Ovarian and Placental Lesions in Sheep from Ingesting Locoweed (Astragalus lentiginosus)

Abstract

Ingestion of 380 g per day of locoweed by pregnant ewes during day 40 to 72 of pregnancy results in vacuolation of the fetal membranes, specifically of the chorionic epithelium. These cells become hypertrophied and their cytoplasm severely vacuolated. It is postulated that this cytoplasmic vacuolation interferes with the transport of nutrients across the placental barrier. The vacuolating factor itself may, or may not, be associated with death of the conceptus and subsequent abortion. A contributing factor may be that luteal cells of the ovary are also extremely vacuolated in the ewes poisoned by locoweed and may not be producing sufficient progesterone to maintain pregnancy.