A Horse's Tale (1954)

Sugarfoot, the faithful old plow-horse, fearing his days and place on the farm are numbered since his master had purchased a tractor, destroys it. The farmer is outraged and banishes Sugarfoot from the farm. Sugarfoot is determined to make the money needed to buy his master a new tractor, and he becomes a movie-double for a screen Wonder Horse of the Movies, and makes enough money to buy a new tractor. The farmer forgives him and, as a reward, takes him to the movies, where Sugarfoot sees the star-horse getting all the credit for all of Sugarfoot's stunt-doubling.

Unfortunately the movie A Horse's Tale is not yet available on HBO Max.