  On the basis of Lagrangian formalism of relativistic field theory
post-Newtonian equations of motion for a rotating body are derived in the frame
of Feynman's quantum field gravity theory (FGT) and compared with corresponding
geodesic equations in general relativity (GR). It is shown that in FGT the
trajectory of a rotating test body does not depend on a choice of a coordinate
system. The equation of translational motion of a gyroscope is applied to
description of laboratory experiments with free falling rotating bodies and
rotating bodies on a balance scale. Post-Newtonian relativistic effect of
periodical modulation of the orbital motion of a rotating body is discussed for
the case of planets of the solar system and for binary pulsars PSR B1913+16 and
PSR B1259-63. In the case of binary pulsars with known spin orientations this
effect gives a possibility to measure radiuses of neutron stars.
