Several studies suggest that dietary supplementation with rumen-protected choline (RPC) during the
transition period may support lactation performance in dairy cows, but the metabolic responses under-
lying these effects remain incompletely understood. We conducted a systematic review and dose–re-
sponse meta-analysis following PRISMA guidelines to evaluate the effects of RPC supplementation on
selected blood metabolites and liver-function indicators in dairy cows. A comprehensive literature search
in Web of Science, Scopus, PubMed, and Google Scholar identified 18 articles and one dissertation, com-
prising 29 studies eligible for meta-analysis. Study quality and risk of bias were assessed using SYRCLE’s
risk of bias tool. A one-stage random-effects dose–response meta-analysis with restricted cubic splines
was used to evaluate the effect of nominal choline chloride dose on blood concentrations of free fatty
acids, b-hydroxybutyrate, glucose, total cholesterol, triglycerides, and aspartate aminotransferase. RPC
supplementation did not significantly affect blood fatty acid, b-hydroxybutyrate, or glucose concentra-
tions before or after calving. Prepartum total cholesterol showed a non-linear response, with the greatest
estimated reduction at approximately 7 g/d of choline chloride and a significant increase from approxi-
mately 27 g/d onward. Prepartum triglyceride concentrations were reduced within the 18–21 g/d dose
range. Postpartum aspartate aminotransferase activity showed the greatest estimated reduction at
approximately 10 g/d, with significant reductions maintained up to approximately 18 g/d. These findings
suggest that RPC supplementation may influence selected lipid-related and liver-function indicators dur-
ing the transition period. However, the dose–response curves are based on nominal choline chloride
equivalents and should not be interpreted as estimates of absorbed or bioavailable choline supply.
These findings should be interpreted cautiously because methionine supply, DM intake, and product-
specific rumen-protection characteristics were inconsistently reported across studies.
