Supplementation with rumen-protected CLA to dairy cows during the transition period increased plasma concentrations of glucose and cholesterol, and milk yield and decreased milk fat percentage and BCS loss. Extending fat supplementation from 21 to 42 dpp increased plasma concentrations of BHBA and NEFA, but did not alter milk composition and yield. Despite the metabolites and productive responses to CLA supplementation, reproductive performance of dairy cows did not differ among dietary treatments.