Estradiol-17β and linseed meal interact to alter visceral organ mass and hormone concentrations from ovariectomized ewes

To evaluate the estrogenic potential of secoisolariciresinol diglycoside (SDG) found in linseed meal (LSM) on visceral organ mass, IGF-I, and thyroid hormone (T₃ and T₄) concentrations, 48 multiparous, ovariectomized ewes (54.6 ± 1.1 kg) were used in a 3 × 4 factorial arrangement. Main effects were length of LSM feeding (0, 1, 7, or 14 d) and length of exposure to estradiol-17β (E₂) implant (0, 6, or 24 h prior to tissue collection). Implanting ewes with E₂ for 24 h increased liver mass relative to empty body weight (EBW; g/kg EBW) compared with ewes implanted for 0 or 6 h (P ≤ 0.03), whereas feeding LSM for 14 d decreased liver mass compared with ewes fed LSM for 1 or 7 d (P ≤ 0.02). There was an LSM × E₂ interaction (P = 0.01) for duodenal mass (g/kg EBW), LSM, and E₂ tended (P = 0.07) to influence the stomach complex mass; however, ileal mass was not affected. Neither LSM nor E₂ affected (P ≥ 0.12) CYP2C or CYP3A mRNA expression or cellularity of the liver. Exogenous E₂ influenced circulating concentrations of IGF-I, T₃, and T₄. The estrogenic or anti-estrogenic potential of LSM is dependent upon the tissue, exposure to E₂, and the duration of LSM feeding. Feeding LSM during gestation, lactation, or during the grow-finish phase warrants further investigation.