Infusion of four 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. Treatments were abomasal infusions of 1) control, 169 to 180 g/d of meat solubles; 2) control plus 450 g/d of mostly saturated fatty acids; 3) canola fatty acids; 4) soybean fatty acids; or 5) sunflower fatty acids. Infusion of fatty acids decreased intakes of DM, CP, and gross energy; yields of milk, FCM, SNF, total solids, CP, NPN, true protein, whey protein, and casein; and percentages of SNF, CP, NPN, true protein, and casein in milk. Cows infused with mostly saturated fatty acids consumed more CP and digestible energy; yielded more milk, FCM, fat, SNF, total solids, CP, true protein, and casein; and had greater percentages of SNF and total solids in milk than cows infused with unsaturated fatty acids. Milk fatty acids reflected the profile of the infused fatty acid mixture. Ruminal characteristics and apparent digestibilities of DM, NDF, energy, and fatty acids generally were not different among treatments. The profile of fatty acids reaching the small intestine may influence responses when supplemental fats are fed to lactating dairy cows.