Overo (O)
Overo,("Frame Overo") is a dominant white spotting pattern that can appear on all three base coat colors.
Overo horses typically have irregular white patches along their sides, neck, and face, often with jagged or sharply defined edges. Unlike Tobiano, the white markings usually do not cross over the horse's topline, leaving the original base color surrounding the white areas.
The amount of white can vary between horses in game, with some displaying extensive white patches while others have very little visible white spotting. Some horses may even appear completely solid despite carrying the gene, this is also known as “Cryptic Overo". Horses may have minimal or no white marking, but have blue eyes despite no white marking surrounding them.
How Overo Works In-Game
Overo can appear on all three base coat colors, with the resulting appearance depending on the horse's original coat and the amount of white spotting present.
In game, Overo horses can display a variety of white markings due to multiple overlays, ranging from smaller patches along the body to much more extensive patterns. Other white spotting genes may also influence the horse's overall appearance, especially if multiple white markings are stacked.
Overo Inheritance
Overo is dominant, meaning only one copy is needed for the pattern to visually show on a horse. However, unlike most other white spotting patterns, inheriting two copies of Overo results in a lethal genetic condition known as Lethal White Overo Syndrome (LWO).
- O/O - The horse has two copies of Overo, resulting in Lethal White Overo Syndrome. Foals with this combination in game will come out solid white and then pass away.
- O/n - The horse has one copy of Overo and has a 50% chance of passing Overo to its offspring.
- n/n - The horse does not have the Overo gene and will not visually display it or be able to pass it to its offspring.
Lethal White Overo Syndrome (LWO)
Lethal White Overo Syndrome is a genetic condition caused by a foal inheriting two copies of the Overo gene, one from each parent.
Foals affected by LWO are typically born entirely white in game and will pass away before growing into an adult - in real life this is due to the gastrointestinal tract not forming correctly while the dam was pregnant.
When breeding two horses carrying Overo (O/n × O/n), the resulting probabilities are:
- 25% O/O - Lethal White Overo Syndrome.
- 50% O/n - One copy of Overo, allowing the horse to display the pattern.
- 25% n/n - No copies of Overo.
Because of this, breeding two Overo carriers together comes with a risk of producing a foal affected by LWO - you may still breed them together, however you understand the risks associated with doing so.
Genetic Testing
Overo is associated with the EDNRB gene in real horses.
In our genetics system, Overo is a testable white marking. Players can have their horses genetically tested at a veterinary office to determine whether they carry the Overo gene, even if the horse has very little or no visible white spotting.