Abstract
Background
Post-ruminal supply of Met during the periparturient period enhances production efficiency (feed conversion to milk) in dairy cows partly through alleviation of oxidant and inflammatory status. Whether alterations in hepatic one-carbon (major contributor of antioxidants) and/or energy-metabolism contribute to these beneficial effects is unknown.
Objectives
Investigate alterations in hepatic one-carbon and energy metabolism and associations with plasma amino acids (AA) and production efficiency in response to enhanced post-ruminal supply of Met.
Methods
Holstein cows (n = 30/group) were fed during the last 28 days of pregnancy a control diet (CON) or the control plus ethyl-cellulose rumen-protected methionine (MET; 0.9 g·kg−1 of dry matter intake). Plasma (n = 15/group) and liver tissue (n = 10/group) were collected throughout the periparturient period to evaluate AA profiles, activity of TCA cycle, and one-carbon metabolism via mRNA abundance, enzyme activity, and targeted metabolomics.
Results
Cows in MET had greater overall (27%, P = 0.027) plasma Met concentrations, but had similar total plasma AA concentrations. Although mRNA abundance of one-carbon metabolism enzymes did not differ, hepatic activity of cystathionine β-synthase (CBS) (51.2 vs. 44.4 mmol·h−1·mg−1 protein; P = 0.032) and concentration (19%, P = 0.048) of the cellular antioxidant glutathione were greater overall in MET. mRNA abundance of aconitase 2 and fumarate hydratase was greater overall (P = 0.049), and phosphoenolpyruvate carboxykinase 1 tended (P = 0.093) to be greater overall in cows fed MET. There was a tendency (P ≤ 0.093) for greater overall hepatic concentrations of malic acid, α-ketoglutaric acid, and isocitric acid in cows fed MET.
Conclusions
Greater activity of CBS in response to enhanced post-ruminal supply of Met likely contributes to alleviating oxidant status by increasing concentrations of glutathione. Hence, transsulfuration plays an important role in the observed improvements in production efficiency of dairy cows during the periparturient period.
Hepatic Cystathionine β-Synthase Activity is Increased by Greater Post-ruminal Supply of Methionine During the Periparturient Period in Dairy Cows
