  We review recent work on the use of the slice energy concept in generalized
theories of gravitation. We focus on two special features in these theories,
namely, the energy exchange between the matter component and the scalar field
generated by the conformal transformation to the Einstein frame of such
theories and the issue of the physical equivalence of different conformal frame
representations. We show that all such conformally-related, generalized
theories of gravitation allow for the slice energy to be invariably defined and
its fundamental properties be insensitive to conformal transformations.
