Neck

From the torso we move up to the neck. Here we can exaggerate the neck movement but still keeping it natural by allowing the neck to rotate forward much more than back. With this in mind, at Frame 5 where the horse is in an almost upright position, Rotate X to about -3.5. Then at Frame 10 increase the rotation to about 6. Notice that we didn't key the neck on the same frames as the torso, as we don't want them to be moving in unison but to show some overlap. After keying go to the graph editor and again smooth out the curve.