Clinical and endocrine studies in mares with known history of repeated conceptus losses

Abstract

Six mares which had lost their conceptuses two to five times during the last six years were used in a study extending over one breeding season. The genital organs were examined by palpation per rectum, ultrasound scanning and vaginoscopy. Cytological, bacteriological and histological examinations of the endometrium were carried out before mating. Blood samples were collected twice daily beginning one estrous cycle before mating until Day 150 of pregnancy. Radioimunoassay systems were used to determine peripheral plasma levels of progesterone, equine chorionic gonadotropin and estrone sulphate. One mare had persistent acute endometritis and was treated before mating. All six mares conceived and five mares had normal pregnancies with live fetuses at the end of the experimental period. One mare aborted, the fetus died around Day 50 of pregnancy and remained intact in the uterus for two months. This mare had the same high levels of progesterone (p) as the other mares until shortly before abortion. The production of equine chorionic gonadotropin (eCG) was relatively low compared with the mares with live fetuses, and estrone sulphate concentrations were significantly lower from Day 61 of pregnancy. Several reasons might have caused the good breeding results of the mares during this trial, but management seems to be the most important factor.