Bite the Bullet (1975)

Continuity mistake: Near the end, Sam Clayton is nearing the finish. The audio leads you to believe that the horse is breathing VERY hard, but when the camera shows the horse, the nostrils are NOT flared as they would be on a horse that has been run to exhaustion (or even down the block). Also, the people filming this scene obviously have no clue about the nature of sweating in horses. They showed "lather" all through the horse's mane. The ONLY places horses will lather while sweating is where something is rubbing, i.e. underneath the saddle, the bridle or breast collar, where the reins rub on the neck or between their back legs.

Norfolk: How much does Parker pay you? Fifty dollars a month? Sixty? Win this race and you could have three years' salary.
Sam Clayton: Mister, did you ever see a horse run himself to death just to please the man on his back? What's the horse get out of it? Cracked bones? Colic? See his picture in the paper? Horse doesn't give a damn who wins a race. Me neither.