OBSERVATIONS ON EARLY-PREGNANCY DIAGNOSIS AND EARLY EMBRYONIC LOSS INTHE MARE

On three closely supervised stud farms, examinations for ovulation (Da y 1) were made at intervals of 24 or 48 hours. Examination for pregnan cy began at Day 11 to 14 and a total of 318 pregnancies were diagnosed . Multiple ovulations occurred in 117 (36.8%) pregnant mares including five (1.6%) triple ovulations. Sixty-two (19.5%) pregnancies were mul tiple including four (1.3%) triplets. Forty-seven (85.5%) multiple pre gnancies were manually reduced successfully (pregnant at Day 40). Most twin vesicles which failed after manual reduction were small-for-age. Seven sets of twins in which one vesicle was small-for-age were succe ssfully allowed to undergo natural reduction, which was complete in ea ch case by Day 21. A vesicle was not identified in seven (2.2%) pregna nt mares on Day 13 nor in four (1.3%) mares on Day 14. When identified subsequently, all vesicles in these mares were small-for-age and of t hose not seen on Day 13 only three (43%) survived whereas none of the four vesicles not identified on Day 14 survived. Embryonic losses were not recorded from pregnancies identified on Day 11 or Day 12. It is c oncluded that examination for pregnancy at the earliest opportunity id entifies a high incidence of multiple pregnancy, eases the choice of e mbryo for manual reduction and may allow prediction of early embryonic failure of single pregnancies.