This is an interesting promotional advertisement from the very early 1950s.
Bomba, The Bowery Boys, Blue Grass of Kentucky – a film title I seem to remember because to me as a child it sounded so good. Don’t think I ever saw the film – must get it.
However I have found this review – as follows :-
A fast-moving racing film with romance, action, and lots of heart, BLUE GRASS OF KENTUCKY rises a cut above most stories of its ilk by virtue of its extremely intelligent screenplay by W. Scott Darling. Lin McIvor (Bill Williams), who owns a racehorse with his father (Ralph Morgan), is in love with millionairess Pat Armistead (Jane Nigh), whom he refuses to marry because she comes from a higher station in life. The twist is that Lin doesn’t know that his beloved horse was sired by a thoroughbred belonging to Pat’s father. Williams is totally believable in his part, and the direction by William Beaudine, a second-feature director whose career spanned more than 40 years, is nearly perfect. Horse-racing fans will be glad to know that there’s lots of track action, with many scenes shot at Louisville’s famed Churchill Downs, home of the Kentucky Derby.