You must rig and animate with the game engine in mind… what types of mesh deformation does it support?
For example, in that tutorial, an animated mesh deformer is used to curl the pages… I’m pretty sure UDK doesn’t know blender’s mesh deformers from pancakes, so you would have to “bake” that animation into the mesh… as in "apply the modifer to the mesh on a frame by frame basis.
That is but one example, I am sure there are more just in this tutorial/object. I’ve been out of game dev for a while know, but generally, if it’s not bone/skeleton/armature based, or a morph target (vertex animation), than it likely not supported by the game engine.
Bottom line: If you are animating an object destined for use in a game engine, you must know what the engine expects and only use those methods.