Antioxidant networks and the microbiome as components of efficiency in dairy cattle

The dairy industry worldwide is confronting unprecedented challenges including climate change and consistently increasing feed costs, the latter representing a major issue for dairy farmers. Thus, renewed efforts for improving feed efficiency by focusing on biological components within the rumen and peripheral tissues of the animal that contribute to feed efficiency are taking center stage. These efforts have been made possible by the growing application of cutting-edge technology along with management practices that have practical application. The last decade has seen a robust focus on approaches to identify feed-efficient cows, linkages among nutrition and gut microbiota, and understanding antioxidant networks in key metabolic tissues. Because of the well-known role in cellular function and the ability of dairy cows to make a successful transition into lactation, oxidant status and its cellular networks across tissues are a unique target for manipulation through management that can impact feed efficiency. Antioxidant supply is a robust strategy to alleviate pro-oxidant states. Recognition that the antioxidant transcription regulator nuclear factor erythroid 2-like 2 (NFE2L2) is present in key metabolic tissues such as adipose and mammary now provides a target for intervention. In addition, the identification of cows capable of maintaining high production levels with lower feed intake has opened a wide field for more efficient animal selection. Recent studies evaluating residual feed intake (RFI) have provided important knowledge on how shifts in ruminal and hindgut microbiome could be part of the mechanism associated with better feed efficiency in dairy cattle. This review mainly focuses on the role of antioxidant networks and gut microbiome in regulating dairy production efficiency.