Effects of an omega-3 and aromatic medicinal plant-enriched diet on milk yield, fatty acid profile and oxidative status in dairy cows

Research in dairy nutrition has shown that milk quality characteristics can be improved through targeted dietary interventions in dairy cows. This study investigated the effects of a diet enriched with omega-3 sources and aromatic and medicinal plants (AMPs) on milk yield and milk quality characteristics. The experiment involved 70 mid-lactation Holstein Friesian cows, randomly assigned to two equal groups ( n = 35); a control group (C), fed a basal diet and a treated group (T), offered the same basal diet supplemented with a mixture (2.48% of TMR) of Mediterranean AMPs (containing oregano, sage, rosemary, lemon balm, thyme, fennel) and omega-3 sources, including flaxseed and a microalgae-derived DHA source for 90 days. Milk yield and blood serum parameters were analyzed using repeated measures mixed models, whereas milk composition, fatty acid profile and oxidative-status indicators were compared between groups at each sampling point using independent t-tests. The supplemented diet was associated with higher milk yield throughout the experimental period ( p < 0.001), without affecting milk chemical composition. However, significant changes were observed in the milk fatty acid profile, particularly in α-linolenic acid (ALA), docosahexaenoic acid (DHA) and total n-3 polyunsaturated fatty acids ( p < 0.05), leading to a lower n-6/n-3 ratio ( p < 0.001). Despite the higher degree of unsaturation, milk malondialdehyde levels decreased ( p < 0.001), while total antioxidant capacity (TAC) and total phenolic content (TPC) increased ( p < 0.05). Moreover, blood serum oxidative markers indicated no evidence of systemic oxidative stress. Overall, these findings suggest that the combination of omega-3 sources and AMPs may enhance the nutritional value and oxidative status indicators of milk.