| Whether it is your first time breeding, or you have had | | | | (b) (bb)red (bb)red |
| many foals at your farm one of the most exciting | | | | To make things a little more complicated we will now |
| things is not knowing exactly what you will get when | | | | breed a black mare (BB) to a chestnut stallion (bb). |
| the baby arrives. There are so many variables that it is | | | | Because both the mare and the stallion must |
| impossible to predict how big your foal will be, whether | | | | contribute one gene the resulting foal will be (Bb) |
| it will have good conformation or whether it will have | | | | carrying one black and one red gene. The foal will be |
| the potential for the discipline you bred it for. One | | | | black in color but will have a recessive red gene. |
| question that always has owners guessing is what | | | | Now let's pretend that we breed the foal from the first |
| color the foal will be. | | | | scenario (bb) to the foal from the second scenario |
| Interestingly enough, you can actually predict the | | | | (Bb). Use the following diagram to see how the genes |
| likelihood of the foal turning out a specific color. While | | | | relate: |
| color prediction is not always 100% accurate, there are | | | | (b) (b) |
| some color combinations that will give you a | | | | (B) (Bb)black (Bb)black |
| guaranteed outcome. How can we be so sure of this? | | | | (b) (bb)red (bb)red |
| It's all in the genes. | | | | As you can see from the diagram there are two color |
| Horses have two basic color genes; black (B) and red | | | | possibilities in this cross. When the foal receives both a |
| (b). All horses carry a combination of these two genes | | | | red gene (b) from one side and a black gene (B) from |
| in a pair. The red gene is recessive to the black gene. | | | | the other, the foal will be born black (Bb). This means |
| This means that whenever you get a combination of | | | | that you have a 50/50 chance of the foal being a |
| black (B) and red (b) genes the black gene will | | | | chestnut or a black. |
| express itself. So, a (BB) gene combination will result in | | | | If you cross a homozygous (meaning that it has two |
| a black horse; a (Bb) combination will also result in a | | | | copies of the B gene) black horse (BB) with a |
| black horse and a (bb) combination will result in a red | | | | heterozygous (meaning that it has one copy of the B |
| horse. | | | | gene and one of the b gene) black horse as you might |
| If that is the case you may wonder why we don't only | | | | expect there would only be one possible color for the |
| have black and red horses. In addition to the base | | | | foal, black. This is because all of the color combinations |
| color genes there are special genes that modify color. | | | | would include at least one dominant black (B) gene. |
| If one of these genes are present it will cause the | | | | (B) (B) |
| base color to be modified and the horse will turn out "a | | | | (B) (BB)black (BB)black |
| different color". | | | | (b) (bB)black (bB)black |
| The most common modifier is the Agouti gene. When | | | | Of course this leaves one more combination, the (Bb) |
| the Agouti gene is present it modifies the black gene. | | | | x (Bb) combination. In this case both the mare and |
| A black horse with the Agouti modifier will fade leaving | | | | stallion carry a recessive red gene but are black in |
| its points black and its body brown. This is of course | | | | color. While at a glance you might expect all the foals |
| the classic bay horse. | | | | from this breeding to be born black this is where you |
| Other modifiers include the grey gene, the roan gene | | | | get the odd surprise foal that is a bright chestnut. In |
| and the cream gene. Each of these genes causes the | | | | fact 25% of all foals from this cross will be chestnut in |
| horse's coat to change according to the instructions | | | | color. That is because of the possibility of the foal |
| written into the DNA code. Because this complicates | | | | getting a pair of red genes, one from each parent. |
| matters for now lets stick with the basic black (bay) | | | | (B) (b) |
| and red genes. To simplify things for now I will use the | | | | (B) (BB)black (Bb)black |
| term "black" to include bay horses. We will discuss the | | | | (b) (bB)black (bb)red |
| Agouti gene further in the next installment. | | | | So now you can see where the basics of color |
| So how can you apply this to actual breeding? Let's | | | | genetics come into play when breeding horses. You |
| start with a simple scenario. You have a chestnut | | | | now know that you will always get a chestnut foal |
| stallion (bb) and you breed it to a chestnut mare (bb). In | | | | when you breed two chestnut horses together. You |
| this case both the stallion and the mare have two red | | | | also know that when you breed two blacks together |
| genes. No matter which way you mix and match | | | | you just might get the odd chestnut foal that crops up. |
| those genes the resulting foal will also have two red | | | | While color is far from the most important thing to |
| genes (bb). The resulting foal from this breeding will | | | | consider when breeding, it is certainly one of the most |
| always be a chestnut. | | | | predictable. With the advances in genetic research we |
| (b) (b) | | | | are always finding more color specific genes and can |
| (b) (bb)red (bb)red | | | | predict color variations with increasing accuracy. |