The relationships between odd‐ and branched‐chain fatty acids to ruminal fermentation parameters and bacterial populations with different dietary ratios of forage and concentrate

Abstract

The objectives of this study were to investigate the effect of different dietary ratios of forage and concentrate (F:C) on ruminal odd- and branched-chain fatty acids (OBCFAs) contents and to evaluate the relationships between OBCFA and ruminal fermentation parameters as well as bacterial populations tested by real-time PCR technique. The experimental design was a 3 × 3 Latin square. Three rumen-fistulated dry Holstein cows were fed three rations with different dietary F:C ratios (F:C; 30:70, 50:50 and 70:30). The rumen samples were collected every two hours (0600, 0800, 1000, 1200, 1400, 1600, 1800, 2000, 2200, 2400, 0200 and 0400 h) over three consecutive days in each sampling period. The results showed that rumen OBCFA profiles are significantly (p < 0.05) affected by the dietary F:C ratios. The concentrations of C11:0, C13:0, iso-C15:0, iso-C16:0, iso-C17:0 and C17:0 were higher in the cows fed dietary F:C ratio of 70:30 than those fed with other two rations. However, the concentrations of anteiso-C15:0, C15:0 and total OBCFA were on the lowest level in the high forage diet. Correlation and regression analysis showed that ruminal OBCFAs had strong relationships with ruminal fermentation parameters and bacterial populations. In particular, the iso-fatty acids had potential power to predict butyrate and isoacids metabolized in the rumen, whereas the fatty acids with 17 carbon atoms correlated with ruminal NH -N content. The OBCFA contents have different relationships with fibrolytic and starch bacteria in the rumen. C17:0 and its isomers might be used to predict populations of fibrolytic bacteria.

Relations of Ruminal Fermentation Parameters and Microbial Matters to Odd- and Branched-Chain Fatty Acids in Rumen Fluid of Dairy Cows at Different Milk Stages

“…The other part of the rumen contents were squeezed through two layers of cheesecloth, and about 5 mL was preserved at −80 • C for the extraction of DNA [26] and nearly 100 mL was preserved at −20 • C for the analysis of OBCFA, microbial bases, and the total nitrogen (N). The samples of OBCFA were treated according to the description of Zhang et al [27] and analyzed by a gas chromatography (GC 2010, Shimadzu, Tokyo, Japan) with an SP-2560 TM column for fatty acid methyl esters (100 m × 0.25 mm × 0.2 µm, Supelco, Pennsylvania, USA). The carrier gas was highly pure, and the injector pressure was held constant at 266.9 Kpa.…”

Profiles of Odd- and Branched-Chain Fatty Acids and Their Correlations With Rumen Fermentation Parameters, Microbial Protein Synthesis and Bacterial Populations Based on Pure Carbohydrate Incubation in Vitro

“…The concentration of NH 3 -N was determined using the phenol-hypochlorite colorimetric method according to Broderick and Kang [15]. The VFA concentrations were measured by using gas chromatograph (GC-2010, Shimadzu Laboratory Supplies Co., Ltd, Shanghai, China) equipped with a ame-ionization detector and a capillary column (HP-Innowax, 19091N-133, Agilent Technologies, Santa Clara, CA), as described by Zhang et al [3].…”

“…Total DNA of ruminal microbes was extracted using the cetyl trimethyl ammonium bromide (CTAB) plus bead-beating method [17]. The air-dried DNA pellet was re-suspended in TE buffer (10 mM Tris-HCl, 1 mM EDTA, pH 8.0) and was stored at -20°C until further processing [3]. The DNA purity (A260/280) was detected using a microplate spectrophotometer (SpectraMax 190, Sunnyvale, USA).…”

“…Odd-and branched-chain fatty acids [OBCFA; including pentadecanoic acid (C15:0), 13-methyltetradecanoic acid (iso-C15:0), 12-methyltetradecanoic acid (anteiso-C15:0), 14-methylpentadecanoic acid (iso-C16:0), heptadecanoic acid (C17:0), 15-methylhexadecanoic acid (iso-C17:0) and 14-methylhexadecanoic acid (anteiso-C17:0)] are promising for predicting ruminal fermentation and microbial matter leaving the rumen [1,2,3], because they are dominant components in microbial membrane lipids [4]. Theoretically, these fatty acids are produced from 2-carbon elongation of propionate (C15:0 or C17:0), isobutyrate (iso-C14:0 or iso-C16:0), isovalerate (iso-C15:0 or iso-C17:0) and 2-methyl-butyrate (anteiso-C15:0 or anteiso-C17:0) with the incorporation of malonyl-CoA fatty acid synthetase [4,5].…”

“…Theoretically, these fatty acids are produced from 2-carbon elongation of propionate (C15:0 or C17:0), isobutyrate (iso-C14:0 or iso-C16:0), isovalerate (iso-C15:0 or iso-C17:0) and 2-methyl-butyrate (anteiso-C15:0 or anteiso-C17:0) with the incorporation of malonyl-CoA fatty acid synthetase [4,5]. Therefore, it is not surprising to have several studies reporting close relationships between OBCFA and rumen VFA patterns both in vitro [1] and in vivo [3]. For instance, the bacterial OBCFA has been testi ed to explain 80% of the variations in acetate, propionate and butyrate under an in vitro culture system [1].…”