In the conclusion to his in-depth analysis of the effects of the age of broodmares and birth rank on the success of racing prospects, the great statistical curmudgeon brings forth some pithy assessments.
How much attention should you pay to either of these two factors? As much or as little as you wish. It is strictly your decision as an informed breeder.
The late J. A. Estes was very interested in birth rank as an outgrowth of the prejudice against first foals that existed at his time. Wrote Estes in The Blood-Horse of December 8, 1934:
Through long years there has grown up a definite idea among breeders and buyers that the firstborn of a mare is at a disadvantage when it comes to racing. That idea was, no doubt, largely responsible for the fact that Mrs. Isabel Dodge Sloane was able to purchase Cavalcade for $1,200. The notion was so widespread, in fact, that I long ago began to doubt its accuracy.
Estes was originally inclined to doubt that first foals were below average, but he changed his mind once he did some actual statistical research into the matter. His ability to change his mind, once he had more facts at his fingers, is a testament to the man. He concluded from his statistical work in that piece that first foals were 21.5% below average. That would correspond to a PPI of 0.785 in my terms, which is very close to the 0.75 figure I have in Table 4.
Estes wrote in another piece in The Blood-Horse of December 4, 1943: “Whether the foal is good, bad, or indifferent depends chiefly on the genetic excellence of the parents, and only in minor degree whether it is a first foal or not.” Although Estes did show differences by all the other birth ranks, I am sure he would agree that this applies to all other birth ranks as well. The genetic excellence of the parents is the most important factor. Birth rank (or age of mare) is only a minor factor.
From that same piece: “So it seems to me that the horseman buying a weanling or yearling does not need to concern himself greatly with the fact that it may be a firstling. He can look the individual over and judge it, along with its pedigree credentials. . . . If the youngster is well developed and meets the horseman’s standards, then I should say that it makes no perceptible difference whether it is a first foal or not.” And the same applies for foals from the highest birth ranks or the oldest mares, as I am sure Estes would agree.
As one who has been misconstrued myself, I really had to laugh at the following from Estes in that same piece: “I must emphasize this point again and again, for I find from experience that there are many people who cannot be trusted with a generalization. You say seldom, and they quote you never. You say top-class race mares are the best prospects for broodmares and they quote you that only top-class race mares are good prospects for broodmares. You say that there are too many claiming races, and they want to know why you are trying to abolish claiming races.”
From the 1934 piece: “Finally, I would ask the reader to remember that the figures I have given deal with probabilities, as indicated against the broad background of actual results. There is nothing to prove that a mare which has produced 14 foals may not, at her fifteenth confinement, give birth to one greater than any of the previous 14. On the other hand, all the indications are that the chances of such a thing happening are very small (one chance in 62, by the table). It is such probabilities that the breeder of Thoroughbreds must work with; he has no certainties at his command.”
Finally, back to the 1943 piece: “Let me repeat that the question of birth rank is still relatively unimportant in comparison with the credentials of the mare herself. The first foals of mares like Swinging and Catalysis can still be Equipoise and Mrs. Ames. The sixteenth foal of a mare like *Filante can still be Fenelon.
“Make the best possible estimate of the individual and its parents and you will never find it necessary to worry about birth rank.”