Rumen microbial responses in fermentation characteristics and production of CLA and methane to linoleic acid in associated with malate or fumarate

Abstract

An in vitro incubation in batch was conducted to investigate the effect of propionate precursor (malate or fumarate) on fermentation characteristics, and production of CLA and methane by rumen microbes when incubated with linoleic acid (C 18:2). Sixty milligrams of C 18:2 alone (LA), 60 mg C 18:2 with 24 mM malic acid (M-LA), or 60 mg C 18:2 with 24 mM fumaric acid (F-LA) was added to 150 ml culture solution consisting of 75 ml strained rumen fluid and 75 ml McDougall's artificial saliva. Culture solution for incubation was also made without malate, fumarate, and C 18:2 (control). Two grams of feed consisting of 1.4 g concentrate and 0.6 g ground alfalfa (DM basis) was also added to the culture solution of each treatment. An in vitro incubation in batch was made anaerobically in a shaking incubator for up to 12 h at 39 °C. The pH of the culture solution was increased (P<0.0001) in M-LA or F-LA treatments from 3 h to 12 h compared with the control and LA treatments. At 12 h incubation, the concentration of total VFA in the culture solution was higher (P<0.01) in M-LA and F-LA than in control and LA treatments. Concentration of C 3 by M-LA and F-LA was increased at 3 h (P<0.01), 6 h (P<0.01) and 12 h (P<0.01) compared with control and LA. However, no difference in C 3 concentration was observed between control and LA, or between M-LA and F-LA. Accumulated total gas produced for up to 12 h incubation was increased (P<0.01) by M-LA or F-LA compared with the control. Accumulated total methane produced for up to 12 h incubation, however, was greatly reduced (P<0.01) by all the supplements compared with control, and its production from M-LA or F-LA was smaller than the LA. The M-LA or F-LA also increased (P<0.05–<0.001) the concentrations of cis9, trans11-CLA for all incubation times and trans10, cis12-CLA at 1 h (P<0.01), 3 h (P<0.05), and 12 h (P<0.05) incubation times compared with LA. It can be concluded that malate and fumarate, as propionate precursors, act as alternative electron sinks and may compete with CH 4 generation and bio-hydrogenation of C 18:2 in the utilization of metabolic H 2. The highest CLA concentration at the early incubation stage (1 h) was accompanied by reduced propionate proportion. Linoleic acid is also considered one of the potential alternatives to suppress CH 4 generation.