Lactating dairy cows require a particular composition of nutritional ingredients depending on their production status. The optimal supply of energy and minerals in diet, one of them potassium, is indispensable for the prevention of disbalances, such as hypokalemia or hypoglycaemia. Potassium balance is the result of potassium intake, distribution in the organism, and excretion, and closely interacts with glucose and electrolyte metabolism, in which postpartum veterinary treatments frequently intervene. We present a mechanistic, dynamic model for potassium balance together with a glucose-insulin model in nonlactating and lactating dairy cows based on ordinary differential equations. Parameter values were obtained from fitting to data of a clinical trial as well as from literature. To verify the mechanistic functioning of the model, we validate the model by comparing simulation outcomes with clinical study findings. Furthermore, we perform numerical experiments and compare them with expected behavior according to mechanistic knowledge. The results give insight into the dynamic behavior of the network and open the way for further open questions and hypotheses to be tested, as hypokalemia development and dynamics of different potassium substitution therapeutic strategies.