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Silver Dilution Test

    Reads the PMEL variant R618C, which lightens black pigment to give the Silver coat and is also the cause of...

    €43.05 Incl. VAT

      AboutAbout

      This test shows whether your horse carries Silver. The same gene change gives the silver coat and an inherited eye disorder, so one result answers a colour question and a health question.

      It is relevant for horses of many breeds, including Warmbloods, and for any horse used for breeding.

      Why test?Why test?

      Breeding. Knowing the result of both parents is the only way to avoid a foal with the severe eye form.

      Finding hidden carriers. Some Silver horses show nothing in the coat. Only the DNA test finds them.

      Predicting foal colour. The result tells you whether a mating can give silver foals.

      Buying and selling. Unlike other colour tests, this result carries health information you can show a buyer.

      Clinical signsClinical signs

      The same gene change affects the coat and the eyes.

      The coat

      Silver lightens black pigment only. It shows most in the mane and tail, which turn to a mix of white and grey hairs.

      • Black becomes silver black, or chocolate: a dark brown-grey body with a flaxen or silver mane and tail
      • Bay becomes silver bay: the red body is unchanged, but the black points and the mane and tail are lightened
      • Chestnut is unchanged: there is no black pigment for Silver to act on

      What fools the eye:

      • A silver bay read as a plain bay, since the body colour barely changes
      • A silver black read as a flaxen chestnut, since both have a dark body and a pale mane
      • A young grey, whose lightening mane can imitate Silver
      • Sun-bleaching of a black mane and tail

      The eyes

      The eye disorder is called Multiple Congenital Ocular Anomalies (MCOA). The defects are present from birth.

      Severe form: fluid-filled cysts inside the eye, an abnormally large and bulging cornea, a thin and poorly formed iris, malformed drainage structures in the eye, and cataracts.

      Milder form: mainly cysts arising from the structures behind the iris or reaching into the outer edge of the retina. Some horses at risk of this form show no signs at all.

      TransmissionTransmission

      One copy is enough to lighten the coat. For the eyes, two copies have a stronger effect than one. 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
      • N/N x N/Z gives 50% N/N, 50% N/Z
      • N/N x Z/Z gives 100% N/Z
      • N/Z x N/Z gives 25% N/N, 50% N/Z, 25% Z/Z
      • N/Z x Z/Z gives 50% N/Z, 50% Z/Z
      • Z/Z x Z/Z gives 100% Z/Z
      PreventionPrevention

      Build the mating plan around the eye risk.

      Never mate two Silver horses. Mate a Silver horse only with a partner that tested negative. No foal can then inherit two copies.

      Have the eyes examined. A Silver horse should be seen by a veterinary eye specialist. The DNA result shows the risk, not whether the eyes are affected, and a normal eye examination does not prove a horse is free of Silver. Your veterinarian decides what to do about an individual horse's eyes.

      Carrying Silver is not on its own a reason to keep a horse out of breeding. Bred only to negative partners, it keeps its line going.

      ResultsResults

      N/N: negative. No Silver lightening and no eye risk from this gene. Cannot pass it on.

      N/Z: one copy, Silver. Risk of the milder eye form. Passes the variant to about half of its foals.

      Z/Z: two copies, Silver. The severe eye form. Passes the variant to every foal.

      Whether Silver shows in the coat, and the exact colour, also depend on the Extension and Agouti results.

      SampleSample

      Hair roots: 20 to 40 hairs pulled (not cut) from the mane or tail, with the roots attached. 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.

      White and pigmented hairs from a Silver mane are equally good for DNA, as long as the roots are attached.

      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

      TurnaroundTurnaround

      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 worksHow 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.

      FAQsFAQs

      What does this test not detect?
      It does not test Cream, Pearl, Champagne, Dun, Grey, Mushroom, the base colour or any white pattern. It does not detect any other cause of eye disease in the horse.

      At what age can a horse be tested?
      Any age. The genotype is fixed at conception and never changes. Testing a foal early is useful.

      For ProfessionalsFor Professionals

      Genetic and clinical detail for veterinarians, geneticists and laboratories.

      • Gene / locus: PMEL (premelanosome protein; also PMEL17, SILV), Silver dapple (Z) locus, ECA6.
      • Variant: missense Arg to Cys. HGVS (EquCab3.0): NC_009149.3:g.74569773G>A; NM_001163889.1:c.1849C>T; NP_001157361.1:p.(Arg617Cys).
      • Alternative designations: published as p.Arg618Cys (R618C; Brunberg et al., 2006) and also as p.(R625C); previously listed in OMIA at g.73665304 (EquCab2.0). R617C, R618C and R625C are the same change numbered against different reference sequences; quote more than one when comparing laboratory results. Genomic G>A and cDNA C>T are the same change on opposite strands. Eye disorder synonyms: Multiple Congenital Ocular Anomalies (MCOA), formerly Anterior Segment Dysgenesis (ASD) or congenital aniridia.
      • Variant identifiers: rs3448111155 (EVA); OMIA variant 903.
      • Variant classification: not currently evaluated (ISAG/AVCG, per OMIA).
      • Mechanism: PMEL forms the melanosomal fibrillar matrix on which eumelanin is deposited, so the variant dilutes eumelanin and leaves phaeomelanin unchanged. The same protein region controls pigment dilution in mice, chickens, dogs and zebrafish.
      • Inheritance: coat dilution autosomal dominant (OMIA code D); MCOA autosomal co-dominant (OMIA code ACD). Pleiotropic effects of the same variant (Andersson et al., 2013).
      • Breeds with documented carriers or cases: documented in American Miniature Horse, American Paint Horse, American Saddlebred, Arab, Ardennes, Comtois, Icelandic Horse, Missouri Fox Trotter, Morgan, Quarter Horse, Rocky Mountain Horse, Shetland Pony and Welsh Pony. Brunberg et al. (2006) showed the association in Icelandic Horse, American Miniature, Rocky Mountain Horse, Morgan, Swedish Warmblood and Ardenne; Reissmann et al. (2016) added Comtois and Kabardian. Detected in 15 of 28 breeds surveyed (Avila et al., 2022; see frequencies). MCOA cases recorded in Icelandic Horse, Kentucky Mountain Saddle Horse, Missouri Fox Trotter and Rocky Mountain Horse; case report in a Missouri Fox Trotter stallion (Herb et al., 2021). Absence in a sample does not prove absence in the breed.
      • Allele / carrier frequencies: allele frequency (Avila et al., 2022; 11,281 horses tested, 6,878 after removing close relatives): Rocky Mountain Horse 32% (n=117), Miniature Horse 13% (n=295), Icelandic 7.6% (n=66), Missouri Fox Trotter 6.5% (n=46), Mustang 3.8% (n=40), Shetland Pony 3.7% (n=260), Gypsy Vanner 3.0% (n=67), Tennessee Walking Horse 3.0% (n=181), Gypsy Cob 1.7% (n=60), Dutch Warmblood 1.5% (n=34), Welsh Pony 1.3% (n=78), Morgan 1.1% (n=265), Lusitano 0.5% (n=102), Paint Horse 0.15% (n=1,019), Quarter Horse 0.11% (n=3,188). The authors note ascertainment bias, as samples were submitted for colour testing, so figures for less-sampled breeds may be overestimated.
      • Clinical / diagnostic notes for veterinarians: Avila et al. (2022) recommend genotyping in breeds where Silver occurs, both for mating decisions and to identify horses for ophthalmic examination.

      Key references:

      • Brunberg E, Andersson L, Cothran G, Sandberg K, Mikko S, Lindgren G (2006). A missense mutation in PMEL17 is associated with the Silver coat color in the horse. BMC Genet 7:46. doi:10.1186/1471-2156-7-46. PMID 17029645.
      • Andersson LS, Wilbe M, Viluma A, Cothran G, Ekesten B, Ewart S, Lindgren G (2013). Equine multiple congenital ocular anomalies and silver coat colour result from the pleiotropic effects of mutant PMEL. PLoS One 8:e75639.
      • Reissmann M, Bierwolf J, Brockmann GA (2007). Two SNPs in the SILV gene are associated with silver coat colour in ponies. Anim Genet 38:1-6.
      • Herb VM, Zehetner V, Blohm KO (2021). Multiple congenital ocular anomalies in a silver coat Missouri Fox Trotter stallion. Tierarztl Prax Ausg G 49:350-354.
      • Avila F, Hughes SS, Magdesian KG, Penedo MCT, Bellone RR (2022). Breed distribution and allele frequencies of base coat color, dilution, and white patterning variants across 28 horse breeds. Genes 13:1641.

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