A cranial mesenteric vein preparation for measurement of amino acid uptake by lambs

Neutze, S. A.; Oddy, V. H.; Gooden, J. M.

doi:10.1017/s0021859600087505

Cited by 6 publications

(11 citation statements)

References 13 publications

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“…The MDV contribution is in agreement with previous studies in sheep, where BF in the cranial mesenteric vein (upstream of the junction with the ileocaecocolic vein) was recorded with transittime ultrasonic probes (Neutze et al 1994;Rémond et al 2000b) or with the microsphere technique (Barnes et al 1983). However, a greater contribution (45 % of PBF) was observed by MacRae et al (1997b) using the dye dilution technique; such a contribution was more generally attributed to the whole intestine (Neutze et al 1994;Han et al 2002).…”

Section: Daily Net Fluxessupporting

confidence: 91%

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Digestion and nutrient net fluxes across the rumen, and the mesenteric- and portal-drained viscera in sheep fed with fresh forage twice daily: net balance and dynamic aspects

et al. 2003

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Digestion and portal net flux of nutrients were studied in sheep fed twice daily with fresh orchard-grass. Digestive flows were measured in six fistulated sheep using the double-marker technique. Three sheep were fitted with catheters and blood-flow probes, allowing nutrient net flux measurements across the portal-drained viscera (PDV), the mesenteric-drained viscera (MDV) and the rumen. Total tract apparent digestion of N was similar to portal net appearance of N, calculated as the sum of free amino acids (FAA), peptide amino acids (PAA), NH 3 , and urea net fluxes. PAA accounted for 25 % of non-protein amino acid net release across the PDV. With the exception of glycine and glutamate, the small intestine was the main contributor to this PAA net release. The essential amino acid (EAA) apparent disappearance between the duodenum and the ileum was lower than the net appearance of EAA (FAA + PAA) across the MDV. The value of PDV:MDV flux of free EAA was, on average, 78 %. The rumen accounted for 30 % of the net uptake of EAA by the PDV tissues not drained by the mesenteric vein. Rumen net release of acetate, propionate, butyrate, 3-hydroxybutyrate, and lactate accounted for 70, 55, 46, 77 and 52 %, respectively, of their portal net releases. Conversely, the small intestine was a net consumer of arterial acetate and 3-hydroxybutyrate. Dynamic study of nutrient net fluxes across the PDV showed that throughout a feeding cycle, the liver faced a constant flux of amino acids (AA), whereas volatile fatty acid and NH 3 net fluxes varied in response to the meal. The present study specified, in forage-fed sheep, the partitioning of nutrient net fluxes across the PDV and the role of peptides in portal net release of AA.Amino acids: Volatile fatty acids: Absorption: Portal-drained viscera: SheepThe gastrointestinal tract, the interface between the diet and the animal, significantly modifies (quantitatively and qualitatively) the pattern of nutrients between the gut lumen and the bloodstream (Seal & Reynolds, 1993). In ruminants, although the portal-drained viscera (PDV) represent less than 10 % of body weight, and about 5 % of body protein mass, they account for one-quarter of total energy expenditure and one-third of total protein synthesis. This high metabolic activity of the gastrointestinal tract generates specific requirements in energy substrates and amino acids (AA). Thus, the portal appearance of volatile fatty acids (VFA), the main energy supply in ruminants, is lower than the amount produced in the gut, each of the individual VFA being metabolised to different extents by

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Section: Daily Net Fluxessupporting

confidence: 91%

“…At the sampling site, the cranial mesenteric vein drained about 85 % of the whole small intestine (Neutze et al 1994). With such a preparation, MDV flux does not take into account the duodenum and the distal ileum, and does not include pancreas drainage.…”

Section: Discussionmentioning

confidence: 99%

Digestion and nutrient net fluxes across the rumen, and the mesenteric- and portal-drained viscera in sheep fed with fresh forage twice daily: net balance and dynamic aspects

et al. 2003

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“…All surgical procedures were as described by Neutze et al (1994). Four lambs were prepared with catheters (polyvinylchloride, Dural Plastics and Engineering, Auburn, NSW, Australia) in the portal vein (PV), cranial mesenteric vein (CMV), femoral artery (FA) and abomasum (10 cm cranial to the pylorus).…”

Section: Feeding and Preparation Of Lambsmentioning

confidence: 99%

“…The tip of the CMV catheter was either 2 cm downstream from the junction of the CMV and the ileocaecocolic vein (' +ICCV',n = 2) or 2-6 cm upstream of this junction (' -ICCV, n = 2). These two alternative locations of CMV catheters were used to compare relative specificities of the two preparations for studying the small intestine (Neutze et al 1994). Data for -ICCV and + ICCV lambs have been combined in the present paper.…”

Section: Feeding and Preparation Of Lambsmentioning

confidence: 99%

“…The approach taken was to measure the quantities and kinetics of a radiolabelled amino acid, phenylalanine (Phe), appearing in various fractions of PV and CMV blood, following abomasal infusion as either free or protein-bound Phe. Further comparisons of the CMV and PV preparations have been presented elsewhere (Neutze et al 1994). The ultimate purpose of this work was to measure unlabelled and labelled amino acid transfers between the blood, small intestinal tissue and lumen to provide data for an experimental model of protein turnover.…”

Section: Introductionmentioning

confidence: 99%

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Uptake of labelled phenylalanine into different blood fractions in the portal vein and cranial mesenteric vein of lambs

1996

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SUMMARYFour lambs (mean 27 kg liveweight) offered 900 g/day lucerne chaff were prepared with catheters in the portal vein (PV), cranial mesenteric vein (CMV), femoral artery (FA) and abomasum. L-[2,6-3H]phenylalanine (Phe) and 14C-(Phe)casein were infused into the abomasum in separate experiments. Concurrent samples of blood from the PV, CMV and FA were prepared as four fractions: plasma, deproteinized whole blood, free Phe in deproteinized whole blood, and whole blood. Ratios of net label uptakes in different blood fractions indicated that red blood cells and blood proteins were unlikely to contribute to net Phe uptake into the PV or CMV. Small peptides may have contributed up to 20% to total appearance of Phe in the PV and CMV. However, net uptake of peptides from the lumen was probably zero. It was concluded that the Phe uptake and, by implication, total amino acid uptake from the lumen of the small intestine into the PV and CMV were as free amino acids.

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Partitioning of nutrient net fluxes across the portal-drained viscera in sheep fed twice daily: effect of dietary protein degradability

et al. 2009

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Extrusion is used to decrease leguminous seed protein degradability in the rumen in order to shift part of the dietary protein digestion towards the small intestine. The effect of such displacement of digestion site on the partitioning of nutrient net fluxes across the gastrointestinal tract was studied using four sheep fitted with catheters and blood-flow probes, allowing measurements across the rumen, the mesenteric-drained viscera (MDV) and the portal-drained viscera (PDV). Two diets containing 34 % of pea seeds were tested in a crossover design. They differed only according to pea treatment: raw pea (RP) or extruded pea (EP) diet. Rumen undegradable protein (RUP) accounted for 23 and 40 % of dietary crude protein for RP and EP diets, respectively. Across the rumen wall, ammonia net flux was lower with EP diet, whereas urea net flux was not different. Across the MDV, free amino acid (FAA) net flux was greater with EP diet, whereas peptide amino acid net flux was not different, accounting for 7 % of the non-protein amino acid net release. From RP to EP diet, PDV net flux of ammonia decreased by 23 %, whereas FAA net release increased by 21 %. The difference in dietary RUP did not affect the PDV net flux of SCFA, 3-hydroxybutyrate, lactate and glucose. In conclusion, the partial shift in pea protein digestion from the rumen to the small intestine did not affect the portal net balance of N, but decreased N loss from the rumen, and increased amino acid intestinal absorption and portal delivery.Amino acids: Peptides: Short-chain fatty acids: Portal-drained viscera Proteins consumed by ruminants are largely degraded in the rumen, up to ammonia production, in order to provide N required for microbial growth. Consequently, the outflow from the rumen of synthesized microbial protein ensures the largest contribution to amino acids (AA) entering the small intestine. Nevertheless some dietary proteins, more resistant, can escape ruminal degradation and complement the microbial AA source quantitatively and qualitatively to meet maintenance and production needs (1) . Conversely, dietary protein readily degraded in the rumen often leads to N wastage through excessive ammonia absorption from the rumen. Processing has thus been developed in order to decrease rumen degradability of feedstuff, and increase the AA delivery to the intestine. However, an increased flow of protein-N to the duodenum does not necessarily imply an increased availability of AA for anabolic purposes due to the intense metabolic activity of the splanchnic bed. More specifically, the digestive tract is one of the most important AA consumers within the body and participates to about 30 % of the whole-body protein synthesis (2) . This metabolism greatly impacts on the quantitative and qualitative net release of AA in the portal vein (3) . Yet, even if the digestive tract is metabolically very active and is withdrawing important quantities of AA, increasing dietary protein supply usually results in a greater portal absorption of AA, as far as the energy supp...

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A cranial mesenteric vein preparation for measurement of amino acid uptake by lambs

Cited by 6 publications

References 13 publications

Digestion and nutrient net fluxes across the rumen, and the mesenteric- and portal-drained viscera in sheep fed with fresh forage twice daily: net balance and dynamic aspects

Digestion and nutrient net fluxes across the rumen, and the mesenteric- and portal-drained viscera in sheep fed with fresh forage twice daily: net balance and dynamic aspects

Uptake of labelled phenylalanine into different blood fractions in the portal vein and cranial mesenteric vein of lambs

Partitioning of nutrient net fluxes across the portal-drained viscera in sheep fed twice daily: effect of dietary protein degradability

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