Effect of microbial oil and fish oil on rumen fermentation and metabolism of fatty acids in artificial rumen

Abstract

The objective of this study was to examine the effect of microbial oil (MO, n-6 fatty acids) and fish oil (FO, n-3fatty acids) used in their blends as supplements (5% wt/wt) to the diet containing 80% of hay and 20% of barley on rumen fermentation and lipid metabolism in artificial rumen. Overall, three different ratios of n-6 and n-3 fatty acids (1:1, 3:1, and 5:1) as the blends of MO and FO were used. Two similar consecutive experiments were carried out within 2 months. Each experiment lasted for 12 days with 6 days of stabilization period. The addition of all three oil blends did not affect the parameters of fermentation such as degradation of dry matter (DM), detergent fibre, total gas production, but increased the degradation of cellulose and hemicellulose in the diets. The supplementation of oil blends to the diet insignificantly (NS) decreased the methane production (mostly the n-6/n-3 ratio 1:1, about 23.5%), increased (<I>P</I> < 0.01) mol% of propionate (mostly the n-6/n-3 ratio 1:1, about 24.1%) and decreased (<I>P</I> < 0.05) mol% of acetate (mostly the n-6/n-3 ratio, 1:1, about 7.7%). The lipid metabolism in artificial rumen was also affected, when the oil blends increased (<I>P</I> < 0.001) the concentration of total fatty acids (FA) and long-chain FA (LCFA) in effluent. The concentration (mg/g rumen fluid DM) of <I>trans (trans</I> 11 C_18:1, TVA-vaccenic acid), <I>cis</I> C_18:1 isomers and CLA-conjugated linoleic acid (<I>cis</I> 9, <I> trans</I> 11 C_18:2) was also increased (<I>P</I> < 0.001) by the oil blends. Finally, the oil blends caused the incomplete FA biohydrogenation by an increase in TVA concentration and TVA/C_18:0 ratio in effluent in artificial rumen.