The use of aivlosin, 3-O-acetyl-4''-O-isovaleryl-tylosin and pharmacologically acceptable (non-toxic) derivatives such as an acid addition salt, for the preparation of a veterinary medicine for the treatment and prophylaxis of diseases and infections of pigs and poultry is described. In particular, the disease and infections treatable by these methods are necrotic enteritis in poultry and Lawsonia infections, Mycoplasma diseases and swine dysentery in pigs.
