Effect of physiological and production activities on the concentration of naturally occurring steroid hormones in raw milk

This study aimed to collect comprehensive experimental data and evaluate the effects of physiological and production activities on the concentration of naturally occurring steroid hormones in raw cow milk. The average levels of the hormones analysed (progesterone = 12 680 ng/kg and cortisol = 284 ng/kg) were comparable with data reported in the literature. Oestradiol, testosterone and methyltestosterone were not detected at their respective limits of quantification. Progesterone concentrations from individual cows have shown large variations ranging from 204 to 26 503 ng/kg, linked to the gestational status (pregnant/nonpregnant), lactation stages and gestational ages of the mammals. The average concentration of cortisol reaches a peak in the morning, decreases in the afternoon and reaches the lowest level at midnight. It is therefore evidenced that physiological and production activities have an effect on some hormonal levels in raw cow milk.