My Pal Trigger (1946)

“Gabby refuses to breed his horse the Golden Sovereign with Roy’s. When the Sovereign and Roy’s horse escape, Skoville shoots the Sovereign by mistake but Roy is blamed and jailed. A year later Roy returns with Trigger, the son of the Sovereign. When Skoville slips and reveals he was present when the horse was shot, Roy sees a chance to clear his name.” -imdb.com