  We analyze the effects of adiabatic ramping of optical lattices on the
temperature of spin-1 bosons in a homogeneous lattice. Using mean-field theory,
we present the isentropes in the temperature-interaction strength ($T,U_0$)
plane for ferromagnetic, antiferromagnetic, and zero spin couplings. Following
the isentropic lines, temperature changes can be determined during adiabatic
loading of current experiments. We show that the heating-cooling separatrix
lies on the superfluid-Mott phase boundary with cooling occuring within the
superfluid and heating in the Mott insulator, and quantify the effects of spin
coupling on the heating rate. We find that the mean-field isentropes for low
initial entropy terminate at the superfluid-Mott insulator phase boundary.
