Pals of the Golden West (1951)

In the 82nd and last of the Republic B-westerns starring Roy Rogers, the latter is a Border Patrolman assigned to stop the increasing threat of hoof-and-mouth disease from Mexican cattle spreading into the United States. (The term hoof-and-mouth is correct and proper usage despite the USDA current term of foot-and-mouth, which only indicates that those people don't know that cattle, goats and sheep don't have feet.) Roy arranges for his friend and counterpart in Mexico, Lopez (Maurice Jara), to also be assigned to the Border Patrol. Lopez encounters Jim Bradford (Anthony Caruso) and Ward Sloan (Roy Barcroft) smuggling cattle across the border, and he is ruthlessly shot down when he tries to arrest them. Bradford, who is actually a wanted gangster named Lucky Guillo, sends henchman Tony (Ken Terrell) to hide the body. Tony is caught by Roy and taken to Borrasco for questioning. Lopez's young son Pancho (Edwardo Jiminez) is captured by Ward and Sloan who offer to trade the boy to the Sheriff (William Ruhl) in exchange for Tony. Roy protests, but reporter Cathy Marsh (Dale Evans) and newspaper owner Elena Maders (Estelita Rodriguez) decide to release Tony to save Pancho's life. Thanks to a picture photographer Pinky (Pinky Lee) has taken, Roy makes a visit to the Sloan ranch and finds Pancho, who tells him that Sloan, Bradford and Tony are on their way to the border to rustle another herd of cattle. Roy and Trigger (billed as usual above the title with Roy) track them through a blinding sand storm.