A study was conducted to assess the biological effects of the polyphenolic compounds of cocoa powder and green tea extract when administered to lactating dairy cows. Treatments were administered via constant abomasal infusion to eight rumen fistulated, lactating dairy cows in a 4x4 balanced duplicated Latin Square design. Cows received the standard TMR each morning and were milked twice daily in the morning and late afternoon. Blood samples were collected daily from the coccygeal vessel, and milk samples were collected daily at each the morning and afternoon milking. Blood samples were analyzed for NEFA and BHB as indicators of liver function, as well as for complete blood count for an indication of overall immune status. A method for HPLC/MS and GC/MS analysis was developed for future analysis of blood and milk samples to determine the transfer efficiency of polyphenols across the digestive tract, through the blood, and to the mammary gland.