Bay (color)

From Freepedia

Image:Horse 2005-08-06 (Cheval).jpg Bay is a color of the hair coats of horses, characterized by a body color of dark red (known as blood bay) to deep brown, with black points (mane, tail, lower legs, and sometimes the muzzle and tip of the ears). Bay is a favorite color among ranchers and horse enthusiasts, and is one of the most common coat colors in many horse breeds.

Genetics

For background, see equine coat color genetics.

A bay horse carries both the extension gene (E) and the agouti gene (A). The extension gene adds black color to their coat and the agouti gene limits it to their points. If they lack the agouti gene, they will be completely black. If they lack the extension gene, they will appear identical to a sorrel, but may produce bays in breedings with black or bay horses.

If a horse carrying the extension and agouti genes additionally has a heterozygous creme gene, it will have the buckskin color, which is similar to bay except that red or brown areas are lightened to a yellow or gold color. If the horse has a homozygous cream gene, it will have a perlino color, where red areas appear nearly white.

Because the extension gene and agouti gene can be either heterozygous or homozygous, the extent to which a bay passes on its color varies widely from one horse to another depending on its genotype and that of its mate:

• Ee Aa bay × sorrel: 25% bay, 25% black, 50% sorrel
• Ee Aa bay × Ee black: 37.5% bay, 37.5% black, 25% sorrel
• Ee Aa bay × EE black: 50% bay, 50% black
• Ee Aa bay × Ee Aa bay: 56.25% bay, 18.75% black, 25% sorrel
• Ee Aa bay × EE Aa bay: 75% bay, 25% black
• Ee Aa bay × Ee AA bay: 75% bay, 25% sorrel
• Ee Aa bay × EE AA bay: 100% bay
• Ee Aa bay × sorrel: 25% bay, 25% black, 50% sorrel
• Ee Aa bay × sorrel: 25% bay, 25% black, 50% sorrel
• EE Aa bay × sorrel/black: 50% bay, 50% black
• EE Aa bay × Aa bay: 75% bay, 25% black
• EE Aa bay × AA bay: 100% bay
• Ee AA bay × sorrel: 50% bay, 50% sorrel
• Ee AA bay × Ee bay/black: 75% bay, 25% sorrel
• Ee AA bay × EE bay/black: 100% bay
• EE AA bay × sorrel/bay/black: 100% bay

In many breeds all of these genotypes are fairly common, making bay breedings unpredictable without a prior blood test for color-related genes.

The following grid shows the two-gene Punnett square for a crossing of two Ee Aa bays, just one of the many possibilities outlined above. Each of the sixteen squares is equally likely. Nine of the results carry both genes (bays), three carry extension but not agouti (blacks), and four do not carry extension (sorrels):

	e a	e A	E a	E A
e a	ee aa	ee Aa	Ee aa	Ee Aa
e A	ee Aa	ee AA	Ee Aa	Ee AA
E a	Ee aa	Ee Aa	EE aa	EE Aa
E A	Ee Aa	Ee AA	EE Aa	EE AA