Basic Guide to Reading Pedigrees

Basic Guide to Reading Pedigrees
This website offers complex pedigree reports and knowing how to read them and understanding what
everything means in a pedigree can really help you out. If you scroll to the bottom of this page, you'll
find the pedigree for Kentucky Derby winner REAL QUIET. We'll be using this pedigree as an
example so you can follow along.
Inbreeding
Inbreeding occurs in a pedigree when the same horse appears twice through different offspring. Real
Quiet's pedigree has a fair amount of inbreeding in it. The Pedigree Database will show inbred horses
by placing a colored bar to the right of names inside the pedigree. Notice in Real Quiet's pedigree
below that there are colored bars next to Dr. Fager, Raise a Native, Cequillo, and Rough'n Tumble. The
bars are color coded so that you can quickly find matching sets of horses. All of these horses appear
more than once in the pedigree through different offspring, notice that Aspidistra also appears more
than once in the pedigree, yet she doesn't have a colored bar next to her name. This is because she only
appears through her son Dr. Fager and no other horses.
Cross Duplicates
Inbred horses that appear in both the dam and sire side of the pedigree are referred to as cross
duplicates. In Real Quiet's pedigree, Raise a Native appears twice, once in Quiet American's pedigree
and once in Really Blue's pedigree. Dr. Fager on the other hand only appears in Quiet American's
pedigree and thus he isn't a cross duplicate. On this site, you can choose to highlight the cross
duplicates in a pedigree or all of the inbred horses. Why is this important? The reason it's important is
that inbreeding is only a factor when both the sire and dam have similar ancestors and the subject horse
can have matching sets of chromosomes (alleles) from a specific ancestors.
Siblings
In thoroughbreds, there are three types of siblings that are generally noted. Full siblings (full
brothers/sisters that share the same sire & dam). 3/4 siblings (horses that share 3 out of 4
grandparents). In Real Quiet's pedigree, Dumure and Killaloe are 3/4 siblings sharing Rough'n Tumble,
Aspidistra, and Cequillo. Half siblings are those that either share two grandparents or have the same
dam. In Real Quiet's pedigree, Quiet Charm and Grand Splendor share the same dam and are thus
considered half siblings. Note that horses that share the same sire are not generally considered half
siblings. In the pedigree database, the relationships will be noted by color coded dotted, dashed, and
solid lines below a horse's name. A solid line will highlight full siblings, a dashed line (like the green
one below Demure's name) shows 3/4 siblings. Dotted lines like the one below Quiet Charm show half
siblings.
Grade I/Champion Horses
In the pedigree database, horses that have either won a grade I race or the equivalent of a grade I race
(before the grading system came out) are always noted in bold text. Gen