Sabino is a group of white patches on a horse that affects the skin and hair. Various irregular color patterns are accepted as sabino. In the strictest sense, "sabino" refers to the white pattern produced by the Sabino 1 gene (SB1), which is a DNA test. However, other horse enthusiasts also refer to patterns that are visually similar to SB1 as "sabino", even if testing indicates that the gene does not exist. The use of the term to describe a non-SB1 ​​"sabino" pattern in a breed that does not seem to carry the gene is hotly debated by researchers and horse breeders.
The Sabino pattern is visually known to be wailing at the edges of white marks, stomach spots, irregular face marks, especially white lengthwise through the eyes or to the chin, white above the knees or hocks, and "splash" or "lacy" marks anywhere in the body, but especially on the abdomen. Some sabinos have patches of roan patterns in body parts, especially the barrel and pelvis. Some sabinos may have dark legs or two, but many have four white legs. Both blue and brown eyes are visible. At one end of the sabino spectrum, the SB1 gene, when homozygous, can produce a nearly completely white horse with pink or partially pigmented skin. Some forms of sabino genetics are also considered the most common reasons for a solid colored horse with "chrome", a term that can refer to horses with thick white marks on the face and high white foot marks. The most generous definition of sabino can include horses with little white like chin or lower lip points.
Although horses with Sabino 1 genes can be completely white, there is no sabino form connected with deadly white syndrome.
Video Sabino horse
gen Sabino 1
Sabino 1 was identified in 2005 by researchers at the University of Kentucky. Gen Sabino 1, and associated spotting patterns, are found in miniature horses, American Quarter Horses, American Paint Horses, Tennessee Walkers, Missouri Fox Trotters, Mustangs, Shetland Ponies and Aztecas. SB1 is mainly absent from Arabian horses, Thoroughbred, Standardbred horses, Shire horses and Clydesdale. There are many proposed genes that are responsible for white patches like sabino in this race and others. The researchers gave their allele the name "Sabino 1" in the hope of finding unnamed genes "Sabino 2", "Sabino 3", and so on.
Although horses with Sabino 1 genes may be completely white, either Sabino 1 or other sabino forms are not associated with white lethal syndrome (LWS). Children who suffer from LWS are born white or almost white, but have a damaged colon and always die within 72 hours after birth. DNA tests exist for Lethal White Syndrome to identify operators.
Sabino 1 mark
Horses with one copy of the Sabino 1 gene are said to be heterozygous for the gene, and have a distinctive white patch pattern. The area of ​​pigmented white hair is rooted in pink skin without pigment. The horses with the Sabino 1 pattern usually have irregular and rough white patches on the extremities and face. These white patches also often include the middle of the body as "stomach spots". White hair interspersed around white marks or on the body, which can resemble roan, is a characteristic of Sabino 1, especially when heterozygous. Typically, Sabino 1 horses have two or more feet or white feet, flames, spots or roots in the abdomen or pelvis, and jagged edges to the white markings. The simple signs of Sabino 1 are often difficult to distinguish from other white signs; phenotype overlap. Blue eyes are not associated with Sabino 1, although horses with Sabino 1 may have blue eyes from unrelated genetic factors.
Sabino-white
Horses with two copies of Sabino 1 gene - one from each parent - are said to be homozygous for the gene. Homozygous Sabino 1 horse is usually at least 90% pink and white skinned at birth. Again, eyes are usually not blue. The term "sabino-white" is used to distinguish homozygous SB1/SB1 horses from so-called "dominant white" horses, which require only one copy of the "white" gene to have a white coat. Without DNA testing, the dominant white horse and sabino white horse can not be distinguished.
Not all "white" horses are white or sabino white or even dominant. Combination of other white patch patterns, such as tobiano with heterozygous frames, can produce a horse that is 90% white or more. The shallow Cremello horse is similar to sabino-white, but the kremelo has blue eyes, reddish red skin, and a cream-colored mantle instead of white. The gray horses have white hair hair as adults but unless they also carry a dilution gene, white, or SB1, they do not have pink skin and are not white at birth.
Genetics
The Sabino 1 focus is on the KIT gene. Sabino 1 is an incomplete dominant trait; each of the different genotypes corresponds to a separate phenotype. Both Sabino 1 and many known forms of dominant white spot on horses involve the same genes, but they are clearly labeled. The "dominant white patch" includes many different phenotypes and genes, while "Sabino 1" is reserved by geneticists for genes that produce an all-white phenotype in a homozygous state.
Alleles, or "versions", of Sabino 1 are set to SB1 and sb1 . The gene in the wildtype of the horse is recessive and the SB1 mutation is dominant.
- sb1/sb1 (also written n/n or/) homozigot recessive, wildtype. Horses will not have the correct Sabino 1 properties, but may still have white markings due to other factors.
- SB1/sb1 (also written SB1/n or SB1/) heterozygous, sabino. Horses will have Sabino 1 properties such as white markings with jagged edges and body spots or roaning.
- SB1/SB1 homozygous sabino, sabino-white. The horse will have pink skin and a white coat on at least 90% of its body from birth.
Mendelian inheritance laws, as summarized in the above table, show that crossing two horses with recessive genotypes (sb1/sb1 or/) will never produce horses with Sabino 1 genes, regardless of the appearance of the mantle. By this same rule, the only way to guarantee the sabino sabote (SB1/) is to breed the sabino-white to non-sabino.
The mutation responsible for Sabino 1 in the KIT gene is a single nucleotide polymorphism designated KI16 1037A. Sabino 1 mutations produce skipping exon 17. Other areas of the KIT gene are responsible for tobiano, true roan, and a dozen dominant white phenotypes. It is also a gene associated with patches of skin and hair that are not pigmented in the extremities and the midline of humans, rats, and pigs. KIT plays an important role in the migration of early pigment cells (melanocytes) from the neural emblem to their final location in the skin. Mutations in KIT appear to limit the migration of melanocytes, leaving the extremities and midline without pigment cells. Other factors, including stochastic events and other genes, affect non-pigmented skin and hair counts in fully developed animals.
A similar phenotype is known in many other species. There are over 90 unique mutations in the mouse KIT gene, resulting in a phenotype that ranges from white toes on the hind legs to "black-eyed white" coats. In mice, the KIT gene is called locus W.
Maps Sabino horse
"Sabino" but not Sabino 1
The term "sabino" can also be used in a descriptive sense for horses with signs often associated with Sabino 1: white feet above knees and hocks with jagged margins, wide flames, and stomach or roaning spots. However, other horse enthusiasts, owners and breeders define the term more broadly, to include "chrome", "white high", "excessive white" or white spots on the lower lip or chin, distal white patches on the feet, or " tapered "foot sign.
The genetics behind the white markings on horses is complicated. Some registries of breeds oppose white fight, while others opt for it; the result is that, before the ability to map the horse's genome and perform DNA testing to verify the offspring, various rules were made to describe "seeing" from "non-spotted". The rules are not based on known white spot gene behavior and many organizations have not yet pursued modern understanding of genetics. Two horses with identical genotypes for certain white patches can be phenotypically considered "solid" or "visible", depending on the number of patterns seen. Furthermore, the white amounts of foals do not depend solely on known white patches of genes. For example, studies show that chestnuts have more white than non-chestnut, and that non-chestnuts carrying masked chestnut alleles have more white than non-chestnut without a chestnut allele. White spot genes also interact with each other, usually cumulatively.
Research shows that there are many genes, and potentially different alleles in those genes, that produce so-called "normal" white markers. Further research shows that when separate genes for the white markers are present together, they have an additional effect, producing more white color together than the gene that will do it on their own. Similar effects were observed in the pinto horse with tobiano patterns and frame overo; these "toveros" often have whiter than tobiano or overo-patterned horse frames. Similarly, two horses that appear to be solidly colored with separate factors for white marks can produce horses that express both, whiter than one of its mother.
In Arabian
It is well known that sabino-like patterns do exist in pure Arab races, although research at the University of California, Davis suggests that genes (or genes) that produce a sabino pattern in Arabs are not SB1, and SB1 has not been found to date. The Arans. White spots produced by the nature of sabino in Arabia at one time are controversial, and the spotting of the body is seen as a sign of "impure" breeding, with the horses excluded from the registry. Today, with DNA tests to verify the offspring, a large number of Arabs fulfill the definition of having characteristics of minimal to moderate sabinos expressed.
The minimal nature of sabinos exists in Arabic and the term "maximum sabino" was created to describe freckled Arabs approaching 50% white. However, very few Arabs who visually look completely white, and sabinoan white are unverified in one of them. A true white horse that was originally identified as "sabino bay" is determined to bring the original mutation of the new dominant form of White Leather, and has inherited this trait to its offspring. The pattern of inheritance observed in sabinoan-like Arabs does not follow the same inheritance as Sabino 1.
In horse concept
The Clydesdale and Shire are closely related draft horses originally bred in England. In addition to large body shapes and excessive feathers, both breeds are known for consistent white markings. The most popular and acceptable forms of white marking on both breeds include thick flames and four even socks. Standard breeds for Clydesdale horses state that "excessive white" is no longer a mistake. In contrast, even in modern times, the Shire horse breeds the standard of counting excessively white, spotting the body, or roaning it as a fault, especially in a stallion.
Among Shire and Clydesdales, high white markings follow a pattern similar to those found in sabino 1 sabinos that express high. The consistency of the design-type sabinoir spotting pattern led the researchers to incorporate these horses in the original study that found Sabino 1. However, no design-type sabino has SB1 alleles. White markings on the face ranging from blistering to bald face to apron face. The signs of a white face often extend to the chin or lips, and may wrap the head with irregular and hairy boundaries. When white marks on the forefoot extend above the knee, they may climb the shoulder or climb to the back of the foot to the elbow with irregular, furry or wrinkled distinctive borders. The white markings on the hocklegs are more common, and usually down the front of the foot to the joints and stiff wings. When the white foot marks extend above the knee or shock, they are often accompanied by spotting the body, usually on the abdomen. These signs are also often accompanied by white hair interspersed which gives horses a roan-like pattern. Such horses are called "roan" by Shire and Clydesdale descendants.
The "sabino-draft" is different from Sabino 1 in that, while it may be inherited predominantly, it does not produce a sabino-white phenotype when homozygous. Since the gene pool for both breeds is limited, most horses are expected to have genes responsible for their unique white spot pattern. However, if the draft-type sabino gene produces sabino-white, a close white coat would be expected in nearly a quarter of the foals. Although Shires and Clydesdales are almost white can be found, they are quite rare.
While the general pattern for Shires and Clydesdales appears to be inherited predominantly and produces a white spot phenotype, it is unlikely that the responsible allele will be categorized as "white dominant." Dominant white is reserved for white allele spots that allegedly produce embryos that do not live in homozygous. There is no evidence that the homozygous embryo for the draft-type sabinoan pattern can not survive.
In the American Quarter Horses
The term "sabino" is rarely used among American Quarter Horse breeders, since the white pattern was initially considered undesirable. Breed American Quarter Horse is traditionally solid colored and marked minimal. Among the Quarter Horse breeders, foals with unqualified numbers of whites born to qualified parents are referred to as "cropouts," and, until 2004, horses that had areas of white hair rooted in leather pink outside the gaskin on hindleg, above the halfway point between the knee and the elbow on the front leg, or outside the eye can not be registered. Because of the sheer number of horses that have these patterns, as well as a large number of double dilute creams also caught by this rule, the American Horse Horse Association (APHA) is formed, allowing these horses to be listed as "Paints". APHA recognizes sabino as one of the "big family" color patterns.
Since white rule relaxation, at least one enrolled Quarter Horse has been tested homozygous for SB1 alleles. Because of this example, as well as the extensive breeding of Quarter Horse in the Paint bloodline, it is clear that the SB1 allele is in the genepool breed and that there are SB1 sabinos that have minimal markings classified as "solid". Quarter Horse can show a sabino-like pattern from the same genetic source as other breeds.
Combination and mime patterns
Sabino may have similarities with other color patterns. Because pintos breeders, especially the American Cat Horse, often cross various color patterns, perhaps a horse carries genes for more than one pattern. The presence of some white patch patterns often produces additive effects and the horses can show the characteristics of both patterns. This can, at times, make identification and registration of horses that look to be a challenge. Conversely, even if spotting genes are present, white body signs may be very minimal in some individuals listed as solid colors. However, they can produce highly colored offspring, sometimes referred to as "cropouts".
Frames and sabino
While the American Paint Horse Association (APHA) refers to the sabino and frame patterns as "overo", they are genetically unrelated and visually distinct. Frame pattern pattern is produced by Ile118Lys mutation in endothelin endothelin type receptor B. The framework is characterized by sharp but sharp patches, horizontally oriented white patches on the neck, shoulders, waist, and hind legs. By itself, the frame pattern does not produce a white mark that crosses the rear, or affects the foot or tail. Indeed, however, it often produces bald faces and blue eyes. Homozygous horses for Ile118Lys mutations in endothelin endogenelin type B gene genes are born all white or almost white with some pigmentation along the topline, and die soon after birth from deadly white syndrome. The expression of the frame pattern varies from small white marks to different frame patterns, with some frames tested by DNA looking sturdy.
Horses carrying both the frame and the sabino gene can be expected to show the characteristics of both patterns. While frames alone are rarely responsible for white footprints, the sabino-frame mix may have body frame marks and white marks on the feet. Similarly, while the frame alone produces signs with sharp but sharp white spots, the addition of sabino can be expected to have a creased edge and moan in the body. The blue eye is not considered a sabino characteristic, but the frame-sabino mix may have many white eyes and even blue eyes. Frames in conjunction with sabino can produce a pattern of "drug caps", where only ears and polls and sometimes topline may have pigment. (Hat horse medicine sometimes also has a "shield" pattern on the chest). Horses with pigments that are even less than hats can be classified as "white stockpiling" by the American Paint Horse Association, possibly also horses with both sabino frames and genes.
Because the APHA overo classification system was created before modern genetic studies, it is based on physical descriptions rather than genetics. Thus, the sabino-frame mixture of different expressions can be considered "solid stock breeding", "overo", or "white stock breeding". Without genetic testing, horses with frame genetics but lacking clear frame characteristics can be cultured against each other or with an identified frame and can produce deadly white foals. The deadly white frame and syndrome patterns are generated by mutation conditions that are similar, not separate, closely related. No other white patches indicate a deadly white syndrome.
Terminology and identification can be challenging even for knowledgeable breeders. Standards for horse breeds that do not carry a pattern of patches or spots, such as the Arabian and Clydesdale, do not regard sabino as an overo pattern, but sometimes classify sabino horses as roan. To confuse the problem further, in Spanish-speaking countries, the term "overo" actually refers to a horse with so-called "sabino" in English; Meanwhile, in South America, the term "sabino", which is literally translated from Spanish means "mottled" or sometimes "roan", refers to the bitten gray.
Splash and sabino
Splash, or splattered white, is a distinct and uncommon pattern that is also classified by APHA as "overo" and has not been mapped genetically. Splash patterns are marked with blue eyes and sharp, subtle signs that make the horse appear to have lowered its head and waded through white paint. The feet, tail, bottom, and head are usually white; white head is different from the frame and the signs of sabino's face, which is jagged or wrapped, in most of the head is white. Horse sparks are sometimes deaf. White splashes are found in paints, Welsh horses, Icelanders, and Morgans. It is theorized that the spark is incompletely dominant and that the heterozygous splash horse often has minimal marks similar to sabinos or generic white marks. The least possible splashes may have only a low bottom and a low back. The Splash-sabino mix will have characteristics of both patterns, such as jagged and roaning patches, blue eyes and yellow white markings. In horses that minimally express both, accurate identification can be very difficult, and without DNA testing for sparks, especially a conjecture.
Tobiano and sabino
The tobiano patterns are easily recognizable and the tobiano horses are categorized separately from other patterns in association breeding for the pinto-spotted horse. Although they are visually quite different, the simple dominant allele responsible for the tobiano pattern is quite close to the known and suspected sabino loci. The tobiano pattern is characterized by subtle, crisp white markings arranged vertically on the body, sometimes as if in a band. The legs are often white, and the tail is often white or partly white. Tobiano is not responsible for facial marks or blue eyes. A tobiano-sabino mixture may have more than the expected number of white signs of the face, and the edges are wrinkled or wrinkled into tobiano white markings. Tobiano signs usually do not occur on stiff and pelvic body parts, while signs of sabino feet often enter these areas; a clear horse marked with a white horse stretching across the legs to the back and pelvis may also be a sabino. Due to the additive effect of some white spot genes, the tobiano-sabino mix may have more white than expected.
Some horses can simultaneously carry genes for the pattern of spotting tobiano and for sabino. This is generally noticed when the tobiano horse has spots with roaring at the edges, or other sabino characteristics such as white belly, white on the chin, or a "white high" sign. Tobiano is a dominant gene, unrelated to sabino, but because pintos with different spotting patterns are often crossed with each other, it is very easy for a horse to carry multiple patterned patch genes.
The Tobiano-sabino mixture listed with the association of the colored breed for horse looks can be categorized as "tovero". Some cases of the pattern of "drug caps", where only ears and polls and sometimes topline (and sometimes chest has a "shield" pattern) may have pigment, and white or nearly white horses may mix tobiano-sabino.
Roan, rabicano, and sabino
Real roan is not sabino or gray; it refers to a white hair pattern interspersed evenly on the body with minimal white hair on the head and legs and a little, if any white marks. The main characteristics of sabino are the white marks on the head and feet, often by roaring by the edges. When both roan and sabino are present on the same horse, it can be difficult to say whether roaning is due to a true sabino or roan, especially if the white marks completely cover the head and dark legs.
In some registries of the breed, the term "roan" is used to record sabinos, especially with pure horses and Arabs. Sabinos or sabinos with roaning have also been described as "roan" by Clydesdale, Shire, and Tennessee Walking Horse registries.
Rabicano is another type of "roaning" or a tick marked with white hair spread in the middle, pelvis, and white hair at the base of the tail. Only in the most extreme circumstances is rabicano associated with the underlying pink skin. It is not known whether the roaning characteristics of some sabino type patterns are due to the presence of additional rabicano or separate mechanisms. Rabicanos are also often identified as roans, even among breeds that have no true roans, such as Thoroughbreds and Arabians.
Gray and sabino
The gray horses undergo a progressive silver that begins on or shortly after birth. The light gray horses often show a mixture of white and colored hair that can be misconstrued as roaning. Grays developed more white hair for several years, most of which eventually lost all or nearly all of their original colored hair. The Sabino sign is permanent, and while some changes do not come out of the usual and drastic color changes, it is not characteristic of the sabino type pattern. If a horse carries both genes, it will show a pattern of spots when young, but they will fade over time when the entire coat turns black to white. Once the horse is completely gray, the pink skin under the original white mark will still exist, but it may not be obvious unless the horse has a hair-cut layer or wet hair.
"Maximum White" Sabino
There are differences in terminology between genetic researchers and certain organizations promoting the color of sabino, especially in Arabia. Some researchers, such as Dr. Phillip Sponenberg, using the term "maximum sabino" rather than "sabino-white" to describe a horse of more than 90% white. Groups promoting the color of sabino have a more generous definition; Arab Horse Registration Sabino considers Sabino "Maximum" as a white horse of more than 50%.
Breeds that recognize the sabino pattern
Standard breeds that recognize sabino patterns include Mustang, American Paint, miniature horses, Morgan, Hackney (and Hackney horses), Tennessee Walking Horse, and heirs of pinto breeds. Horse breeds are generally solid colored and do not allow most pinto dyes in their offspring, but who may have representations with sabino gene patterns expressed by white, high stomach, lacy or spotted and white spots extend through the eyes including Clydesdale , Arabic, Thoroughbred and Shire.
The most controversial expression of the sabino gene complex is in the American Quarter Horse, which for years did not register horses with "cropout" or blue eyes, a typical sabino pattern, or cremello or perlino horses. The exceptions of these plant children, even from two solid-skinned parents, led some to the establishment of the APHA registry. However, since the discovery of DNA testing to confirm offspring, AQHA has revoked this controversial "white rule", allowing light-colored horses and people with freckles to register.
See also
- Horsehair Color
- Combine the mantle color genetics
- White (horse)
- Dominant white
References
External links
- Horse Sabino Registration
- The horse's genetic test for colors and patterns
- American Cat Horse Association - Sabino Spotting
- Animal Genetics Inc.
Source of the article : Wikipedia
0 Comments