Correlation of oxidative stress-related indicators with milk composition and metabolites in early lactating dairy cows

Background: In highly intensive dairy farms, cows often suffer from metabolic disorders that cause severe oxidative stress. Objectives: This study aimed to observe correlations and associations of oxidative stress-related indicators with milk compositions andmetabolites. Methods: Twenty-two multiparous Holstein dairy cows in early lactation were randomly selected from a commercial dairy farm. The morning milk was collected for composition and metabolites analysis. Blood was sampled via the tail vein to analyze oxidative stress-related indicators (reactive oxygen species, ROS; catalase, CAT; superoxide dismutase, SOD; glutathione peroxidase, GPX; malondialdehyde, MDA) and metabolites. Results: Results showed that ROS were positively correlated with CAT, GPX, SOD, and MDA. However, the levels of CAT, GPX, and SOD were negatively related to milk fat (P < 0.05). Nineteen serum and 7 milk metabolites were selected from detectable metabolites according to their correlations with ROS, CAT, GPX, and SOD (P < 0.05). Metabolic pathway analysis and the Kyoto Encyclopedia of Genes and Genomes (KEGG) database revealed that these metabolites are primarily involved in themetabolic pathways of carbohydrates and amino acids. Conclusions: This study gave us a better understanding on oxidative stress that ROS not only increased oxidative damage (MDA) in dairy cows, but also altered some metabolites involved in amino acid and carbohydrate metabolism.