Pure white horses

There are certain genes which cause a horse to fade to pure white, in some cases it can be a number of dominant genes, such as those outlined in the 'broken white markings' section, however in many cases a horse is pure white due to the presence of a single dominant gene, specifically the Grey and Sabino genes.

These are both white 'cover' genes, they are not true horse colours, rather white is a loss of pigmentation whereby the horses true genetic colouring is 'hidden' underneath the white.

Both genes are detecatable using DNA testing, this may be useful to simply determine Grey's presence (for a horse which has not yet faded) or to determine whether a Grey horse will consistently produce Grey foals. Since Grey is a dominant gene, if a foal inherits just one copy of the gene from either parent, it will fade-out over time and in many cases end up as pure white. Grey is a cover colour which if present, is certain to be expressed. Please see the Grey section for more specific information.

Sabino is slightly different, as with Grey genetic testing exists to determine the presence of Sabino and to verify Homozygosity. Secondly Sabino works in a 'dosage' effect. If a foal inherits Sabino from just one parent, it will display broken white markings, sometimes small roaned patches, however if a horse is Homozygous for Sabino, it is often pure-white in appearance and guaranteed to pass the Sabino gene to it's foals. See the Sabino Test section for more.