This dose was based on a typical human dose of 1 to 4 g/d which can be extrapolated to a dose of approximately 10 to 40 g/d for an average Holstein cow. According to product literature the EN product was estimated to provide 40 % bioavailable NA which would result in supplemrentation of 9.6 g/d .Cow entered the study from June 2008 to August 2008. Dry matter intake and milk production were housed in a tie-stall facility in randomly assigned stalls milked 3 times daily and fed twice daily at 110% of the previous day is intake. Prepartum and postpartum diets were formulated to meet requirements . All cows were fed similarly except that treated cows received 12 g of EN at each feeding mixed by hand into the top 10% of the ration.