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Five lactating Holstein cows averaging 13 wk postpartum were used in a Latin square design to examine the effect of daily abomasal infusion of choline (22 g), myo-inositol (37 g), soy oil (325 ml), or crude soy lecithin (900 ml) on lactation performance. Dry matter intake was reduced by infusion of soy lecithin as compared with infusion of water (18.1 and 21.1 kg/d, respectively). Plasma beta-hydroxybutyrate concentration was increased when cows received the myo-inositol or soy lecithin infusion, and plasma glucose was lower when cows received the choline or soy lecithin treatment. Infusion of soy lecithin caused approximately a twofold increase in plasma triglyceride-rich lipoprotein concentration. Milk fat percentage and milk fat yield were greater during soy lecithin infusion (3.54%, 1.11 kg/d) than during water (3.09%, .98 kg/d) or soy oil (3.06%, .98 kg/d) infusion. This resulted in greater 3.5% FCM yield during soy lecithin infusion (31.6 kg/d) than during water (29.5 kg/d) or soy oil (29.6 kg/d) infusion. Infusion of phospholipid with triglyceride allowed more fatty acid to be infused without causing diarrhea. Infusion of triglyceride in the presence of phospholipid increased milk fat synthesis whereas infusion of triglyceride alone did not.