To evaluate the estrogenic potential of secoisolariciresinol diglycoside (SDG) found in linseed meal (LSM) on visceral organ mass, uterine mass, jejunal cellularity, jejunal vascularity, and angiogenic factor expression in the jejunum, 48 multiparous, ovariectomized ewes were used in a 3 x 4 factorial. Ewes were fed a diet containing 12.5% LSM for 0, 1, 7, or 14 d and implanted with estradiol 17-ß (E2) for 0, 6, or 24 h before tissue collection. This study confirmed that LSM interacts with E2 to alter uterine and duodenal mass; that E2 is capable of altering liver, duodenal, and uterine mass; and that LSM is capable of altering liver and duodenal mass. In addition to altering organ mass, LSM interacted with E2, causing E2 to have no effect on cellular proliferation rate of the jejunum when LSM was fed for 1, 7, or 14 d, whereas cellular proliferation was increased in the duodenum in response to E2 when LSM was fed for 0 d. However, neither LSM nor E2 altered any measurement of vascularity. Expression of angiogenic factor mRNA was also examined. Implanting ewes with E2 for 6 h increased eNOS mRNA expression; whereas, LSM and E2 interacted to alter mRNA expression of its receptor, sGC, as well as VEGF's 2 receptors, FLT and KDR. Although this study confirmed LSM's ability to interact with E2, further research is needed to investigate its effects on intact cyclic animals as well as in pregnant animals and their offspring.