PREGNANCY LOSS REPRESENTS A SUBSTANTIAL ECONOMIC COST FOR LIVESTOCK PRODUCERS. TRANSFER OF IN VITRO PRODUCED (IVP) EMBRYOS HAS INCREASED DRAMATICALLY IN THE US AND IS CRITICAL FOR GENETIC PROGRESS IN BOTH DAIRY AND BEEF CATTLE; HOWEVER, RECIPIENTS OF IVP EMBRYOS EXPERIENCE HIGH RATES (10-20%) OF PREGNANCY LOSS. TRANSFER OF CLONED EMBRYOS IS AN INTERESTING MODEL FOR PREGNANCY LOSS IN WHICH PREGNANCIES PER EMBRYO TRANSFERAT 32 DAYS IS SIMILAR TO IVP EMBRYOS (~50%), HOWEVER, HALF OF THESE PREGNANCIES ARE LOST DURING THE SECOND MONTH OF PREGNANCY. TO REDUCE PREGNANCY LOSS, MORE BASIC KNOWLEDGE IS NEEDED ON THE MECHANISMS THAT MAINTAIN THE PREGNANCY AND ON THE MECHANISMS THAT LEAD TO LOSS OF PREGNANCY. THIS RESEARCH WILL INVESTIGATE TWO IMPORTANT POTENTIAL MECHANISMS THAT ARE INVOLVED IN THIS PROCESS.THE FIRST MECHANISM IS THE INCREASE IN UTERINE BLOOD FLOW THAT OCCURS DURING PREGNANCY. WE WILL MAINPULATE UTERINE BLOOD FLOW BY EITHER INCREASING OR DECREASING UTERINE BLOOD AND EVALUATE THEEFFECT ON MAINTENANCE OF PREGNANCY OR PREGNANCY LOSS.THE SECOND KEY MECHANISM IS THE HORMONE, PROGESTERONE. THIS HORMONE CIRCULATING IN THE BLOOD AND IS RESPONSIBLE FOR MAINTAINING THE PREGNANCY IN ALL MAMMALS, INCLUDING CATTLE. OUR EXPERIMENTS WILL INCREASE CIRCULATING PROGESTERONE CONCENTRATIONS TO SEE IF WE CAN IMPROVE FERTILITY IN COWS AFTER EMBRYO TRANSFER BY REDUCING PREGNANCY LOSS.THESE EXPERIMENTS ARE IMPORTANT FOR DETERMINING HOW WE CAN REDUCE PREGNANCY LOSS IN CATTLE AND THUS IMPROVE THE EFFICIENCY OF REPRODUCTION IN THE US CATTLE INDUSTRY.