Effect of abomasal infusions of docosahexaenoic acid on nutrient digestibility, plasma fatty acids, and production responses of mid-lactation dairy cows

Our objective was to evaluate the effect of abomasal infusions of increasing doses of docosahexaenoic acid (DHA; 22:6n-3) on plasma and milk fatty acids (FA) and milk production of mid-lactation dairy cows. Eight multiparous ruminally cannulated Holstein cows (97 ± 37 DIM, 49.2 ± 3.3 kg/d milk) were assigned to a 4 × 4 Latin square design. Treatments consisted of abomasal infusions of 0, 2, 4, and 6 g/d of DHA with 11-d treatment periods and 10-d washout periods. The DHA was provided via an enriched algal oil (65% DHA) and suspended in ethanol (∼200 g/d). Samples were collected during the final 4 d of each period. Pre-planned orthogonal contrasts included the linear, quadratic, and cubic effects of increasing DHA. Results are presented in the following order: 0, 2, 4, and 6 g/d of DHA. Increasing DHA dose did not affect yields of milk, FCM, ECM, milk fat, or milk protein. Increasing DHA dose linearly increased DHA in plasma phospholipids (0.30, 0.50, 0.64, 0.82 g/100 g FA), triacylglycerols (0.09, 0.25, 0.40, 0.51 g/100 g FA), and cholesterol esters (0.04, 0.04, 0.05, 0.06 g/100 g FA). Similarly, increasing the dose of DHA linearly increased milk fat content of DHA (0.01, 0.04, 0.06, 0.08 g/100 g FA), total n-3 fatty acids (0.56, 0.57, 0.63, 0.63 g/100 g FA), and the yield of DHA in milk (0.19, 0.58, 0.91, 1.18 g/d). Absorbed DHA was positively correlated with the DHA in total plasma lipids (0.42), plasma phospholipids (0.70), plasma triacylglycerols (0.92), and milk fat (0.93). In conclusion, these findings indicate that although short-term DHA supplementation did not alter milk production, it increased DHA incorporation into key plasma lipids and milk fat and reduced SCC. Plasma or milk fat DHA content may serve as indicators of DHA absorption in practical feeding scenarios.