A system for optimising the production performance of a milk producing animal herd is provided. The system comprises a milk sampling apparatus, an analytical apparatus comprising separate equipment for analyzing compounds or parameters that in the presence of compounds indicative of the physiological or nutritional condition of the herd member, generates detectable signals, and apparatus directing a part of the milk sample (directing apparatus) to each separate equipment, which is controlled by data for the physiological and nutritional state of a herd member, so that the directing apparatus is only activated at pre-selected points in time or at pre-selected time intervals in the production and / or lactation cycles. Specific compounds are compounds indicative of mastitis, including beta-N-acetylhexosaminidase (NAGase) E.C. 3.2.1.52 and lactate dehydrogenase (LDH), protein balance, including milk urea nitrogen (MUN) and total protein, ketosis, including acetolactate, beta-hydroxybutyrate, acetone and lipids, fat and state in reproduction cycle, including a steroid or peptide hormone, e.g., progesterone. Furthermore, the system comprises equipment for signal detection to record and process the signals, equipment to store data and equipment to produce data output. Methods for optimizing the production performance of a milk producing animal herd and an apparatus therefor.