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Change in the volatile fatty acids content of laboratory stored sterilized and non-sterilized swine wastes.

The influence of urine and microbial activity was studied as possible factors leading to the generation of volatile fatty acids in non-sterilized stored swine wastes. Urine was found to promote the generation of the volatile acids. The microbial origin of the volatile acids in the wastes was ascertained by the growth of an anaerobic bacterial strain (Peptostreptococcus anaerobius). Significant generation and transformation of these acids was observed in sterilized swine waste samples stored under conditions similar to the non-sterilized samples.

Animals↗

Influence of meal frequency on postprandial variations in the production and absorption of volatile fatty acids in the digestive tract of conscious pigs.

Five Large White pigs of 62.2 +/- 1.4 kg mean body weight were fitted with permanent catheters in the portal vein and carotid artery and with an electromagnetic flow probe around the portal vein to study the absorption of volatile fatty acids (VFA) by measuring the concentration of these metabolites in hourly blood samples, and by determining the portal blood flow rate for a period of 12 h after intake of a single 800-g meal (6% crude fiber) preceded by 12 or 24 h of fasting. The portal concentration of VFA mixture always highly exceeded the arterial concentration. The arterial concentrations of propionic, butyric, valeric and isovaleric acids were nearly null, accounting for an almost complete uptake of these VFA by the liver. Acetic acid also was taken up, but to a lesser extent. Total VFA absorption during 12 h was 64% higher (P less than .05) after 12 h (1,160 +/- 100 mmol/12 h) than after 24 h of preprandial fasting (740 +/- 83 mmol/12 h). It increased after the meal (P less than .05) from 82.3 +/- 7.8 mmol/h between the first and fourth hour to 107.8 +/- 7.5 mmol/h between the fifth and tenth hour when the preprandial fasting lasted 12 h; a nonsignificant increase also was found when fasting prior to the meal lasted 24 h. The composition of the VFA mixture was not modified by the length of preprandial fasting. With this type of diet there was a large predominance of acetic acid (52%) followed by propionic and butyric acids (36 and 8.5%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

The chemical composition of Phyllanthus discoideus and its effect on the ruminal ammonia and volatile fatty acid concentration when fed to west African dwarf sheep.

The feeding value of Phyllanthus discoideus (also called Margaritaria discoidea) leaves was evaluated using eight two-year-old West African Dwarf sheep fed natural grass hay. Four of the animals were fistulated ruminally and used for ammonia and volatile fatty acid determination in the fluid. Dried leaves of Phyllanthus discoideus were offered at two levels (25% and 50% of DMI, diets D25% and D50%, respectively) as supplements to the basal hay diet. The CP content of the control, D25% and D50% diets were 11.5, 12.6 and 13.6%, respectively, and their digestible energy amounted to 58.2, 61.1 and 56.9%, respectively. Rumen liquor was sampled one hour before and one, three and five hours after the morning feeding. Sheep fed the control diet had a higher ruminal ammonia concentration than those fed diet D25%. Similarly, ruminal ammonia concentration was higher in sheep fed the control diet than those fed the diet D50%. Five hours after feeding the ruminal ammonia concentration was significantly lower than one hour after feeding. The VFA concentrations in rumen fluid of sheep fed the control diet was inferior to those fed diets D25% and D50%. Sheep fed diet D50% showed significantly higher VFA concentrations than those fed diet D25%. Digestibility of organic matter and digestible energy did not show any significant difference. However, a marginal increase in organic matter digestibility of 3.5% was observed in diet D25% compared with the control diet. There was no significant difference in the N-digestibility in sheep fed the control, D25% and D50% diets. Nevertheless, a marginal improvement in N-digestibility (1.5%) and N-retention (2.7%) was observed with the highest level of Phyllanthus discoideus (D50%). In conclusion, Phyllanthus discoideus appears as a particularly valuable feedstuff because it contains low levels of condensed tannins (12.8 g/kg), high CP content (156 g/kg) and a relatively high GE content (19.3 kJ/g DM). Although the improvement in N-digestibility and N-retention were only marginal the feeding of Phyllanthus discoideus could be justified under extreme shortage of feed resources during dry season. It should also be mentioned that a much more pronounced effect by supplementation with Phyllanthus discoideus could be expected when poor quality grass hay prevalent in West Africa during the dry season is fed. Phyllanthus discoideus could serve as a supplement to poor quality grass at 25% to 50% of supplementation.

Ammonia↗

Effect of mesenteric venous volatile fatty acids (VFA) infusion on GH secretion in sheep.

The effects of mesenteric venous infusion of acetate, propionate and butyrate mixture (20.3, 40.5 and 81.0 micromol kg[-1] min[-1] over 4 h) on the secretion of GH was examined to investigate the effects of an increase in portal volatile fatty acids (VFA) on GH secretion in relation to inhibition of GH secretion after feeding in sheep. The mesenteric venous infusion at the rate of 40.5 micromol kg(-1) min(-1) increased the portal plasma VFA concentration within the approximate physiological range after feeding. Plasma GH was noticeably suppressed only at the infusion rate of 81.0 micromol kg(-1) min(-1) and the change in the mean concentration from the base line was significantly less than in the control. Although GRF injection rapidly increased plasma GH, the change in the mean concentration from the base line tended to suppress only at the infusion rate of 81.0 micromol kg(-1) min(-1). Plasma FFA was suppressed in a dose-dependent manner after VFA infusion. The change in the mean concentration from the base line was significantly suppressed only at the infusion rate of 81.0 micromol kg(-1) min(-1) relative to the control infusion, but plasma glucose was unchanged by VFA infusion. It is concluded that because the increase in the portal plasma VFA concentration within the range of feeding did not suppress GH secretion, VFA absorbed by the digestive tract may not play a significant role in suppressing GH secretion after feeding in sheep.

Animals↗

Influence of maturity of grass silage and flaked corn starch on the production and metabolism of volatile fatty acids in dairy cows.

An experiment employing a Latin square design was used to quantify the effects of two stages of maturity of grass silage (early cut and late cut) and three concentrations of flaked corn starch (0, 2, and 4 kg) on the molar proportion of rumen volatile fatty acids (VFA), the production of rumen VFA, and the net fluxes of VFA in the splanchnic tissue of cows. The molar proportions of VFA in rumen fluid were similar for cows fed both silages. When the silage diets were supplemented with starch, the proportion of propionic acid increased for cows fed diets containing early cut grass silage, but no effects were found for cows fed diets containing late cut grass silage. Estimated gastrointestinal production of acetate, propionate, butyrate, and branched-chain fatty acids plus valerate was related to intake of metabolizable energy and organic matter fermented into VFA. The portal release of acetate was approximately 14% lower than the estimated production of acetate by cows fed diets containing early cut grass silage, but cows fed diets containing late cut grass silage showed a variable difference between estimated production and portal release (31, 24, and 15%, respectively) as starch supplementation increased. The portal release of butyrate plus beta-hydroxybutyrate and the release of branched-chain fatty acids plus valerate were approximately 70 and 25%, respectively, of the estimated gastrointestinal production. Propionate production was similar to the portal release of propionate. Net flux measurements in splanchnic tissue in combination with gastrointestinal digestion and kinetics provide information that increases the knowledge of pathways and metabolism and quantifies the availability of individual nutrients for milk production in dairy cows.

Animals↗

Liver blood flow and volatile fatty acid utilization in sheep before and after carbon tetrachloride treatment.

Liver blood flow and the net uptakes of acetate, propionate and butyrate were estimated in control and carbon tetrachloride (CCl4) treated sheep after an 18 h fast and during intra-ruminal infusion of a solution of the above volatile fatty acids (VFA). Portal venous blood flow was increased and the hepatic arterial blood flow reciprocally decreased by the VFA infusions in the control sheep and, even more so, in the CCl4-treated sheep. In the control sheep, increased hepatic availability of propionate was accompanied by increased hepatic uptake so that the propionate extraction percentage was maintained. In the CCl4-treated sheep, the propionate extraction percentage was greatly reduced when the propionate availability was increased and consequently the systemic blood concentrations of propionate were greatly elevated in these circumstances. Neither VFA infusion nor CCl4 treatment caused changes in hepatic acetate utilization. However, the systemic blood concentrations of acetate were significantly increased in the VFA-infused CCl4-treated sheep, suggesting changes in extra-splanchnic acetate utilization in this group. Increased hepatic butyrate availability was accompanied by increases in hepatic uptakes without changes in percentage extraction in both the control and CCl4-treated sheep.

Acetates↗

[Measurement of the appearance of volatile fatty acids in the portal vein during digestion in conscious pigs].

A method used to measure the nutrient exchanges between the intestinal lumen and the portal blood was applied to 3 pigs receiving 800 g of a diet containing 6% of cellulose. During a postprandial period of 24 hrs., the mixture of volatile fatty acids (90 mM/h) appearing in the portal vein was composed of acetic acid (57%), propionic acid (30%), butyric acid (9%), isovaleric (2.5%) and valeric acid (1.5%). The composition of this mixture differed from that of the colic contents because of its acetic acid enrichment at the expense of butyric acid. The resulting energy supply to the animal represented about 600 to 700 kcal/24 hrs.

Animals↗

Comparative effects of dietary wheat bran and its morphological components (aleurone and pericarp-seed coat) on volatile fatty acid concentrations in the rat.

Adult male rats were fed on diets containing 100 g dietary fibre/kg either as alpha-cellulose or wheat bran or the pericarp-seed coat or aleurone layers prepared from that bran by sequential milling and air elutriation and electrostatic separation. After 10 d, concentrations of total volatile fatty acids (VFA) in caecal fluid were significantly different between groups and fell in the order: aleurone greater than wheat bran greater than pericarp-seed coat greater than cellulose. This ranking probably reflected the ease of fermentation of fibre polysaccharides by colonic bacteria which also resulted in a considerably higher faecal bacterial mass in the aleurone group. Because of the differences in the volume of caecal digesta, the mass of caecal VFA was considerably the highest in the aleurone group, intermediate with wheat bran and equally low in the pericarp-seed coat and cellulose groups. The diet based on aleurone gave a relatively higher proportion of propionate but with both pericarp-seed coat and wheat bran the contribution of butyrate was raised. VFA concentrations in hepatic portal venous plasma were proportional to caecal concentrations with very high (greater than 3 mM) values being recorded in the aleurone group. The findings are discussed in relation to the apparent susceptibility of the morphological components of wheat bran to fermentation by large bowel bacteria.

Animals↗

Protein utilization during energy undernutrition in sheep sustained by intragastric infusion: effects of protein infusion level, with or without sub-maintenance amounts of energy from volatile fatty acids, on energy and protein metabolism.

Utilization of endogenous and exogenous energy for protein accretion during energy undernutrition has been studied. Nine lambs nourished by intragastric infusion were given either progressively increasing or decreasing amounts of casein-N up to 2550 mg/kg metabolic weight (W0.75), with or without 250 kJ/kg W0.75 of volatile fatty acids daily. Energy balance (respiration calorimetry) and N balance were measured. While all experimental animals were in negative energy balance, N balance increased curve-linearly with the increase in casein-N infusion and attained positive N balance. Endogenous energy (presumably body fat) was found to meet the energy needs for protein accretion during energy undernutrition. It is concluded that body fat can be effectively utilized to support lean-tissue growth during energy undernutrition, so that the classical nutritional concept of dietary energy:protein ratio is only meaningful when both endogenous and exogenous energy are considered.

Adipose Tissue↗

Influence of the nature of carbohydrate intake on the absorption chronology of reducing sugars and volatile fatty acids in the pig.

The results of three successive experiments were compared in order to analyse the chronology of absorbed energy amounts resulting from enzymatic or microbial digestion, respectively. These experiments were undertaken in the pig to study the absorption kinetics of reducing sugars and amino-nitrogen formed during enzymatic digestion and of volatile fatty acids (VFA) formed through the action of the digestive flora. The animals were given well-balanced semi-synthetic diets containing poorly digestible or indigestible carbohydrates. These diets contained the following ingredients: (Experiment A) purified cellulose at two levels of incorporation (LC diet 6%, HC diet 16%); (Experiment B) alfalfa meal (22%) supplying 6% crude fibre (HA diet) versus lactose (22%) with an addition of 6% purified cellulose (HL diet); (Experiment C) sorbitol in the form of maltitol (53%) with an addition of 6% purified cellulose (SHyd diet) versus maltose under the same conditions (53%, SNat diet). Each diet was fed to five pigs fitted with catheters placed in the portal vein and carotid artery and with a flow probe around the portal vein, which made it possible to study the nutrient absorption after one meal (800 g). Under our experimental conditions (intake: 2 200-2 300 kcal, except HC 1 930 kcal) the higher level of crude fibre or the presence of osides in the diet which are poorly digestible in the small intestine (lactose, maltitol), depressed the absorption of reducing sugars (RS) (amount absorbed within 12 h relative to intake %: SNat 92.8; LC 82.7; HL 78.7; HA 76.0; HC 72.5; SHyd 71.3). The absorbed energy supply resulting from the VFA increased accordingly, in the presence of poorly digestible or indigestible carbohydrates (as a percentage of the total energy absorbed as RS, lactic acid (LA) and VFA: SNat 3.4; LC 7.1; HL 8.9; HC 10.4; SHyd 13.1) with one exception (HA: 6.0%). For all diets, the greatest energy absorption (42-63% according to the diet) occurred during the first 4 h after the meal, the larger fraction resulting from RS (86.8-94.8% according to the diet). The energy supply due to the absorption of VFA became large between the 5th and the 12th hour, and was larger for diets containing poorly digestible or indigestible carbohydrates (as a percentage of the total RS + LA + VFA: SNat 6.5; LC 8.7; HC 14.3; HC 14.4; SHyd 23.3) with one exception (HA: 9.0%). Although the late absorption of VFA was insufficient to compensate for the energy deficit due to a lower of RS, it may bridge the energy gap during the interprandial period.

Animals↗

The use of cumulative gas and volatile fatty acid production to predict in vitro fermentation kinetics of Italian ryegrass leaf cell walls and contents at various time intervals.

Differences between the fermentation characteristics of cell contents (CC) and protease-treated cell walls (CW) of young leaves of Italian ryegrass (Lolium multiflorum Lam.) cultivar Multimo (tetraploid), were studied in vitro. Gas and volatile fatty acid (VFA) production rates were measured at regular intervals, as was the degradability of organic matter (OM) of CW. The measured VFA were used to predict the gas production and fermentable OM using stoichiometric calculations. For CW the volume and kinetics of measured gas production were the same as those predicted from the VFA formed. In contrast, the measured gas production for CC was consistently less than predicted, indicating that the stoichiometric equations were not valid for rapidly fermenting substrates. For both CC and CW, the relative rate of acetic acid production levelled off more slowly than for other VFA, resulting in an increasing gas yield (in ml/g fermentable OM) after 12 (CW)-24 (CC) h incubation. Consequently, the fermentation of OM was not linearly related to gas production kinetics. For CW, the kinetics of decline of degradable OM and fermentable OM were the same, after correction for a constant 'lost fraction' of degradable OM of 205 g/kg OM. This work indicates the value of detailed studies of fermentation processes to evaluate herbage quality. In particular, the role of CC and the difference between degradation and fermentation require further attention.

Cell Wall↗

On-line removal of volatile fatty acids from CELSS anaerobic bioreactor via nanofiltration.

The CELSS resource recovery system, which is a waste-processing system, uses aerobic and anaerobic bioreactors to recover plants nutrients and secondary foods from the inedible biomass. The anaerobic degradation of the inedible biomass, by means of culture of rumen bacteria, generates organic compounds such as volatile fatty acids (VFA) (acetic, propionic, butyric) and ammonia. The presence of VFA in the bioreactor medium at fairly low concentrations decreases the microbial population's metabolic reactions due to end-product inhibition. Technologies to remove VFA continuously from the bioreactor are of high interest. Several candidate technologies were analyzed, such as organic solvent liquid-liquid extraction, adsorption and/or ion exchange, dialysis, electrodialysis, and pressure-driven membrane separation processes. The proposed technique for the on-line removal of VFA from the anaerobic bioreactor was a nanofiltration membrane recycle bioreactor. In order to establish the nanofiltration process performance variables before coupling it to the bioreactor, a series of experiments was carried out using a 10,000 molecular weight cutoff (MWCO) tubular ceramic membrane module. The variables studied were the bioreactor slurry permeation characteristics, such as: the permeate flux, VFA and nutrient removal rates as a function of applied transmembrane pressure, fluid recirculation velocity, suspended matter concentration, and process operating time. Results indicated that the permeate flux, VFA, and nutrients removal rates are directly proportional to the fluid recirculation velocity in the range between 0.6 and 1.0 m/s, applied pressure when these are lower than 1.5 bar, and inversely proportional to the total suspended solids concentration in the range between 23,466 and 34,880 mg/L. At applied pressure higher than 1.5 bar the flux is not more linearly dependent due to concentration polarization and fouling effects over the membrane surface. It was also found that the permeate flux declines rapidly during the first 5-8 h, and then levels off with a diminishing rate of flux decay.

Anaerobiosis↗

A viscous fibre (methylcellulose) lowers blood glucose and plasma triacylglycerols and increases liver glycogen independently of volatile fatty acid production in the rat.

1. Adult male rats were maintained on diets containing 80 g methylcellulose/kg of low (25 cP), medium (400 cP) and high (1500 cP) viscosity. 2. After 10 d, the viscosity of stomach and caecal contents was found to have increased in proportion to that of the dietary fibre. Concentrations of volatile fatty acids in caecal digesta were lowest with the high-viscosity fibre but acetate was the major acid present with all three diets. Acetate was the only acid found in significant quantities in hepatic portal venous plasma and concentrations of this acid were unaffected by diet. 3. Concentrations of glucose in arterial blood were low with the medium- and high-viscosity diets while the content of liver glycogen was high. These effects of fibre were not directly on glucose absorption as the intestines were net removers of the hexose at the time of sampling. 4. Hepatic lipogenesis and plasma triacylglycerol concentrations were both higher in rats fed on the low-viscosity fibre. Plasma cholesterol concentrations, hepatic cholesterol synthesis and faecal bile acid excretion were not altered by dietary fibre viscosity. 5. We conclude that the effects of dietary fibre on carbohydrate absorption and storage and fatty acid synthesis are a function of the viscosity of the fibre in solution, high viscosity slowing the digestion and absorption of nutrients in the small intestine. Large-bowel microbial fermentation is not of direct significance to these events. In contrast, effects of fibre polysaccharides on sterol metabolism seem not to be related to their rheological properties.

Animals↗

Atmospheric ammonia, volatile fatty acids, and other odorants near beef feedlots.

Intensive livestock operations can release odorous gases from stored or land-applied manure. We measured concentrations of dust and 14 odor-causing gases at increasing distances from four feedlots near Lethbridge, southern Alberta, Canada. Concentration was determined from the amount of total dust or gas accumulated in the sampIers, and the volume of air sampled. Adjacent the feedlots, the maximum concentration of many volatile fatty acids exceeded reported odor detection thresholds; the maximum ammonia concentration was close to the threshold. Ammonia and butyric acid approached or exceeded their individual odor thresholds as far as 200 m downwind of the feedlots. Highest concentrations were measured adjacent to land where manure was being applied. None of the odorant concentrations exceeded their irritation threshold. There was a positive relationship between ammonia concentration and odor intensity as well as dry deposition. Much of the emitted ammonia was deposited to soil immediately downwind, enough to supply all the nitrogen needed for crop growth. Odorant concentrations declined sharply with distance, though measurable odor occasionally persisted to 1 km from the feedlot, beyond the minimum separation guidelines (Alberta) for a single residential dwelling. The weekly averaged total suspended particulates (> 5 microm) were below the Alberta guideline criterion except for one period. Differences among feedlots in odorant plume concentrations were partly related to the stocking density of feedlots, which presumably affects manure moisture and amount of volatiles within the pens.

Air Movements↗

Magnesium absorption in the caecum of rats related to volatile fatty acids production.

Rats were fed with a semi-synthetic diet with or without raw potato starch. (The level of minerals was the same in the two diets.) Because of its special structure raw potato starch was not attacked by rat enzymes. The rats fed on the raw potato starch diet showed increase in caecal weight. The increase in caecal volatile fatty acids (VFA) and decrease in pH were evidence of increased microbial fermentation from the presence of substrate in the caecum. There was also an increase in the arteriovenous difference in VFA and Mg in the caecum. Nutritional balance study was performed and confirmed the better Mg absorption in rats fed on the raw potato starch diet. The lower parts of the digestive tract seem to play an important role in Mg absorption and further studies on the relations between caecal volume, pH, VFA, microbial activity and Mg absorption are necessary.

Animals↗

Effects of volatile fatty acids on a thermophilic anaerobic hydrogen fermentation process degrading peptone.

Hydrogen fermentation using glucose as a single substrate caused abrupt pH drops and the gradual losses of hydrogen producers, which in turn led to system failure. In this study the use of a proteinaceous substrate, peptone, avoided the abrupt pH drops in the reactive system and allowed for further exploration of volatile fatty acids (VFAs) and pH effects on the hydrogen fermentation process. Our results showed that: (1) during the hydrogen fermentation tests, the abrupt pH drops were avoided thus system stability increased due to the production of ammonia from the peptone fermented, (2) pH control was not necessary and the addition of acetate to the process had little effect on the hydrogen fermentation process, (3) at the extreme pHs the addition of acetate either lengthened the lag phase (pH < or = 6) or slowed the hydrogen production rate (pH > or = 8), and both situations were not desired, and (4) high VFA content in the system sped up the consumption of hydrogen gas. Results of this study suggested that the hydrogen fermentation using the protein-containing substances as substrate was beneficial in maintaining the system pH. As long as the pH was maintained around 6-8, system inhibition due to VFAs accumulation was minimized. Thus, the optimal operation of a hydrogen fermentation process would be achievable via the control of substrate composition at a certain carbohydrate-to-protein ratio.

Bioelectric Energy Sources↗

Fecal D- and L- lactate, succinate, and volatile fatty acid levels in young dairy calves.

For evaluation of physiologically significant organic anions in the colonic environment, 87 samples of normal feces were collected from the rectum of 15 calves less than 60 days old. The calves were fed milk replacer with free access to starter diet and hay. After fecal extraction with water, pH, D- and L-lactate, succinate, and volatile fatty acid (VFA) concentrations were determined. There was wide variation in fecal pH (4.3 to 7.7). Higher lactate concentrations were observed in feces samples with lower pH, and most of these samples were collected during the first 4 weeks of life. Elevated lactate concentrations included both the D- and L-isomers, and the D-isomer comprised approximately 30-50% of total lactate. Elevated succinate concentrations were observed in only 8 fecal samples, while other samples had lower or trace amounts of succinate. Elevated fecal succinate showed no relationship with fecal pH or VFA concentrations. Fecal VFA concentrations were lower in samples collected in the early postnatal stage, but fecal VFA concentrations were not necessarily related to age. We confirmed that fecal D- and L-lactate concentrations increased with a concomitant decrease of VFA in the acidic lumen of the colon, although acidic feces were not necessarily accompanied by elevated concentrations of lactate. In contrast, succinate production was not related to fecal pH or VFA concentrations.

Animals↗

Absorption of electrolytes and volatile fatty acids in the hind-gut of the rabbit. Circadian rhythm of hind-gut electrolytes and plasma aldosterone.

Interrelationships between the amount of water, solute concentrations in the hind-gut, plasma aldosterone concentrations, and the excretory cycle in the rabbit were studied as well as the effects of hormones generally implicated in electrolyte regulation. It appeared that the levels of water, electrolytes and volatile fatty acids (VFA) in the large intestine varied cyclicly with the excretion pattern: during the soft-phase, water, sodium, chloride and VFA were absorbed and potassium secreted as in other mammals; during the hard-phase two opposite phenomena occurred: secretion in the ascendant colon and absorption in the rest of the colon. Absorption of water, Na, K, chloride and VFA was increased and by this means only material without nutritional value was lost. Plasma levels of aldosterone showed a circadian rhythm parallel to hind-gut changes, i.e. the higher values were found during the hard-phase. Exogenous aldosterone enhanced secretive and absorptive processes, which occurred normally when hard faeces were elaborated.

Aldosterone↗