As much as the average person wants to believe that any beautiful horse can be a winner on the track, there is much more to success than image. When we Pinhook or when owners buy our horses, we always have to look at the Thoroughbred bloodlines to get a better feel for where the horse came from and where they might be going. So how do you evaluate thoroughbred bloodlines? Let’s take a closer look.

Important Terminology

There are some important terms used when discussing horse pedigrees. Even though each breed has some specific language regarding bloodlines, many are the same. You can read more about that here.

For example, mares produce foals, but stallions sire them. And with horses, you’ll see language like “by” or “out of.” A horse will be by the stallion and out of the mare. Of course, these terms also relate to the sire or dam of the horse, which in human terms would be father and mother.


Bloodlines are traced several generations back. The sire is the stallion, and you want to have as desirable a sire as possible in horse racing. You can do this by checking their pedigree and evaluating the performance of other offspring.

To see an example of a pedigree, check out Secretariat here. Everyone knows Secretariat and his reputation as a winner, so you’ll be able to see how bloodlines were evaluated along the way.


Evaluating the dam is just as essential. There is a lot of science and statistics involved, which you can learn more about here. The interesting takeaway is that foals out of unraced mares have a slightly decreased chance of becoming superior runners.

There are certainly instances of mares who never raced producing quality racers when paired with a winning stud.

Generations, a resource for understanding breeding, offers more information about researching generations in a pedigree. They look at generations going back ten years to develop their statistics and knowledge of a horse’s background.

You will probably also see a lot about inbreeding, which is typically considered negative. However, there is much to know about inbreeding and its role in thoroughbred development. To better understand it, check out this article from Bloodhorse.


Along with the resources listed above, there are other places to source information about bloodlines and pedigrees.

And talk with the team at horseOlogy to see how we can help you better understand investing in horses at all stages. We offer Bloodstock Advising to help you make a sound investment decision.

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