Patterns - Tobiano, Overo & Tobero, Sabino and Splash


While Tobiano and Overo do not occur in Welsh ponies and cobs they
will be found in Part Welsh. Sabino and Splash are very commonly
found in Welsh ponies & cobs and result in excessive white and blue
eyes. When assessing a ‘coloured’ pony or cob it is important to realise
that often more than one pattern is present and it is also important to
consider the genetic makeup of the parents when determining the colour
definition.


All of these patterns can occur in a very minimal form which can be difficult
if not impossible to determine which is why two parents with very
little in the way of white markings can suddenly produce a loudly
coloured foal.

Tobiano and Overo are dominant genes which means that a horse only
needs one copy of the gene for it to be expressed.


TOBIANO

This is where the patches of white cross the spine. The
patches are reasonably regular and the white appears to travel downwards
from the spine. Legs tend to be white. If a horse has a tobiano
gene it will generally be easily visible although minimal tobianos may
only have the white expressed as a small patch in the dock and very
rarely no colour will be observed even though the horse will be proven
to be tobiano by means of DNA testing. Homozygous tobianos can
occur and these will produce tobianos 100% of the time.


OVERO

(also known as Frame) This was thought to be recessive for
many years but has now been proven to be dominant. In these animals
the white appears to extend upwards. The patches have jagged edges
and the legs are dark although they may have normal leg markings eg
socks and stockings. Some individuals are almost totally white with
only a small amount of colour around the ears. Where two overos are
bred together there is the chance of a homozygous animal and as Overo
is lethal in its homozygous state these animals will die or be euthanised
shortly after birth. The overo colour in a minimally expressed horse
may be difficult or impossible to find and it is therefore important to
DNA test any animal with an overo parent before breeding it to another
overo or a lethal foal may result.


TOBERO

(tovero) These horses have inherited both tobiano and overo
genes. Some look very like a tobiano and again it is important to DNA
test to establish if the overo gene is present.


SABINO & SPLASH

Sabino and Splash are very commonly found in Welsh
ponies and cobs, in fact there would be very few animals
not carrying at least one of these genes. The
method of inheritance is not yet known and it is often
called ‘wild white’ as it can appear in a foal when
both parents have minimal white themselves.


SABINOS

Have stockings which tend to spear, usually a patch on the
chin and very often a small amount under the belly. Many have ticking,
some of which is so heavy that they are sometimes mistakenly classed as
roan. Irregular body splashes are common and can be extensive enough
to resemble an overo and extreme sabino will result in an individual that
is totally white, often still with dark eyes and maybe a small amount of
ticking on the ears or poll. This is the pattern that gives rise to the
‘white’ Thoroughbreds. The mechanism of inheritance is not yet known
but there is certainly more than one gene which can cause the pattern.
Clydesdales are a breed in which sabino is the characteristic colour.


SPLASH HORSES

Appear like a solid coloured horse which has been
dipped in white paint. They can be hard to distinguish from the other
patterns but splash horses tend to have blazes that broaden over the muzzle,
in fact that is characteristic of splash. Splash is also the gene which
causes blue eyes when the blaze is not near the eye. The stockings of a
splash horse tend to be straight edged, unlike the speared stockings of a
sabino.

Splash traits include blazes which come from behind the eyes
like a mask, blue eyes when the blaze does not touch the eye and also
those horses which have a snip and no other face marking. Splash is
thought to be an incomplete dominant gene so a horse with one splash
gene (heterozygous) will express the colour although possibly in a minimal
form while one which is homozygous (two spash genes) will often
show very extensive patterning. A splash horse which is totally solid
coloured apart from a blaze over the muzzle may suddenly produce a
foal with excessive white and blue eyes.


It is important to realize that splash and sabino are very commonly found
in the Welsh breeds and therefore all breeders are likely at some stage to
produce a foal with more white than they would desire and the occasional
foal with one or both blue eyes. These animals are not ‘pinto’ which is genetically
tobiano or overo (frame) or a combination of these (tobero) even
though they may be eligible for registration with pinto societies.

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