Sabino horse
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- For the municipality in Brazil, see Sabino.
Sabino is a color spotting pattern in horses that is usually recognized as a form of pinto horse color. A sabino horse has a dark base coat with a unique overlying spotting pattern. It is one of the most confusing colors to explain because a wide range of patterns are considered acceptable. Further, the polygenic combination of genes that produce this color pattern is not yet fully understood and is hotly debated by both researchers and horse breeders.
One of the many possible genes that creates the Sabino pattern, the Sabino (SB1) gene, now can be detected by a DNA test.[1]
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[edit] Sabino Markings
Sabino coloring is usually characterized by roaning at the edges of white markings, belly spots, irregular face markings, especially white extending past the eyes, white above the knees or hocks, and "splash" or "lacy" marks anywhere on the body, but particularly on the belly. Many sabinos have patches of roan coloring on part of the body, especially the barrel and flanks. Some sabinos may have a dark foot or two, but most have four white feet. Both blue and brown eyes are seen. A wide variety of irregular color patterns are accepted as Sabino.
Sabino genetics are also thought to be the most common cause of solid-colored horses with "chrome," i.e. horses that have lots of facial white and high leg white, with the occasional belly spot or roan patch. White stockings that extend past the knee or hock, sometimes combined with a bald face (white extending to or past the eyes) is considered the minimal expression of the gene-complex, but usually there is additional evidence that these are not the usual white marks on a narrow and long extension up the leg.
[edit] Breeds that recognize sabino coloring
Breeds that recognize sabino coloring include the Mustang, American Paint Horse, Miniature horse, Morgan and the Pinto horse color breed. Horse breeds that are generally solid-colored and do not allow most Pinto coloring in their breed registries, but who may have representatives with the Sabino gene pattern expressed by high white, belly spots, lacy or roaning patches and white extending past the eyes include the Clydesdale horse, Arabian horse, Tennessee Walker, Thoroughbred and Shire.
The most controversial expression of the Sabino gene-complex was in the American Quarter Horse, which for years did not register horses with "cropout" color or blue eyes, i.e. typical Sabino patterns as well as cremello and perlino horses. This exclusion of cropout foals, even from two solid-colored parents, led in part to the formation of the American Paint Horse registry. However, since the advent of DNA testing to confirm parentage, the AQHA has repealed this controversial "white rule," allowing light-colored horses and those with body spots to be registered.
[edit] Overo or Sabino?
Sabino is included in the Overo family of spotting patterns by the American Paint Horse Association, though other breeds which do not recognize Overo spotting patterns in their horses, such as the Arabian horse and the Clydesdale horse, do not. Research indicates that a true Sabino color is polygenic, caused by a gene complex that is not the same as that which creates the overo pattern.[2] [3] [4] For example, there are a few Arabian horses that are sabino, but Arabians never have any other type of pinto coloring.[5] Genetic sabinos, even those with maximum white, also do not appear to carry the gene for lethal white syndrome, but some overos might. On the other hand, the frame overo pattern does appear at times to combine with the sabino pattern, creating a horse with a coat color that has characteristics of both.
To confuse matters further, in Spanish-speaking countries, the term "Overo" itself actually refers to horses with what is called Sabino in the USA, and in South America, the term "Sabino," which literally translated from Spanish means "speckled" or sometimes "roan," refers to a flea-bitten gray.[6]
[edit] Roan versus Sabino
Sabino color may at times resemble a roan, but it is quite different genetically. In fact, Sabino and roan patterns have even been confused by some breed associations, including the Arabian, Thoroughbred, Tennessee Walker, Clydesdale and Shire registries, all of which still use the term "roan" to describe Sabinos.
A true roan is differentiated from a Sabino by the absence of splashy white markings and usually has a head that is darker than the body. Most roans have very little white, in fact. However, again, the sabino gene does sometimes occur in conjunction with a roan-colored coat, producing a horse with both roan and sabino traits.
[edit] "Maximum White" Sabino
A "Maximum Sabino" is all white--essentially is either one big white spot, or is so covered with white spots that no darker color shows through. Such a horse will have pink skin and may have blue or brown eyes, though a maximum sabino must not be confused with a genetically white horse. A maximum sabino is produced is if the foal is homozygous for the sabino1 (SB1) gene, and thus if a foal is ill at birth, testing for SB1 can determine if a white foal is a maximum sabino (with, presumably, an unrelated treatable illness) or if it carries the lethal white gene (and thus will need to be euthanized). Sabino1 as it is not present in all sabino-patterned horses. It is most commonly found in Tennessee Walking Horses. Other breeds in which the SB1 mutation has been found include: Miniature horses, American Paint Horses, Aztecas, Missouri Foxtrotters, Shetland Ponies, Spanish Mustangs and Pony of the Americas. Other breeds of horses have sabino patterns, such as Clydesdales and Arabians, have so far tested negative for SB1, and neither breed produces white horses[7]
[edit] References
- ^ The Sabino Pinto test
- ^ "the genetics of sabino horses"
- ^ Equine Color Genetics Information: Sabino
- ^ APHA site: "Genetic Equation: Sabino"
- ^ UC Davis horse coat color tests
- ^ Equinecolor.com sabino page
- ^ Sabino 1 information from UC Davis web site
