Blood and liver biomarkers and transcriptome alterations during the transition period reveal beneficial effects of rumen-protected methionine supplementation on health status and performance in dairy cows

The early postpartal period is characterized by marked changes in hormonal, metabolic, and immune/stress-like conditions all of which may contribute to regulating dry matter intake (DMI) and the supply of nutrients to mammary gland. Peripartal cows are likely to undergo a negative methionine (Met) balance due to increased requirements of tissues and cells for methylated compounds and Met for milk protein production. Therefore, supplementation of rumen-protected Met during the peripartal period may improve yield of milk and protein, and also help coordinate immunometabolic adaptations of the cow. Supplementation of rumen-protected Met in the form of MetaSmart (MS) or Smartamine (SM) improved milk production at least in part by increasing voluntary DMI and perhaps by optimizing the use of body lipid reserves as observed in chapter 2. In fact, an overall milk protein and milk fat was positively affected by Met supplementation. Improvements in production were accompanied by a faster recovery to a positive energy balance coupled with a lower predisposition to develop ketosis in Met-supplemented cows, which indicates that overall health was at least not compromised and perhaps improved. Results from chapter 3 indicate that supplementing Met during the peripartal period promoted favorable alterations of inflammatory and oxidative stress status of cows. The greater albumin in response to Met-supplementation may indicate enhanced liver function and improved AA status. Overall blood and liver biomarkers analyzed indicated that improved postpartal performance when feeding SM and MS was due partly to a better immunometabolic status. Relative mRNA expression of targeted genes associated with biological processes of interest such as the Met cycle, inflammation, and oxidative stress, among others, were evaluated in chapter 4. Results indicated that feeding MS or SM to cows during the peripartal period could profoundly affect the hepatic transcriptomics of Met metabolism, PPARA activation, hepatokines synthesis, and gluconeogenesis. To better understand the molecular effects of peripartal Met-supplementation on hepatic metabolism in Holstein dairy cows, a microarray platform with advanced computational and bioinformatics techniques were used in chapter 5. Hepatic transcriptome analysis revealed a high impact on metabolism especially in pathways AA metabolism. Overall supplementing rumen-protected Met to peripartal dairy cows will improve DMI, milk yield and components, and energy balance by enhancing liver function, increasing antioxidant capacity, and ameliorating the inflammatory response, and that in turn these effects are controlled at the molecular level by cross-talk of gene expression