The effect of feeding soybean-derived phytoestogens on their concentration in plasma and milk of lactating dairy cows

Abstract

The objective of this study was to determine the effect of dietary soybean phytoestrogens, daidzein and genistein, on yield and composition of milk and excretion of phytoestrogens and their metabolites into milk. The experiment was carried out on four lactating Holstein cows as replicated Latin square in a double reversal design. The experiment was divided into four periods of 42 days consisting of a 21-day preliminary period and a 21-day experimental period. Cows were divided into two groups. The control group (Group R) was fed a diet based on extruded rapeseed cake while the experimental group (Group S) received a diet containing extruded full-fat soybeans. Compared to Group R, in Group S the daily intake of daidzein and genistein was about 40 and 75 times higher, respectively. In the milk of Group S the concentration of daidzein and its metabolite equol was significantly higher (p < 0.001) and the concentration of genistein tended to be higher than in Group R. Total excretion of daidzein, genistein and equol in milk of Group S, being 384, 958 and 1300 μg/d, respectively, was higher than in Group R (285, 794 and 80 μg/d, respectively, p < 0.001). In Group S the concentration of daidzein, genistein and equol in plasma was also increased (p < 0.001).