WITH REDUCED AVAILABILITY OF GRAZING LAND, ANNUAL AND INTER-ANNUAL VARIABLE PRECIPITATION, AND HIGH PRODUCTION COSTS, COW HERD PRODUCTION EFFICIENCY HAS TO INCREASE TO MEET THE PROJECTED INCREASE IN BEEF CONSUMPTION. IN DOING SO, COW-CALF PRODUCERS HAVE FOCUSED SELECTION EFFORTS ON INCREASED MILK PRODUCTION AND GREATER CALF GAINS TO IMPROVE OUTPUT-RELATED GROWTH TRAITS. HOWEVER, DURING THAT SAME TIME PERIOD, LALMAN ET AL. (2019) INDICATED CALF WEANING BODY WEIGHTS MAY HAVE BECOME STAGNANT IN SOME REGIONS OF THE UNITED STATES. THIS MAY INDICATE ENVIRONMENTAL CONSTRAINTS ON GROWTH TRAITS THROUGH MATERNAL GENETICS WITHIN FORAGE-BASED PRODUCTION SYSTEMS. IN ADDITION, THE CONTINUAL INCREASE IN SELECTION FOR MILK PRODUCTION HAS RESULTED IN BEEF COWS THAT ARE UNDER GREATER NUTRITIONAL STRESS IN CRITICAL PHYSIOLOGICAL PERIODS, SUCH AS EARLY LACTATION, THAT WILL ULTIMATELY REDUCE REPRODUCTIVE AND PRODUCTION EFFICIENCY. IN SELECTING FOR GROWTH WITH MATERNAL MILK, EDWARDS ET AL. (2017) REPORTED NO DIFFERENCE IN CALF WEANING WEIGHT, BUT A DECREASED IN REPRODUCTIVE PERFORMANCE IN HIGH-MILKING BEEF COWS. AS MILK PRODUCTION POTENTIAL INCREASES IN BEEF COWS, COW MAINTENANCE REQUIREMENTS DURING GESTATION AND LACTATION INCREASE. FOR INSTANCE, ENERGY REQUIREMENTS FOR COWS WITH A HIGH MILK PRODUCTION REQUIRED 11% MORE ENERGY TO SUPPORT AN INCREASED LEVEL OF MILK PRODUCTION COMPARED TO LOW MILK COWS. MATCHING COW TYPE OR GENETIC POTENTIAL TO THE PRODUCTION ENVIRONMENT IS AND WILL BE MORE IMPORTANT AS COST OF PRODUCTION INCREASES. PROJECTED ENVIRONMENTAL CHALLENGES AND INCREASED GLOBAL DEMAND FOR BEEF IN UPCOMING DECADES UNDERSCORE THE NEED TO UNDERSTAND THE BASIS FOR, AND IMPORTANCE OF INCREASE PRODUCTION EFFICIENCY IN BEEF COWS. FAILURE TO DO SO WILL IMPEDE EFFORTS TO OPTIMIZE EFFICIENCY UNDER LIMITING RESOURCES. IN THIS PROJECT, WE WILL DETERMINE THE IMPACT OF DAM MILK PRODUCTION LEVEL ON COW-CALF PERFORMANCE, GRAZING BEHAVIOR, AND PROFITABILITY. OUR GOAL IS TO INCREASE PRODUCTION EFFICIENCY IN GRAZING LACTATING BEEF COWS BY SELECTING FOR THE OPTIMAL COW TYPE (I.E., MILK POTENTIAL). THE OVERALL OBJECTIVE IN THIS APPLICATION IS TO DETERMINE THE IMPACT OF MILK PRODUCTION LEVEL ON COW PERFORMANCE, PROGENY PRE- AND POST-WEANING GROWTH. THE RATIONALE FOR THIS PROJECT IS THAT BALANCING THE ENVIRONMENT (FORAGE QUALITY AND QUANTITY) AND COW REQUIREMENTS IS THE FOUNDATION FOR PRODUCTION EFFICIENCY AND WILL IMPROVE THE PRODUCTION EFFICIENCY, PROFITABILITY, AND COMPETITIVENESS OF THE U.S. BEEF INDUSTRY.