WHAT GRAVITATIONAL FIELD IS
As previously stated, there is no such single thing as "the" gravitational field, as is assumed in the Newtonian sense.
G-field is a conglomerate of many component potentials and other entities.
Rigorously, anything that "curves spacetime" is a gravitational field.
In the modern view, all forces ultimately arise, by some means, from the curving of spacetime. Thus all forces and force fields are related to -- and caused by, so to speak -- gravitational field.
If the vacuum stress is uniform from one place to another in an observerís frame, then the observerís spacetime is uncurved. The observerís frame, is said to be linear or uncurved; or a Lorentz, frame. In such a situation the conservation laws rigorously apply for macroscopic, closed systems.
If the vacuum stress is not uniform from one place to another, then the spacetime is curved. In such a situation the conservation laws may be violated for macroscopic systems, since they are "opened" to the vacuum stress, and vacuum virtual particle flux gradients exist across the system or portions of it.
Note that the overall stress magnitude may be constant across a region, but its composition may change. That is, two or more components may vary canonically. In that case, the spacetime is uncurved in the gross external sense, but contains specialized "internal" curvature patterns locally. Depending upon reaction to the canonical infolded curvature patterns, some macroscopic systems will still exhibit conservation, but certain other macroscopic systems may not.
An example is symmetry-breaking. Here charge, parity, and time symmetry may be violated individually or in pairs, but not all three simultaneously. An overall conservation law is obeyed, but any two of the three conservation laws can be (and are) violated.