Influence of dietary oils rich in omega-6 or omega-3 fatty acids on rumen microbiome of dairy cows.

The objective of this study was to compare the effect of supplementing dairy cow diets with contrasting sources of omega-6 (soybean oil) and omega-3 (fish oil) PUFA on rumen microbiome. For 63 d, 15 mid-lactating cows were fed a control diet (n = 5 cows; no fat supplement) or control diet supplemented with 2.9% dry matter (DM) of either soybean oil (SO; n = 5 cows) or fish oil (FO; n = 5 cows). Ruminal contents were collected on days 0, 21, 42, and 63 for 16S rRNA gene sequencing. Beta diversity and Shannon, Simpson and Chao1 diversity indices were not affected by dietary treatments. In terms of core microbiome, Succiniclasticum, Prevotella, Rikenellaceae_RC9_gut_group, and NK4A214_group were the most prevalent taxa regardless of treatments. Bifidobacterium was absent in SO diet, Acetitomaculum was absent in FO, and Sharpea was only detected in SO. Overall, results showed that at 2.9% DM supplementation of either SO or FO over 63 days in dairy cow diets does not cause major impact on bacterial community composition and thus is recommended as feeding practice.

Freeze-dried Nannochloropsis oceanica biomass protects eicosapentaenoic acid (EPA) from metabolization in the rumen of lambs.

Eicosapentaenoic acid (EPA) from freeze-dried biomass of Nannochloropsis oceanica microalgae resists ruminal biohydrogenation in vitro, but in vivo demonstration is needed. Therefore, the present study was designed to test the rumen protective effects of N. oceanica in lambs. Twenty-eight lambs were assigned to one of four diets: Control (C); and C diets supplemented with: 1.2% Nannochloropsis sp. oil (O); 12.3% spray-dried N. oceanica (SD); or 9.2% N. oceanica (FD), to achieve 3 g EPA /kg dry matter. Lambs were slaughtered after 3 weeks and digestive contents and ruminal wall samples were collected. EPA concentration in the rumen of lambs fed FD was about 50% higher than lambs fed SD or O diets. Nevertheless, the high levels of EPA in cecum and faeces of animals fed N. oceanica biomass, independently of the drying method, suggests that EPA was not completely released and absorbed in the small intestine. Furthermore, supplementation with EPA sources also affected the ruminal biohydrogenation of C18 fatty acids, mitigating the shift from the t10 biohydrogenation pathways to the t11 pathways compared to the Control diet. Overall, our results demonstrate that FD N. oceanica biomass is a natural rumen-protected source of EPA to ruminants.