While the marquee horses and seven-figure fireworks are long since in the rear-view mirror when the Keeneland September Sale--the largest of its kind in the world--reaches its later books, there are still horses to be sold, even as the demand for those youngsters could begin to wane. Several years ago, in an effort to drum up interest in the latter stages of the sale, officials at the Lexington auction house began mining smaller, off-the-beaten-path markets, and those efforts have borne fruit in places like Russia, where Lyudovik (Constitution) became the...