Abstract: For the treatment of trace element deficiency in animals over a prolonged period of time there is orally administered a tablet containing said trace element in a composition which releases said trace element slowly in the stomach of said animal, said tablet having a minimum dimension such that it cannot leave the stomach through the pylorus during said prolonged period of time. For animals such as piglets, about 3 mm is a suitable minimum dimension. The tablet may comprise a homogeneous mixture of a slow release substance and the trace element and/or there may be a slow release coating on the tablet, such as a polymer of vinylidene chloride, an acrylic acid ester, vinyl chloride or vinyl propionate.