** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** THE MATERNAL ENVIRONMENT DURING PREGNANCY INCLUDING THE MOTHER'S NUTRITIONAL STATUS, CAN DIRECTLY INFLUENCE THE GROWTH AND DEVELOPMENT OF THE FETUS AND IMPACT METABOLISM, GROWTH, AND HEALTH BORTH SHORT-TERM AND LONG-TERM. IN BEEF CATTLE, POOR NUTRITIONAL MANAGEMENT OF THE PREGNANT FEMALE, SUCH AS UNDERNUTRITION, CAN SIGNIFICANTLY AFFECT OFFSPRING GROWTH, DEVELOPMENT, AND ADULT PRODUCTIVITY LATER IN LIFE. RISING CATTLE FEED AND LABOR COSTS DRIVE PRODUCERS TO SEEK STRATEGIES TO REDUCE THESE EXPENSES, ESPECIALLY DURING THE COSTLY FALL AND WINTER MONTHS. ONE STRATEGY IS TO ALLOW PREGNANT CATTLE TO GRAZE PASTURES AFTER THE GROWING SEASON, RESULTING IN A DIET OF LOW-QUALITY, LOW-PROTEIN GRASSES. IN THIS SCENARIO, FETUSES EXPOSED TO LOW-PROTEIN DIETS THROUGH THE DIET OF THEIR MOTHERS CAN HAVE RESTRICTED GROWTH AND ALTERED MUSCLE TISSUE COMPOSITION AND QUANTITY, AS MUSCLE TISSUE IS DEVELOPED PRIMARILY PRENATALLY. CHANGES TO OFFSPRING MUSCLE DEVELOPMENT DURING PREGNANCY NOT ONLY INFLUENCES FETAL GROWTH BUT CAN ALSO IMPACT SKELETAL MUSCLE AND ANIMAL SIZE POSTNATALLY, ULTIMATELY INFLUENCING MEAT PRODUCTS AVAILABLE TO CONSUMERS. ADDITIONALLY, FEEDING SUPPLEMENTAL PROTEIN TO CATTLE GRAZING LOW-PROTEIN FORAGES CAN INCREASE FORAGE UTILIZATION, ALLOWING LONGER GRAZING PERIODS AND GREATER BODY WEIGHT GAINS. THESE IMPACTS CAN ULTIMATELY REDUCE FEED AND LABOR COSTS FOR THE RANCHER AND POTENTIALLY IMPROVE FINANCIAL RETURN AT SALE. THUS, MATERNAL NUTRITION DURING PREGNANCY, ESPECIALLY IN REGARD TO PROTEIN CONTENT IN THE DIET, MAY BE IMPACTFUL FOR THE GROWTH OF THE PREGNANT COW, UTILIZATION OF GRAZED FORAGES, OPTIMAL DEVELOPMENT OF THE OFFSPRING, AND PRODUCTION OF QUALITY MEAT PRODUCTS AVAILABLE TO THE CONSUMER.THE PRIMARY PROJECT GOALS ARE TO EVALUATE THE IMPACTS OF FEEDING SUPPLEMENTAL PROTEIN TO PREGNANT CATTLE GRAZING LOW-PROTEIN FORAGES ON SKELETAL MUSCLE DEVELOPMENT AND GROWTH OF THE OFFSPRING, WHILE SUPPORTING THE PD'S ESTABLISHMENT OF A WELL-FUNDED RESEARCH AND TEACHING LABORATORY WITH THE PRIMARY MISSION OF ENHANCING LONGEVITY, PRODUCTIVITY, AND OVERALL SUCCESS OF COW-CALF HERDS. WE WILL PROVIDE PROTEIN SUPPLEMENTATION TO 25 PREGNANT BEEF HEIFERS ON A SINGLE, LOW-QUALITY PASTURE, WHILE ANOTHER 25 PREGNANT BEEF HEIFERS WILL GRAZE THE SAME PASTURE WITHOUT SUPPLEMENTATION DURING THE SECOND TRIMESTER OF PREGNANCY (MID-GESTATION). WE WILL EVALUATE THE CALVES BORN TO ALL 50 HEIFERS, COLLECTING MUSCLE BIOPSIES AND RECORDING WEIGHTS THROUGHOUT THEIR LIVES TO DETERMINE IF THE MOTHER'S DIET INFLUENCED SKELETAL MUSCLE DEVELOPMENT AND WEIGHT GAIN OF THE OFFSPRING. SPECIFIC VARIABLES EXAMINED WILL INCLUDE MUSCLE FIBER SIZE AND NUMBER, COLLAGEN CONTENT, FAT CONTENT, AND GENE EXPRESSION IN MUSCLE TISSUE. THESE VARIABLES WILL HELP US UNDERSTAND HOW MATERNAL DIET DURING PREGNANCY AFFECTS SKELETAL MUSCLE DEVELOPMENT, IMPACTING MEAT TOUGHNESS OR TENDERNESS, MUSCLE SIZE, AND GENETIC CONTROL OF THESE TRAITS. RESULTS WILL BE COMMUNICATED TO PRODUCTION AND SCIENTIFIC AU,DIENCES AT INTERNATIONAL, NATIONAL, AND LOCAL VENUES THROUGH PRESENTATIONS, RADIO AND WEBINAR SERIES, AND WRITTEN PUBLICATIONS, INCLUDING PEER-REVIEWED ARTICLES AND LOCAL RESEARCH REPORTS. ACHIEVING THE PRIMARY PROJECTGOALS WILL HELP DEVELOP TARGETED FEEDING STRATEGIES FOR PREGNANT CATTLE, IMPROVE COW HEALTH AND BODY WEIGHT, INCREASE UTILIZATION OF LOW-QUALITY FORAGES, AND POSITIVELY IMPACT SKELETAL MUSCLE DEVELOPMENT IN THE GESTATING OFFSPRING AND FUTURE MEAT PRODUCTION. FURTHERMORE, THE DEVELOPMENT OF THE PD AS A YOUNG SCIENTIST IS AN INVALUABLEASPECT OF THIS PROJECT, AND DIRECTING THE MANAGEMENT AND EXECUTION OF THIS PROJECT, PRESENTING RESEARCH ACROSS THE WORLD, AND TRAINING TO PERFORM HANDS-ON PROCEDURES AND HANDLE LARGE DATASETS FROM EXPERTS IN THE FIELDWILL ALLOW THE PD TO GAIN GLOBAL NETWORKS OF COLLABORATORS, DISCUSS RESEARCH FINDINGS WITH INTERNATIONAL AND LOCAL AUDIENCES, AND EFFECTIVELY INTERPRET RESULTS AND COMMUNICATE IMPLICATIONS FOR COW-CALF PRODUCTION. THIS PROJECT HAS SOCIETAL IMPACTS ON RANCHERS, INDUSTRY LEADERS, STAKEHOLDERS, GRADUATE STUDENTS, RESEARCHERS, AND CONSUMERS ALIKE, AND SUCCESSFUL DIRECTION OF THIS PROJECT AND INTERPRETATION OF RESULTS WILL PROVIDE VALUABLE INSIGHTS TO HERD IMPROVEMENT STRATEGIES THAT TRANSLATE INTO IMPROVING BEEF INDUSTRY'S CONTRIBUTIONS TO THE GROWING GLOBAL FOOD SUPPLY.