In certain camera angles, it can be seen that the horses playing Ruffian are actually male ( geldings) and not fillies.
The match race between Foolish Pleasure and Ruffian which provides the crisis of the movie takes place on July 6. 1975 in Elmont, New York. However, the foliage that consistently appears in the background is sparse, consistent with April for southern New York (or March in New Orleans where the movie was shot).