Abstract: A formulation includes one or more active ingredients of poor water solubility for medical or non-medical use in the rearing of animals. The formulation is suitable for administration to the animals via their drinking water. It exhibits superior stability. The formulation comprises an active ingredient, a thickener combination and water, wherein the thickener combination comprises at least one thickener selected from the following groups A, B, C and D: (A) cellulose derivatives, such as methyl cellulose, sodium carboxy methyl cellulose, (B) non-cellulosic polysaccharide thickeners such as xanthan gums, Arabic gum, (C) cross-linked polyacrylic acid polymers, (D) hydrocolloidal hydrated silicates.