We have analyzed the recent magneto-thermal and elastic data on dysprosium antimonide. Within the framework of the molecular field approximation we fit the data by using a model Hamiltonian which contains besides the crystal field term, bilinear and biquadratic pair interactions and a strain coupling of the lattice to the magnetic ions. The softening of the elastic constant (1/2)(C11-C12) above the transition at 9.5°K is due to a strain coupling. This coupling dominates over the remaining biquadratic pair interactions of comparable magnitudes but opposite signs. We determine the bilinear coupling by fitting the magneto-thermal data below the ordering temperature. We find that in DySb the biquadratic coupling is as important as the bilinear.