Fatty Acid Profiles Associated with Microbial Colonization of Freshly Ingested Grass and Rumen Biohydrogenation

Abstract

Two in situ studies were conducted to examine the use of odd-chain fatty acid profiles to study microbial colonization of freshly ingested herbage in the rumen as well as fatty acid biohydrogenation. In the first study, fresh perennial ryegrass was subjected to a range of sample preparation methods before incubation in the rumen for 2 or 7 h. In the second study, fresh perennial ryegrass was chopped into 1-cm lengths and incubated in polyester bags in the rumen for 2, 8, and 24 h. After removal of bags from the rumen, 4 different washing methods, ranging from manual squeezing to machine washing, were applied. Fatty acids were extracted from washed residues and determined, as methyl esters, by gas chromatography. The main odd-chain fatty acids (with the exception of anteiso C(15:0)) were not found in fresh grass and were useful markers of the effects of incubation time, sample preparation method, and washing method on microbial colonization/contamination. The concentration of these and other odd-chain fatty acids increased with incubation time in both studies. The results indicate rapid and continued microbial colonization of freshly ingested forages, although patterns of odd-chain fatty acids did not reveal any further information about the types of bacteria-colonizing herbage. Principal component, biplot analysis provided a useful overall description of the processes of microbial colonization and degradation of plant fatty acids on fresh herbage incubated in the rumen. Bolus formation during mastication and ingestion results in extensive damage to herbage; none of the techniques (cutting, crushing, and drying/grinding) investigated in this work was able to replicate the effects of bolus formation in the animal. The study provided further evidence of loss of unfermented feed particles through polyester bag pores, especially when feeds are dried and ground. Biohydrogenation of the polyunsaturated fatty acids of fresh herbage was used principally by solid-associated bacteria to enable them to take up high levels of trans-11 C(18:1) and C(18:0) fatty acids. Although trans-11 C(18:1) was strongly associated with bacterial markers (odd- and branched-chain fatty acids), its precursor (cis-9, trans-11 C(18:2)) was not associated with bacterial variation, suggesting that its production in the rumen under these conditions was mainly extracellular.

Lipid metabolism in the rumen: New insights on lipolysis and biohydrogenation with an emphasis on the role of endogenous plant factors

“…Bessa et al (2009) studied the FA composition of LAB, SAB1 and SAB2 with the aim of identifying these bacteria from their FA profile, and found marked differences in FA composition between LAB and SAB (i.e., detachable plus undetachable solid associated bacteria) populations, consistent with others (Bauchart et al, 1990a;Kim et al, 2005;Vlaeminck et al, 2006b). LAB had a lower FA content and a higher proportion (g/kg FA) of odd branched chain FA (OBCFA) than did SAB, which had a higher proportion of C18 biohydrogenation derived FA (C18:0; especially trans C18:1 and CLA).…”

“…Indeed, except for C17:1 which is endogenously synthesized by the action of 9 desaturase (Fievez et al, 2003), C15:0 and C17:0 are partially de novo synthesized (Vlaeminck et al, 2006a;Cabrita et al, 2007). OBCFA have been confirmed to be extremely relevant as markers of ruminal microbial activity, especially when effects of incubation time of substrate or sample preparation methods of microbial colonization/contamination in vivo and in vitro need to be evaluated (Kim et al, 2005). Attempts to validate relationships between rumen OBCFA output and milk OBCFA are mixed compared with microbial markers such as diaminopimelic acid (DAPA) and purine bases (PB; Fievez et al, 2003).…”

In vitro gas production of five rations of different maize silage and concentrate ratios influenced by increasing levels of chemically characterized extract of Salix babylonica

“…Examples included fatty acids and their methyl esters such as hexadecanoic acid, octadecatrienoic acid, octadecenoic acid, and pentadecanoic acid, which are relatively common essential oils in higher plants. Hexadecanoic acid is one of the major odd-and branched-chain fatty acids in rumen microorganisms (21).…”

Effect of fish oil on ruminal biohydrogenation of C18 unsaturated fatty acids in steers fed grass or red clover silages

“…Branched-and odd-chain fatty acids Use of branched-and odd-chain fatty acids as microbial markers have indicated that differences in the flows of these particular fatty acids may represent variations in rumen microbial ecology (Kim et al, 2005). In the current study, flows of these particular fatty acids at duodenum, C13:0, C15:0, C15:0 anteiso, C15:0 iso and C17:0 in particular, differed between red clover and grass silage diets, which suggests that forage species may have altered the rumen microbial population.…”