Reading Pedigrees

The horse you see--or the foal you envision--reflects generations of ancestors. Owners of those ancestors made decisions on mating horses, planning each generation. They selected animals by examining the successes of previous horsemen, as recorded in pedigrees.

Each breed includes individuals which meet a standard of a breed registry. The registry--an association or a government agency--maintains the records in a studbook.

To understand more about the effects of breeding decisions, you'll learn how to read a horse's pedigree, and how to examine the ancestry beyond the names listed in the chart. Knowing bloodlines helps you predict a horse's suitability as a performer or as future breeding stock.

Pedigree research can be a lifelong pursuit, involving the science of genetics. For starters, here's a three-step approach covering some popular registries, along with the European sport horses.

Trace The Chart

A pedigree chart portrays a horse's family tree. You'll see charts included in advertisements of horses for sale and stallions at stud, in sales catalogues, and farm brochures.

When you research an individual horse, a certificate of registration (the "papers") establishes that animal's identity. The registry that issued the certificate verifies the accuracy of ancestry, citing stallions and mares recorded in studbooks. On the certificate, a chart might list four generations: sire and dam, the four grandparents, the eight great-grandparents, and the 16 great-great-grandparents. Most pedigrees read from left to right, branching on the "top line" (the sire and his ancestors) and the "bottom line" (the dam and her ancestors).

The certificate should cite registration number, birth date, color, markings, sex, breeder, and owner. Ancestors' names might include their registration numbers, breed (in crossbreds, which would be breeds other than the Thoroughbred, Arabian, and Trakehner), and color. A European sport horse might include the date of branding, proving acceptance by a representative of the studbook.

On the certificate, you'll notice abbreviations for sexes and colors. For a Thoroughbred, c and f represent colt and filly. A German-bred horse would replace the colors of b (bay), ch (chestnut), and dkb/br (dark bay or brown) with b (braun), f (fuchs), and db (dunkelbraun).

As you read the ancestors' names, you learn to recognize major sires and dams. Every established breed has certain famous bloodlines, which become prominent through the progeny's accomplishments. These names will indicate a well-bred foal.

Learning the lines requires looking at lots of pedigrees, and identifying the names. For example, Quarter Horse names include Doc, Poco, Bar, Zip, Peppy, and Leo. Breeders might refer to some of these lines as "foundation-bred," implying dominant sires of the late 19th and early 20th Centuries. A few stallions that established the type as a recognized breed include Joe Bailey, King, and Peter McCue.

Breeders in subsequent generations might build on a parent's name. The Quarter Horse names carry down through decades, incorporated into the names of generations of foals.

Most registries limit the number of characters. Some European studbooks require that an individual be named with the first initial the same as the sire's (Hanoverian), or dam's (Trakehner). In others, such as France's Selle Francais, all horses born in a certain year use the same initial.

Learn the jargon of pedigrees. A horse's second dam is his maternal granddam (the dam's mother). Sport horse breeders often refer to the sire of the dam; you'll see a horse listed as XX-xx-xxx-xxxx (meaning XX is the horse in question, sired by xx and produced by the mare xxx who was sired by xxxx). With a Thoroughbred, you'll hear the term, "broodmare sire" (which means sire of the dam of the horse in question). You also might encounter terms such as "own son" and "own daughter," which indicate a direct sire or dam. in the Quarter Horse world.

In tracing ancestry, pedigree researchers advise studying the closest generations. Peter Birdsall, DVM, specializes in tracing sport horses of Thoroughbred and warmblood breeding. He said, "I usually follow back to the fourth generation. All the genes don't come from the mother or father. You can get genes farther back than the parents'." (Here Birdsall refers to genes as inherited traits.)

"The first three generations are the most important to judge a horse by--such as a good broodmare sire. You'd like to see a daughter of his in a pedigree. It's important to see him at that area of the pedigree."

Look At The Genotype

Starting with the pedigree, you begin investigating the geneology. Every horse's ancestry forms its genotype, or the traits it inherited. Sire and dam contribute toward each foal, and the individual reflects parents, grandparents, and beyond.

Susan Ewart, DVM, PhD, is an Assistant Professor at the College of Veterinary Medicine, Michigan State University. She said, "Having a basic understanding of the contributions of both mare and stallion to the offspring is important. That includes understanding how to intensify or select for a good trait, and how that simultaneously occurs with selecting for potentially negative traits."

Your investigation collects information about ancestors' accomplishments. You'll explore how each mating resulted in performance on the track or the show ring. How did an equine athlete rate in type, soundness, elegance, or speed? You also might want to learn more about the coat color inheritance of a horse's ancestors. And if you really become entranced with equine family trees, you can trace an individual back to a registry's first studbook, published in the 19th or early 20th Century. (Thoroughbreds trace back to the 18th Century, with the publication of the first General Stud Book in England.)

Besides identifying each ancestor by its phenotype (external factors such as coat color and markings), you'll want to confirm its registration. In any breed that isn't a purebred (the three named earlier), you must be able to recognize codes that indicate the breed.

The major North American breeds are simple: in a Quarter Horse pedigree, TB means Thoroughbred, and in a Paint's, AQHA represents Quarter Horse. However, the many studbooks of Europe use multiple abbreviations and codes, requiring more study. A Thoroughbred has xx added to its name, an Arabian, ox, and Anglo-Arabian x. Each studbook is represented by an abbreviation: Hann (Hannoverian), Holst (Holsteiner), SF (Selle Francais), Old (Oldenbourg), KWPN (Dutch), etc. Breeders in Europe frequently crossbreed to individuals from other studbooks.

Registries recognize the value of crossing back to "improvement" sires. The running Quarter Horse developed with the influx of Thoroughbred sprinters. Most sport horses competing at Olympic level are the result of crossing Thoroughbred stallions on warmblood mares. (The Hannoverian state stud has imported U.S. Thoroughbreds to cross with German mares.)

Birdsall points out an outstanding improvement sire for jumpers. "Ramzes was an Anglo-Arab, by a Thoroughbred out of an Arabian mare. Generations later he's commonly found in pedigrees. Horses of the Ramiro line go back to Ramzes--he's been a useful ingredient."

Over the centuries, the Trakehner breed has infused Thoroughbred, Arabian, and Anglo-Arabian lines to maintain its refinement. In 1998, the American Trakehner Association accepted its first-ever Arabian mare born in the U.S., Al-Marah Xanthium. The mare's approval is part of a pilot program to study the effect of adding select Arabian and Thoroughbred blood to the Trakehners bred in North America.

To go beyond the basics of the certificate, you'll employ resources produced by breed registries and scholars. You can purchase studbooks in print form or on CD-ROM. You also can read books by breed experts, who report on the major lines. Several such experts have web sites, where they share some information at no charge.

Some registries have established ratings to classify individuals' performance. In the United States, the Arabian Registry established a system of Achievement Awards in 1965. Superior horses receive points in recognition of their consistency in the show ring, on the racetrack, or in competitive trail and endurance rides. Specific symbols become part of the horse's name, and you'll see these in pedigree charts:

Legion of Honor +

Legion of Supreme Honor +/

Legion of Merit ++

Legion of Supreme Merit +++

Legion of Excellence +//

Legion of Masters ++++

Quarter Horses registered with the AQHA also can earn similar awards, such as the Register of Merit (ROM). A horse which earned an AQHA Championship adds a # to his name; a few outstanding performers win the title of Supreme Champion. A racing Quarter Horse achieves a speed index rating, where a 100 matches a track's record. A high speed index, which might be abbreviated as s.i., indicates a fast race time. A racer which runs a speed index of 80 or higher earns a Racing ROM; the AA and AAA ratings also categorize racers.

Thoroughbreds earn distinction as winners of stakes races. In a performance chart, you'll see codes of racing records. The letters SW indicate stakes winner. Stakes are rated as grade I, grade II, or grade III, with additional notes as turf (T) or restricted by other than age or sex (R). Advertisements and sales catalogs print names of stakes winners in bold face type, called "black type."

Thoroughbreds also are rated by breeding statistics. Stallions and mares have an Average-Earnings Index (AEI). This reflects the horse's progeny racing performance, compared with other foals racing at that time. A Comparable Index (CI) reports the average earnings of progeny produced by mares bred to one sire when the same mares are bred to other stallions. Both the AEI and CI start at an average of 1.00, which makes 2.00 twice the average.

For sport horses, the French have established the Best Linear Unbiased Predictor (BLUP) to measure a horse's genetic potential for show jumping. The World Breeding Federation for Sport Horses' yearbook ranks active performers in the three Olympic disciplines, along with sires. Individual horses earn points for performance; their positions on the list also qualify their studbooks for annual awards.

Pedigree researchers record their findings. You might choose the card system, copying information onto a 3 x 5 card for each ancestor. Or, you can develop a computerized database that includes a record for every horse you're tracking. To simplify your records even more, try a specialized computer program (two names are CompuSire and TesioPower). Whatever medium you choose, carefully transfer names and details. Double-check your writing or typing to verify you're copying the information exactly as it appeared in the original resource.

Interpret The Impact

In this step, you ask "Why?" Why did a breeder decide to mate a mare with a specific stallion? Your analysis explores the reasons behind matings, and produces clues toward improving the next generation.

Recording animals within a breed helps breeders select the best animals, improving the breed's performance through superior individuals. Systematic breeding aims to improve good qualities, while reducing or eliminating negative traits.

Thoroughbred breeders look for that elusive "class" that makes a runner win stakes races. Arabian fanciers aim to increase the breed's traits of elegance, along with correct conformation and movement.

Breeding horses is a science, and you'll need a basic background in genetics. You'll need to understand the differences between heterozygous and homozygous genes. Ewart explained, "Every gene we carry, we have two copies--one from each parent. Those can either be identical or different. In an individual, you can have two copies that are identical, if homozygous, or one of each, heterozygous. The interaction determines your phenotype." (For more on genetics see Genetic Testing in The Horse of December 1998 and Genetics Primer in the issue of November 1997.)

Many breeders follow the practice of line breeding, or crossing relatives in the effort to concentrate superior traits. Ewart terms line breeding as "a polite way of saying you're breeding closely related individuals. The problem with inbreeding is that you are more likely to get the homozygous or identical copies of a gene. This may be good in a desirable trait, or it could be bad."

Certain ancestors have proved to be prepotent, or capable of perpetuating their traits in their offspring. A few notable examples include the Arabian Bask, the French jumper Galoubet, and the Morgan's foundation sire Justin Morgan.

In the Thoroughbred, the Dosage theory is based on a list of prepotent sires. This type of pedigree analysis identifies patterns of ability in horses, with the sires (each identified as a chef-de-race) classified into one or two of five categories. A point system predicts the racing ability of a mating. The Dosage Index (DI) is a number that indicates a horse's potential for speed or stamina.

Breeders debate the success of line breeding vs. breeding type to type. No one knows for sure the results of crossing one horse with another, but analyzing the ancestors can help you make more practical predictions.

Outcrosses bring "hybrid vigor" to a gene pool. Ewart said, "Hybrid vigor is a sound principle. Most individuals are healthier when they have a limited number of homozygous genes. The heterozygous genes tend to have more heartiness, more vigor, and are more reproductively sound. It's probably a more sound way to produce an athlete--but it's harder to predict the results of an individual offspring of a mating."

In analyzing a pedigree, realize that some lines carry negative traits, such as gene-linked diseases. Ewart noted that you might be able to track this inheritance by examining the sire and dam.

Maternal inheritance (or qualities passed on from the mare) has been in the news as the X-factor. However, a recent theory of the X-factor breeding a larger heart currently has no scientific evidence.

Breeders look for the "nick," or how one line consistently crosses well with another. However, one horse resulting from a mating might excel, while his or her siblings might be average in their conformation and performance. Breeders also wrestle with the concept of the individual sire or dam producing one outstanding foal, when others from the same cross were less-than-stellar performers.

Birdsall advised breeders to plan matings for a horse's performance. "If you breed for a purpose, know which horses are at the top of the sport and how they're bred. Think several years down the road. Know what's winning and where those horses come from--then base your decisions on that knowledge." 

About the Author

Charlene Strickland

Award-winning writer Charlene Strickland lives in Bosque Farms, N.M. She has published 8 books and over 600 magazine articles, and is a member of the International Alliance of Equestrian Journalists.

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