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1.
Caerulein administered by slow intravenous infusion at increasing dosage rates (0.1, 1.0, 5.0 and 10.0 ng/kg/min ± 30 min) stimulated pancreatic juice production in sheep as well as the protein content, the amylolytic, the lipolytic and proteolytic activities of pancreatic juice samples collected at 30 min intervals.
A long lasting (300 min) infusion of a high dose of Caerulein by subcutaneous route elicited stimulatory effects with reduced intensities, slower onsets but more sustained durations than those produced by the same dose level administered intravenously.  相似文献   

2.
The diversion of pancreatic juice and bile stimulates pancreatic exocrine secretion but the mechanism behind this process is still not clear. The present study investigates the influence of long lasting (10 h) bile diversion or pancreatic juice and bile diversion on the pancreatic secretion in conscious pigs. The experiments were performed on 4 weaned piglets, which had a catheter inserted to the accessory pancreatic duct and bile duct and two cannulas to the duodenum. The depletion of bile alone or both bile and pancreatic juice (PJ) resulted in an increased preprandial pancreatic juice outflow, as compared to controls. Bile diversion increased the pancreatic response to feeding. PJ volume, protein outflow, and trypsin activity values were significantly higher in bile diverted pigs than in control pigs during the prandial and postprandial periods. While in pancreatic juice and bile diverted piglets the PJ protein outflow and trypsin activity slightly increased in response to feeding, their values were lower than those of the control piglets. In conclusion, both pancreatic juice and bile present in the small intestine play an important role in the regulation of the pancreatic juice secretion.  相似文献   

3.
Five crossbred steers (348 +/- 12 kg) fitted with a pancreatic pouch draining the main pancreatic duct and duodenal re-entrant and abomasal infusion cannulas were used in a 5 x 5 Latin square design to determine the influence of postruminal carbohydrate source and level on pancreatic exocrine secretion in beef steers. Abomasal infusion treatments (250 mL infused/h) were water (control), 20 g/h glucose, 40 g/h glucose, 20 g/h starch hydrolysate (SH), and 40 g/h SH. Infusion periods were 8 d with 3 to 4 d of rest between periods. Pancreatic juice was collected for 6 h on d 8 of each collection period. Every 30 min a 10% subsample was composited and frozen and the remainder was infused into the duodenum via the reentrant cannula. Abomasal infusion of glucose or SH increased (P < 0.10) total secretion of pancreatic juice and decreased (P < 0.10) secretion of alpha-amylase activity. Abomasal carbohydrate infusion did not influence total secretion of protein, trypsin activity, or chymotrypsin activity. This experiment indicates that increasing postruminal glucose or SH decreases pancreatic alpha-amylase secretion.  相似文献   

4.
瘤胃内丁酸钠灌注对山羊瘤胃发酵类型的影响   总被引：1，自引：0，他引：1  
本试验通过对青年山羊进行瘤胃丁酸钠灌注研究其对瘤胃发酵类型的影响。6只安装有瘤胃瘘管的山羊分为试验组(n=3)和对照组(n=3),每天饲喂精料2次,并自由采食羊草。试验组每日早晨喂食1 h后开始每天按体重灌注丁酸钠(0.3 g/kg),对照组灌注等量蒸馏水,持续14 d。于灌注期的第1,5,10和14天分别于灌注前1.5 h,灌注后2 h、4 h采集瘤胃液,以气相色谱测定挥发性脂肪酸(VFA)的浓度。结果显示:灌注前、后,试验组瘤胃内乙酸、丙酸摩尔百分比和总挥发性脂肪酸浓度无显著变化;两组之间差异不显著。但试验组丁酸摩尔百分比在灌注2 h后显著上升(P<0.01),4 h后呈下降趋势,次日采食前恢复至正常生理范围。对照组与试验组pH在各采样时间点间基本无显著差异。试验表明青年山羊瘤胃灌注该剂量丁酸钠不引起瘤胃发酵类型的改变。  相似文献   

5.
A novel macro in vitro system was used to test the theory that rumen proportions of acetate, propionate and butyrate are not representative of their respective net production rates. Whole rumen content (10–16 kg) from two cows was mixed with a bicarbonate buffer and incubated separately in two 40‐l in vitro vessels for 3 h. A total of six experimental periods were used. In this study, a total of six cows were used and fed 1/8 of the daily ration by hand every 3 h. To obtain differences in rumen volatile fatty acids (VFA) composition, 1 l of acetate (416 mm ), propionate (108 mm ), butyrate (79 mm ), lactic acid (300 mm ) or nothing was infused during 24 h into the rumen before collection of representative samples of rumen contents. Infusions of acids were then continued during the in vitro incubations in exact proportion to the digesta removed from the rumen. In Periods 1 and 2, the cows were alternatively infused with acetate or nothing. In Periods 3 and 4, the infusions consisted of propionate or butyrate and in Periods 5 and 6 of lactate or nothing. Nine liquid samples were obtained between 3 and 180 min after the start of incubation and analysed for concentrations of VFA. Changes in proportions of individual VFA were estimated by linear regression. No differences in VFA proportions were observed in the absence of infusion (p > 0.5) over time, but when individual VFA were infused, their respective proportions increased. This was interpreted as the result of a decreased in vitro fermentation rate of digesta substrates compared with that in the rumen. Lactate infusion increased butyrate proportion in vitro. It is concluded that this study could not provide any evidence that ruminal VFA proportions are unrepresentative of the proportions of net production.  相似文献   

6.
Our objective was to evaluate the effect of postruminal protein infusion on pancreatic exocrine secretions. One Holstein, two crossbred, and five Angus steers (305 +/- 5 kg) with pancreatic pouch-duodenal reentrant cannulas and abomasal infusion catheters were used in a replicated 4 x 4 Latin square. All steers were abomasally infused with 1,050 g/d of raw cornstarch with treatments of 0, 60, 120, or 180 g/d of sodium casein suspended in water to yield 6,000 g/d of infusate daily. Steers were limit-fed (1.5 x NEm; 12 equal portions daily) a 90% corn silage, 10% supplement diet formulated to contain 12.5% CP. Periods consisted of 3 d of adaptation to infusion, 7 d of full infusion, 1 d of collection, and 7 d of rest. Pancreatic juice was collected in 30-min fractions continuously for 6 h. Total juice secreted and the pH of individual fractions were recorded, a 10% subsample was retained to form a composite sample, and remaining fluid was returned to the duodenum. Juice composite samples were stored (-30 degrees C) until analyzed for total protein and activities of alpha-amylase, trypsin, and chymotrypsin. Casein infusion linearly increased alpha-amylase concentration (182 to 271 units/mL; P < 0.02; 17.5 to 24.6 units/mg of protein; P < 0.03) and secretion rate (26,847 to 41,894 units/h; P < 0.01). Total juice secretion (155 g/h), pH of pancreatic juice (8.13), secretion rate of protein (1,536 mg/h), and concentration of protein (10.2 mg/mL) in pancreatic secretions were not affected (P > 0.05) by casein infusion. Similarly, casein infusion did not change 0.05) trypsin and chymotrypsin concentrations (1,379 and 349 units/L or 0.134 and 0.033 units/mg of protein, respectively) or secretion rates (206 and 52 units/h, respectively). Abomasal infusion of protein with starch stimulated a greater pancreatic secretion of alpha-amylase activity into the intestine than infusion of starch alone.  相似文献   

7.
Effects of short-chain fatty acids on pancreatic exocrine secretion were studied under anesthesia in calves within 2 weeks of age (2-wks calves) given only whole milk and milk replacement and in which rumen fermentation has not begun yet, and in calves at 13 weeks of age (13-wks calves) weaned at 40 days of age and in which rumen fermentation has already begun. Basal rate of juice flow and protein concentration and amylase activity in pancreatic juice under basal condition were significantly lower in the 2-wks calves than those in the 13-wks calves. Intravenous administrations of acetate, propionate and butyrate stimulated pancreatic juice secretion and protein and amylase output in both groups of calves. Those responses were increased with increasing carbon number in the molecule of fatty acids. Although the response of amylase output (/kg of body weight) in the 2-wks calves was significantly less than that in the 13-wks calves, the response of juice flow and protein output (/kg of body weight) in the 2-wks calves were equivalent to or greater than those in the 13-wks calves. These results indicate that the characteristic of pancreas, being stimulated by short-chain fatty acids, in calves and probably in other ruminants is not generated on the process of postnatal development, but has been already acquired before rumen fermentation begins.  相似文献   

8.
Three sheep fitted with a ruminal cannula and an abomasal catheter were used to study water kinetics and absorption of VFA infused continuously into the rumen. The effects of changing VFA concentrations in the rumen by shifting VFA infusion rates were investigated in an experiment with a 3 x 3 Latin square design. On experimental days, the animals received the basal infusion rate of VFA (271 mmol/h) during the first 2 h. Each animal then received VFA at a different rate (135, 394, or 511 mmol/h) for the next 7.5 h. Using soluble markers (polyethylene glycol and Cr-EDTA), ruminal volume, liquid outflow, apparent water absorption, and VFA absorption rates were estimated. There were no significant effects of VFA infusion rate on ruminal volume and water kinetics. As the VFA infusion rate was increased, VFA concentration and osmolality in the rumen were increased and pH was decreased. There was a biphasic response of liquid outflow to changes in the total VFA concentration in the rumen, as both variables increased together up to a total VFA concentration of 80.1 mM, whereas, beyond that concentration, liquid outflow remained stable at an average rate of 407 mL/h. There were significant linear (P = 0.003) and quadratic (P = 0.001) effects of VFA infusion rate on the VFA absorption rate, confirming that VFA absorption in the rumen is mainly a concentration-dependent process. The proportion of total VFA supplied that was absorbed in the rumen was 0.845 (0.822, 0.877, and 0.910 for acetate, propionate, and butyrate, respectively). The molar proportions of acetate, propionate, and butyrate absorbed were affected by the level of VFA infusion in the rumen, indicating that this level affected to a different extent the absorption of the different acids.  相似文献   

9.
The objective of this study was to determine the influence of the level of feed intake and a 2-d feed restriction period on the postweaning adaptation of pancreatic exocrine secretions. At 33 d of age, 18 piglets fitted with 2 permanent catheters (for pancreatic juice collection and reintroduction) were weaned and allocated to 1 of the following 2 dietary treatments for 5 d: restricted feed allocation (restricted) or gradually increasing feed allocation (control). Pancreatic juice was collected daily during both basal and prandial periods. The basal period was defined as the period from 1400 to 1700 h (i.e., 5 to 8 h after the morning meal), whereas the prandial period was defined as the period from 30 min before to 60 min after the morning meal (given at 0900). Digestive enzyme activities and antibacterial activity were determined. Pancreatic protein secretion was 44% less (P < 0.05) in restricted piglets than in control piglets during the basal period. Trypsin secretion was affected by feed-restriction of piglets. The meal did not affect protein and trypsin secretions in restricted piglets, whereas at d 3 postweaning, protein and trypsin secretions and trypsin specific activity in control piglets were 9-, 105-, and 25-fold greater (P < 0.001) during the first 30 min after the meal than before the meal. Lipase and amylase secretions were not affected by variations in feed intake. The secretion of antibacterial activity in restricted piglets was greater (P < 0.05) than that of control piglets only at d 5. The extended feed restriction period increased the basal secretion of antibacterial activity (P = 0.09) and postprandial secretion of amylase (P = 0.05). In conclusion, a low level of feed intake during the early postweaning period decreased pancreatic protein and trypsin secretions, whereas a 2-d feed restriction period enhanced secretions of amylase and antibacterial activity. In addition, our results indicate that during periods of dietary adaptation, such as at weaning, measurements of enzyme activities in the tissue do not accurately reflect the enzyme secretion.  相似文献   

10.
In six normal‐weight and six obese cats, the metabolic effect of propionate absorbed from the colon was assessed. Two colonic infusions were tested in a crossover design with intervals of 4 weeks. The test solution contained 4 mmol sodium propionate per kg ideal body weight in a 0.2% NaCl solution. Normal saline was given as control solution. Solutions were infused into the hindgut over 30 min. Blood samples were obtained prior to and at various time points after starting the infusion. As body condition did not affect evaluated parameters, all data were pooled. Plasma glucose concentrations showed differences neither over time nor during or after infusion with propionate or control. Plasma amino acid concentrations rose over time (p < 0.001), but were similar for both infusions. Plasma propionylcarnitine rose markedly towards the end of the propionate infusion and decreased afterwards (p < 0.001), whereas 3‐hydroxy‐3‐methylglutarylcarnitine was lower 30 (p = 0.005) and 60 min (p = 0.032) after ending propionate infusions and acetylcarnitine tended to fall at the same time points (p = 0.079; p = 0.080), suggesting inhibition of gluconeogenesis from pyruvate and amino acids, but initiation of propionate‐induced gluconeogenesis. In conclusion, propionate absorbed from the colon is hypothesized to act as gluconeogenic substrate, regardless of the cat’s body condition.  相似文献   

11.
Four yearling goats (31.2 ± 2.5 kg), surgically fitted with common bile duct reentrant and duodenal catheter, were used in two 4 × 4 Latin square design experiments to investigate the effects of duodenal infusion of phenylalanine for different times on pancreatic exocrine secretion (PES). In experiment 1 (the long‐term experiment), goats were duodenally infused with 0, 2, 4 or 8 g/day phenylalanine for 14 day. Pancreatic juice and jugular blood samples were collected over 1‐h intervals for 6 h daily from day 11 to day 14 to encompass a 24‐h day. In experiment 2 (the short‐term experiment), goats were infused with phenylalanine for 10 h continuously at the same infusion rate as experiment 1 after feed deprivation for 24 h repeated every 10 day. Pancreatic juice and blood samples were collected at 0, 1, 2, 4, 6, 8 and 10 h of infusion. The volume and pH of pancreatic juice were measured, and a 5% subsample was composited and frozen until analysis of enzyme activities. Plasma was frozen until analysis of insulin and cholecystokinin (CCK). In experiment 1, pancreatic juice, α‐amylase secretion and plasma CCK concentration responded quadratically (p < 0.05), with the top value observed at the 2 g/day phenylalanine. Trypsin secretion had a quadratic response (p < 0.05), with secretion increasing up to 4 g/day phenylalanine and decreasing thereafter. Phenylalanine linearly decreased pancreatic protein and lipase secretion (p < 0.05). The results of correlation analysis showed significant correlations (p < 0.05) between plasma CCK concentration and secretion of α‐amylase and trypsin. However, the short‐term phenylalanine infusion did not influence (p > 0.05) pancreatic juice, protein, α‐amylase, lipase, trypsin secretion and plasma CCK concentration. These results indicate PES of ruminants is stimulated by phenylalanine and is potentially mediated by CCK in the long‐term duodenal infusion treatment, but is not influenced by phenylalanine in the short‐term duodenal infusion treatment.  相似文献   

12.
Eight Angus steers (290 +/- 8 kg), surgically prepared with pancreatic pouch-duodenal reentrant cannulas and abomasal infusion catheters were used in a replicated 4 x 4 Latin square experiment to investigate the effects of abomasal infusion of starch hydrolyzate (SH) and/or casein on pancreatic exocrine secretion and plasma concentration of hormones. Steers were fed a basal diet of alfalfa (1.2 x NEm) in 12 equal portions daily. Abomasal infusion treatments (6-L total volume infused per day) were water (control), SH [2.7 g/(kg BW x d)], casein [0.6 g/(kg BW x d)], and SH + casein. Periods were 3 d for adaptation and 8 d of full infusion. Pancreatic juice and jugular blood samples were collected over 30-min intervals for 6 h on d 11. Weight and pH of pancreatic samples were measured, and a 10% subsample was composited and frozen until analysis of total protein and pancreatic enzyme activities. The remaining sample was returned to the duodenum. Plasma was harvested and frozen until analyzed. Pancreatic juice (67 mL/h) and protein (1.8 g/h) secretion rates were not affected by nutrient infusion. There were SH x casein interactions for all pancreatic enzyme secretions (U/h; alpha-amylase, P < 0.03; trypsin, P < 0.08; and chymotrypsin, P < 0.03) and plasma insulin concentration (P < 0.10). Secretion of pancreatic enzymes was increased by SH (trypsin) and casein (alpha-amylase, trypsin, and chymotrypsin) but not when SH + casein were infused together. Glucose (P < 0.10) and cholecystokinin octapeptide concentrations (CCK-8; P < 0.05) were increased by SH, but glucagon was decreased (P < 0.10). Casein decreased (P < 0.10) plasma CCK-8 concentrations. These data indicate that positive effects of postruminal casein on enzyme secretion were inhibited by SH, emphasizing the complexity of the regulatory mechanisms involved in dietary adaptation of pancreatic exocrine secretion. Changes in hormone concentration may not relate directly to changes in enzyme secretion.  相似文献   

13.
Four goats (30.1 ± 1.3 kg) with common bile duct re‐entrant catheter and duodenal catheter were used to evaluate the effects of duodenal leucine infusion on pancreatic exocrine secretion and plasma parameters with two 4 × 4 Latin square design experiments. In the long‐term infusion experiment, goats were fed twice daily [700 g/day, dry matter (DM) basis] at 8:00 and 18:00 hours and were duodenally infused with 0, 3, 6, 9 g/day leucine for 14 days. Pancreatic juice and jugular blood samples were collected over 1‐h intervals for 6 h daily from d 11 to 14 days to encompass a 24‐h day. In the short‐term experiment, goats were infused leucine for 10 h continuously at the same infusion rate with Experiment 1 after feed deprivation for 24 h repeated every 10 days. Pancreatic juice and blood samples were collected at 0, 1, 2, 4, 6, 8 and 10 h of infusion. The results showed that the long‐term leucine infusion did not affect pancreatic juice secretion, protein output, trypsin and lipase secretion and plasma insulin concentration, but linearly increased α‐amylase secretion. No changes in pancreatic protein and lipase secretion were observed in the short‐term infusion. Pancreatic juice and α‐amylase secretion responded quadratically, with the greatest values observed in the 3 and 6 g/day leucine respectively. Trypsin secretion linearly decreased, while plasma insulin concentration increased linearly with increased leucine infusion. The results demonstrated that duodenal leucine infusion dose and time dependently regulated pancreatic enzyme secretion not associated with the change in plasma insulin concentration.  相似文献   

14.
Before and after infusion of propionate and butyrate the concentrations of volatile fatty acids (VFA) in the blood of heifers were determined by gas chromatography, in order to indicate activity and regulation of the carbohydrate metabolism. 14 heifers were loaded after food deprivation with intravenous infusions of propionate and butyrate. Concentrations of acetate, propionate, isobutyrate, butyrate, and valerate were measured in blood samples which were taken later on. The methods used for clearance and extraction as well as for gas chromatographic analysis are described. Retention times and blood concentrations are given for each VFA. Concentrations prior to infusion were for: acetate 10.14 +/- 2.51 microliters/ml; propionate 0.42 +/- 0.35 microliters/ml; iso-butyrate 3.72 +/- 1.37 microliters/ml; butyrate 3.44 +/- 0.68 microliters/ml blood plasma. The concentrations of the infused VFA showed a 100 (butyrate) to 1000 (propionate) fold increase followed by a subsequent decrease to the initial values. These investigations on the profile of VFA elucidated criteria of the energy metabolism.  相似文献   

15.
To investigate the metabolism of 1,2-propanediol (PPD) in lactating cows independently of normal rumen microbial metabolism, three ruminally cannulated lactating Holstein cows were subjected to three experimental infusion protocols under washed reticulo-ruminal conditions in a Latin square design. Reticulo-ruminal absorption rates were maintained for 420 min by continuous intraruminal infusion of VFA and PPD. With the control treatment, 1,246 +/- 39 mmol/ h of acetate and 213 +/- 5 mmol/h of butyrate were absorbed from the reticulorumen. With the propionate treatment, 1,148 +/- 39 mmo/h of acetate, 730 +/- 23 mmol/h of propionate and 196 +/- 5 mmol/h of butyrate were absorbed from the reticulorumen. With PPD treatment, 1,264 +/- 39 mmol/h of acetate, 220 +/- 5 mmol/h of butyrate and 721 +/- 17 mmol/h of PPD were absorbed from the reticulorumen. Glucose irreversible loss rate (ILR), as well as the relative enrichment of plasma lactate and alanine, were determined by primed continuous infusion of [U-13C]glucose in a jugular vein. Treatments did not affect (P > 0.10) the plasma concentrations of glucose (4.2 +/- 0.1 mmoVL), alanine (0.14 +/- 0.01 mmol/L), or insulin (80 +/- 25 pmol/L). The plasma concentration of lactate was higher (P < 0.05) with both propionate (0.84 +/- 5 mmol/L) and PPD treatment (0.81 +/- 5 mmol/ L) compared with the control treatment (0.29 +/- 0.5 mmol/L). The plasma concentration of pyruvate was higher (P < 0.05) with the propionate treatment (0.09 +/- 0.01 mmol/L) compared with the control treatment (0.03 +/- 0.01 mmol/L). The plasma concentration of 3-hydroxybutyrate was lower (P < 0.05) with the propionate treatment (0.15 +/- 0.03 mmol/L) compared with the control treatment (0.40 +/- 0.03). With the PPD treatment, the plasma concentrations of pyruvate and 3-hydroxybutyrate were in between the other treatments and tended (P < 0.10) to be different from both. The plasma concentration of PPD increased throughout the infusion period with the PPD treatment and reached a concentration of 4.9 +/- 0.6 mmol/L at 420 min. The ILR of glucose was not affected (P > 0.10) by treatments (441 +/- 35 mmol/h). The relative 13C enrichment of plasma lactate compared with that of glucose decreased (P < 0.05) with the PPD treatment compared with the control treatment (44 to 21 +/- 3%). It was concluded that PPD has a low rate of metabolism in cows without a normal functioning rumen, although about 10% of the absorbed PPD was metabolized into lactate.  相似文献   

16.
Infusion of the vasopressin analogue DDAVP into five normal dogs at doses of 0.1-2.0 micrograms DDAVP per kg body weight induced dose-dependent increases in the plasma content of coagulation factor VIII and von Willebrand factor. Plasma concentrations of von Willebrand factor (determined antigenically as factor VIII-related antigen and functionally as coagglutinin cofactor activity) and coagulation factor VIII were measured immediately before and at 10, 30, and 120 min after 10-min intravenous infusions of DDAVP. The greatest increases in coagulation factor VIII were produced with the 2.0 micrograms/kg dose. Ten minutes after infusion the mean increase in coagulation factor VIII was 32 units/dl (concentrations of all indices were reported relative to concentrations in a standard canine plasma pool, arbitrarily assigned a concentration of 100 units/dl) and this increase did not change significantly throughout the duration of the experiment. At 10 min post-infusion, the mean factor VIII-related antigen concentration increased 81 units/dl (dose = 2.0 micrograms/kg) and did not change significantly for the duration of the experiment. The maximum mean increase in coagglutinin cofactor activity, 141 units/dl, occurred 10 min after infusion (dose = 1.0 microgram/kg). Coagglutinin cofactor activity decreased significantly from peak activity by 120 min post-infusion.  相似文献   

17.
An experiment was performed using lambs fitted with chronic indwelling catheters in appropriate blood vessels for portal-drained visceral (PDV) flux measurements. The objective of the experiment was to evaluate PDV nutrient flux in alfalfa-fed and intragastrically infused lambs and to evaluate the effects of amount of energy and N infused on PDV nutrient metabolism. Lambs were fed alfalfa or infused with 1.64 and 10.9; 1.82 and 12.3; or 2.37 and 15.0 Mcal GE and g N/d, respectively. Arterial concentrations and PDV fluxes of glucose, L-lactate, acetate and portal blood flow were not different (P greater than .10) between alfalfa-fed and infused lambs. Net flux of alpha-amino N, ammonia N and branched-chain VFA were lower (P less than .05) and net flux of propionate, butyrate and total VFA were higher for intragastric infusion vs alfalfa. No consistent differences in PDV fluxes were noted among the three levels of energy and N infused, although the energy and N levels tested were near maintenance requirements. Nitrogen retention increased as level of energy and N infusion increased. Approximately 47, 70 and 22% of ruminally infused acetate, propionate and butyrate, respectively, were found on a net basis in portal blood as VFA. Measurements of net nutrient utilization by the PDV that eliminate the influence of ruminal fermentation are possible. How the changes in PDV tissues due to intragastric infusion influence these estimates is unknown.  相似文献   

18.
Caerulein administered to anaesthetized pigs by slow i.v. infusions at doses of 0.5, 1.0 and 2.0 ng kg–1min–1 for 30 min, stimulated pancreatic juice production, increased the protein content of the juice and enhanced its amylolytic, lipolytic and proteolytic activities. In a single experiment, an i.v. infusion of secretin (0.001 U kg–1min–1) lasting through the whole experimental time, provoked potentiation of the caerulein stimulatory effects on pancreatic juice production, protein content and amylolytic activity.  相似文献   

19.
The net portal appearance of volatile fatty acids (VFA) was investigated in four ruminally fistulated and multicatheterized sheep. During the experiments, the sheep were fed once every hour for 14 h and intraruminally infused with mixtures of VFA for the 12 h commencing 2 h after the initiation of the hourly feeding protocol. Paired arterial and portal blood samples were obtained hourly during the last 6 h of the experiments. In the control treatment (1), only water was infused intraruminally. In Treatments 2 through 4, the intraruminal infusion rates of propionate (40 mmol/h), isobutyrate (5 mmol/h), and valerate (5 mmol/h) were unchanged. In Treatments 2, 3, and 4, the acetate infusion rate was 100, 60, and 20 mmol/h, respectively, and the butyrate infusion rate was 10, 30, and 50 mmol/h, respectively. Thus, the infusion rate of VFA carbon was constant across Treatments 2 through 4. Portal recovery estimated from the increased net portal appearance in Treatments 2 through 4 compared to the control treatment was 85% for propionate and 60% for isobutyrate, and these recoveries were unaffected by treatment. The portal recovery of butyrate increased (from 21 to 32%) with increasing infusion rate of butyrate and decreasing infusion rate of acetate, as did the portal recovery of valerate (from 14 to 31%). The portal recovery of acetate was 55%, when measured as net portal appearance. Thus, it seems that the capacity for beta-oxidation in ruminal epithelium is limited, which would explain the increasing portal recovery of butyrate and valerate with increasing infusion rate of butyrate, when infusion rate of VFA carbon is unchanged.  相似文献   

20.
Four steers fitted with a ruminal cannula and chronic indwelling catheters in the mesenteric artery, mesenteric vein, hepatic portal vein, hepatic vein, and the right ruminal vein were used to study VFA absorption from bicarbonate buffers incubated in the washed reticulorumen, and metabolism by splanchnic tissues. Portal and hepatic vein blood flows were determined by infusion of p-aminohippurate into the mesenteric vein. The steers were subjected to four experimental treatments in a Latin square design. The treatments were Control (ruminal bicarbonate buffer with [mmol/kg]: acetate = 72; propionate = 30; isobutyrate = 2.1; butyrate = 12; valerate = 1.2; caproate = 0; and heptanoate = 0); Val (same as control except for valerate = 8 mmol/kg); Cap (same as control except for caproate = 3.5 mmol/kg); and Hep (same as control except for heptanoate = 3 mmol/kg). All buffers were incubated for 90 min in the rumen, and ruminal VFA absorption rates were maintained by continuous intraruminal infusion of VFA. The arterial concentrations of valerate and heptanoate showed a small increase (< or = 1 micromol/L; P < 0.05) with inclusion of the respective acid in the ruminal buffer, but no change (P = 0.57) in arterial concentration of caproate was detected. Valerate increased (P < 0.05) the net portal flux of butyrate and valerate, as well as the net splanchnic flux of propionate, butyrate, and valerate. With Cap and Hep, the net portal flux of caproate and heptanoate accounted for 54 and 45% of ruminal disappearance rates, respectively, indicating that these acids were extensively metabolized by the ruminal epithelium. Caproate was ketogenic both in the ruminal epithelium and in the liver, and Cap increased (P < 0.05) the arterial concentration, ruminal vein minus arterial concentration difference, net hepatic flux, and net splanchnic flux of 3-hydroxybutyrate. The net hepatic flux of glucose decreased (P = 0.02) with Cap and Hep compared with Control and Val; however, no effect (P = 0.14) on the net splanchnic flux of glucose could be detected. We conclude that the strong biological activity of valerate, caproate, and heptanoate warrant increased emphasis on monitoring their ruminal presence and their potential systemic effects on ruminant metabolism.  相似文献   

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