How do you define a "mother line"?

We all know that a good mare from a good family is the cornerstone of breeding success. But how, exactly, do you define a mother line/dam line?

How far back do you go? 4 generations? 16? As far back as the record shows? If you go back far enough, of course, you’ll hit the “Eve” of the species - but we obviously don’t consider all horses to be of the same mother line.

I have been pouring over pedigrees in my studbook of choice and trying to synthesize the information available. One thing that I’ve noticed is that some powerhouse producers seem to rise up out of “nothing”. Granddam and dam may have produced nothing of note, but suddenly, a mare (who may not be much of a performer herself) gives birth to gold no matter what stallion she is paired with. Many of her offspring go on to be fantastic producers, too.

Is this magical mare the “beginning” of a “new” stamm? How does she come to be - blind luck of fortunate genetic mutation, finding the perfect nick of a stallion? Does her prolific record as a producer reflect anything positive back to her seemingly mediocre tail female ancestors?

This is the “joy” of breeding horses. Supreme quality can suddenly pop up, and far outperform the pedigree. Breeders each have theories, and tend to follow those theories. But they do not always “breed true”, and quality can come from all sorts of different and previously untried or unproven sources. So many qualities are necessary to come together to create an equine athlete that following a direct line can be deceiving. “Breeding the best to the best and hoping for the best” is an oversimplification. Remember that arguably the most successful TB race breeder ever, Frederico Tesio, was known at “That Crazy Italian” for this breeding decisions, yet turned the TB race industry on it’s ear more often than not. Someone who thinks they have a theory, has to put their money where their mouth is, and produce foals who prove or disprove those theories. IMO, sport performance quality can come from “anywhere” in a pedigree, you may not know where that may be. With race breeding, when supreme performance is seen from less than stellar pedigrees, and everyone scratches their head. California Chrome. Seabiscuit. John Henry. Mine That Bird. Just a few of the superstars of the past with pedigrees that are less than stellar. Sometimes these horses go to stud, sometimes they don’t. Sometimes they are important influences in breeding decisions, sometimes they aren’t. The female line is important, because the mare raises the foal, imparts some learned and inherited attitudes, and mothering ability is important. Zenyatta has yet to produce an offspring that can win a race.
Think that you have a theory? Breed your mare, and see how it turns out for ya! Do that for 40 or 50 years, and have more success than the average, and you might be onto something.

1 Like

Evaluating sporthorse pedigrees is different than evaluating racing pedigrees just because it takes longer to see success and there are so many more outside influences.

1 Like

I think this will vary a bit across breeds/disciplines. In the Arabian world, we define the dam line by the “tail female” - i.e. the furthest back recorded ancestor in the direct dam line. This will ultimately classify the horse into one of five (usually - there are technically more than five, but only five that have significant numbers representing them today) “strains”. There is a subset of Arabian breeders (smaller every day but still out there) focused on “pure in strain” breeding, or only breeding individuals to others of the same strain to preserve the traits associated with this female line.

1 Like

In TB breeding it’ is also ‘tail female’ . the mother of the mother and so forth, back to the 16 hundreds and this groups the current descendents into mare families.
Modern research has somewhat thrown a wrench in the works, some families have become subdevided, or they found out that somewhere they crossed wires…

but, no, you don’t magically create a new mare family.
You are just sitting ona a blue hen.


I would imagine that in 400 years of breeding - at least 40 generations, possibly up to 100 - the only thing left from that 1600s tail mare is the mtDNA, and it’s possible (likely?) that it has been subject to mutations along the way. Two horses born today with the same tail mare that far back likely have extremely little in common genetically aside from that.

Is the mtDNA so critical that it alone is enough to define an entire “family” by?

I guess that’s where the family splits came from.

Super interesting. I’ve known a few amazing horses out of well known KWPN tail female lines, both easily identified by their naming conventions -Daula and -Oeska.

The modern warm blood sport horse registries are more recent and more open than the TB or Arabians. Also more explicit quality control goes into the modern European warm blood registry acceptance.

1 Like