In Red Dead Redemption for the PS3 and Xbox 360, there is a cheat you can turn on to give your horse infinite stamina. Once a cheat is turned on, you won’t be able to save your game and you won’t earn achievements, but you CAN make your horse into a beast of a runner!
To turn on cheats, go into Options, select Cheats and hit the Y button on the 360 or Triangle on the PS3 and enter the following code:
MAKE HAY WHILE THE SUN SHINES