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

Lay Summary When cows are fed with different dietary lipid sources, some changes are found at the rumen level which is later reflected in overall animal's metabolism and performance. This study determined the effect of dietary lipids on rumen bacteria communities. For this, 15 cows were divided into three groups and were assigned a control diet and then this diet was supplemented with either soybean oil or fish oil. Results show minor effects on bacteria communities regardless of dietary lipid sources.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.This study showed mild effects of dietary lipids on rumen microbiome in cows. Minor effects can occur when cows are fed with 2.9% DMinclusion of dietary polyunsaturated fatty acids.