The story of the beautiful and haunting riderless horse in Ronald Reagan's funeral procession begins with the truth that a race horse suffering a case of the slows costs just as much in room and board as Secretariat did. The slows can be hazardous to a horse's health because some owners, sentimental as fire hydrants, dump horses faster than J-Lo dumps husbands. As to where they dump them, the words to remember are these from Dave Brandwine: "I didn't want to send him to the glue factory." Yikes. But business is business. Like his horses, Brandwine has to eat, and,...