A Little About Colour

TOBIANO

While many lump all coloured horses together as "Pintos" and
"Paints", there are actually many distinct - and not-so-distinct,
colour patterns. "Tobiano" is just one of the terms used to
describe the pattern of white and coloured patches found on the "coloured"(piebald and skewbald) horses.
The Tobiano may either be predominantly black/brown or
white. Body markings will usually be large on the body and
distinct, with rounded or smooth edged patterns that extend
down over the neck and chest giving the appearance of a shield.
The white will most usually cross over the spine of the horse
between the withers and the tail.
The head will usually be marked like a solid-coloured horse,
sometimes being solid or having a blaze, stripe, star or snip.
All four legs will usually be white, at least below the hocks and
knees. However, purists will say, that a "true" Tobiano,
carrying no other colour genetically, will have a solid dark
face with no white. "True" Tobianos are actually extremely rare.
Those which we these days refer to as "Tobianos" - are in most
cases a mix of Tobiano and other patterns. I have never yet seen
a true Tobiano Gypsy Horse. Not saying they don't exist, but
given their background I doubt there are any about. Rather than get into extremely technical descriptions here, we will consider all horse of patched colour with white, as Tobiano.

Tobiano is inherited by a simple "dominant" gene, so you only
need one copy of the gene for the colour to be apparant(displayed)
So if a foal is Tobiano, you know that at least one parent
was also Tobiano. If one parent is tobiano and one is solid
coloured, for the offspring to be coloured, the tobiano parent
has to pass on the tobiano gene. Therefore, there is a 50% chance,
every time, of the offspring being a coloured/colour-patched, foal.

If both parents are tobiano, and each carry a single copy of
the tobiano gene, there is a 75% chance of the gene being passed
on (as each parent has a 50% chance of passing it on). This occurs
when each of the coloured horses being used for breeding had
one solid coloured parent and one tobiano one.

A horse who carries two copies of the tobiano gene, is called
"homozygous". A homozygous horse can only be produced from two
tobiano horses, and will occur 25% of the time (as 50% will be
heterozygous, and 25% will be solid coloured). A homozygous horse
will always produce a coloured offspring, regardless of the
colour of the other parent. Within all the colours, the pattern
is expected to display on different levels.


This Colt, is a "Minimal Expression" Tobiano.


This is a "Medium Expression" Tobiano.


This is a "Maximum Expression" Tobiano.
However some might classify her as a "Tovero" (See below)


Here's a wonderful example of a Tobiano mare with tons of
Inkspots. Inkspots such as these - although not always so
pronounced, often mean the horse is Homozygous for that colour.
Not always, but more often than not. Don't be fooled however,
into thinking that if your horse has no inkspots, that it's
not Homozygous. Many Homozygous horses display no inkspots at all.

OVERO
Sabino, Splash, Tovero and Frame coloured horses, are most
often lumped together under the name "Overo". Some of the
above, have quite distinct markings, while others might be
more difficult to distinguish. Others might display several
types of colour patterns, making true identification quite
difficult.
Overo horses, while patterned much like Tobianos, generally
have white under their bellies and on the sides of their
abdomens and necks. The white usually does not cross the back
of the horse. At least one leg, and often all four, will be
the dark color. Head markings are often bald, apron or
bonnet-faced and the white markings on the body tend to be
scattered, splashy or rough-edged. The tail is usually one color.

In the past, it was always assumed that the overo pattern was
due to a recessive gene because of the unexpected and
unpredictable occurrence of overo foals from two horses of
solid color (cropouts). According to Dr. Ann Bowling, of the
University of California at Davis Veterinary Genetics Laboratory,
who reviewed studbook records and photographic archives from
the American Paint Horse Association, it appears that the
overo pattern "is" transmitted as a dominant gene.
By following the model of overo being transmitted as recessive,
breeders interested in producing color would often cross two
overos, assuming that the product would be another overo. By
crossing two horses homozygous recessive for a gene, the only
result could be another homozygous recessive. As it turns out,
three possibilities occur from the crossing of two overos:
overos, solid colors, and the lethal white. White foals fail
to pass food through their digestive tract due to a lack of
nerve cells in the intestinal tract (aganglionosis), a lethal
defect. A rare human genetic disease associated with a white
forelock (Hirschsprung disease) and at least three white spotting
genes in mice cause similar problems. (The "Lethal White"
problem is also noted in many dog breeds. ie. Harlequin Great
Danes, Boston Terriers, Bulldogs, Border Collies, Australian
Shepherds and many more.)The three classes better fit a model
of overo being transmitted as a dominant gene with the lethal
effects in the homozygous overo condition.
By following the model of overo being transmitted as a dominant
trait, breeders can cross an overo to a solid and expect a 50%
chance of getting another overo instead of the previously thought
chance occurrence. The studbook records of various cropout
Paint stallions (product of two solid parents) revealed that when
bred to solid mares, approximately 50% turned out overo and 50%
turned out solid. Furthermore, with overo being dominant,
the solid colored foal from a solid to overo cross probably
would not carry an overo gene to be passed on. If breeding for
color, crossing two overos may not be the best choice because
of the chance of getting a lethal white foal or the chance of
getting a solid colored foal.

SABINO
"Sabino" and "splashed white" are names sometimes given to other
white patterns which fall into the overo category. Though
definitions vary, sabino horses generally have four white socks,
a white belly and face, white on the insides of the stifles,
and either the edges of the markings or the whole body will
have a lot of roan coloring. On Sabinos the patches of colour
have very ragged edges. They are also most often, marked by a lip spot on
an otherwise extended white face. Some, as the cute mare below,
displays Sabino and Tobiano markings which is not unusual since
both genes may be present in the same horse.

It should be noted, that there are many different types of Sabino and tests are still not available for all. Some Sabino horses can be obvious, by certain characteristics they display but others, quite well could be sabino and white, blue roan and white or gray and white. Some fade with age and some don't. Sometimes this does help to identify just what colour a horse might be, in the absense of the ability to test for certain colours.



Here's another little filly displaying Sabino
and Tobiano colouring.

TOVERO
Tovero horses combine the characteristics of both overos and
tobianos and often have a substantial amount of white throughout
their body.
Tovero horses appear to have two different
dominant white pattern genes. When two toveros are crossed, or
when a tovero is crossed with a solid, four possibilities occur:
solids, overos, toveros and tobianos. It should be noted that
there is no actual Tovero Gene. It's purely a name given to
horses when they display several different types of coat pattern.

You can see many interesting colours, found in Gypsy Horses, on our Webshots album HERE.

A few interesting sites to learn more about Coat Colours.

  • HORSE GENETICS
    A great place to start.

  • ANIMAL GENETICS
    A site to get possible percentages, of colours
    to expect when breeding certain colours together.

  • Introduction to Genetics.
    An easy to understand intro into colour Genetics.

  • EquineColor.com
    A great place on the net to learn about Equine colour genetics.

  • Coat Colors. Genetics Behind the Hide
    This site on Colour Genetics, makes interesting reading.

  • The Colorful World of Paints and Pintos.
    While not showing Gypsy Horses, this site nevertheless,
    shows colour patterns with informative text.



  • There are hundreds of sites on the net which deal in Equine
    Coat Colour.
    Do your own searches and discover some more of interest.


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