Abstract: The present invention related to a technique for determining the progesterone-associated physiological state of a lactating cow. The technique comprises determining at least one Milk Solid (MS)-related parameter in at least one milk sample from a lactating cow; and determining the progesterone-associated physiological state according to the Milk Solid (MS)-related parameter. Determining the progesterone-associated physiological state may comprise determining the progesterone level of the cow by correlating the MS-related parameter with calibrated data. The MS related parameter may comprise at least one of size, synthesis, composition of a MS, a pattern of progesterone concentration or direction of progesterone concentration, or at least one dielectric parameter of the MS.