**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 PURPOSE OF THIS RESEARCH PROJECT IS TO DETERMINE IF FEEDING LAYER HENS A DAIRY BYPRODUCT BUTTERMILK WILL CHANGE THE NUTRITIONAL COMPOSITION OF EGGS, IMPACT HEN PERFORMANCE, AND TO ASSESS THE COST TO BENEFIT OF THIS PRACTICE. THE CENTRAL HYPOTHESIS IS THAT FEEDING BUTTERMILK TO LAYERS WILL INCREASE THE NUTRITIONAL VALUE OF EGGS, SERVE AS A SAFE FEED ADDITIVE WITHOUT ADVERSELY AFFECTING LAYER PERFORMANCE, AND BE A COST-EFFECTIVE FEED ADDITIVE. TO TEST THE HYPOTHESIS THIS STUDY HAS THE FOLLOWING AIMS: 1) ENRICH EGG YOLKS WITH BUTTERMILK SOURCED HEALTH PROMOTING NUTRIENTS, SUB-AIM 1) EVALUATE THE MAXIMUM INCLUSION OF BUTTERMILK AS A FEED ADDITIVE WITHOUT IMPACTING LAYER PERFORMANCE, SUB-AIM 2) EVALUATE THE COST TO BENEFIT OF UTILIZING BUTTERMILK AS A FEED ADDITIVE FOR LAYERS. THE EXPECTED OUTCOME IS THAT BUTTERMILK SOURCED NUTRIENTS WILL ACCUMULATE WITHIN EGG YOLKS AND THAT THERE WILL BE AN OPTIMAL DIETARY AMOUNT OF BUTTERMILK FOR MAXIMIZING THIS ENRICHMENT IN EGGS. THE ANTICIPATED IMPACT IS THAT THIS WORK WILL PROVIDE A BASIS FOR UTILIZING BUTTERMILK AS A FEED INGREDIENT FOR ANIMAL DIETS TO ENHANCE THE NUTRITIONAL VALUE OF ANIMAL PRODUCTS, IMPROVE HUMAN NUTRITION OUTCOMES, AND IMPROVE THE SUSTAINABILITY OF THE DAIRY INDUSTRY.