Dairy animal treatment assembly, comprising a teat treatment device to apply a liquid, a control device for the teat treatment device,wherein the teat treatment device comprises a liquid line and a sensor system with:- a through-flow cell (2)- a detector device (6) to measure a characteristic of the liquid in the cell (2) and to generate an associated detector signal, and- a sensor control (7) which is configured to analyse the detector signal, configured to detect a liquid changeover (8) in the through-flow cell (2) if a change per time unit in the detector signal and/or a change in the detector signal is greater than a predefined change threshold value or than a predefined threshold value, wherein the dairy animal treatment assembly furthermore comprises a storage container (30) for the liquid and a buffer device (24), wherein the buffer device (24) is directly connected to the liquid line (27), and wherein the storage container (30) and the buffer device (24) are directly interconnected by means of a buffer delivery line, wherein the buffer delivery line comprises the through-flow cell (2).
