Net Portal-drained Viscera Flux Research Articles

PSVIII-9 Effects of different sources and levels of dietary iron and selenium on the postprandial net portal appearance of these minerals in pigs

Abstract This study compares the post-absorptive levels of iron (Fe) and selenium (Se) in pigs fed different sources and levels of these minerals. Twelve 55-kg pigs were surgically equipped with portal and carotid catheters and a portal ultrasonic flow probe and used in a cross-over design to assess the 11-hours net portal-drained viscera (PDV) flux of serum Fe and Se after ingestion of boluses containing adequate (A; 200 and 0.6 mg) or high (H; 400 and 1.2 mg) levels of these minerals from dietary inorganic (I) or organic (O) sources. Arterial Fe concentrations increased (158 %) within the first six hours post-meal and gradually decreased thereafter (P < 0.01). Values for I were greater than O until six hours post-meal (P < 0.01) and for A than H between five and eight hours post-meal (P ≤ 0.01). There was a tendency for the interaction source x level (P = 0.07) on net PDV fluxes of Fe where values for AI were greater than AO (P = 0.02). The cumulative Fe PDV appearance (% of intake) was greater for I (2.2 %) than O (-1.7 %) after four hours post-meal (P = 0.02) but this effect was no longer detected at 11 hours post-meal. Arterial Se concentrations decreased by 7 % from pre-meal values until 11 hours post-meal (P < 0.01) and this decline was more pronounced for O than I (P = 0.03). Net PDV flux of Se was positive but only during the first 90 minutes post-meal (P < 0.01). The cumulative Se PDV appearance (% of intake) was greater for I (20.0 %) than O (-3.8 %) at 45 minutes post-meal (P = 0.04) but this effect did not persist thereafter. In conclusion, net availability of Fe and Se was greater for I than O during the early post-meal period. Whether these results reflect non-absorption or greater O intestinal retention remains to be elucidated.

Impact of dietary zinc:copper ratio on the postprandial net portal appearance of these minerals in pigs1.

The present study compared the net intestinal absorption of zinc (Zn) and copper (Cu) after meals containing different dietary ratios among these trace elements. Ten 46-kg pigs were used in a cross-over design to assess the 10-h net portal-drained viscera (PDV) flux of serum Cu and Zn after ingestion of boluses containing ZnSO4 and CuSO4 in different Zn:Cu ratios (mg:mg): 120:20; 200:20; 120:8; and 200:8. Arterial Zn concentrations peaked within the first hour post-meal and responses were greater with 200 (0.9 to 1.8 mg/L) than with 120 mg (0.9 to 1.6 mg/L) of dietary Zn (dietary Zn × time, P = 0.05). Net PDV flux of Zn was greater (P = 0.02) with 200 than with 120 mg of dietary Zn and tended to be greater (P = 0.10) with 20 than with 8 mg of dietary Cu. The cumulative PDV appearance of Zn (% of dietary intake) was greater with 120 than 200 mg of dietary Zn from 8 h post-meal (P ≤ 0.04) and with 20 than 8 mg of dietary Cu from 7 h post-meal (P ≤ 0.05). At the end of the postprandial period (10 h), estimated PDV appearance of Zn was 16.0%, 18.4%, 12.0%, and 15.3% of Zn intake for 120:8, 120:20, 200:8, and 200:20 ratios, respectively. For Cu, irrespective of treatment, arterial values varied (P < 0.01) by less than 5% across postmeal times. Net PDV flux was not affected by treatments (P ≥ 0.12), but the value for ratio 120:20 was different from zero (P = 0.03). There was an interaction dietary Zn × dietary Cu on cumulative PDV appearance of Cu (% of dietary intake) at 30 min post-meal (P = 0.04) and thereafter at 3 h post-meal (P = 0.04). For the whole postprandial period (10 h), estimated PDV appearance of Cu was 61.9%, 42.1%, -17.1%, and 23.6% of Cu intake for 120:8, 120:20, 200:8, and 200:20 ratios, respectively. In conclusion, the present dietary amounts and ratios of Zn and Cu can affect the metabolic availability of both trace minerals for pigs. Ratios with 120 mg of dietary Zn maximized the postintestinal availability of both Zn and Cu.

Portal drained-viscera heat production and net flux of volatile fatty acids in Iberian pigs fed acorn

The aim of the present study was to determine the portal-drained viscera (PDV) heat production (HP) and net PDV flux of volatile fatty acids (VFA: acetic, propionic and butyric acids) in Iberian pigs (34-kg bodyweight) fed with acorn from evergreen oak, and to ascertain whether there is an effect of acorn feeding over time. In addition, potential contribution of both parameters to the energy budget of the animal was calculated. The following two sampling periods were conducted with six gilts: after 1 day (I) and after 1 week (II) of acorn feeding. Postprandial PDV HP was 29% greater (P &amp;lt; 0.01) in Sampling period II than in Sampling period I, but net PDV flux of VFA was only slightly greater (5%, P &amp;gt; 0.1). Potential proportional contribution of VFA to the whole HP was almost identical in both sampling periods (0.057, on average), representing 0.109 (on average) of the metabolisable energy requirements for maintenance. Pigs adapted for 1 week to an acorn diet had increased PDV HP without an increase in the net PDV flux of VFA, indicating that, apparently, nutrients other than VFA were responsible for the increased PDV HP.

Influence of para-aminohippuric acid analysis on net portal-drained viscera flux of nutrients in pigs

In nutrition studies, para-aminohippuric acid (PAH) is a marker frequently used to measure blood flow in pigs, which is essential for estimating portal-drained viscera (PDV) flux of nutrients. The aim of this study was to evaluate the PAH analytical method by means of qualimetric statistical procedures to estimate the matrix effect and the accuracy and limits of quantitation of the method. Net PDV flux of nutrients was determined in five multi-catheterized pigs using water, plasma or commercial serum as standard matrix. A proportional systematic error due to matrix effect was found for plasma and serum. Mean recovery was 99.4%, and intra- and inter-day precision of the method was 2.4% and 3.8% relative standard deviation, respectively. The limit of quantification was 0.22 mg PAH/l. Use of water for the PAH standard curves underestimated portal blood flow compared with PAH standards prepared with plasma or commercial serum (706, 954 and 927 ml/min; P<0.05, respectively). Consequently, PDV O2 consumption, glucose and amino acids fluxes were underestimated by 33% (P<0.001). In conclusion, our results stress the importance of using plasma from pigs not infused with PAH or alternatively commercial pig serum to prepare PAH standards to determine blood flow in pigs to avoid underestimation of blood flow.

Energy metabolism by splanchnic tissues of mature sheep fed varying levels of lucerne hay cubes

The objective of this study was to determine the pattern of energy metabolites net flux across the portal-drained viscera (PDV) and total splanchnic tissues (TSP) in mature sheep fed varying levels of lucerne hay cubes. Four Suffolk mature sheep (61.4 ± 3.6 kg BW) surgically fitted with multi-catheters were fed four levels of dry matter intake (DMI) of lucerne hay cubes ranging from 0.4- to 1.6-fold the metabolizable energy (ME) requirements for maintenance. Six sets of blood samples were simultaneously collected from arterial and venous catheters at 30-min intervals. With increasing DMI, apparent total tract digestibility increased linearly and quadratically for dry matter (P < 0.05), quadratically (P < 0.05) with a linear tendency (P < 0.1) for organic matter and tended to increase quadratically (P < 0.1) for NDF. PDV release of volatile fatty acids (VFA) and β-hydroxybutyric acid was relatively low at 0.4 M and then linearly increased (P < 0.05) with increasing DMI. Net PDV flux of non-esterified fatty acids showed curvilinear decrease from 0.4 to 1.2 M and then increased at 1.6 M. The respective proportions of each VFA appearing in the portal blood differed (P < 0.05) with DMI and this difference was more obvious from 0.4 to 0.8 M than from 0.8 to 1.6 M. Heat production, as a percentage of ME intake (MEI), decreased linearly (P < 0.05) with increasing DMI accounting for 37%, 21%, 16% and 13% for PDV and 62%, 49%, 33% and 27% for TSP at 0.4, 0.8, 1.2 and 1.6 M, respectively. As a proportion of MEI, total energy recovery including heat production, decreased linearly with increasing DMI (P < 0.05) accounting for 113%, 83%, 62% and 57% for PDV and 140%, 129%, 86% and 83% for TSP at 0.4, 0.8, 1.2 and 1.6 M, respectively. Regression analysis revealed a linear response between MEI (MJ/day per kg BW) and total energy release (MJ/day per kg BW) across the PDV and TSP, respectively. However, respective contributions of energy metabolites to net energy release across the PDV and TSP were highly variable among treatments and did not follow the same pattern of changes in DMI.

Glucagon-like peptide-2 (GLP-2) increases net amino acid utilization by the portal-drained viscera of ruminating calves

Glucagon-like peptide-2 (GLP-2) increases small intestinal mass and blood flow in ruminant calves, but its impact on nutrient metabolism across the portal-drained viscera (PDV) and liver is unknown. Eight Holstein calves with catheters in the carotid artery, mesenteric vein, portal vein and hepatic vein were paired by age and randomly assigned to control (0.5% bovine serum albumin in saline; n = 4) or GLP-2 (100 μg/kg BW per day bovine GLP-2 in bovine serum albumin; n = 4). Treatments were administered subcutaneously every 12 h for 10 days. Blood flow was measured on days 0 and 10 and included 3 periods: baseline (saline infusion), treatment (infusion of bovine serum albumin or 3.76 μg/kg BW per h GLP-2) and recovery (saline infusion). Arterial concentrations and net PDV, hepatic and total splanchnic fluxes of glucose, lactate, glutamate, glutamine, β-hydroxybutyrate and urea-N were measured on days 0 and 10. Arterial concentrations and net fluxes of all amino acids and glucose metabolism using continuous intravenous infusion of [U13-C]glucose were measured on day 10 only. A 1-h infusion of GLP-2 increased blood flow in the portal and hepatic veins when administered to calves not previously exposed to exogenous GLP-2, but after a 10-day administration of GLP-2 the blood flow response to the 1-h GLP-2 infusion was substantially attenuated. The 1-h GLP-2 infusion also did not appreciably alter nutrient fluxes on either day 0 or 10. In contrast, long-term GLP-2 administration reduced arterial concentrations and net PDV flux of many essential and non-essential amino acids. Despite the significant alterations in amino acid metabolism, glucose irreversible loss and utilization by PDV and non-PDV tissues were not affected by GLP-2. Fluxes of amino acids across the PDV were generally reduced by GLP-2, potentially by increased small intestinal epithelial growth and thus energy and amino acid requirements of this tissue. Increased PDV extraction of glutamine and alterations in PDV metabolism of arginine, ornithine and citrulline support the concept that GLP-2 influences intestine-specific amino acid metabolism. Alterations in amino acid metabolism but unchanged glucose metabolism suggests that the growth effects induced by GLP-2 in ruminants increase reliance on amino acids preferentially over glucose. Thus, GLP-2 increases PDV utilization of amino acids, but not glucose, concurrent with stimulated growth of the small intestinal epithelium in post-absorptive ruminant calves.

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.

Effects of Abomasal Vegetable Oil Infusion on Splanchnic Nutrient Metabolism in Lactating Dairy Cows

Changes in the metabolism of nutrients by the portal-drained viscera (PDV) and liver may contribute to the reduction in dry matter intake (DMI) and other production responses generally observed in lactating dairy cows fed supplemental long-chain fatty acids (LCFA). In the present study, effects of a 7-d abomasal infusion of vegetable oil on arterial concentration and splanchnic (PDV and liver) metabolism of nutrients were measured in six cows at 55 (early lactation [ELAC]) and 111 (midlactation [MLAC]) d postpartum. Cows were fed for ad libitum DMI at 8-h intervals, and blood samples for measurement of splanchnic metabolism were obtained over 8h beginning 2h before feeding at 0830h. Blood flow for the PDV and liver was increased by oil infusion and was greater in ELAC, despite similar-feed DMI during blood sampling. Increased blood flow in ELAC was associated with greater liver oxygen removal and glucose release that accompanied greater milk yield. In contrast, oil infusion had no effect on splanchnic oxygen use. Greater blood flow during oil infusion may have been due to specific effects of intestinal LCFA supply on PDV blood flow. Net PDV release and liver removal of branched-chain volatile fatty acids (VFA) and ammonia were increased by oil infusion. Net PDV release of longer-chain (4 and 5C) VFA and NEFA was greater in ELAC, but net PDV flux of other nutrients was not affected by lactation stage, possibly due to the similarity of feed DMI. Oil infusion increased arterial concentration and net PDV release and liver removal of NEFA, and it decreased net liver release and arterial concentration of glucose. Effects of oil infusion on liver glucose release were associated with decreased daily DMI. In ELAC, arterial concentration and net liver removal of NEFA were also increased, but liver release of glucose was greater than in MLAC. Oil infusion and ELAC both increased net liver removal of l-lactate. The resulting decrease in net total splanchnic release of l-lactate in ELAC reflects decreased tissue energy balance of the cows. Generally, stage of lactation and relative milk yield had greater effects on metabolism of the liver than the PDV, in which metabolism was largely dictated by DMI. In the present study, there was little evidence to suggest an effect of stage of lactation on the metabolic response of the PDV and liver to postruminal LCFA supply.

Effect of the Methodology on Circulating Peptides Determination and Consequences on Net Flux Measurements Across the Gastrointestinal Tract of Sheep

Two methodologies for the measurement of peptide amino acids (PAA) in blood were compared to evaluate their effects on the measurement of the net flux of peptides across the gastrointestinal tract of sheep. These methods consisted of a chemical deproteinization of blood samples with sulfosalicylic acid (1.6M, 0.1 ml for 1 ml of sample) or perchloric acid (1M, 1 ml for 1 ml of sample) followed by ultrafiltration through a 3,000-Da cut-off filter (SSA+UF3kD) or gel filtration through a Sephadex G-15 column (1,500-Da cut-off filter; PCA+G-15), respectively, prior to PAA analysis. Peptide concentrations as determined by amino acid concentrations before and after hydrolysis of samples were slightly greater with the SSA+UF3kD (991 µM) than with the PCA+G-15 (605 µM) methodology. However, both methodologies gave similar net portal-drained viscera flux data in sheep fed on alfalfa pellets with histidine as the only significant uptake of peptide amino acid.

Effect of resistant starch on net portal-drained viscera flux of glucose, volatile fatty acids, urea, and ammonia in growing pigs.

Net portal-drained viscera (PDV) flux of glucose, VFA, ammonia, and urea was determined in pigs fed diets with or without resistant starch. Diets consisted of 65% cornstarch (diet CS), 32.5% cornstarch and 32.5% raw potato starch (diet CPS), or 65% raw potato starch (diet PS); the remaining 35% supplied all amino acids, fat, fiber, minerals, and vitamins. The diets contained twice the maintenance requirement for energy and were fed twice daily to four barrows (initial BW 56 kg) in three periods in a crossover design. The pigs were fitted with catheters in a mesenteric vein, a mesenteric-artery, and the portal vein, and net PDV flux was calculated by multiplying portal-arterial concentration differences and corresponding portal vein flow. Net PDV flux of glucose was significantly less after feeding diets CPS and PS, and portal absorption of ileally digested glucose was 89, 66, and 41% for diets CS, CPS, and PS, respectively. Net PDV flux of VFA was lowest after feeding diet CS and three to four times higher after feeding diets CPS and PS. Net PDV flux of ammonia was highest for diet CS and almost halved after feeding diets CPS and PS. There was a small negative net PDV flux of urea for diets CS and CPS, which significantly increased after feeding diet PS. These results suggest that excretion of nitrogen is shifted from urine to feces primarily by reduction of the net PDV flux of ammonia when resistant starch is fed.

Effects of mesenteric vein L-alanine infusion on liver metabolism of organic acids by beef heifers fed diets differing in forage: concentrate ratio2

Effects of diet forage:concentrate ratio and mesenteric vein L-alanine infusion on net VFA metabolism by portal-drained viscera (PDV) and liver were determined in four multicatheterized Hereford x Angus heifers (443 kg BW) fed in equal meals every 2 h pelleted, isonitrogenous diets containing 75% alfalfa or 75% corn:soybean meal (SBM) in a balanced single reversal of diets with 6 wk for adaptation. In addition, effects of L-alanine infusion on net metabolism of individual amino acids (AA) by PDV and liver was determined when heifers were fed 75% corn:SBM. Four measurements of blood flow (p-aminohippurate dilution) and net flux of VFA and AA (venous-arterial difference times blood flow) were obtained at 30-min intervals immediately before beginning and ending a 24-h mesenteric vein infusion of L-alanine at 75 mmol/h. Net PDV absorption of acetate (P < .02), propionate (P < .02), and total VFA (P < .02) was lower when 75% corn:SBM was fed, reflecting increased carbohydrate digestion postruminally and only partially balanced by increases in net PDV glucose absorption reported previously. In addition, net PDV absorption of n-butyrate was lower when 75% alfalfa was fed. Excluding acetate, net liver removal of VFA was 83 to 108% of their net PDV release. L-Alanine infusion did not affect net PDV or liver flux of VFA but decreased net total splanchnic (PDV plus liver) release of propionate (P < .07) and n-butyrate (P < .03) and decreased (P < .10) net PDV release and liver removal of glycine. In spite of the increase in liver L-alanine removal, the ratio of glucose release to precursor removal remained remarkably constant across the liver when L-alanine was infused, emphasizing the tight control of liver glucose release and the dynamic interplay of precursor supply and removal in the maintenance of liver carbon balance.