Relationships of Circulating and Preovulatory Follicular Fluid Hydrogen Peroxide Levels with Body Condition Score and Metabolome Profiles of Lactating Beef Cows

Nutrient requirements for lactation often lead to a negative energy balance accompanied by reduced body condition and fertility in cattle. A previous study identified an increased abundance of serum metabolites associated with tissue mobilization and reactive oxygen species (ROS) generation in postpartum beef cows with a thin versus moderate body condition. No studies, however, have measured ROS levels in the serum and follicular fluid of postpartum beef cows for comparison with body condition. We hypothesized that beef cows with a thin body condition would have elevated levels of ROS, as indicated by hydrogen peroxide (H 2 O 2 ), in serum and preovulatory follicular fluid. Serum and follicular fluid samples from thin ( n = 12), moderate ( n = 11), and obese ( n = 16) cows underwent a H 2 O 2 bioluminescence assay. Levels of H 2 O 2 in each biofluid were then assessed to determine relationships with cow body condition and serum or follicular fluid metabolites. Levels of H 2 O 2 did not differ among body condition categories. In thin cows, the serum H 2 O 2 level was positively related to the abundance of 3 metabolites with antioxidant activity. Among all animals, the follicular fluid H 2 O 2 level was positively associated with the abundance of 13 metabolites, many of which had antioxidant roles. The results suggest an impact of postpartum beef cow metabolism on ROS levels in preovulatory follicular fluid or serum and highlight the need for additional studies to further investigate this potential impactor of reproductive efficiency and sustainable beef production.