Portal Flux Research Articles

Net Absorption and Metabolism of β-Hydroxy- β-Methyl Butyrate during Late Gestation in a Pig Model.

The leucine metabolite, β-hydroxy-β-methyl butyrate (HMB), is widely used in human nutrition and animal production as a nutritional supplement. Although the HMB usage during late gestation has been demonstrated to have a positive effect on fetal development, knowledge on net absorption and metabolism of HMB and impact of HMB on branched chain amino acids (BCAAs) metabolism is lacking. To address this, we conducted a study using pigs during the perinatal period as a model organism. Eight-second parity sows were fitted with indwelling catheters in the femoral artery and in the portal, hepatic, femoral, and mesenteric veins. Eight hourly sets of blood samples were taken starting 30 min before the morning meal on day –10 and day –3 relative to parturition. Four control (CON) sows were fed a standard lactation diet from day –15 and throughout the experiment, and 4 HMB sows were fed the control diet supplemented with 15 mg Ca(HMB)2/kg body weight mixed in one third of the morning meal from day –10 until parturition. Blood gases, plasma metabolites, milk compositions, and apparent total tract digestibility of nutrients were measured. Arterial plasma concentrations of HMB (p < 0.001), Cys (p < 0.001), and Lys (p < 0.10) were increased in HMB supplemented sows, while arterial plasma triglycerides concentration was decreased (p < 0.05). The net portal recovery of Ala and Asp were increased in HMB sows (p < 0.05). Sows fed HMB had increased hepatic vein flow and net hepatic fluxes of Met, Asn, and Gln (p < 0.05). In contrast, the femoral extraction rates of Ala and Ser were decreased by dietary HMB supplementation (p < 0.05). Dietary HMB treatment and sampling time relative to feeding had an interaction on arterial concentrations, net portal fluxes, and femoral extraction rates of BCAAs. The net portal recovery of HMB was 88%, while 14% of supplemented HMB was excreted through urine and 4% through feces. Moreover, the gastrointestinal tract metabolized 8% while the liver metabolized 12%. Finally, 26% of the daily intake of HMB was secreted via colostrum at the day of farrowing. This study demonstrated that dietary HMB supplementation increased net uptake of amino acids and increased fatty acid oxidation through improving blood flow and insulin sensitivity during the late gestation. Most importantly, oral HMB administration could maintain a stable postprandial absorption and altered metabolism in BCAAs. Net portal flux of HMB at 5.5 to 6.5 h after feeding approached zero, indicating that HMB ideally should be administrated two or three times, daily.

Net absorption and liver metabolism of amino acids and heat production of portal-drained viscera and liver in multiparous sows during transition and lactation

BackgroundDetermination of nutrient requirements in the late gestating and lactating sows is essential to optimize sow productivity. The objectives of the present study were to quantify amino acid (AA) fluxes and heat production across portal-drained viscera (PDV) and liver in multiparous sows during transition and lactation.MethodsEight second parity sows were fitted with indwelling catheters in the femoral artery and in the mesenteric, portal and hepatic veins. Eight hourly sets of blood samples were taken starting 0.5 h before feeding at − 10, − 3, + 3, and + 17 d in milk (DIM). Blood gases, plasma metabolites and apparent total tract digestibility (ATTD) of nutrients were measured.ResultsFeed intake, the ATTD of DM, energy, nitrogen, fat and crude fiber changed with DIM (P < 0.001). Except for Glu, O2, and urea, all net portal fluxes were positive, and all were affected by DIM (P < 0.05) and by sampling time (P < 0.01). Compared with pre partum levels, net portal uptake of AA was 3-63% lower at + 3 DIM but 40-100% higher at + 17 DIM. Net portal fluxes of AA peaked at 1.5 to 2.5 h after feeding except for Glu, and they were positively correlated with changes in sow feed intake across DIM. The net portal recovery was low for Met (49%), Thr (54%), and His (54%) and high for the remaining essential AA (63-69%) and none of them differed across DIM. Net hepatic uptake (i.e. hepatic oxidation) of Lys, Thr, Ile, Leu and Phe peaked at 0.5 to 2.5 h after feeding, whereas uptake of Trp, Val, and His was constant, while that of Met was close to zero.ConclusionThe net portal recovery was substantially lower for Met, Thr, and His than the remaining essential AA. Hepatic AA oxidation peaks 0.5 to 2.5 h after feeding. The heat production in PDV and liver was approximately two-fold higher at peak lactation compared to other stages. The study suggests that lysine was the limiting AA in peak lactation but not in early lactation.

Low-Protein Diets Decrease Porcine Nitrogen Excretion but with Restrictive Effects on Amino Acid Utilization.

Reducing dietary crude protein (CP) intake effectively decreases nitrogen excretion in growing-finishing pigs but at the expense of poor growth when dietary CP content is reduced by ≥3%. In this study, we investigated the main disadvantages of low-protein diets supplemented with lysine, methionine, threonine, and tryptophan in pigs. First, changes in the nitrogen balance in response to differences in dietary CP content (18%, 15%, and 13.5%) were investigated in barrows (40 kg). Then, barrows (40 kg) surgically fitted with catheters in the mesenteric vein, portal vein, hepatic vein, and carotid artery were used to investigate changes in amino acid (AA) metabolism in the portal-drained viscera and liver in response to differences in dietary CP content. The results showed that low-protein diets reduced fecal and urinary nitrogen excretion ( P < 0.05) meanwhile resulted in significant decreases in nitrogen retention ( P < 0.05). Moreover, a reduction in the dietary CP content from 18% to 13.5% resulted in decreases in the net portal fluxes of NH3, glycine, and alanine as well as in the urea production in the liver ( P < 0.05), whereas their values as a percentage of nitrogen intake did not decline ( P > 0.05). The net portal fluxes of nonessential AA (NEAA) were reduced in the low-protein diet groups ( P < 0.05), while essential AA consumption in the liver increased ( P < 0.05). Thus, low-protein diets result in reductions in both nitrogen excretion and retention, and NEAA deficiency may be a major disadvantage of low-protein diets.

Choline absorption and evaluation of bioavailability markers when supplementing choline to lactating dairy cows.

The metabolites of choline have a central role in many mammalian biological processes, and choline supplementation to the periparturient dairy cow improves hepatic lipid metabolism. However, variability in responses to choline supplementation has highlighted a lack of understanding of choline absorption in the lactating dairy cow. Our objective was to determine net choline absorption by measuring net portal fluxes of choline and choline metabolites in cows receiving either dietary supplements of rumen-protected choline (RPC) or abomasal delivery of choline (ADC). We also evaluated markers for choline bioavailability by examining relationships between net portal absorption of choline and choline metabolites in plasma and milk. Five late-lactation Holstein cows were used in a 5×5 Latin square design, with 5-d treatment periods and a 2-d interval between periods. Treatments were (1) control (0g/d of choline), (2) 12.5g/d of choline fed as RPC, (3) 25g/d of choline fed as RPC, (4) 12.5g/d of choline provided as ADC, and (5) 25g/d of choline provided as ADC. At the end of each 5-d period, milk was sampled and 9 blood samples were collected simultaneously from an artery and portal vein at 30-min intervals. Plasma, milk, and feed ingredient concentrations of acetylcholine, betaine, free choline, glycerophosphocholine, lysophosphatidylcholine, phosphatidylcholine, phosphocholine, and sphingomyelin were quantified by hydrophilic interaction liquid chromatography-tandem mass spectrometry. With an increasing dose of ADC, the net portal flux of free choline increased and regression analysis indicated 61% net absorption of the infused dose. Among the choline metabolites, only concentrations of betaine, free choline, and phosphocholine increased in both arterial plasma (3.9, 1.9, and 0.4 times, respectively) and milk (2.5, 1.4, and 1.0 times, respectively) with 25g/d of ADC relative to the control. For RPC, the net portal flux of free choline was low relative to ADC (13%), which was similar to the relative difference observed in the concentrations and yields of milk free choline and betaine (averaged 21%). When evaluating markers for choline bioavailability, betaine was the leading candidate. Betaine in plasma and milk (alone or in combination with phosphocholine) was strongly associated with net free choline portal flux (coefficient of determination ranging from 0.64 to 0.79). In summary, free choline supply to the lactating dairy cow increases only specific choline metabolites in plasma and milk, which can be potential markers for choline bioavailability.

Postprandial portal glucose and lactate fluxes, insulin production, and portal vein-drained viscera oxygen consumption in growing pigs fed a high-fiber diet supplemented with a multi-enzyme cocktail.

Information on effects of supplementing fibrous diets with exogenous enzymes on nutrient absorption and energetic demands of visceral organs is scarce. Therefore, this study investigated the effects of supplementing a high-fiber (HF) diet with a multi-enzyme cocktail (MC) on net glucose and lactate portal fluxes, insulin production, and O consumption by the portal-drained viscera (PDV) and whole animal in growing pigs. The MC supplied (analyzed values) 5,397 U of xylanase, 162 U of β-glucanase, and 2,000 U of protease per kg of diet, and guaranteed minimum activities of 1,000 U of α-amylase and 25 U of pectinase per kg of diet. Three isocaloric-nitrogenous diets based on corn and soybean meal with 0% (control) or 30% distillers' dried grains with solubles (DDGS; 1:1 corn and wheat mixture; HF) and HF supplemented with MC (HF + MC) were used. Five gilts (initial BW = 22.8 ± 1.6 kg) fitted with permanent catheters in the portal vein and carotid artery (for blood sampling), and ileal vein (to infuse para-amino hippuric acid to measure blood flow rate) were fed the 3 diets at 4% BW once daily at 0900 h for 7 d in a replicated 3 × 3 Latin square design. On d 7, pigs were placed in an open-circuit indirect calorimeter to measure whole-animal O consumption and sample blood for 7 h postprandial. Net glucose and insulin production were calculated from portal-arterial differences × portal blood flow, and PDV O consumption was calculated as arterial-portal O differences × portal blood flow. Diet had no effect on postprandial whole-animal O consumption, flow rate, and lactate flux. In addition, diet had no effect on overall mean postprandial PDV O consumption. Pigs fed control had greater ( < 0.05) portal insulin and glucose fluxes, from 90 to 300 min and net glucose flux from 90 to 240 min postprandial. However, pigs fed control and HF + MC had similar net glucose flux, which was greater ( < 0.05) than in pigs fed the HF diet. In conclusion, diets did not affect the energetic demand of the PDV but adding MC to the HF diet improved postprandial net glucose portal flux in growing pigs.

Postprandial portal fluxes of essential amino acids, volatile fatty acids, and urea-nitrogen in growing pigs fed a high-fiber diet supplemented with a multi-enzyme cocktail.

The present study investigated the effects of adding a multi-enzyme cocktail (MC) to a high-fiber diet on net portal-drained viscera (PDV) fluxes of essential AA (EAA), volatile fatty acids (VFA), and blood urea-N (BUN) in growing pigs. Five female pigs (22.8 ± 1.6 kg BW), with catheters in the portal vein, ileal vein, and carotid artery, were fed 3 isocaloric-nitrogenous diets at 4% of their BW once daily at 0900 h for 7 d in a replicated 3 × 3 Latin square design. The diets contained corn and soybean meal with 0% (control) or 30% distillers' dried grains with solubles (DDGS; HF) produced from a 1:1 mixture of wheat and corn. The third diet was supplemented with MC in addition to the 30% DDGS (HF + MC). The MC supplied (analyzed values) 5,397 U of xylanase, 162 U of β-glucanase, and 2,000 U of protease and guaranteed minimum activities of 1,000 U of α-amylase and 25 U of pectinase per kg of diet. On d 7, para-amino hippuric acid was infused into the ileal vein (to measure flow rate), and blood was sampled from the portal vein and carotid artery for 7 h after feeding to assay EAA, urea-N, and VFA. Portal absorption of nutrients was derived by multiplying the porto-arterial plasma concentration differences by portal vein blood flow. Diet had no effect on postprandial portal vein plasma flow rate and net BUN flux, but portal BUN tended to be lower ( = 0.070) and arterial BUN was lower ( 0.05) over the 7 h in pigs fed control. Postprandial portal Arg, Ile, Leu, Trp, and Val or net fluxes were lower ( 0.05) in HF-fed pigs from 30 to 240 min than control-fed pigs and MC supplementation tended (0.05 ≤ ≤ 0.10) to or improved ( 0.05) portal appearances of those AA, but not their fluxes. Control-fed pigs had higher ( 0.05) net portal fluxes of most EAA and pigs fed HF + MC had higher ( 0.05) Lys, and similar Met and Phe net portal fluxes were compared with control-fed pigs. Portal VFA was not affected by diet. However, total portal VFA flux was lower ( 0.05) in the HF-fed pigs than in the control pigs. The MC supplementation improved the total portal VFA flux, although it did not improve arterial VFA concentration relative to the HF diet. In conclusion, supplementing the HF diet with MC improved net portal appearance of some EAA and fluxes of total VFA, whereas fluxes of EAA did not change. The HF diet increased EAA demand by the PDV, but MC addition was not able to reduce this demand.

Resistant starch and arabinoxylan augment SCFA absorption, but affect postprandial glucose and insulin responses differently – CORRIGENDUM

The effects of increased colonic fermentation of dietary fibres (DF) on the net portal flux (NPF) of carbohydrate-derived metabolites (glucose, SCFA and, especially, butyrate), hormones (insulin, C-peptide, glucagon-like peptide 1 and glucose-dependent insulinotropic peptide) and NEFA were studied in a healthy catheterised pig model. A total of six pigs weighing 59 (SEM 1·6) kg were fitted with catheters in the mesenteric artery and in the portal and hepatic veins, and a flow probe around the portal vein, and included in a double 3 × 3 cross-over design with three daily feedings (at 09.00, 14.00 and 19.00 hours). Fasting and 5 h postprandial blood samples were collected after 7 d adaptation to each diet. The pigs were fed a low-DF Western-style control diet (WSD) and two high-DF diets (an arabinoxylan-enriched diet (AXD) and a resistant starch-enriched diet (RSD)). The NPF of insulin was lower (P= 0·04) in AXD-fed pigs (4·6 nmol/h) than in RSD-fed pigs (10·5 nmol/h), despite the lowest NPF of glucose being observed in RSD-fed pigs (203 mmol/h, P= 0·02). The NPF of total SCFA, acetate, propionate and butyrate were high, intermediate and low (P< 0·01) in AXD-, RSD- and WSD-fed pigs, respectively, with the largest relative increase being observed for butyrate in response to arabinoxylan supplementation. In conclusion, the RSD and AXD had different effects on the NPF of insulin and glucose, suggesting different impacts of arabinoxylan and resistant starch on human health.

Resistant starch and arabinoxylan augment SCFA absorption, but affect postprandial glucose and insulin responses differently

The effects of increased colonic fermentation of dietary fibres (DF) on the net portal flux (NPF) of carbohydrate-derived metabolites (glucose, SCFA and, especially, butyrate), hormones (insulin, C-peptide, glucagon-like peptide 1 and glucose-dependent insulinotropic peptide) and NEFA were studied in a healthy catheterised pig model. A total of six pigs weighing 59 (SEM 1·6) kg were fitted with catheters in the mesenteric artery and in the portal and hepatic veins, and a flow probe around the portal vein, and included in a double 3 × 3 cross-over design with three daily feedings (at 09.00, 14.00 and 19.00 hours). Fasting and 5 h postprandial blood samples were collected after 7 d adaptation to each diet. The pigs were fed a low-DF Western-style control diet (WSD) and two high-DF diets (an arabinoxylan-enriched diet (AXD) and a resistant starch-enriched diet (RSD)). The NPF of insulin was lower (P= 0·04) in AXD-fed pigs (4·6 nmol/h) than in RSD-fed pigs (10·5 nmol/h), despite the lowest NPF of glucose being observed in RSD-fed pigs (203 mmol/h, P= 0·02). The NPF of total SCFA, acetate, propionate and butyrate were high, intermediate and low (P< 0·01) in AXD-, RSD- and WSD-fed pigs, respectively, with the largest relative increase being observed for butyrate in response to arabinoxylan supplementation. In conclusion, the RSD and AXD had different effects on the NPF of insulin and glucose, suggesting different impacts of arabinoxylan and resistant starch on human health.

Point of Care Perioperative Coagulation Management in Liver Transplantation and Complete Portal Vein Thrombosis

Liver transplantation (LT) is a serious hemostatic challenge in patients with portal vein thrombosis (PVT). Advances in monitoring systems have improved surgery in this setting. We report the successful application of a point-of-care (POC) rotational viscoelastic thromboelastometry-guided (TEM) testing system (ROTEM) which allowed management of coagulation during LT in a 64-year-old cirrhotic patient with a model for end-stage liver disease (MELD) score of 16. Perioperatively, the patient showed complete PVT, hepatomegaly, splenomegaly, recanalization of the umbilical vein, and portosystemic shunt. Macroscopic liver and spleen adherences with collateral circulation were evident. Coagulation factors and fibrinolysis were assessed preoperatively and at graft reperfusion to evaluate the need of hemostatic therapy. Based on ROTEM findings, the patient received 16 g of human fibrinogen concentrate, half preoperatively (with prothrombin complex concentrate 2000 IU, tranexamic acid 1 g, and platelets 2 IU), and two doses of 4 g before and after graft reperfusion; we achieved normalization of all monitored parameters. No ischemia-reperfusion syndrome was present. Postoperatively portal vein flux at Color-Doppler ultrasonography was normal. After a 3-day ICU stay, the patient was moved to the Department of Surgery and discharged on day 14. The postoperative course was uneventful and did not require any further haemostatic therapy.

Effects of β-hydroxy β-methyl butyrate supplementation to sows in late gestation on absorption and hepatic metabolism of glucose and amino acids during transition

A multicatheter sow model was established to study the effects of dietary β-hydroxy β-methyl butyrate (HMB) supplementation on net portal flux (NPF) and net hepatic flux (NHF) of HMB, glucose, and the AA Ala, Gly, Ile, Leu, Phe, Tyr, and Val. Eight second parity sows were fitted with permanent indwelling catheters in an artery and in the portal, hepatic, and mesenteric veins. Eight hourly sets of blood samples were taken starting 30 min before the morning meal on day -3 and day 3 relative to parturition. Four control (CON) sows were fed a standard lactation diet from day -15 and throughout the experiment, and 4 HMB sows were fed the control diet supplemented with 15 mg Ca(HMB)(2)/kg BW mixed in one third of the morning meal from day -10 until parturition. Net portal flux of HMB was affected by treatment (Trt; P < 0.01) and peaked in the HMB sows at 6.9 mmol/h 30 min after the morning meal and then decreased towards preprandial level (0.0 mmol/h) 3.5 h after the meal, revealing that dietary HMB was rapidly absorbed from the intestine. The NHF of HMB tended to be affected by Trt (P = 0.06) showing a small hepatic uptake of HMB (1.1 mmol/h) in HMB sows. Net portal flux of glucose and all measured AA, except for Gly and Tyr, were affected the Trt × time interaction (P < 0.01). The NPF was positive for all nutrients, indicating absorption from the intestine to the portal blood. Absorption rates appeared to be more stable for HMB than for CON sows. Net hepatic flux of glucose was not affected by Trt. It was negative from 1.5 to 2.5 h after the meal, indicating hepatic uptake, but positive before and after, indicating net hepatic release of glucose. Net hepatic fluxes of AA were negative and were not affected by Trt (P > 0.10), except for Phe (P < 0.05). In conclusion, HMB reduced the variation in net portal flux of glucose and AA during 8 h of blood sampling and suggest that the improved sow productivity observed by others may be due to a more uniform nutrient absorption pattern into portal blood.

Effect of time duration of ruminal urea infusions on ruminal ammonia concentrations and portal-drained visceral extraction of arterial urea-N in lactating Holstein cows

The effects of a 6 versus 24h ruminal urea infusion in lactating dairy cows fed a basal diet deficient in N on ruminal ammonia concentration, arterial urea-N concentration, net portal-drained viscera (PDV) urea-N flux, arterial urea-N extraction across the PDV, and renal urea-N kinetics were investigated. Three Danish Holstein cows fitted with ruminal cannulas and permanent indwelling catheters in major splanchnic blood vessels were randomly allocated to a 3 × 3 Latin square design with 21-d periods. Treatments were ventral ruminal infusion of water for 24h (water INF), 24-h infusion of 15g of urea/kg of dry matter intake (DMI; 24-h INF), and 6-h infusion of 15g of urea/kg of DMI (6-h INF). The 6-h INF was initiated 0.5h after the afternoon feeding, and ran until 2230h. Eight sample sets of arterial, portal, and hepatic blood, ruminal fluid, and urine were obtained at 0.5h before the morning feeding and 0.5, 1.5, 2.5, 3.5, 4.5, 5.5, and 6.5h after feeding (i.e., 9 to 15.5h after the 6h infusion was terminated). A substantial decrease in DMI for 6-h INF compared with 24-h INF and water INF was observed, and it has to be recognized that DMI may have confounding effects. However, the experimental setting plan was met (i.e., to cause changes in the daily pattern of ruminal ammonia and blood urea-N concentrations). The arterial urea-N concentration for 24-h INF and 6-h INF were greater than the arterial urea-N concentration with water INF throughout the sampling window. However, the arterial urea-N concentration for 6-h INF decreased steadily with sampling time reflecting a carryover effect from the ruminal urea infusion. The ruminal ammonia concentration and net portal flux of ammonia for 6-h INF were not different from water INF; hence, no carryover effect on ruminal ammonia concentration was observed. The portal flux of urea-N was not affected by treatment (i.e., even the combination of low ruminal ammonia and high arterial urea-N concentration with 6-h INF was not used by the cow to increase the uptake of urea-N across the PDV). Arterial urea-N extraction across the PDV was increased with water INF especially from 0.5 to 3.5h postprandial relative to the urea infusion treatments, reflecting increased epithelial permeability for urea-N. This indicates that daily ruminal peak of ammonia or blood urea-N concentrations overruled potential signals from low ruminal ammonia concentration observed during the sampling window. In conclusion, dairy cows appear unable to increase transport of urea-N from blood to gut in periods with low ruminal ammonia concentrations, even in a situation with infrequent N supply and apparent carryover effects on blood urea-N. It is speculated that mechanisms responsible for downregulation of epithelial urea-N transport based on daily maximum concentrations of ammonia in the rumen or urea-N in the blood suppresses any short-term signal from low ruminal ammonia during periods with low ruminal N supply.

Metabolic effects of feeding high doses of propanol and propylacetate to lactating Holstein cows

Three lactating Holstein cows implanted with ruminal cannulas and permanent indwelling catheters in major splanchnic blood vessels were used to investigate alcohol metabolism and metabolic effects of feeding high doses of propanol and propylacetate. Cows were fed three diets control (basal ration; C), propanol (C plus 50g propanol/kg DM; P), and propylacetate (C plus 50g propanol/kg DM and 15g propylacetate/kg DM; PPA) in a 3×3 Latin square design with 14d period. Daily rations were fed in three equally sized portions at 8 hour intervals and 8 hourly sets of ruminal fluid, arterial, hepatic portal vein, and hepatic vein samples were collected at day 14 of each period. Milk fat yield decreased for P and PPA compared with C, however, dry matter intake and milk yield were not affected by treatment. Portal uptake of propanol accounted for 48 to 61% of ingested propanol and differed among all 3 treatments C≪PPA<P. A number of metabolic variables responded to P and PPA treatments including decreased proportion of ruminal acetate to total VFA; increased proportions of ruminal propionate, isovalerate, valerate, and caproate; increased arterial glucose concentration; decreased arterial BHBA and acetate concentrations; increased net portal flux of propanol; increased net hepatic flux of glucose; and increased propanol, isopropanol, and caproate uptake by the liver. Contrary to our hypothesis that propylacetate supplementation would exacerbate the metabolic effects of propanol, we observed for a number of variables that treatment differences between C and P were partly reversed in PPA. This applied to ruminal propanol and propylacetate; arterial concentrations of ethanol, propanol, isopropanol, and isobutyrate; net portal flux of ethanol, propanol, and isopropanol; net hepatic flux of BHBA, propanol, isopropanol, and isobutyrate; net splanchnic flux of propionate; hepatic extraction of ethanol and portal recovery of dietary ethanol. The overall metabolic effect of feeding large doses of propanol was a glucogenic response presumably driven by hepatic metabolism of propanol to propionate and the increased glucogenic status was followed by a decreased milk fat yield. Inclusion of propylacetate in the diet apparently activated increased metabolism of propanol in either the rumen or ruminal epithelium and reduced the metabolic impact of the combined presence of propanol and propylacetate.

Effects of ruminal ammonia and butyrate concentrations on reticuloruminal epithelial blood flow and volatile fatty acid absorption kinetics under washed reticulorumen conditions in lactating dairy cows

The effect of reticuloruminal epithelial blood flow on the absorption of propionate as a volatile fatty acid (VFA) marker in 8 lactating Holstein cows was studied under washed rumen conditions. The cows were surgically prepared with ruminal cannulas and permanent catheters in an artery and mesenteric, right ruminal, and hepatic portal veins. The experiment was designed with 2 groups of cows: 4 cows adapted to high crude protein (CP) and 4 to low CP. All cows were subjected to 3 buffers: butyric, ammonia, and control in a randomized replicated 3 × 3 incomplete Latin square design. The buffers (30kg) were maintained in a temporarily emptied and washed rumen for 40min. The initial concentration of VFA was 84.2mmol/L. Butyrate was increased from 4 to 36mmol/L in butyric buffer by replacement of acetate, and ammonia (NH3) was increased from 2.5 to 22.5mmol/L in ammonia buffer by replacement of NaCl. Increasing amounts of deuterium oxide (D2O) were added to the buffers as the order of buffer sequence increased (6, 12, and 18g of D2O). Ruminal clearance of D2O was used to estimate epithelial blood flow. To increase accuracy of the epithelial blood flow estimates, data of ruminal liquid marker (Cr-EDTA), and initial and final buffer volumes were fitted to a dynamic simulation model. The model was used to estimate ruminal liquid passages, residual liquid, and water influx (saliva and epithelia water) for each combination of cow and buffer (n=24). Epithelial blood flow increased 49±11% for butyric buffer compared with control. The ruminal disappearance of propionate (marker VFA) was affected by buffer and followed the same pattern as for epithelial blood flow. The correlation between ruminal disappearance of propionate and epithelial blood flow (r=0.56) indicates that the removal of propionate can be limited by epithelial blood flow. The ruminal disappearance of propionate increased 30±12% for the butyric compared with ammonia buffer and 12.5±8% when compared with control. The net portal flux of propionate increased 32±6% in butyric compared with control. In conclusion, rumen epithelial blood flow is positively correlated with ruminal disappearance of propionate and affects the kinetics of ruminal VFA absorption.

Relation of net portal flux of nitrogen compounds with dietary characteristics in ruminants: A meta-analysis approach

Decrease of N intake (NI) with the aim of increasing efficiency of N utilization and decreasing the negative environmental effects of animal production requires assessment of the forms in which N is absorbed. A meta-analysis was conducted on 68 publications (90 experiments and 215 treatments) to study the effect of NI on net portal appearance (NPA) of nitrogenous nutrients [amino acids (AA), ammonia, and urea] in ruminants. In addition, the effect of several dietary energy and protein factors on this relationship was investigated. These factors were: dry matter intake; proportion of concentrate; diet concentrations and intakes of nonfiber carbohydrates and neutral detergent fiber (NDF); diet concentrations of total digestible nutrients (TDN) and crude protein; rumen-degradable protein and rumen-undegradable protein, as percent dry matter or percent crude protein. The effect of species and physiological stage was also investigated. Within-experiment analyses revealed that the NPA of AA-N and ammonia-N increased linearly, whereas the NPA of urea-N decreased (or recycling of urea-N increased) linearly with NI. Besides NI, many significant covariates could be introduced in each NPA model. However, only TDN and neutral detergent fiber intake (NDFi) were common significant covariates of NI in each NPA model. In this database, ruminants converted 60% of incremental NI into NPA of AA-N with no species effect on that slope. However, at similar NI, TDN, and NDFi, sheep absorbed more AA-N than did cattle and dairy cows. On the other hand, species tended to affect the slope of the relationship between NPA of ammonia-N and NI, which varied from 0.19 for the sheep to 0.38 for dairy cows. On average, the equivalent of 11% of incremental NI was recycled as urea-N to the gut through the portal-drained viscera, which excludes salivary contribution, and no species difference was detected. Overall, at similar TDN and NDFi, sheep and cattle increased their NPA of AA-N relative to NI increment by a similar magnitude. The higher absorption of AA-N observed in sheep compared with cattle, at similar NI, TDN, and NDFi, might result from lower losses of AA through portal-drained viscera metabolism.

Metabolic effects of feeding ethanol or propanol to postpartum transition Holstein cows

Eight lactating Holstein cows implanted with a ruminal cannula and permanent indwelling catheters in major splanchnic blood vessels were used to investigate metabolism of propanol and ethanol in the postpartum transition period. Cows were randomly allocated to 1 of 4 treatments in a randomized design with a 2 by 2 factorial arrangement of treatments. Factor 1 was 2.6g of calcium carbonate/kg of dry matter (DM) versus 1.5g of 2-hydroxy-4-(methylthio)-butanoic acid isopropyl ester/kg of DM. Factor 2 was supplementation with 14g of propanol/kg of DM (propanol treatment; PT) versus 14g of ethanol/kg of DM (ethanol treatment; ET). Only factor 2 data are presented in the present paper. Treatments were administered in silage-based total mixed rations and cows were fed the experimental total mixed ration from the day of parturition. Daily rations were fed in 3 equally sized portions at 8-h intervals. Eight hourly sets of ruminal fluid, arterial, and hepatic portal and hepatic vein samples were collected at day −15±5, 4, 15, and 29 relative to parturition. Dry matter intake and milk yield increased with days in milk (DIM), but were not affected by treatment. From prepartum to 4 DIM ruminal concentrations of propanol and ethanol increased with PT and ET, respectively. Postpartum, alcohol intake increased 49% in PT and 34% in ET from 4 to 29 d in milk, respectively. Ruminal concentrations of the alcohols remained unaffected by DIM. Treatments did not affect total ruminal volatile fatty acid concentrations, but the molar proportion of acetate increased in ET and the molar proportion of propionate increased in PT compared with the contrasting treatment. Propanol treatment decreased milk fat content at 15 to 29 DIM compared with ET. The net portal release of propanol and ethanol increased with increasing ruminal concentration of the respective alcohol. The portal release of alcohol accounted for 43 to 85% of ingested propanol and 36 to 57% of ingested ethanol. Hepatic uptake of propanol and ethanol equaled the net portal flux and no effect of treatment was detected for net splanchnic release of propanol and ethanol. In conclusion, ruminal metabolism is a major component of alcohol metabolism in dairy cows. The postpartum transition dairy cow has sufficient metabolic capacity to cope with high dietary concentrations of primary alcohols even when alcohol intake is abruptly increased at the day of calving. Alcohol intake affects milk fat content and alcohol composition of silage might be important to improve predictions of milk composition.

Net nutrient flux in visceral tissues of goats fed diets based on maize or wheat

The objective of this study was to investigate the effects of dietary starch sources on the net portaldrained viscera (PDV) flux of metabolites in goats fed diets based on maize and wheat, respectively. Eight 8-month-old Liuyang Black wether goats, with catheters surgically in the mesenteric vein, the portal vein and the carotid artery, were assigned to one of two diets for determination of net nutrient flux across the PDV. There were no differences (P>0.05) in plasma concentrations of glucose and ammonia-nitrogen (N) in the portal vein and carotid artery, and net PDV flux of glucose and urea-N between maize diet and wheat diet. The portal plasma urea-N concentration and net PDV flux of ammonia-N of goats fed maize diet were lower (P<0.05) than those of goats fed wheat diet. Plasma concentrations in the portal vein and carotid artery and net PDV flux of certain essential amino acids of goats fed maize diet were higher (P<0.05) than those of goats fed wheat diet. The results of this study suggested that dietary starch source could affect N absorption and utilization in goats.

Complications of Congenital Portosystemic Shunts in Children: Therapeutic Options and Outcomes

Congenital portosystemic shunts are rare vascular malformations that lead to severe complications. Their management is controversial. The aim of this study was to propose a clear definition of the risks and management of congenital portosystemic shunts in children according to our experience and a review of the literature. Twenty-two children with a complicated congenital portosystemic shunt were studied in our institution. When necessary, management included portal pressure measurement and portal vein angiography during an occlusion test and closure of the shunt by surgical and/or endovascular methods. Five neonates with intrahepatic shunts presented with cholestasis that resolved spontaneously, and 17 older children presented with liver tumors (13) and/or hepatopulmonary syndrome (2), pulmonary artery hypertension (3), portosystemic encephalopathy (3), heart failure (1), and glomerulonephritis (1). The portosystemic shunt was extrahepatic (11) or intrahepatic (6). Portosystemic shunts were closed by endovascular methods in 5 children and surgically in 10, 4 of whom had portal pressure during occlusion above 35 mmHg and extremely hypoplastic or undetectable portal veins requiring banding of the fistula before closure. Shunt closure resulted in restoration of intrahepatic portal flow in all, with complete or partial regression of benign liver masses, and regression or stabilization of pulmonary, cardiac, neurological, and renal complications. Congenital portosystemic shunt carries risks of severe complications in children. Closure of a shunt persisting after age 2 years should be considered preventively. Intrahepatic portal flux restoration can be expected, even when intrahepatic portal veins are extremely hypoplastic or undetectable.

Effects of particle size and dry matter content of a total mixed ration on intraruminal equilibration and net portal flux of volatile fatty acids in lactating dairy cows

Effects of physical changes in consistency of ruminal contents on intraruminal equilibration and net portal fluxes of volatile fatty acids (VFA) in dairy cows were studied. Four Danish Holstein cows (121±17 d in milk, 591±24kg of body weight, mean ± SD) surgically fitted with a ruminal cannula and permanent indwelling catheters in the major splanchnic blood vessels were used. The experimental design was a 4 × 4 Latin square with a 2 × 2 factorial design of treatments. Treatments differed in forage (grass hay) particle size (FPS; 3.0 and 30mm) and feed dry matter (DM) content of the total mixed ration (44.3 and 53.8%). The feed DM did not affect chewing time, ruminal variables, or net portal flux of VFA. However, decreasing the FPS decreased the overall chewing and rumination times by 151±55 and 135±29 min/d, respectively. No effect of the reduced chewing time was observed on ruminal pH or milk fat percentage. Cows maintained average ventral ruminal pH of 6.65±0.02, medial ruminal pH of 5.95±0.04, and milk fat of 4.42±0.12% with chewing time of 28.0±2.1 min/kg of DM when fed short particles. The medial ruminal pool of wet particulate matter was decreased by 10.53±2.29kg with decreasing FPS, thereby decreasing the medial pool of total VFA, acetate, propionate, butyrate, isobutyrate, and isovalerate by 1,143±333, 720±205, 228±69, 140±51, 8.0±2.3, and 25.2±5.6 mmol, respectively. Ventral pool variables were not affected by treatments. Relatively large intraruminal differences of VFA concentrations and pH between the ventral and medial pools were observed, VFA concentrations being largest and pH being the lowest medially. This indicates that the ruminal mat acts as a barrier retaining VFA. The effects of reduced FPS were limited to the VFA pool sizes of the mat, leaving ruminal pH, ruminal VFA concentrations, and net portal flux of VFA unaffected. Consequently reduced FPS affected the intraruminal equilibration of VFA between mat and ventral rumen with an estimated turnover rate of isobutyrate increasing from 50±3%/h with long particles to 61±3%/h with short particles. The estimated ruminal fluid flow and therefore intraruminal VFA transport between medial and ventral phase was not affected by the FPS. In conclusion, the ruminal mat pool of VFA was proportional to the size of the mat and the only detected effects of decreasing FPS were decreasing the mat size and an increasing turnover of the mat pool of VFA.

Effect of viscosity and fermentability of purified non‐starch polysaccharides (NSP) on kinetics of net glucose and short chain fatty acids (SCFA) portal flux and insulin secretion in porto‐arterial catheterized pigs

The NSP may lower glycemic and insulin responses, but specific contributions of viscosity and fermentability are unknown. Thus, the effects of NSP on net nutrient portal flux and insulin responses were studied in 4 pigs with 2 catheters [portal vein, carotid artery] and 1 blood flow probe [portal vein]. Semi‐purified [cornstarch, casein] diets supplemented with 5% purified NSP sources were fed in a 2 (low, high viscous; V) × 2 (low, high fermentable; F) factorial arrangement using: low V, low F cellulose (CEL1), high V, low F carboxymethylcellulose (CMC), low V, high F cellulose (CEL2), and high V, high F oat β‐glucan (HVG). Blood was sampled for 12 h postprandially and net nutrient portal flux and insulin secretion were calculated from plasma portal‐arterial differences × flow. Blood flow, portal and carotid glucose and net glucose portal flux peaked at 45 min after feeding (P&lt;0.001) and were not affected by NSP. However, fermentable NSP (CEL2 and HVG) increased (P&lt;0.05) net glucose portal flux 46% over 12 h postprandially. Insulin secretion was 44% lower (P&lt;0.05) for viscous than non viscous NSP. The CEL2 and HVG diets increased (P&lt;0.05) net SCFA portal flux for propionate and butyrate 48%, indicating increased colonic fermentation. In conclusion, viscosity of NSP reduced insulin secretion and fermentable NSP increased net portal flux of glucose, propionate, and butyrate.Grant Funding Source: ALMA, Danisco, and Alberta Pulse Growers

Effect of abomasal glucose infusion on splanchnic amino acid metabolism in periparturient dairy cows

Six Holstein cows fitted with ruminal cannulas and permanent indwelling catheters in the portal vein, hepatic vein, mesenteric vein, and an artery were used to study the effects of abomasal glucose infusion on splanchnic AA metabolism. The experimental design was a split plot, with cow as the whole plot, treatment as the whole-plot factor and days in milk (DIM) as the subplot factor. Cows were assigned to 1 of 2 treatments: control or infusion of 1,500 g/d of glucose into the abomasum from the day of calving to 29 DIM. Cows were sampled prepartum and at 4, 15, and 29 DIM. Postpartum dry matter intake increased at a lower rate with infusion compared with the control. Arterial concentrations of all essential AA (EAA) were lower with infusion compared with the control. Net portal fluxes of His, Ile, Leu, Lys, Met, Phe, Thr, Val, Ala, Pro, Ser, and Tyr were lower with infusion compared with the control and the net portal fluxes of these AA showed positive correlations with dry matter intake, whereas the net portal fluxes of Asp, Glu, and Gln were unaffected by treatment. Net hepatic fluxes of EAA were not affected by treatment but increased as lactation progressed with both treatments. On a net basis, all EAA were removed by the liver prepartum and at 4 DIM, whereas Met, Phe, and Thr were the only EAA being removed at 29 DIM. Except for Ala, AA removed by the liver might be used primarily for noncatabolic processes, as exemplified by the 16% of hepatic Gly uptake accounted for as urinary hippurate. The measured hepatic uptake of glucogenic precursors (glucogenic AA, volatile fatty acids, lactate, and glycerol) accounted for 50 to 90% of the hepatic release of glucose. The hepatic urea output accounted for more than 100% of the hepatic ureagenic precursor uptake, indicating that the glucogenic precursors unaccounted for are nonnitrogen-containing compounds. In conclusion, an increased exogenous glucose supply to the small intestine did not seem to affect the amount of EAA and non-EAA available for peripheral tissues in early lactation, and the study did not indicate an AA-sparing effect of small intestinal glucose absorption. In periparturient dairy cows, hepatic catabolism of AA was not driven by the increased whole-body demand for glucose, and Ala was the only AA that contributed substantially to hepatic gluconeogenesis. In very early lactation, the supply of EAA might be of greater concern than the supply of glucogenic substrates.