Revalor®-S is a growth promotant with slow release of trenbolone acetate and oestradiol which induces the increased laying down of lean meat without increasing fat deposition. There is an improvement in mass gain and feed conversion. The active principles have short half-lives on release into the plasma obviating carcass residue problems. A growth promotant with slow release of active principle which induces the increased laying down of lean meat without increasing fat deposition.