The immediate postpartum period in lactating dairy cattle is the time when cows are most vulnerable to metabolic disorders such as ketosis and fatty liver. These disorders often predispose the animal to additional diseases and may impair reproduction. A potential marker of metabolic distress and protein imbalance is fibroblast growth factor 21 (FGF21). The goal of this project is to investigate the relationship between FGF21, protein metabolism and reproduction during the early postpartum period in dairy cows. Samples will be collected to determine if increases in FGF21 are associated with negative protein balance, which in turn may delay ovulation. This study will provide undergraduate students the opportunity to gain experience in several research techniques and lay the foundation for future studies during this critical time period. Data from this work will improve our understanding of the early postpartum period and contribute to improvements in animal health, diagnosis and interventions.