Dear Marion, I just read your posting that you have bought special cat milk. Well, since a few weeks, I am buying normal (for human use) lactose-free milk for my cats of the brand Campina (na ja, do not know whether you can find this in Germany, but maybe something similar). However, this means that my cats drink as much as they want of this milk without getting a diarrhea. But I can tell you that there is a serious difference in price. Special cat milk here in Belgium costs about 1 euro per small bottle of 250 ml, whereas this milk is costing the same for an entire liter!!!! And believe me, they all adore it. So maybe, you also may want to consider the use of this milk. In any event, the price of it is nicer to your wallet and my vet told me that it is definitely a good substitute.