A slow release bolus for the treatment of conditions such as facial eczema and the like zinc-deficiency manifestations in ruminants comprises zinc metal particles of less than lmm largest dimension dispersed in a wax binder, wherein the zinc metal particles provide about 85-95 % by weight of the bolus, and the wax binder is adapted to permit sustained release of zinc from the bolus for a period of at least 40 days.
