INFUSION OF 4 LONG-CHAIN FATTY-ACID MIXTURES INTO THE ABOMASUM OF LACTATING DAIRY-COWS

Five Holstein cows were utilized in a Latin square design to determine the effects of postruminal profile of fatty acids on DMI, milk yield and composition, nutrient digestibilities, and metabolites in blood. T reatments were abomasal infusions of 1) control, 169 to 180 g/d of mea t solubles; 2) control plus 450 g/d of mostly saturated fatty acids; 3 ) canola fatty acids; 4) soybean fatty acids; or 5) sunflower fatty ac ids. Infusion of fatty acids decreased intakes of DM, CP, and gross en ergy; yields of milk, FCM, SNF, total solids, CP, NPN, true protein, w hey protein, and casein; and percentages of SNF, CP, NPN, true protein , and casein in milk. Cows infused with mostly saturated fatty acids c onsumed more CP and digestible energy; yielded more milk, FCM, fat, SN F, total solids, CP, true protein, and casein; and had greater percent ages of SNF and total solids in milk than cows infused with unsaturate d fatty acids. Milk fatty acids reflected the profile of the infused f atty acid mixture. Ruminal characteristics and apparent digestibilitie s of DM, NDF, energy, and fatty acids generally were not different amo ng treatments. The profile of fatty acids reaching the small intestine may influence responses when supplemental fats are fed to lactating d airy cows.