REPRODUCTIVE FAILURE IS THE ONE OF THE GREATEST CAUSES OF ECONOMIC LOSS IN CATTLE, AND EMBRYONIC DEATH/MORTALITY IS A PRIMARYCONTRIBUTOR TO THIS LOSS. EMBRYONIC MORTALITY CAN OCCUR EARLY (< DAY 28) OR LATE (≥ DAY 28-60) DURING GESTATION. EVEN THOUGH IT ISWIDELY ACCEPTED BY THOSE IN THE CATTLE BUSINESS THAT LATE EMBRYO MORTALITY IS A MAJOR PROBLEM (INCIDENCE ~12% IN LACTATING DAIRYCOWS), LITTLE PROGRESS HAS BEEN MADE TOWARDS UNDERSTANDING THE DETAILED BIOLOGY AND INTERACTIONS THAT LEAD TO THIS PERIOD OFLOSS. THEREFORE, THE CENTRAL HYPOTHESIS OF THIS PROPOSAL IS THAT LATE EMBRYONIC MORTALITY IN CATTLE BETWEEN DAYS 28 AND 40 AFTERBREEDING IS DUE TO A DEFICIENCY IN THE FUNCTIONS OF THE PLACENTA AND(OR) ENDOMETRIUM THAT LEAD TO COMPROMISED PLACENTOMEFORMATION. THIS RESEARCH PROPOSAL HAS TWO SPECIFIC AIMS THAT WILL EXAMINE THE EFFECTS OF EMBRYONIC LOSS IN CATTLE, 1) IDENTIFY THEEFFECT OF EMBRYONIC LOSS BETWEEN DAYS 28 AND 40 OF PREGNANCY ON HORMONE LEVELS IN THE CIRCULATING BLOOD AND THOSE HORMONESCOMING DIRECTLY FROM THE OVARIES, AND 2) EXAMINE THE MORPHOLOGICAL AND MOLECULAR ATTRIBUTES OF PREGNANCY IN CATTLE CARRYINGEMBRYOS PREDICTED TO SURVIVE OR UNDERGO EMBRYONIC MORTALITY AFTER DAY 28 OF GESTATION. GAINING KNOWLEDGE IN THIS AREA WILL LEADTO A BETTER UNDERSTANDING OF THE CAUSES AND POTENTIAL STRATEGIES TO PREVENT SUCH REPRODUCTIVE LOSS, WHICH IS PROVIDING MAJORPROBLEMS FOR THE INDUSTRY. EVENTUAL EFFORTS WILL FOCUS ON IMPROVING FERTILITY TO INCREASE THE SUSTAINABILITY OF ANIMAL PRODUCTION ANDENSURE THAT THIS ASPECT OF AMERICAN AGRICULTURE REMAINS ECONOMICALLY VIABLE.

Texas A&M Agrilife Research, College Station TX

Investigators