, Jude R, Brooks SA, Leeb T (2008). An equine chromosome 3 inversion is associated with the tobiano spotting pattern in German horse breeds. Anim Genet 39:306-309.
- Metallinos DL, Bowling AT, Rine J (1998). A missense mutation in the endothelin-B receptor gene is associated with Lethal White Foal Syndrome: an equine version of Hirschsprung disease. Mamm Genome 9:426-431.
- Santschi EM, Vrotsos PD, Purdy AK, Mickelson JR (2001). Incidence of the endothelin receptor B mutation that causes lethal white foal syndrome in white-patterned horses. Am J Vet Res 62:97-103.
- Magdesian KG, Williams DC, Aleman M, LeCouteur RA, Madigan JE (2009). Evaluation of deafness in American Paint Horses by phenotype, brainstem auditory-evoked responses, and endothelin receptor B genotype. J Am Vet Med Assoc 235:1204-1211.