The adiabatic temperature change DeltaT is studied theoretically in perovskite oxides such as La1-xCaxMnO3 crystals. We use a two-parameter phenomenological model which accounts for electron-phonon coupling. The model predicts the linear dependence of DeltaT on magnetic field DeltaH if only the electronic specific heat is accounted for. In order to determine the peak value of DeltaT at T-C it is enough to measure the magnetization vs the magnetic field. The calculated quantities are discussed in the context of various measurements.