Rumen biohydrogenation of linoleic and linolenic acids is reduced when esterified to phospholipids or steroids.

Saman Lashkari,Søren Krogh Jensen,Majbritt Bonefeld Petersen

doi:10.1002/fsn3.1252

Abstract

Manipulation of rumen biohydrogenation (BH) is of great importance, since decreased BH of linolenic acid (LNA) and linoleic acid (LA) is linked to increased content of the beneficial polyunsaturated fatty acids (PUFA) in dairy products and decreased content of trans fatty acids (FAs). We hypothesized that PUFA esterified to the complex lipid fractions are less prone to BH compared with PUFA esterified to the simple lipid fractions due to reduced lipolysis. In vitro rumen BH of different single lipid fractions was investigated, including free fatty acids (FFA), and esterified FA to triglycerides (TG), cholesterol esters (CE), and phospholipids (PL). A mixture of a buffer solution and rumen fluid was incubated with different lipid fractions, and C18 FAs were quantified by gas chromatography. In vitro BH kinetic parameters were quantified according to Michaelis–Menten equation and the maximum BH (Vmax) and time to achieve 50% of maximum amount (KM) estimated. Regardless of fatty acids, BH in CE and PL was lower than FFA and TG. The highest amount of cis‐9, trans‐11 conjugated linoleic acid (CLA) and trans‐10, cis‐12 CLA was observed in lipid fractions containing LA and LNA, respectively, regardless of lipid fractions. The present study demonstrates the importance of lipid fractions on BH of LNA and LA and formation of CLA isomers. The results show that BH of FAs depends on the lipid fractions.

Highlights

Milk fat composition of cow and goat is composed of more than 400 different fatty acids (FAs) as a consequence of the high microbial activity in the rumen and the de novo synthesis in the mammary gland (Chilliard et al, 2007)
The amount of BH in linolenic acid (LNA) and linoleic acid (LA) modeled according to Michaelis–Menten occurred in the following order: free fatty acids (FFA) > TG > PL, regardless of the FA esterified to the different lipid fractions
Comparison of amount of conjugated linoleic acid (CLA) isomers in same lipid fraction showed that irrespective of incubation time, the amount of cis‐9, trans‐11 CLA in FFA_LA, TG_LA, and LP was higher than the amount of trans‐10, cis‐12 CLA, while in CE_LA, no significant difference was observed between the amount of cis‐9, trans‐11 and trans‐10, cis‐12 CLA after 4, 6, and 11 hr of incubation

Summary

| INTRODUCTION

Milk fat composition of cow and goat is composed of more than 400 different fatty acids (FAs) as a consequence of the high microbial activity in the rumen and the de novo synthesis in the mammary gland (Chilliard et al, 2007). Earlier studies have shown that lipolysis takes place in the herbage itself, the rumen microorganisms are the main responsible for lipolysis in the ingested plant lipid complexes (Hespell & O'Bryan‐Shah, 1988). The mixture was prepared for all samples at once, and each incubated sample contained either 5 mg FFA, 10 mg TG or CE, or 15 mg of PL After mixing, these mixtures were placed in a fume cupboard, and the added ether was allowed to evaporate, while the mixture was frequently stirred to ensure homogeneous samples. Mixtures containing lipid fractions with LNA (FFA and TG) were placed under a stream of N2 to prevent oxidation of the LNA. 500 mg of the prepared lipid–straw mixture, 22 ml of strained rumen fluid, and 22 ml of buffer solution were transferred to 60‐ml tubes. The contents of the tubes were freeze‐ dried and stored at −20°C until further analysis

| MATERIALS AND METHODS

| Statistical methods

| DISCUSSION

Findings

| CONCLUSION