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PubMed1986

Volatile fatty acids in adult and young ruminants: an evaluation of a gas chromatographic method.

A gas chromatographic method was evaluated for the quantification of volatile fatty acids in blood plasma from ruminants. Amounts of .002 mg acetic acid and .001 mg of propionic and butyric acid could be quantified. Diurnal variation in acetate and propionate was found when blood samples were taken during 1 d from five cows. Jugular blood samples were taken from the five cows 8 wk before parturition to 10 wk after parturition and from three of their calves to 32 wk of age. Acetate decreased in cows at the weeks around parturition. Calves had very low acetate during the first 10 wk of life, but the concentration subsequently increased to that in adult ruminants. Propionate concentration was below .17 mM and butyrate concentration below .08 mM in all samples. It was concluded that this method was suitable for analyzing volatile fatty acids in blood plasma from ruminants, which is of importance in the study of metabolic diseases.

Acetates↗
PubMed1984

Discriminant analysis of volatile fatty acids produced in culture medium: a novel approach to the identification of Pseudomonas species.

The volatile fatty acids produced in culture medium by 357 Pseudomonas strains belonging to eight species were determined quantitatively by GLC. The resultant chromatograms were submitted to discriminant analysis. Stable discriminant functions were computed and included in a computerized identification system which also involved some distinctive volatile fatty acids regarded as two-state qualitative characters (presence or absence characters). Using a test group of 249 strains belonging to the studied species, more than 89% of the identifications made by this system agreed with those made by conventional biochemical methods despite the relatively poor differentiation between P. putida and P. fluorescens. When the individual species within the matrices were weighted with prior probabilities reflecting results given by two simple biochemical tests, 96% of the 249 strains were correctly identified.

Chromatography, Gas↗
PubMed1987

Effects of feeding or infusing ammonium salts of volatile fatty acids on ruminal fermentation, plasma characteristics, and milk production of cows.

Eight rumen-fistulated Holstein cows, averaging 77 d postpartum, were used in a replicated 4 X 4 Latin square design with 28-d periods to investigate the effect of ammonium salts of isobutyrate, 2-methylbutyrate, isovalerate, and n-valerate on animal performance and their possible mechanism(s) and site(s) of action. Each cow was fed ad libitum a complete mixed diet of 55% corn silage and 45% concentrate on a dry basis that was supplemented with 1.8 kg of premix daily. Treatments were 1) control, 2) ammonium salts of volatile fatty acids in premix, 3) ammonium salts of volatile fatty acids ruminally infused, or 4) ammonium salts of volatile fatty acids abomasally infused. Mean ruminal fluid pH and concentrations of ammonia and volatile fatty acids for treatment comparisons were not different. Plasma concentrations of isobutyrate, 2-methylbutyrate, and valerate differed among treatments, but there was no significant effect on dry matter intake, milk production, milk composition, or efficiency of feed utilization. Apparent nutrient digestibility; disappearance of dry matter, cellulose, and nitrogen from polyester bags suspended in the rumen; and plasma concentrations of glucose, free fatty acids, and growth hormone also were not significantly affected by treatment.

Abomasum↗
PubMedDate not supplied

Effect of pH on fecal recovery of energy derived from volatile fatty acids.

We assessed the effect of pH on volatilization of short-chain fatty acids during lyophilization. Acetic, propionic, valeric, and butyric acids were added to a fecal homogenate in amounts sufficient to raise the energy density by 18-27%. Fecal homogenate samples were either acidified (pH 2.8-3.2), alkalinized (pH 7.9-8.7), or left unchanged (4.0-4.8) prior to lyophilization and subsequent bomb calorimetry. Alkalinizing the fecal samples prevented the 20% loss of energy derived from each of these volatile fatty acids observed in samples either acidified or without pH adjustment. These data suggest that in energy balance studies involving subjects with active colonic fermentation, fecal samples should be alkalinized prior to lyophilization and bomb calorimetry.

Calorimetry↗
PubMed2004

A streamlined approach to the analysis of volatile fatty acids and its application to the measurement of whole-body flux.

Volatile fatty acids (VFAs) are produced in the human colon by the bacterial breakdown of carbohydrates that escape digestion and absorption in the small intestine. They have important local and systemic effects on gastrointestinal and nutritional functions. Measuring their production is difficult because of inaccessibility of sampling sites and low circulating concentrations. Stable isotope tracer techniques are a way to measure VFA production but require measurement of isotope dilution in blood and other biological fluids. We have developed a streamlined and robust method to measure the concentration and enrichment of [(2)H]-labelled VFAs by gas chromatography/mass spectrometry (GC/MS) and [(13)C]-labelled VFAs by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). Both types of analysis were carried out on the same samples allowing multiple tracer studies to be conducted. Good accuracy and repeatability were found for GC/MS analysis of [(2)H]-labelled VFAs. Careful handling of the background contribution, especially acetate, allowed quantitation of concentration and enrichment within the analysis. GC/C/IRMS analysis of [(13)C] VFAs was also achieved with good accuracy and repeatability. This methodology was used to determine whole-body acetate production in two subjects using multiple tracers ([(2)H(3)]- and [1-(13)C]acetate) and blood and urine sampling. Whole-body acetate flux was similar when measured either with [(2)H(3)]- or [1-(13)C]acetate, and when flux was determined from plasma or urine tracer enrichment. This new method will permit rapid and accurate measurement of VFA flux using [(2)H]- and/or [(13)C]-labelled VFAs as tracers. Measurements of the contribution of colonic VFA production to whole-body VFA flux are now possible.

Acetates↗
PubMed1990

[The direct detection of volatile fatty acids by gas chromatography in microbiological diagnosis].

The gas chromatographic analysis of volatile fatty acids (VFA) is of great significance in the diagnosis of anaerobes and anaerobic infections, respectively. The ether extraction commonly used for this purpose is relatively consuming in time and material. In this relation, the presented method of detection of VFA in the aqueous phase directly shows essential simplifications but has a lower sensitivity. Therefore, this method cannot replace the ether extraction to investigate broth cultures of anaerobes for taxonomical purposes. But it enables the determination of VFA with sufficient sensitivity in clinical materials of patients. Herewith, the detection of acetic acid only indicates an infection without anaerobes if the concentration is higher than 20 mg/100 ml. On the contrary, a high correlation exists between the detection of n-butyric acid as well as isovaleric acid and the cultural isolation of anaerobic microorganisms.

Bacteria, Anaerobic↗
PubMedDate not supplied

[Taxonomic value of the characterization of Pseudomonas by the analysis of volatile fatty acids produced in culture].

Gas liquid-chromatography was used in order to characterize the volatile fatty acids produced in culture supernatants by 632 Pseudomonas strains. Statistical analysis of these results allowed testing of the discriminatory power of this analytical methodology (factor analysis) to point out the presence of subgroups (clustering according to the variance) and to show the relationship between species and subspecies (three-dimensional plot). Fourteen Pseudomonas species could be accurately characterized by this methodology; the classification of Pseudomonas build up, on the basis of qualitative and quantitative aspects of their volatile fatty acids production, agrees with the current classification based on rRNA/DNA homology complexes.

Chromatography, Gas↗
PubMed1978

A rapid method for the determination of volatile fatty acids in biological fluids.

A rapid and simple method for the determination of volatile fatty acids in plasma and urine without any pretreatment is described. The gas chromatographic method reported here allows us to detect and quantitate in approx. 20 min biological VFA characteristics of various metabolic diseases. Conditions used are very mild so to avoid as much as possible any thermal decomposition of biological compounds.

Chromatography, Gas↗
PubMed1986

Colonic absorption of inorganic ions and volatile fatty acids in the rabbit.

Net fluxes of water, Na+, K+, Cl-, HCO3- and volatile fatty acids (VFA) were investigated in three different segments of rabbit colon. Two opposite phenomena occurred: secretion of water and inorganic ions in the oral part of the colon and absorption in the remaining colon; VFA were always absorbed. The movement of cations was closely correlated with those of VFA and Cl-. Results are consistent with the presence of exchange: Na+/H+, K+/H+, in the colon brush border membrane. In fact net absorption of cations and VFA seems linked to the availability of protons. In the absence of net cation transport an additional source of protons may be provided by hydration of luminal CO2. So VFA could enter mucosa by passive diffusion as the undissociated acids.

Animals↗