(By Avalyn Hunter)
In his article "Class Action" (The Blood-Horse, 10-23-2010), Evan Hammonds surveyed the Jockey Club database to draw a number of statistical conclusions regarding the likelihood of getting a stakes winner from any particular mare. Among his findings was a definite dropoff in racing quality among foals born late in a mare's producing career, particularly from a mare's 10th foal onwards.
One frequently cited reason for this decline is that older mares, particularly those that have not previously produced a good runner, are often put to inferior sires as they age. But other factors may be in play. For instance, deterioration of the quality of a mare's eggs may occur, just as it does in human females, resulting in a greater likelihood of internal or external birth defects in foals produced by an aging matron. In so finely tuned a breed as the Thoroughbred, even a very minor defect, one that does not compromise the animal's longevity or quality of life, may be enough to make a difference in racing performance. Or the foal, though not defective, may be a little less vigorous than those born earlier in the mare's life.
Another possibility is that the older mare provides a less favorable environment for the growth and development of her unborn foal, perhaps due to small reductions in blood circulation or to depletion of trace elements from the mare's body during successive pregnancies. Some older mares become increasingly vulnerable to infections as they age; others are unable to extract maximum nutrition from their diets because of poor dentition. And some, if not watched carefully, are pushed away from their feed or the best of the grazing by younger, more vigorous mares.
Still some older mares do come up with the best runners of their career quite late. The immortal Secretariat was the 13th foal of his dam Somethingroyal and was produced when she was 18; Battle Creek Girl produced grade II winners Parade Ground and Parade Leader as her 15th and 16th foals, respectively. In Europe, the mares Lacerta, Anonyma, and Mercia all waited until their 20s before producing European classic winners. So, obviously, older mares sometimes do come up with good ones. But what makes the difference between those that do and those that do not? Race record? Pedigree? Overall care? Nutrition? Readers, what say you? What have your experiences been with older mares?