Here's why:
* Dapple grey is a pattern, not a base color. It's a dilution of a base coat color, like bay, chestnut, or black, that results in a grey coat with darker patches (dapples).
* The gene for grey is dominant. This means that any horse with a grey gene will be grey, even if the other parent has a different color.
* The pattern of dapples is unpredictable. While a grey horse is more likely to have dapples, it's not guaranteed. Some greys may have very little dappling, and some may even have a solid grey coat.
To increase the chances of getting a dapple grey foal:
* Breed a grey stallion to a mare with a dark base coat. This increases the chance of the foal inheriting the gene for grey and having a dark enough base coat to create visible dapples.
* Breed a grey stallion to a mare that has a history of dapples in its lineage. This suggests that the mare carries the genes for dapples, even if she herself is not dapple grey.
Keep in mind: You can't control the outcome of every breeding! Horse color genetics are complex and unpredictable.