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PubMed2007

Performance of a down-flow fluidized bed reactor under sulfate reduction conditions using volatile fatty acids as electron donors.

The use of a down-flow fluidized bed (DFFB) reactor for the treatment of a sulfate-rich synthetic wastewater was investigated to obtain insight into the outcome of sulfate reduction in a biofilm attached to a plastic support under a down-flow regime. Fine low-density polyethylene particles were used as support for developing a biofilm within the reactor. The reactor treated a volatile fatty acids mixture of acetate or lactate, propionate, and butyrate at different chemical oxygen demand (COD) to sulfate ratios ranging from 1.67 to 0.67 (g/g). Organic loading rate changed from 2.5 to 5 g COD/L x day and sulfate loading rate increased from 1.5 to 7.3 g SO(4) (2-)/L x day. At the beginning of continuous operation, methanogenesis was the predominant process; however, after 187 days, sulfate reduction became the main ongoing biological process. After 369 days, a COD removal of 93% and a sulfate removal of 75% were reached. Total sulfide concentrations in the reactor ranged from 105, when the reactor was mainly methanogenic, to around 1,215 mg/L at the end of the experiment. The high sulfide concentrations did not affect the performance of the reactor. Results demonstrated that the configuration of the DFFB reactor was suitable for the anaerobic treatment of sulfate-rich wastewater.

Biofilms↗

PubMed1978

[The effect of types of rations on a straw basis on fermentation and volatile fatty acid production in the rumen of lactating cows. 2. Ruminal fermentation and milk yield criteria after use of a high-fiber straw pellet batch as a basic ration component].

Lactating Black-Pied (DSR) cows were used to study, over a period of 100 days, the influence of different basal ration types (experimental group - straw pellets; control group - dried forage + fodder root crops) on fermentation response and daily production rate of volatile fatty acids (VFA) as well as on some criteria of milk yield. Whilst only slight differences were found between the experimental groups in the molar proportions of VFA, the straw pellet-concentrate ration resulted in a lower VFA production as compared to the conventional ration. The control group's VFA production relativated to energy intake, was found to be of the same level (4.1, 4.3 and 3.9 Mol/1 kilo energetic feed equivalents/cattle) after 30, 60 and 100 days of feeding, respectively. The corresponding values in the experimental group declined from 3.3 to 2.3 and 1.9 Mol/1 kilo EF/cattle when feeding a high-fibre straw-pellet batch as basal ration component. The VFA production rates rather diverging between both groups were not found to have a uniform effect on the milk synthesis processes. Both the daily and the first 100-day milk yields did not differ between the groups but within the range of statistical error. Statistically secured positive correlations were found to exist between concentration and production of VFA which, however, depend on the basal ration type and revealed a relatively wide deviation.

Animal Feed↗

PubMed1981

Regulation of volatile fatty acid uptake by mitochondrial acyl CoA synthetases of bovine heart.

Purification of components of heart mitochondria activating short chain fatty acids prepared from tissue of lactating Holstein cows demonstrated predominantly one acyl CoA synthetase, acetyl CoA synthetase activating acetate, and propionate. Activity of butyryl CoA synthetase was low. Propionyl CoA synthetase characteristically in bovine liver and kidney tissue could not be demonstrated in heart mitochondria. Thus, of the ruminally derived volatile fatty acids only acetate can be used by heart mitochondria as a primary energy source because of small quantities of propionate in peripheral blood. Acetyl CoA synthetase was a glycoprotein composed of a single polypeptide chain of apparent molecular weight 67,500. The Michaelis-Menten constant for acetate was 1.8 x 10(-4)M. By comparison with literature for blood acetate concentration we concluded that enzyme is saturated with substrate at all physiological concentrations of acetate. These kinetic properties ensure a constant supply of acetate as an energy source for maintaining heart function in ruminants.

Acetate-CoA Ligase↗

PubMed1983

The effect of changes in the amount of energy infused as volatile fatty acids on the nitrogen retention and creatinine excretion of lambs wholly nourished by intragastric infusion.

The nitrogen balance and creatinine excretion of wether lambs of 30-48 kg, wholly nourished by the intragastric infusion of nutrients, were measured in two experiments. Four lambs were used in each experiment. In Expt 1 a constant amount of casein was infused into the abomasum (640 mg N/kg body-weight (W)0.75 per d) and the amount of volatile fatty acids (VFA) infused into the rumen ranged from 0 to 670 kJ/kg W0.75 per d as six increments. Expt 2 was of similar design but two levels of casein were infused (530 and 1060 mg N/kg W0.75 per d) and, with each level of casein, VFA infused ranged from 0 to 700 kJ/kg W0.75 per d as seven increments. Daily creatinine excretion was not constant, but varied between 2-d means with standard deviations of between 7.1 and 16.5% (average 13.1%) of the over-all means. There was an apparent correlation between creatinine excretion and the amount of energy infused in six out of eight lambs. There was no effect of the amount of casein infused. In both experiments N balance was negative only when the amount of energy infused was substantially below published values for energy maintenance. In Expt 1, N equilibrium was calculated to be achieved at a gross (VFA plus protein) energy infusion level of 162 (SE 29) kJ/kg W0.75 per d. In Expt 2 it was observed that, at a given level of energy infusion, N retention was greater when the amount of energy had been increased from the previous level, than when it had been decreased. It is concluded that the animal appears to allocate available amino acids to protein synthesis, rather than to oxidation, even when in negative energy balance. It is also concluded that enhanced N retention observed when the amount of energy infused had been increased represented compensation after a period of energy restriction.

Animals↗

PubMed2004

Eugenol stimulates lactate accumulation yet inhibits volatile fatty acid production and eliminates coliform bacteria in cattle and swine waste.

AIM: To determine how eugenol affects fermentation parameters and faecal coliforms in cattle and swine waste slurries stored anaerobically. METHODS AND RESULTS: Waste slurries (faeces:urine:water, 50:35:15) were blended with and without additives and aliquoted to triplicate 1-l flasks. Faecal coliforms were eliminated in cattle and swine waste slurries within 1 or 2 days with additions of eugenol at 10.05 mm (0.15%) and 16.75 mm (0.25%). At these concentrations volatile fatty acids (VFA) were reduced ca 70 and 50% in cattle and swine waste, respectively, over 6-8 weeks. Additionally, in cattle waste, eugenol stimulated the accumulation of lactate (>180 mm) when compared with thymol treatment (20 mm lactate). In swine waste, lactate accumulation did not occur without additives; eugenol and thymol stimulated lactate accumulation to concentrations of 22 and 32 mm, respectively. CONCLUSIONS: Eugenol added to cattle waste may be more beneficial than thymol because not only does it effectively control faecal coliforms and odour (VFA production), it also stimulates lactate accumulation. This in turn, causes the pH to drop more rapidly, further inhibiting microbial activity and nutrient emissions. SIGNIFICANCE AND IMPACT OF THE STUDY: Plant essential oils have the potential to solve some of the environmental problems associated with consolidated animal feeding operations. Thymol and eugenol reduce fermentative activity, thus, have the potential to reduce emissions of greenhouse gases and odour, and curtail transmission of pathogens in cattle and swine wastes.

Animals↗

PubMed1981

Effects of primary, secondary and tertiary amines on in vitro cellulose digestion and volatile fatty acid production by ruminal microorganisms.

Decanamine hydrochloride (a C10 primary amine), N-methylundecanamine (a C11 secondary amine) and N, N-dimethyldodecanamine (a C12 tertiary amine) were tested for their effects upon in vitro cellulose digestibility by unadapted ruminal microorganisms. The three amines exhibited similar patterns of inhibition of cellulose digestibility in 48-hr in vitro incubations. Cellulose digestion was depressed to 97, 89, 31, 11 and 12% of the control value by 5, 10, 25, 50 and 100 ppm of the amines, respectively. Total volatile fatty acid production was depressed to 89, 85, 61, 40 and 32% of the control value by 5, 10, 25, 50 and 100 ppm of the amines, respectively. Propionate production was inhibited to a greater extent than was acetate production, and acetate to propionate ratios increased in the presence of the amines. The results demonstrate that these primary, secondary and tertiary amines inhibit those microorganisms which digest cellulose in the rumen.

Amines↗

PubMed1992

Relationship between volatile fatty acids and magnesium absorption in mono- and polygastric species.

In monogastric animals magnesium is absorbed from the small and large intestine. In ruminants the forestomach system, in particular the rumen, is the most important site of magnesium absorption. Various mechanisms are involved in intestinal magnesium absorption (solvent drag, diffusion, carrier-mediated transport). In the large intestine and rumen an active transepithelial magnesium transport from the mucosal to the serosal side of the epithelium was recently demonstrated. Since in the large intestine and in the rumen, volatile fatty acids (VFA, mainly acetate, propionate, butyrate) deriving from fermentation of carbohydrates represent the major anions, the influence of VFA on magnesium absorption from these parts of the gut was recently investigated. VFA at physiological concentrations stimulated magnesium absorption in both cases. In the rat large intestine VFA enhanced only magnesium absorption by the distal colon, sodium and water absorption remaining unaffected. Both in sheep rumen and in the distal colon of the rat butyrate was most effective in this regard, followed in descending order by propionate and acetate. Sodium absorption by the rat proximal colon and caecum, and by the sheep rumen, was similarly enhanced by VFA. It has been suggested that the latter effect is due to the function of VFA as intracellular proton donators for the Na+/H+ exchanger located in the apical membrane of the epithelial cells. In analogy a Mg2+/H+ exchanger, located in the apical membrane of the epithelium in the distal colon and rumen, is fully consistent with the stimulatory effects of VFA on magnesium absorption at these sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1985

Stimulation of absorption of volatile fatty acids and minerals in the cecum of rats adapted to a very high fiber diet.

The effects of a high fiber diet containing about 50% pectin, gum, crude potato starch and the fiber components of wheat bran and soya seed cake on the cecal absorption of substrates were studied by parallel measurements of cecal arteriovenous differences and blood flows. Rats fed the high fiber diet had heavier cecae and higher cecal wall weight and blood flow than rats fed a fiber-free diet. Very high arteriovenous differences in volatile fatty acids (VFA) were observed and VFA absorption in cecal vein reached 17.5 mumol/min in the high fiber diet group. This process was concomitant to a moderate absorption of Na+ and partly offset by a secretion of Cl-. In contrast, K+, Mg2+ and Ca2+ were absorbed in large amounts along a favorable concentration gradient. About 10% of arterial urea was removed, and there was a substantial reabsorption of ammonia, despite the lower cecal ammonia and the acidic pH in the cecum when the high fiber diet was fed. The present study suggests that rats may tolerate large amounts of diversified fibers or related compounds in the diet. Such a model could contribute to the assessment of the role of VFA in the effect of fiber.

Adaptation, Physiological↗

PubMed1990

Forage intake, ruminal dry matter disappearance, and ruminal blood volatile fatty acids for steers in 18 and 32 degrees C temperatures.

Six steers with rumen cannulas and exteriorized carotid arteries were fed chopped alfalfa, orchardgrass, or tall fescue hay in ambient temperatures (18 and 32 degrees C) using a factorial arrangement of forage and temperature with repeated measurements. Arterial blood, venous blood, and rumen fluid were sampled for VFA at 0, 2, 4, and 7 h after forage was offered. Rate of digestion of plant cell wall was determined by in vitro methods. Rate of ingesta and particulate passage was determined by 144Ce marker. Volatile fatty acid concentrations in blood plasma and rumen fluid were not related to forage voluntary intake. Voluntary forage intake was related to calculated ruminal disappearance of cell wall (r2 of .94). Elevated ambient temperature, 32 degrees C, depressed voluntary forage intake but did not increase ruminal or blood VFA concentrations.

Animal Feed↗

PubMed1996

Production rates of volatile fatty acids in the minke whale (Balaenoptera acutorostrata) forestomach.

Minke whales (Balaenoptera acutorostrata) have developed a compartmentalized stomach system, which includes a non-glandular forestomach containing high concentrations of indigenous bacteria. The forestomach contents serve as microbial substrate, and samples were collected from five adult minke whales eating capelin (Mallotus villosus) and crustaceans (Thysanoessa sp.). Chemical analysis of the forestomach contents revealed that they consisted of crude protein (650 (SD 58) g/kg DM), lipid (330 (SD 77) g/kg DM) and water-soluble carbohydrates (53.3 (SD 7.3) g/kg DM). The contribution of energy from volatile fatty acids (VFA), produced by forestomach bacterial fermentation, to the total energy budget was estimated. The forestomach concentration of VFA ranged from 13.2 to 68.5 mmol/l, and the pH was 5.83 (SD 0.41). VFA pool size ranged from 72.8 to 638.1 mmol and represented from 0.169 to 2.107 kJ/kg live weight (W)0-75. Maximal recorded forestomach VFA production rate was 1694 mmol/h in one capelin-eating minke whale with 42.6 litres of forestomach fluid. Energy from VFA produced by forestomach fermentation represented 6-107 kJ/kg (W)0-75 per d, which accounts for only 0.9-16.9% of the average daily energy expenditure of minke whales. This study suggests that the bacterial fermentation in the minke whale forestomach varies, depending on the volume and the quality of substrate available, influencing fermentation rates and concentration of VFA. Due to the small relative size of the forestomach, the contribution of VFA to the daily energy requirement in minke whales would be of less importance than in ruminants even when assuming the same production rate of VFA as in a ruminant.

Animals↗

PubMed1995

[Energetic and/or nitrogen underfeeding in the dry cow. Effects on volatile fatty acids in the rumen, some plasma metabolites and hormones and urinary excretion of 3-methylhistidine].

In order to study the effects of a nitrogenous and/or energetic underfeeding on some metabolites and hormones, 4 dry cows were fed in 2 equal daily meals with hay-based rations. Four rations were distributed. They supplied too much (HN) or too little (LN) digestible protein in the small intestine and too much (HE) or too little (LE) net energy, ie the diets were HN-HE, HN-LE, LN-HE, and LN-LE. Continuous collection of rumen liquor samples (volatile fatty acids or VFA determination), venous blood samples (amino acids (alanine Ala, glutamine Gln, glycine Gly and serine Ser), urea, glucose, insulin and growth hormone (GH) measurements) and urine samples (determination of the amount of 3-methylhistidine 3-MeHi excreted) was carried out for 24 consecutive hours. By comparison with the reference diet (HN-HE), underfeeding was accompanied by a reduction in ruminal VFA concentrations, an increase in those of plasma Gly and GH, and a maintenance of glycemia levels. Furthermore, nitrogenous and energetic underfeeding (LN-LE) was accompanied by a decrease in plasma Ala, Gln and insulin concentrations. Nitrogenous underfeeding (LN-HE) caused a decrease in uremia levels, an increment in those of serinemia and no variation in circulating insulin concentrations. The energetic underfeeding (HN-LE) was accompanied by a reduction in insulinemia levels and an increase in those of alaninemia and serinemia. Such changes suggest that dry cattle adapt to underfeeding by mobilizing endogenous proteins. However, only the 2 diets with reduced energetic supplies were accompanied by an increase (P < 0.05) in the amount of the urinary 3-MeHi excreted per 24 h, suggesting that the level of energy in the diet is the main trigger for protein mobilization. Finally, the study of the 24-h evolution of the parameters revealed the influence of the feeding time (morning or evening) and the level of the dietary nitrogen and energy supplied on the variation in their concentration.

Alanine↗

PubMed2005

Effect of enzymatic pretreatment on solubilization and volatile fatty acid production in fermentation of food waste.

Food waste can be a valuable carbon source in biological nutrient removal (BNR) systems because of the high C/N and C/P ratio. However, pretreatment is necessary to promote hydrolysis of food waste because of the high concentration of volatile solids associated with organic matter. The influence of the enzymatic pretreatment on acid fermentation of food waste was investigated in this study. Solubilization of particulate matter in food waste was carried out using commercial enzymes. The acidification efficiency and the volatile fatty acid (VFA) production potential of enzymatically pretreated food waste were examined. The highest volatile suspended solid (VSS) reduction was obtained with an enzyme mixture ratio of 1:2:1 for carbohydrase: protease: lipase. An optimum enzyme dosage for solubilization of food waste was 0.1% (V/V) with the enzyme mixture ratio of 1:2:1. In the acid fermentation of enzymatically pretreated food waste, the maximum VFA production and the highest VFA fraction in soluble COD (SCOD) were also achieved at 0.1% (V/N) of total enzyme dosage. Increase in VFA production at this level of enzyme dosage was over 300% compared with the control fermenter. The major form of VFA produced by fermentation was n-butyrate followed by acetate.

Acetates↗

PubMed1984

Methane formation in faunated and ciliate-free cattle and its relationship with rumen volatile fatty acid proportions.

Twelve steers fitted with rumen cannulas were used in three separate experiments to investigate the effects of the presence or absence of rumen ciliate protozoa on methane production. The diet consisted of 850 g barley and 150 g protein supplement/kg, and was given in three feeds daily at a restricted level of 61 g/kg live weight 0.75. Animals were defaunated initially by allowing ad lib. consumption of this diet and were then maintained ciliate-free by isolation or were faunated by inoculation with a mixed ciliate suspension. Samples of rumen fluid were taken routinely for the assessment of microbial populations and for volatile fatty acid (VFA) analysis and energy and nitrogen balances and digestibility measurements were made at intervals while animals were confined in respiration chambers. In each experiment the rumen VFA proportions changed from a high-propionate pattern under ciliate-free conditions to a low-propionate, high-butyrate pattern in the presence of ciliates: differences between treatments were highly significant (P less than 0.001). There were also marked differences between treatments in CH4 production but a reliable comparison was possible only in Expt 3, in which CH4 was significantly higher (P less than 0.001) in the presence of a rumen ciliate population. In Expt 3 the increased loss of energy as CH4 in the faunated animals amounted to 4.8 MJ/100 MJ energy intake. Stoichiometric estimates of CH4 production derived from the observed VFA proportions showed good agreement with CH4 production as measured in respiration chambers. On average, the stoichiometric CH4 values overestimated CH4 production by a factor of 1.08. Highly significant linear relationships (P less than 0.001) were observed between the molar proportion of each major VFA and the quantity of CH4 produced: the proportion of propionic acid was inversely related to CH4 and showed the lowest residual standard deviation of all the relationships examined. The losses of energy in faeces and urine did not differ between treatments hence the increased loss of energy as CH4 in the faunated animals resulted in a significant reduction in the metabolizability of the diet from 0.73 to 0.69 (P less than 0.05). No significant differences were detected between treatments in heat production, apparent digestibility coefficients or N balance. It is suggested that the rumen ciliates, by modifying the rumen VFA proportions, are directly responsible for the increased CH4 production in faunated animals.

Animals↗

PubMed2002

Effects of an abrupt increase of starch-rich concentrates in the diet of dairy cows on concentrations of volatile fatty acids in the rumen and large intestine and on myoelectric activity of the spiral colon.

OBJECTIVES: To describe the effects of an abrupt increase of concentrates in the diet of dairy cows on myoelectric activity of the spiral colon and on fermentation patterns in the rumen and large intestine. ANIMALS: 6 healthy lactating Simmental x Red-Holstein cows. PROCEDURES: The diet of 6 cows implanted with bipolar electrodes in the spiral colon was changed from hay only to a ration of 50% hay:50% starch-rich concentrates during a period of 60 hours. Myoelectric activity of the spiral colon, concentrations of absolute and undissociated volatile fatty acids (VFA), and pH of ruminal and large intestinal contents were monitored before, during, and after the dietary change. RESULTS: Significant changes in patterns of myoelectric activity of the spiral colon were restricted to phases III and IV of the bovine migrating myoelectric complex and to propagation velocity. Significant alterations were not observed in pH or VFA concentrations in ruminal fluid, but pH decreased and VFA concentrations increased significantly in fecal specimens after the change of diet. CONCLUSIONS AND CLINICAL RELEVANCE: Although rumen fluid is of limited value for measurement of certain indicators of fermentation, fecal samples can be used for measurement of pH and VFA concentrations, which serve as indicators of fermentation patterns in the large intestine. Increased concentrations of VFA and low pH in large intestinal digesta have a minimal influence on myoelectric activity of the spiral colon. Increased luminal VFA concentrations are unlikely to play an important role in the etiopathogenesis of motility disorders of the large intestine in cattle.

Animal Feed↗

PubMed1999

Relative importance of trophic group concentrations during anaerobic degradation of volatile fatty acids.

Although obligate syntrophic reactions cannot proceed without hydrogenotrophs, it has been unclear from the literature whether potential improvements are achievable with higher concentrations of hydrogenotrophs. In this study, the relative importance of formate-/H(2)-utilizing and acetate-utilizing trophic groups in the anaerobic degradation of butyrate and propionate was assessed by adding various proportions of these enriched cultures to a mixed anaerobic seed inoculum. The improvement resulting from the additional acetate-utilizing cultures was much greater than with formate/H(2) utilizers. Furthermore, formate/H(2) utilizers did not improve propionate utilization significantly, suggesting the importance of optimum utilization of hydrogenotrophic capacity. During most of the volatile fatty acid (VFA) degradation period, the system responded with characteristic hydrogen levels to maintain the Gibbs free energy of oxidation approximately constant for both butyrate (-6 kJ) and propionate (-14 kJ). These free-energy values were independent of methanogenic activity, as well as the volume of the seed inoculum and the VFA concentrations present. By comparing the experimental results with kinetic and mass transfer models, it was postulated that the diffusional transfer of reducing equivalents was the major limiting factor for efficient VFA degradation. Therefore, for optimum utilization of the hydrogenotrophs, low acetate concentrations are vital to enable the system to respond with higher formate/H(2) levels, thus leading to improved transfer of reducing equivalents. Due to the small number of propionate utilizers (and hence their limited surface area) and low bulk liquid concentrations, the additional formate/H(2) utilizers were of minimal use for improving the degradation rate further. The butyrate degradation rates strongly correlated with the cumulative activity of hydrogenotrophs and acetotrophs over the experimental range studied, indicating the need to model obligate syntrophic reactions as a dependent function of methanogenic activity.

Acetates↗

PubMed1976

Rumen volatile fatty acids and milk composition from cows fed hay, haylage, or urea-treated corn silage.

Alfalfa-brome hay, haylage, .5% urea-treated corn silage, or .5% urea plus 1% dried whey-treated corn silage was fed as the only forage to one of four groups of 10 lactating cows per group for a lactation trial of 10 wk. Rumen samples were collected via stomach tube 3 to 4 h after the morning feeding. The pH of the rumen samples from cows fed hay was higher than for cows fed haylage, urea-treated corn silage, and urea-whey corn silage, 6.69 versus 6.36, 6.40, and 6.50. Total volatile fatty acids and propionate were highest from cows fed urea-whey corn silage and were higher on all three fermented forages than cows fed hay. Acetate/propionate ratio was highest from cows fed hay and lowest from cows fed corn silages. Butyrate was highest from cows fed haylage or hay. Milk protein composition was not affected by ration although nonprotein nitrogen of milk was highest from cows fed the urea-treated corn silages. Oleic acid and total unsaturated fatty acids were lowest in milk fat from cows fed hay while palmitic acid was highest from cows fed hay and haylage. These results suggest that type of forage fed may cause small changes in rumen fermentation and in milk composition. The importance of these changes is unknown but may affect properties of dairy products produced from this milk.

Animal Feed↗

PubMed1990

The role of intestinal volatile fatty acids in the Salmonella shedding of pigs.

Factors affecting colonization of the intestinal tract by salmonellas were studied in two pig herds. In herd H 18% of the faecal samples taken from live pigs and 30% of the colon content samples collected at slaughter contained salmonellas. In contrast, the 50 faecal samples taken from pigs of herd L were negative and only 2% of the colon contents collected at the yielded salmonellas. An antibacterial effect inhibiting salmonella multiplication was demonstrable in vitro in colon contents from pigs of herd L. No such effect was found to exist in samples taken from pigs of herd H. The antibacterial effect is due to the non-dissociated volatile fatty acid (VFA) molecules present in the colon content. As the degree of VFA dissociation depends on the pH of the environment, at lower pH values (pH 6.1 +/- 0.2) of the colon contents from herd L the ratio of non-dissociated VFA molecules is higher and the resulting antibacterial effect is stronger than in samples from herd H (pH 7.1 +/- 0.3).

Animals↗

PubMed1982

[Effect of volatile fatty acid concentration in the rumen on blood flow in the mesenteric vessels of sheep].

The studies were performed on sheep with chronic rumen fistulae and implanted electromagnetic recorders of blood flow in the anterior mesenteric vein and the anterior mesenteric artery. The animals were fed the diet consisting of sugar beet, urea and mineral salts (diet I) or sugar beet and mineral salts (diet II--nitrogen deficient). The diet caused an increase of blood flow in the mesenteric artery and the mesenteric vein: this increase reached the highest level after 2 hours since the application of the diet. There was noted a positive correlation between the changes of blood flow in the mesenteric vessels and the volatile fatty acid concentration in the rumen. The composition of the diet, differing by a protein level, did not influence significantly the differences in blood flow in the mesenteric vessels. It was suggested that an increase of blood flow in the mesenteric vessels was caused by fermentation of carbohydrates in proventriculi, and hence an increased concentration of VFA in the content attaining the duodenum, stimulation of chemoreceptors in the rumen mucosa and increased activity of cholinergic system in internal organs of the abdominal cavity.

Animal Feed↗