William Campbell Gault (1910 - 1995) wrote prolifically; both short stories and novels. He was keen on sport, which featured in much of his work. One of his private detectives, Brock Callahan, was a former basketball player. Gault used sympathetic ethnic characters in his work; one of the earliest to do so.
Amongst his sporting fiction is at least one horse book; it’s quite possible there are more that I haven’t tracked down.
Terri Wear: Horse Stories - An Annotated Bibliography
William Campbell Gault
E P Dutton, New York, 1954, 188 pp, illus Pers Crowell
Denny Nolan is convinced that Endeavor is the best thoroughbred that his foster father has ever raised. Jeff Sutherland, a vet, convinces Denny’s foster father, to sell Endeavor to him. Denny goes too as the colt’s jockey. Jeff gambles, and loses Endeavor in a poker game. Endeavor is run in a claiming race, and the Colonel gets him back for Denny, but then Denny struggles to support him. He enters Endeavor in the Cavanaugh race, but his chance of starting in the race is jeopardized when a horse from the barn he is riding for turns out to be doped.