In cattle, energy requirements after parturition increase exponentially, primarily, due to increase in milk production. Negative energy balance hampers reproductive efficiency, inflicting heavy economic losses to dairy industry. Poor reproduction is the most important cause of culling dairy cows. Feed supplementation with vitamins improves energy balance. Also, observations in humans indicate that folic acid and vitamin B12 improve oocyte quality and pregnancy establishment. Unfortunately, these vitamins are degraded to large extent while their passage through rumen, making oral supplementation practically inefficient in cattle. Recently, JEFO® has developed a rumen-non-degradable vitamin feed supplement called “Vicomb®” for cattle. Initial studies showed that Vicomb® improves serum concentrations of various vitamins. However, there is no information available about the impact of Vicomb® on reproductive efficiency. Our objectives are to evaluate Vicomb® effects on reproductive efficiency through gene expression and metabolic analyses. Vicomb®, if found effective, would result in great economic gains for dairy industry.