Abomasal infusion of an exogenous emulsifier improves fatty acid digestibility and milk fat yield of lactating dairy cows.

The objective of our study was to determine the effects of abomasal infusion of an emulsifier on fatty acid (FA) digestibility and production responses of lactating dairy cows. Eight rumen-cannulated cows (109 ± 18 d in milk) were randomly assigned to a treatment sequence in replicated 4 × 4 Latin squares with 18-d periods including 7 d of washout and 11 d of infusion with sampling on the last 4 d. Treatments were abomasal infusions of water carrier only (CON) and 3 levels of increasing doses of Tween 80 (polysorbate 80, Tween 80, Sigma-Aldrich, St. Louis, MO) delivering 15 (D-15), 30 (D-30), and 45 (D-45) g/d. The Tween 80 was dissolved in water before infusions, which were delivered at 6-h intervals. Cows were fed the same diet, which contained (% dry matter) 31% neutral detergent fiber, 17% crude protein, 25% starch, and 4% FA (2% dry matter from a saturated fat supplement containing 33% C16:0 and 51% C18:0). Increasing emulsifier infusion dose quadratically increased digestibility of total FA (60.7, 65.3, 70.9, and 66.8%), 16-carbon FA (61.7, 63.9, 70.4, and 66.7%), and 18-carbon FA (59.8, 65.6, 71.1, and 66.6%, respectively). Increasing emulsifier infusion dose quadratically increased absorbed total FA (625, 670, 744, and 658 g/d), 16-carbon FA (151, 157, 197, and 157 g/d, quadratic), and 18-carbon FA (420, 460, 500, and 444 g/d). Increasing emulsifier infusion dose tended to quadratically decrease dry matter intake (29.0, 28.8, 29.6, and 27.6 kg/d). Increasing emulsifier infusion dose quadratically increased milk fat content (3.23, 3.35, 3.45, and 3.35%), milk fat yield (1.54, 1.61, 1.65, and 1.55 kg/d), ECM (45.7, 46.9, 47.5, and 45.3 kg/d), and plasma nonesterified fatty acid concentration (95.6, 98.4, 101.2, and 98.6 μEq/L). On a yield basis, we observed that de novo, mixed, and preformed FA responded quadratically to Tween 80 infusion due to FA yield increasing up to D-30. Treatments had no effect on milk yield (47.9, 48.3, 48.0, and 46.6 kg/d). In conclusion, short-term infusion of an exogenous emulsifier improved FA digestibility and milk fat yield responses when cows were fed a diet containing a saturated fat supplement. Most digestion and production measurements responded quadratically because the highest dose of exogenous emulsifier (45 g/d) decreased dry matter intake and performance.