Abstract
The objective of this study was to evaluate differences in pathophysiology of the placenta when exposed to ergot alkaloids found in endophyte-infected tall fescue seed during mid and late gestation. Thirty-six Suffolk ewes (78.24 ± 9.5 kg) estimated to be carrying twins at d35 were randomly assigned to one of two treatments: endophyte-free tall fescue seed (E-; 0.0 µg ergovaline + ergovalinine/g) or endophyte-infected tall fescue seed (E+; 0.8 µg ergovaline + ergovalinine/g) during MID (d35 – d85) or LATE (d86 – d133) gestation creating four unique dietary treatments: E-/E-, E-/E+, E+/E-, and E+/E+. Endophyte-infected tall fescue seed was fed at a level to provide 1772µg of ergovaline + ergovalinine/hd/d for E+ treatments while an equal weight of endophyte-free seed (0.0 µg ergovaline + ergovalinine) was fed for the E- treatments. Fetal and maternal necropsies were performed at day 133 of gestation. Placental samples were weighed and samples were frozen in O.C.T. Cotyledon tissue weights were reduced by 25% in ewes on E+ treatment during LATE gestation compared to E- treatment (P < 0.002; 663.46 and 498.61 g for E- and E+, respectively). A subsample (n = 3) was selected for E-/E- and E+/E+ treatments for immunohistochemistry. Placentome samples were sectioned and stained using H&E and Ki67. H&E staining revealed large regions of proteinaceous deposits. An immunofluorescence study was begun to identify the specific proteins involved in the deposits. Staining for the cell proliferation marker, Ki67, found a staining pattern similar to that of the protein deposits observed through H&E staining. Placental aging is often marked by deposits of collagen; therefore, further studies to determine the staining pattern of collagen in the tissue are underway. Advanced aging of the placenta may contribute to insufficient fetal growth during LATE gestation and explain shorter gestation lengths observed with exposure to ergot alkaloids.