The present invention relates to a formulation comprising one or more active ingredients of poor water solubility for medical or non-medical use in the rearing of animals. The inventive formulation is suitable for administration to the animals via their drinking water. It exhibits superior stability. Said 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.