** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** CATTLE AND CALVES ACCOUNT FOR MORE THAN $60 BILLION OF CASH RECEIPTS IN THE US ANNUALLY. SALE OF CALVES IS THE MOST IMPORTANT PRODUCT FOR COW-CALF PRODUCERS. DESPITE THIS, BEEF COWS USE APPROXIMATELY 70% OF THEIR NUTRIENT INTAKE TO MAINTAIN THEMSELVES, MAKING NUTRIENT USE OF COWS AND CALVES CRITICAL. BEEF COW-CALF PRODUCTION OCCURS IN DIVERSE ENVIRONMENTS ACROSS THE U.S. AND WORLD, OFTEN USING LANDS OF POOR QUALITY OR LIMITED OTHER USE TO AGRICULTURE. PERIODS OF POOR NUTRIENT AVAILABILITY FOR COWS HAPPEN REGULARLY, INCLUDING WHEN FEEDING POOR QUALITY FORAGE DURING LAST GESTATION, OR WHEN MANAGING COWS DURING THEIR FIRST PREGNANCY. IMPROVED UNDERSTANDING OF MECHANISMS DIRECTING NUTRIENT USE BY BEEF COWS AND HEIFERS IN PREGNANCY AND LACTATION IS NECESSARY TO MAKE THE BEST FEEDING AND BREEDING DECISIONS AND INCREASE CALF HEALTH AND GROWTH. ALTHOUGH WE KNOW THAT NUTRIENT PARTITIONING IN THE PREGNANT COW IS IMPACTED BY HER NUTRIENT BALANCE ALONG WITH FETAL INFLUENCES, WE KNOW OF NO INTENSIVELY-MANAGED PUBLISHED EXPERIMENT THAT PROVIDES A MEANS FOR ESTABLISHING MECHANISMS FROM THIS PERIOD. WE ALSO KNOW THAT ENVIRONMENT DURING DEVELOPMENT CAN LEAVE EPIGENETIC MARKS ON THE GENOME, CHANGING ANIMAL PERFORMANCE, BUT FEW EPIGENOMIC DATA EXIST LINKING COW NUTRIENT USE TO CALF EPIGENETIC STATUS. IN THESE EXPERIMENTS, WE WILL ESTABLISH EFFECTS OF MATERNAL NUTRIENT AVAILABILITY VERSUS FETAL GROWTH GENETIC POTENTIAL ON NUTRIENT USE BY THE COW, FETAL CALF, AND PRE-WEANING CALF. WE WILL ALSO DETERMINE THE ROLE OF EPIGENOMIC REGULATION ON THE PLACENTA AND CALF MUSCLE DUE TO MATERNAL NUTRIENT AVAILABILITY VERSUS FETAL GROWTH GENETIC POTENTIAL. IN EXPERIMENT 1, THE EFFECTS OF HIGH AND LOW FETAL GROWTH GENETIC POTENTIAL WILL BE STUDIED IN COWS FED A CONTROL OR NUTRIENT-RESTRICTED DIET DURING LATE GESTATION. IN EXPERIMENT 2, THE EFFECTS OF HIGH AND LOW FETAL GROWTH GENETIC POTENTIAL WILL BE STUDIED IN MATURE COWS VERSUS HEIFERS DURING THEIR FIRST PREGNANCY. THIS RESEARCH CAN LEAD TO INCREASED EFFICIENCY AND SUSTAINABILITY OF BEEF COW-CALF PRODUCERS THROUGH BETTER MANAGEMENT OF PREGNANT AND LACTATING COWS BASED ON BREEDING DECISIONS, WHICH WILL LEAD TO MORE SELLABLE PRODUCT (CALF WEIGHT) FROM THEIR FARMS AND RANCHES.