Supplementation with sunflower or soybean oil: ruminal parameters and fatty acid profile in a Rusitec system

The current worldwide demand for healthier animal-derived foods has led to modifications in ruminant diets aimed at improving product composition, particularly the fatty acid profile. Supplementing dairy cow diets with vegetable oils may be an effective strategy to improve fatty acid composition. This study evaluated the inclusion of two vegetable oils with different fatty acid profiles in a high-quality forage-based diet. Five diets were incubated in a Rusitec system: a basal diet (C) containing alfalfa and a commercial concentrate (65:35, DM basis), and the same diet supplemented with sunflower oil (SF) or soybean oil (SB) to reach 60 g/kg DM (SF60 and SB60) and 75 g/kg DM (SF75 and SB75). After a 5-day adaptation period, fermentation parameters, nutrient degradability, and the ruminal fatty acid profile were evaluated. Oil supplementation did not affect ruminal pH, gas production, total volatile fatty acid concentration, or nutrient degradability. All supplemented treatments increased trans-vaccenic acid (C18:1 t11, TVA) by approximately 42–47% compared with the control diet (0.001P < ). In addition, dietary treatment affected oleic acid (C18:1 c9), monounsaturated fatty acids (MUFA), and saturated fatty acids (SFA), with higher oleic acid and MUFA concentrations observed in SF75, SB60, and SB75 than in the control, whereas SFA concentrations were lower in SF75 and SB60. These results indicate that supplementation with sunflower or soybean oil at levels up to 75 g/kg DM does not negatively affect ruminal fermentation or nutrient disappearance in vitro, indicating that both oils are promising dietary strategies for improving the ruminal fatty acid profile.