Portal blood flow and net absorption of ammonia-nitrogen, urea-nitrogen, and glucose in nonlactating Holstein cows

A Mix of Dietary Fibres Changes Interorgan Nutrients Exchanges and Muscle-Adipose Energy Handling in Overfed Mini-Pigs

This study evaluates the capacity of a bread enriched with fermentable dietary fibres to modulate the metabolism and nutrients handling between tissues, gut and peripheral, in a context of overfeeding. Net fluxes of glucose, lactate, urea, short chain fatty acids (SCFA), and amino acids were recorded in control and overfed female mini-pigs supplemented or not with fibre-enriched bread. SCFA in fecal water and gene expressions, but not protein levels or metabolic fluxes, were measured in muscle, adipose tissue, and intestine. Fibre supplementation increased the potential for fatty acid oxidation and mitochondrial activity in muscle (acox, ucp2, sdha and cpt1-m, p < 0.05) as well as main regulatory transcription factors of metabolic activity such as pparα, pgc-1α and nrf2. All these features were associated with a reduced muscle fibre cross sectional area, resembling to controls (i.e., lean phenotype). SCFA may be direct inducers of these cross-talk alterations, as their feces content (+52%, p = 0.05) was increased in fibre-supplemented mini-pigs. The SCFA effects could be mediated at the gut level by an increased production of incretins (increased gcg mRNA, p < 0.05) and an up-regulation of SCFA receptors (increased gpr41 mRNA, p < 0.01). Hence, consumption of supplemented bread with fermentable fibres can be an appropriate strategy to activate muscle energy catabolism and limit the establishment of an obese phenotype.

Productive and physiological responses of lactating dairy cows supplemented with phytogenic feed ingredients

This experiment compared milk production, milk composition, and physiological responses in lactating dairy cows supplemented with or without a mixture of condensed tannins, encapsulated cinnamaldehyde, curcumin, capsaicin, and piperine. Thirty-six lactating, multiparous, pregnant ¾ Holstein × ¼ Gir cows were maintained in a single drylot pen with ad libitum access to water and a total-mixed ration and were milked twice daily (d -7 to 84). On d 0, cows were ranked by days in milk (86 ± 3 d), milk yield (27.8 ± 1.0 kg), body weight (BW; 584 ± 10 kg), and body condition score (BCS; 3.04 ± 0.06) and assigned to receive (SUPP; n = 18) or not (CON; n = 18) 30 g/cow daily (as-fed basis) of Actifor Pro (Delacon Biotechnik GmbH; Steyregg, Austria). From d 0 to 84, SUPP cows individually received (as-fed basis) 15 g of Actifor Pro mixed with 85 g of finely ground corn through self-locking headgates before each milking of the day. Each CON cow concurrently received 85 g (as-fed basis) of finely ground corn through self-locking headgates. Throughout the experimental period (d -7 to 84), cows from both treatments were administered 500 mg of sometribove zinc at 14-d intervals and were monitored daily for morbidity, including clinical mastitis. Individual milk production was recorded daily, whereas milk samples were collected weekly for analysis of milk composition. Cow BW, BCS, and blood samples were also collected weekly. Cows receiving SUPP gained more BCS (P = 0.05) and had greater (P = 0.04) milk yield during the experiment compared with CON cows (0.22 vs. 0.07 of BCS, SEM = 0.05; 29.5 vs. 27.9 kg/d, SEM = 0.5). Milk composition did not differ (P ≥ 0.15) between SUPP and CON cows; hence, SUPP cows also had greater (P ≤ 0.02) production of fat-corrected and energy-corrected milk. Incidence of clinical mastitis did not differ (P ≥ 0.49) between SUPP and CON cows. No treatment differences were also detected (P ≥ 0.21) for serum concentrations of glucose and serum urea N. Mean serum haptoglobin concentration during the experiment was greater (P = 0.05) in CON vs. SUPP cows. Cows receiving SUPP had less (P ≤ 0.04) serum cortisol concentrations on d 21 and 42, and greater (P ≤ 0.05) serum concentrations of insulin-like growth factor-I on d 7, 35, and 63 compared with CON cows (treatment × day interactions; P ≤ 0.02). Collectively, supplementing phytogenic feed ingredients improved nutritional status and milk production of lactating ¾ Holstein × ¼ Gir cows.

Profound Changes in Net Energy and Nitrogen Metabolites Fluxes within the Splanchnic Area during Overfeeding of Yucatan Mini Pigs That Remain Euglycemic

A dysregulation of nutrient exchange between tissues (gut, liver, muscles, adipose) occurs during overnutrition and could induce obesity and metabolic diseases. We aimed to evaluate how, in overfed mini pigs, nutrients use and partition were regulated in the gut and liver. Net nutrients fluxes were assessed in the fed (PP) and post absorptive (PA) states at 1, 14 and 60 days of adaptation to overfeeding in five adult Yucatan female multicatheterized minipigs. Pigs PA glycaemia and PP-induced hyperglycemia remained unchanged over the experimental period, suggesting that the management of the excess of energy intake allowed the maintenance of glucose levels. This was associated with (1) an increased PA plasma insulin, (2) an increased gut lactate production (increased lactate net release +89%, 1 h PP, D1 vs. D60) probably from an increased glucose oxidation, (3) a shift in utilization of gluconeogenic precursor (lactate, propionate) in the liver, and (4) a reduced gut utilization of nitrogen moieties for energy purposes (glutamine), a nitrogen sparing effect at the whole body level (decreased plasma urea in PA (−24% D1 vs. D60) and PP states) and a specific increased level of AA involved in lipids handling and bile recycling in the gut lumen (taurine and glycine).

Oxygen uptake and net flux of metabolites by splanchnic tissues of sheep in response to short-term mesenteric infusion of nitrogenous compounds

This study was conducted in an attempt to quantify the impact of N load on splanchnic tissues metabolism of sheep. The trial was conducted with four male sheep (45 ± 2.5 kg body weight (BW)) surgically implanted with chronic indwelling catheters into the portal, hepatic and mesenteric veins. Blood flow and metabolic flux through portal-drained viscera (PDV), liver and total splanchnic tissues (ST) were measured daily following a 4 × 4 Latin Square experimental design, where sheep were continually infused into the mesenteric vein with a physiological saline (0.15 m NaCl) solution during 90 min followed by the infusion, during more 120 min, of either solution: physiological saline (control), 0.250 mNH₄ HCO₃ , 0.250 m L-alanine or 0.125 m L-arginine, all of them infused at a rate of 1.5 ml/min to provide 375 μmol N/min. During the treatment infusion period, the net removal of ammonia N and the net production of urea N by liver were higher (p < .05) in NH₄ HCO₃ infused sheep_. Based on oxygen consumption, and on average of all treatments, the heat produced by liver and ST was on average 6 and 14 kcal/kg BW representing 16% and 38% of the metabolizable energy intake respectively. Linear relationships between variables indicated that gluconeogenesis and ureagenesis occurred concomitantly and both processes accounted for approximately 50% of total liver energy expenditure, two-thirds of it associated with gluconeogenesis. The results of the current study did not present clear evidence of the expected energy costs associated with ammonia N, alanine or arginine metabolism by liver. However, they indicated that gluconeogenesis is on average a more energy expensive process than ureagenesis.

Yeast Culture and Vitamin E Supplementation Alleviates Heat Stress in Dairy Goats

This study was conducted to determine and compare the effects of yeast yeast culture (YC) and vitamin E (VE) supplementation on endotoxin absorption and antioxidant status in lactating dairy goats suffering from heat stress (HS). Three first lactation Saanen dairy goats (body weight 30±1.5 kg) were surgically fitted with indwelling catheters in the portal vein, mesenteric vein and carotid artery, and were randomly assigned to a 3×3 Latin square design. Dietary treatments were the basal diet, and the basal diet supplemented with either 100 IU VE or 30 g YC. Goats were kept in temperature and humidity-controlled room at 35°C from 8:00 to 20:00 and at 24°C from 20:00 till the next morning at 8:00. The relative humidity was kept at 55%. HS increased dairy goats' rectum temperature and respiration frequency (p<0.01). HS reduced plasma flux rate of milk goats (p<0.01), but the plasma flux rate increased when the animal was under the conditions of the thermo-neutral period (p<0.01). The VE supplementation lowered dairy goats' rectum temperature during thermo-neutral period (p<0.01). Meanwhile, no significant differences were observed between the control and YC treatment in rectum temperature and respiration frequency (p>0.05). Dietary supplementation of VE and YC reduced heat stressed dairy goats' endotoxin concentration of the carotid artery and portal vein (p<0.01). However, the endotoxin concentration of the YC treatment was higher than that of the VE treatment (p<0.01). Both VE and YC supplementation decreased heat stressed dairy goats' absorption of endotoxin in portal vein (p<0.01). The endotoxin absorption of YC treatment was higher than the VE treatment (p<0.01). The addition of VE and YC decreased dairy goats' superoxide dismutase (SOD) concentration during HS and the whole experiment period (p<0.01). The addition of VE lowered SOD concentration during thermo-neutral period (p<0.01). Likewise, the addition of VE and YC lowered dairy goats' malonaldehyde (MDA) concentration during HS and the whole experimental period, and the MDA concentration in the VE treatment was lower than the YC treatment (p<0.05). The addition of VE decreased MDA concentration during thermo-neutral period. On the contrast, the addition of VE increased dairy goats total antioxidant potential (TAP) concentration during HS, thermo-neutral and the whole experimental period (p<0.01). The addition of YC increased TAP concentration only during HS period (p<0.01). It is concluded that both VE and YC are useful in alleviating HS of dairy goats by weakening endotoxin absorption and promoting antioxidant capacity. Compared with YC, VE is much more powerful in easing dairy goats HS.

Amino acid metabolism in the portal-drained viscera of young pigs: effects of dietary supplementation with chitosan and pea hull

Recent studies indicate extensive catabolism of amino acids (AA) by the portal-drained viscera (PDV) of pigs and humans. Because of ethical concerns over invasive surgical procedures on infants or adults, in vivo investigations are often performed with the pig which is both an agriculturally important livestock species and a widely used animal model for nutritional and physiological studies in humans. Here, we described a new technique for implanting chronic catheters into the portal vein, ileal mesenteric vein, and carotid artery to study AA metabolism in the PDV of young pigs. This method allowed for the reduction of surgery time by 1 h and measurements of the entry of dietary AA into the portal circulation. Using such an approach, we found that dietary supplementation with 100 mg/kg chitosan (a prebiotic and a polysaccharide not digested by animal cells) reduced oxygen consumption, as well as the net absorption of dietary AA into the portal vein, thereby enhancing their bioavailability for extraintestinal tissues. In contrast, opposite results were obtained with dietary supplementation of 12% pea-hull (containing 95% of fermentable nonstarch polysaccharide). Thus, this improved technique is useful to quantify in vivo absorption and metabolism of dietary AA in young pigs.

Intrauterine bacterial inoculation and level of dietary methionine alter amino acid metabolism in nulliparous yearling ewes1

Using an intrauterine bacterial inoculation method, our objective was to determine the effects of acute sepsis and level of dietary metabolizable Met (MM) on splanchnic metabolism of AA in ewes. Twenty-four nulliparous yearling Rambouillet-cross ewes (initial BW = 65.1 +/- 0.6 kg), surgically fitted with chronic-indwelling catheters in hepatic and portal veins, a mesenteric vein and artery, and the uterine lumen, were assigned to a 2 x 2 factorial arrangement of treatments. Factors were intrauterine bacterial inoculation (noninoculated vs. inoculated) and level of MM [low (2.28 g/d) vs. high (3.91 g/d)]. Beginning 12 h before sampling, inoculated and noninoculated ewes received 10-mL intrauterine infusions of Escherichia coli (9.69 x 10(11) cfu) + Arcanobacterium pyogenes (2.76 x 10(12) cfu) and of sterile saline, respectively. Uterine infection was induced in ewes that received intrauterine bacterial inoculations, but not in ewes infused with sterile saline. Bacterial inoculation resulted in increased hepatic release and plasma concentrations of aromatic AA used for acute-phase protein synthesis, increased hepatic removal and decreased plasma concentrations of AA used for glutathione synthesis, and decreased plasma concentrations of some gluconeogenic and acetogenic AA used for glucose recycling and anaerobic energy production, respectively (P < 0.05). In ewes fed high-MM diets, compared with low-MM diets, a consistent net hepatic uptake of Phe occurred throughout the sampling period, more Asp was released from the portal-drained viscera, and hepatic vein glucose concentrations were greater (P < 0.05). We conclude that Met seemed to be limiting in low-MM ewes, and as such, would continue to be limiting during sepsis. However, additional MM, in excess of the dietary requirement, would not necessarily result in a benefit to ewes experiencing acute sepsis.

Radiofrequency ablation (RFA): development of a flow model for bovine livers for extensive bench testing

PURPOSE

To develop a flow model for bovine livers for extensive bench testing of technical improvements or procedure-related developments of radiofrequency ablation excluding animal experiments.

METHODS

The perfusion of bovine livers directly from the slaughterhouse was simulated in a liver perfusion tank developed for the experimental work. The liver perfusion medium used was a Tyrode solution prepared in accordance with physiologic criteria (as for liver transplants) which was oxygenated by an oxygenator and heated to 36.5 degrees C. Portal vein circulation was regulated via a flow- and pressure-controlled pump and arterial circulation using a dialysis machine. Flow rate and pressure were adjusted as for the physiology of a human liver converted to bovine liver conditions. The fluid discharged from the liver was returned into the perfusion system through the vena cava. Extendable precision swivel arms with the radiofrequency probe attached were mounted on the liver perfusion tank. RFA was conducted with the RF3000 generator and a 2 cm LeVeen needle (Boston Scientific, Ratingen, Germany) in a three-dimensional grid for precise localization of the generated thermolesions.

RESULTS

Four bovine livers weighing 8.4 +/- 0.4 kg each were prepared, connected to the perfusion system, and consecutively perfused for the experiments. Mean arterial flow was 569 +/- 43 ml/min, arterial pressure 120 mmHg, portovenous flow 1440 +/- 305 ml/min, and portal pressure 10 mmHg. Macroscopic evaluation after the experiments revealed no thrombi within the hepatic vessels. A total of 136 RF thermolesions were generated with an average number of 34 per liver. Mean RF duration was 2:59 +/- 2:01 min:sec with an average baseline impedance of 28.2 +/- 3.4 ohms. The mean diameter of the thermolesions along the puncture channel was 22.98 +/- 4.34 mm and perpendicular to the channel was 23.27 +/- 4.82 mm.

CONCLUSION

Extracorporeal perfusion of bovine livers with consecutive standardized RF ablation was feasible. The bovine liver flow model seems to allow extensive, standardized evaluation of technical or procedure-related developments of RF systems.

Net portal and hepatic flux of nutrients in growing wethers fed high-concentrate diets with oscillating protein concentrations

We hypothesized that oscillating dietary CP would improve N retention by increasing the uptake of endogenous urea N by portal drained viscera (PDV), compared with static dietary CP regimens. Chronic indwelling catheters were surgically implanted in the abdominal aorta, a mesenteric vein, a hepatic vein, and the portal vein of 18 growing Dorset x Suffolk wethers (44.6 +/- 3.6 kg of BW). Wethers had ad libitum access to the following diets in a completely randomized block design: 1) Low (9.9% CP), 2) Medium (12.5% CP), or 3) Low and High (14.2% CP) diets oscillated on a 48-h interval (Osc). Dry matter intake was greater (P = 0.04) for the Osc diet (1,313 g/d) than the Low diet (987 g/d) and was intermediate for the Medium diet (1,112 g/d). Nitrogen intake was not different between the wethers fed the Osc (25.4 g/d) and Medium diets (22.2 g/d), but was lower (P < 0.01) in wethers fed the Low diet (16.0 g/d). Wethers fed the Osc diet (6.7 g/d) retained more (P < 0.04) N than did those fed the Medium diet (4.0 g/d). Hepatic arterial blood flow was not different (P = 0.81) between wethers fed the Osc (31 L/h) or Medium diet (39 L/h) but was greater (P = 0.05) in wethers fed the Low diet (66 L/h). Net release of alpha-amino N by the PDV did not differ (P = 0.90) between the Low (37.8 mmol/h) and Medium diets (41.5 mmol/h) or between the Osc (53.0 mmol/h) and Medium diets (P = 0.29). Net PDV release of ammonia N was less (P = 0.05) for the Low diet than for the Medium diet, and this was accompanied by a similar decrease (P = 0.04) in hepatic ammonia N uptake. Urea N concentrations tended to be (P = 0.06) less in arterial, portal, and hepatic blood in wethers fed the Low diet compared with those fed the Medium diet. Wethers fed the Osc diet tended (P = 0.06) to have a greater PDV uptake of urea N than did those fed the Medium diet, but there was no difference between the Osc and Medium diets (P = 0.72) in hepatic urea N release. Net PDV uptake of glutamine tended to be greater (P < 0.07) in wethers fed the Low diet (6.7 mmol/h) than those fed the Medium diet (2.7 mmol/h). These data indicate that oscillating dietary protein may improve N retention by increasing endogenous urea N uptake by the gastrointestinal tract.

Major advances in fundamental dairy cattle nutrition

Fundamental nutrition seeks to describe the complex biochemical reactions involved in assimilation and processing of nutrients by various tissues and organs, and to quantify nutrient movement (flux) through those processes. Over the last 25 yr, considerable progress has been made in increasing our understanding of metabolism in dairy cattle. Major advances have been made at all levels of biological organization, including the whole animal, organ systems, tissues, cells, and molecules. At the whole-animal level, progress has been made in delineating metabolism during late pregnancy and the transition to lactation, as well as in whole-body use of energy-yielding substrates and amino acids for growth in young calves. An explosion of research using multicatheterization techniques has led to better quantitative descriptions of nutrient use by tissues of the portal-drained viscera (digestive tract, pancreas, and associated adipose tissues) and liver. Isolated tissue preparations have provided important information on the interrelationships among glucose, fatty acid, and amino acid metabolism in liver, adipose tissue, and mammary gland, as well as the regulation of these pathways during different physiological states. Finally, the last 25 yr has witnessed the birth of "molecular biology" approaches to understanding fundamental nutrition. Although measurements of mRNA abundance for proteins of interest already have provided new insights into regulation of metabolism, the next 25 yr will likely see remarkable advances as these techniques continue to be applied to problems of dairy cattle biology. Integration of the "omics" technologies (functional genomics, proteomics, and metabolomics) with measurements of tissue metabolism obtained by other methods is a particularly exciting prospect for the future. The result should be improved animal health and well being, more efficient dairy production, and better models to predict nutritional requirements and provide rations to meet those requirements.

Effects of Vascular Perfusion on Coagulation Size in Radiofrequency Ablation of Ex Vivo Perfused Bovine Livers

OBJECTIVES

A standardized perfused ex vivo bovine liver model was used to evaluate the effect of organ perfusion on coagulation size and energy deposition during radiofrequency ablation (RFA) procedures.

MATERIALS AND METHODS

Bovine livers were perfused in a tank after rinsing the prepared liver vessels with anticoagulants. Tyrode's solution, oxygenated and heated to 36.5 degrees C, was used as perfusion medium. A flow and pressure controlled pump regulated Portal vein circulation; a dialysis machine provided pulsatile arterial circulation. Impedance-guided radiofrequency ablations were performed with 4-cm LeVeen electrodes with and without underlying liver perfusion. Two-dimensional diameters (Dv, Dh) of each ablation area were measured after dissecting the livers.

RESULTS

In 4 bovine livers weighing 8.85 +/- 0.83 kg per organ (min, 7.7 kg; max, 9.7 kg) altogether 40 RF ablations were performed. A total of 20 ablations were generated with underlying liver perfusion (group 1) and 20 ablations with no liver perfusion (group 2). In group 1, Dv was 28.4 +/- 5.3 mm, Dh 38.6 +/- 7.8 mm, and energy deposition 36.9 +/- 18.0 kJ. The 20 ablation areas generated without liver perfusion displayed statistically significant differences, with Dv being 35.7 +/- 6.5 mm (P = 0.001), Dh 49.5 +/- 9.4 mm (P = 0.001), and energy deposition 25.5 +/- 13.0 kJ (P = 0.018).

CONCLUSION

The model reproduced the cooling effect of perfused tissue during RFA. The ablation areas produced under perfusion conditions had smaller diameters despite longer exposure times and higher energy deposition.

Clearance of para-aminohippuric acid in wethers consuming locoweed

AIM

To validate the use of para-aminohippuric acid (PAH) as a marker for measuring blood flow in wethers consuming a mixed diet of locoweed and blue grama hay.

METHODS

Fourteen sheep, stratified by bodyweight (BW), were assigned to one of three treatments: 0.8 mg swainsonine (SW)/kg BW (HI), 0.2 mg SW/kg BW (LO), and no SW (Control). Sheep were fed various ratios of locoweed and blue grama hay to deliver SW treatments, for 28 days prior to infusion of PAH. Concentrations of SW and activities of alkaline phosphatase (Alk-P) and aspartate aminotransferase (AST) in serum were measured to confirm exposure to SW and subclinical intoxication. A single 20-ml injection of 5% PAH was delivered into the jugular vein after subclinical intoxication had been achieved. Blood samples were collected and serum analysed for PAH immediately prior to injection, then every 5 min from 5-30 min, and every 10 min from 30-60 min, following injection of PAH.

RESULTS

Effective delivery of SW was evident from the greater concentrations of SW measured in the serum of HI compared with LO animals (p<0.05). No significant differences were detected in the rate of elimination (range 0.097-0.108 L/min), elimination half-life (range 6.62-7.24 min), apparent volume of distribution for the central compartment (range 7.14-9.72 L), and clearance (range 0.73-0.92 L/min) of PAH, between treatments.

CONCLUSIONS

Subclinical intoxication with SW did not affect the pharmacokinetics of PAH. Thus, use of downstream dilution of PAH is a valid method to determine the rate of blood flow in nutrient flux experiments that involve consumption of locoweed.

Influence of grazing dormant native range or winter wheat pasture on subsequent finishing cattle performance, carcass characteristics, and ruminal metabolism

A winter grazing/feedlot performance experiment repeated over 2 yr (Exp. 1) and a metabolism experiment (Exp. 2) were conducted to evaluate effects of grazing dormant native range or irrigated winter wheat pasture on subsequent intake, feedlot performance, carcass characteristics, total-tract digestion of nutrients, and ruminal digesta kinetics in beef cattle. In Exp. 1, 30 (yr 1) or 67 (yr 2) English crossbred steers that had previously grazed native range (n = 38) or winter wheat (n = 59) for approximately 180 d were allotted randomly within previous treatment to feedlot pens (yr 1 native range = three pens [seven steers/pen], winter wheat = two pens [eight steers/pen]; yr 2 native range = three pens [eight steers/pen], winter wheat = four pens [10 or 11 steers/pen]). As expected, winter wheat steers had greater (P < 0.01) ADG while grazing than did native range steers. In contrast, feedlot ADG and gain efficiency were greater (P < 0.02) for native range steers than for winter wheat steers. Hot carcass weight, longissimus muscle area, and marbling score were greater (P < 0.01) for winter wheat steers than for native range steers. In contrast, 12th-rib fat depth (P < 0.64) and yield grade (P < 0.77) did not differ among treatments. In Exp. 2, eight ruminally cannulated steers that had previously grazed winter wheat (n = 4; initial BW = 407 +/- 12 kg) or native range (n = 4; initial BW = 293 +/- 23 kg) were used to determine intake, digesta kinetics, and total-tract digestion while being adapted to a 90% concentrate diet. The adaptation and diets used in Exp. 2 were consistent with those used in Exp. 1 and consisted of 70, 75, 80, and 85% concentrate diets, each fed for 5 d. As was similar for intact steers, restricted growth of cannulated native range steers during the winter grazing phase resulted in greater (P < 0.001) DMI (% of BW) and ADG (P < 0.04) compared with winter wheat steers. In addition, ruminal fill (P < 0.01) and total-tract OM digestibility (P < 0.02) were greater for native range than for winter wheat steers across the adaptation period. Greater digestibility by native range steers early in the finishing period might account for some of the compensatory gain response. Although greater performance was achieved by native range steers in the feedlot, grazing winter wheat before finishing resulted in fewer days on feed, increased hot carcass weight, and improved carcass merit.

Percutaneous ultrasound-guided over-the-wire catheterization of the portal and hepatic vessels in cattle

A new method for catheterization of the portal and hepatic veins in cattle by means of the over-the-wire system was investigated to maintain more reliable long-term patency of catheters. Four cattle were used to evaluate the success rate, patency and safety of the procedure. The catheters, coated by urokinase were patent as long as they were in situ. In addition, the introducer was useful to prevent the catheter from being broken. No complications developed during the10 days after the procedure. Two cows were then euthanized. Post mortem findings were minimal. The results of the study reported here are promising, the benefits are significant and there is no apparent disadvantage to its use.

Ultrasound-guided catheterization of the portal vein in 11 cows using the Seldinger technique

Catheterization of the portal vein using the Seldinger technique [Acta Radiol. (1958) 38, 368] was performed in 11 cows. Ultrasound-guided percutaneous portocentesis, using a 25-cm, 14-gauge steel cannula, was performed from the 10th, 11th or 12th intercostal space on the right side. A stylet was placed through the cannula, which was then removed, and a polyurethane balloon-tipped catheter was advanced over the stylet into the portal vein and sutured to the skin (Seldinger, 1952). Blood samples were collected from the catheter at least once daily. The catheter was removed 9-15 days later when blood could no longer be aspirated. The cows were then slaughtered and a post-mortem examination was performed. During the study, appetite remained normal in nine of 11 cows. In three cows, the general behaviour and demeanour were mildly, but transiently, abnormal. Four cows had leucopoenia. The most frequently encountered problem was occlusion of the catheter, which usually was resolved by flushing with heparinized saline. The most common post-mortem lesion observed was an increase in fibrous connective tissue at the site of cannulation. In nine of 11cows, there was a thrombus in the portal vein at the site of catheterization. Generally, the severity of the lesions was mild. The results of this study demonstrated that ultrasound-guided percutaneous catheterization of the portal vein, using the Seldinger technique, is possible in cows. The catheter may be left in place for collection of blood samples for up to 15 days.

Splanchnic and mammary nitrogen metabolism by dairy cows fed dry-rolled or steam-flaked sorghum grain

Objectives were to determine net release or uptake of alpha-amino N, ammonia N, and urea N across portal-drained viscera, liver, splanchnic, and mammary tissues of lactating Holstein cows (n = 8, 86 +/- 8 d in milk) fed alfalfa hay-based total mixed rations containing 40% dry-rolled or steam-flaked sorghum grain. The total mixed rations were offered at 12-h intervals in a crossover design. Blood samples were obtained from indwelling catheters in the portal, hepatic, and mammary veins and mesenteric or costoabdominal arteries, every 2 h for each cow and diet. Steam-flaking increased in vitro rate of starch hydrolysis compared with dry-rolled sorghum (66 vs. 25%). Diet did not alter dry matter intake (18.2 +/- 0.3 kg). Daily milk yield (27.6 +/- 0.8 kg), efficiency of production, and most milk components did not differ between diets, but fat yield was reduced (0.86 vs. 0.91 kg/d) by steam-flaked sorghum, and lactose concentration was increased (4.99 vs. 4.82%). Blood flows in portal and hepatic veins did not differ between diets. Steam-flaking tended to increase urea N cycling to the gut (162 vs. 95 g/d) compared with dry-rolling of sorghum, whereas net absorption of ammonia N and alpha-amino N across portal-drained viscera were decreased. Net mammary uptake of a-amino N increased more than 20% (83 vs. 67 g/d), resulting in a higher mammary extraction ratio (15 vs. 11%) for steam-flaked versus dry-rolled sorghum. Flaking of sorghum improved the efficiency of postabsorptive N metabolism by increasing urea N cycled to the gut and alpha-amino N uptake by the mammary gland.

Echo-guided studies on portal and hepatic blood in cattle

The objectives of the present study were (1) to establish and maintain catheters non-surgically in the portal and hepatic veins of cattle for long-term monitoring of postprandially absorbed metabolites, and (2) to assess the safety of the technique used. Aspiration and catheterization were not performed if there was risk of bleeding, as determined by hemostatic data and enlargement of portal and hepatic veins. In five Holstein cattle, before and 60-min after feeding, percutaneous ultrasound-guided aspiration of portal and hepatic blood, together with jugular blood, was performed utilizing 17G x 17.5 cm needles. Concentration of ammonia nitrogen tended to be higher after feeding, but that of urea nitrogen and glucose were not significantly changed. In five other Holstein cows liver veins were catheterized with 14 x 16.5 cm guide-needles attached with 50 cm polyethylene tubes and blood samples were collected from portal, hepatic and jugular veins at 30-min intervals for 4.5 hr. The concentration of plasma acetate and 3-hydroxybutyrate (3-HB) were significantly increased after feeding, while that of lactate was not changed. Catheters in the portal and hepatic veins enabled the collection of blood samples up to 15 days (mean, 7 days). After a 7-day observation period, five cows were euthanised and necropsied. Changes in the intercostal musculature, peritoneum and liver were negligible. During the observation period, clinical profiles, aspartate aminotransferase, alanine aminotransferase and total and differential WBC counts were within normal ranges.

Ultrasound-guided percutaneous portocentesis in 21 cows

An ultrasound-guided portocentesis was performed in 21 clinically healthy cows, and blood was collected for haematological, biochemical and blood-gas analyses. At the same time blood samples were collected from the left jugular vein of each cow for the same analyses. Immediately after the centesis, portal blood pressure was measured. The cows were examined daily thereafter for eight days and then slaughtered for postmortem examination of the internal organs. The mean (sd) portal blood pressure was 37.1 (5.47) mmHg, and ranged from 24 to 49 mmHg. There were small but significant differences between many of the haematological and biochemical parameters in jugular and portal blood, and the concentration of bile acids was on average 2.7 times higher, and the concentration of ammonia was 19.3 times higher in portal blood. The demeanour and behaviour of the cows, and their appetite and rectal temperature remained normal during the eight-day observation period. The haematocrit, total and differential leucocyte counts, and the concentrations of total solids and fibrinogen were not affected by portocentesis. On postmortem examination, no lesions were apparent in the peritoneum, liver and portal vein.

Adaptation of energy metabolism to undernutrition in ewes. Contribution of portal-drained viscera, liver and hindquarters

Adaptation of energy metabolism to undernutrition and to the duration of undernutrition was studied in adult, non-pregnant, non-lactating ewes at the whole-animal, portal-drained viscera, liver and hindquarters levels. Arterio-venous and indirect calorimetry techniques were used. Animals were successively fed at 1 times (3 weeks) and at 0.5 times (7 weeks) their metabolizable energy requirements for maintenance (MEm). Portal, hepatic and hindquarters blood flows in quietly standing ewes decreased by 22, 19 and 11% respectively within the first week of undernutrition and remained at that level thereafter. Standardizing hindquarters blood flow to that in a given posture (quietly standing) reduced blood flow by 9.8%. In the portal-drained viscera and liver, O2 extraction rates decreased, leading to 34 and 38% drops in O2 consumption with underfeeding respectively. In the hindquarters, O2 extraction rate increased, partly counterbalancing the drop in blood flow. Thus O2 consumption of hindquarters tended to decrease but the effect was not significant. All changes appeared to be completed from day 5 of underfeeding. Consequently, the portal-drained viscera, liver and carcass were responsible for 39, 32 and 5% respectively of the drop in whole-animal O2 consumption with underfeeding. At the end of the 0.5 x MEm period, in vivo metabolic rates averaged 1.65, 4.89 and 0.38 mmol O2 consumed/d per g fresh weight of adipose-tissue-free portal-drained viscera, liver and boneless hindquarters respectively. Undernutrition imposed a much greater nutritional challenge to splanchnic tissues than to hindquarters. The former reduced their energy expenditure whereas hindquarters metabolism adapted by counteracting the slight drop in nutrient supply.

Macromineral nutrition by heat stress interactions in dairy cattle: review and original research

This paper examines whether or not responses of dairy cattle to various dietary macromineral elements differed in hot weather compared with thermoneutral conditions. The consequences of heat stress and the interrelationships of macromineral elements on feed intake, digestive function, use of dietary buffers, mineral element uptake from the portal-drained viscera, perturbation of acid-base physiology and related mineral element nutrition, effects of dietary macromineral element concentrations on lactational performance as affected by season, and influence of mineral elements in drinking water are reviewed, and new research results are presented. Dietary mineral buffers aided in alleviation of the decline in DMI and milk yield induced by heat stress. New research results showed that portal plasma flow declined with heat stress or by restriction of DMI in a thermoneutral environment and that uptake of P from the portal-drained viscera by lactating cows was reduced 50% by heat stress compared with that of cows with the same DMI in a thermoneutral environment. Accelerated respiration rate caused respiratory alkalosis and apparently compensated metabolic acidosis, changing the demand for Na and K during heat stress. There is need to characterize more accurately the nyctohemeral pattern of acid-base physiology in the heat-stressed lactating dairy cow and to relate it to macromineral element needs. A large data set (n = 1444 cow period means) was used to compare milk yield and DMI responses to varying dietary concentrations of P, Na, K, Cl, Ca, Mg, and cation-anion difference in summer compared with those in winter. Interactions of dietary concentrations of Cl, Ca, and Mg with season on DMI and K, Ca, and Mg with season on 4% FCM yield were detected. Interactions of Na by Cl, Na by P, and Cl by P with season on DMI and of Cl by P with season on 4% FCM yield were detected. High concentrations of sulfate and chloride in drinking water jeopardized productivity of cows during hot weather.

Site of digestion of starch in the gastrointestinal tract of dairy cows and its effect on milk yield and composition

Physical and chemical processing of feed ingredients and feeding management strategies are major instruments of manipulating amount and site of starch digestion in the gastrointestinal tract. Generally, as rumen escape of starch increases, postruminal starch digestion increases, and there does not appear to be a limitation to intestinal starch digestion. However, the efficiency with which postruminal starch is digested decreases, which represents a limitation that warrants investigation. Even though digestible dietary starch is presented to the intestine, there is no net glucose absorption at the portal vein, and plasma glucose levels remain relatively unaffected. This result may be associated with the large metabolic requirement for postruminally absorbed glucose, which is preferentially used for oxidative metabolism at the visceral tissue level. In addition, peripheral glucose concentration is highly regulated. A possible implication is that the exogenous glucose supply may spare endogenously synthesized glucose for gut metabolism, allowing more to be directed to the mammary gland. Amino acids also may be spared (less metabolism of dietary and tissue amino acids in the gut). Current production studies yield no clear evidence as to the benefits of postruminal digestion of starch to enhance milk yield or to change its composition. However, studies suggest that starch digested postruminally is used more efficiently for milk synthesis than that digested in the rumen.

Techniques for measuring blood flow in splanchnic tissues of cattle

A useful approach of the study of nutrient absorption and metabolism is in vivo measurement of blood flow across portal-drained viscera and liver, and flux of bloodborne metabolites, successful application of the approach requires correct placement of chronic catheters in appropriate blood vessels. Additionally, catheters must stay patent long enough to allow the animal to recover from surgery and to complete an experimental protocol. This paper describes surgical techniques to install chronic catheters in mesenteric veins, the hepatic portal vein, and an hepatic vein of cattle. Techniques for access to arterial blood are described also. Materials, equipment, and supplies required for surgery, blood sampling, and blood flow determination are described. Commercial sources of supplies are suggested. Blood flow is measured by downstream dilution of para-aminohippurate, which is infused into a mesenteric vein. Examples of blood flow data for three types of cattle are provided.

Net portal-drained visceral and hepatic metabolism of glucose, L-lactate, and nitrogenous compounds in lactating holstein cows

Net portal-drained visceral and hepatic flux of glucose, L-lactate, alpha-amino N, NH3N, urea N, glutamate, and glutamine were measured in four Holstein cows. Cows were fed a 60:40 corn silage: concentrate diet ad libitum and milked at 12-h intervals. Six to 16 d postpartum chronic catheters were established in hepatic portal, hepatic, and mesenteric veins and a carotid artery was elevated. Twelve Measurements of net flux, the mathematical product of blood flow (measured by p-aminohippurate dilution) and venous-arterial concentration difference, were obtained for each cow at hourly intervals during 1 d of wk 4 and 8 postpartum. Dry matter, N, and energy digestion trials began 1 to 2 d after blood sampling. Dry matter intake and milk yield averaged 15.6 and 32.2 kg/d. Portal-drained visceral blood flow averaged 80% of hepatic blood flow (2041 L/h). Net flux of NH3N, urea N, and alpha-amino N across portal-drained viscera represented 68, 54, and 51% of N apparently digested. There was net use of glucose by portal-drained viscera. Hepatic glucose production (3.1 kg/d) exceeded calculated mammary glucose requirements. Net hepatic removal of L-lactate, alpha-amino N, and NH3N represented 115, 43, and 101%, respectively, of their net absorption by portal-drained viscera. Net hepatic L-lactate and alpha-amino N removal could account maximally for 17.4 and 16.5% of glucose produced.

Method for continuous measurement of blood metabolite hepatic balance in conscious preruminant calves

A method of continuous in vivo flow measurement of plasma metabolites through the liver in calves was described. Five 2-wk old male calves were fitted with chronic catheters in the hepatic and portal veins and in the hepatic artery and with electromagnetic blood flow probes in the portal vein and in the hepatic artery. The reliability of measurements was tested during a 3-wk period in which calves were fed milk diets that curdled or did not curdle (uncurdled) in the abomasum. In comparison with a conventional curdled milk diet, the intake of uncurdled milk diet did not modify mean portal vein (47 to 49 ml.mn-1.kg live weight-1) or hepatic arterial (5.6 to 5.7 ml.mn-1.kg live weight-1) blood flows but did influence nycthemeral variations in portal blood flow rates, especially during the second part of the night.

Blood flow to hindquarters of steers measured by transit time ultrasound and indicator dilution

The objective was to compare blood flow to the hindquarters of steers measured by transit time ultrasound with blood flow determined by indicator (p-aminohippurate) dilution. Five Hereford steers had ultrasonic flow probes on the abdominal aorta and catheters in the abdominal aorta and inferior vena cava inserted through both sets of circumflex iliac vessels. Indicator was infused continuously into the abdominal aorta through both arterial catheters simultaneously, then through each of the arterial catheters in succession. Samples of blood from the inferior vena cava and jugular vein were taken during infusion for measurement of p-aminohippurate. Blood flow determined by the ultrasonic flow probe was averaged over each blood sampling interval. Compared with the ultrasonic flow probe there was no difference in mean blood flow measured by p-aminohippurate, regardless of method of infusion. Correlation of individual values between ultrasound and p-aminohippurate was .87 when p-aminohippurate was infused into both arterial catheters, .44 when p-aminohippurate was infused into the left arterial catheter, and .78 when p-aminohippurate was infused into the right arterial catheter. The respective ranges for ultrasonic measurements and p-aminohippurate were 3.62 to 10.99 L/min and 2.25 to 30.43 L/min. Although means by the two methods do not differ, there is a greater range and incidence of occasional high values with p-aminohippurate dilution.

Net absorption from portal-drained viscera of nitrogenous compounds by beef heifers fed on diets differing in protein solubility or degradability in the rumen

The objective of the present study was to evaluate effects of in vitro rumen solubility or degradability of dietary protein on net absorption of nitrogenous compounds from portal-drained viscera of beef heifers. Four protein sources, casein, soya-bean meal, maize-gluten meal and blood meal provided about two-thirds of total dietary nitrogen in semi-purified diets given to four beef heifers in a 4 X 4 Latin square design. Although in vitro degradability of dietary N ranged from 842 (casein) to 310 (blood meal) g/kg total dietary N, net absorption of ammonia-N or alpha-amino-N was not significantly different (P greater than 0.10) among diets. However, net absorption of NH3-N tended to decrease and net absorption of alpha-amino-N tended to increase as intake of in vitro undegradable N increased. Net transfer of urea-N from plasma to portal-drained viscera was greater (P less than 0.10) when heifers were fed on soya-bean meal than when fed on maize-gluten meal or blood meal. The findings show with all diets that the non-protein-nitrogenous compounds, NH3 and urea, played a substantial role in absorption and transfer of N. Overall, net absorption of NH3-N was 61% of net absorption of alpha-amino-N, and transfer of urea-N from plasma to portal-drained viscera was 80% of net absorption of alpha-amino-N.

Net absorption of glucose, L-lactate, volatile fatty acids, and nitrogenous compounds by bovine given abomasal infusions of starch or glucose

Three experiments were conducted to evaluate effects of abomasal infusion of glucose or starch on absorption of metabolites (glucose, L-lactate, volatile fatty acids, and nitrogenous compounds) from portal-drained viscera of a nonlactating Holstein cow and two Hereford X Angus heifers. Portal blood and plasma flow were determined by dilution of para-aminohippuric acid. Net absorption was portal-arterial concentration difference times portal plasma flow. Plasma concentration and portal-arterial difference of glucose increased rapidly and directly in response to increased rates of abomasal glucose infusion in the cow (Experiment 1). In the cow (Experiment 2), net absorption of L-lactate was greater with carbohydrate than with water infusion; net absorption of L-lactate was greater and of n-butyrate was less with starch than with glucose infusion. These responses were not evident in the heifers (Experiment 3). Net absorption of alpha-amino-N in the heifers was greater with starch than with glucose infusion. Increased concentrate intake by the heifers did not interact with responses to abomasal infusions. Recovery of infused glucose as absorbed glucose was similar for the cow and the heifers (65%). However, heifers absorbed (as glucose) 35% of infused starch and the cow only 8%.

Oxygen consumption by portal-drained viscera of cattle: comparison of analytical methods and relationship to whole body oxygen consumption

Two experiments were conducted to compare methods of determining oxygen consumption by portal-drained viscera and to relate this consumption to total oxygen consumption by lactating dairy cows. Oxygen consumption was the product of portal blood flow (determined by dilution of dye infused into a mesenteric vein) and portal-arterial concentration differences of oxygen. In Experiment 1, portal-arterial concentrations of oxygen were determined in samples from three cows using equations based on blood pH, hemoglobin, partial pressure of carbon dioxide, and partial pressure of oxygen (method 1) or by direct oxygen determination with an oximeter (method 2). Overall, there were no differences in oxygen concentrations or oxygen consumption by portal-drained viscera between methods. In Experiment 2, oxygen consumption by portal-drained viscera (method 2) and total oxygen consumption were measured in two lactating cows. Oxygen consumption by portal-drained viscera accounted for 18% of total oxygen consumption.

Absorption and metabolism of glucose by the mesenteric-drained viscera of sheep fed on dried-grass or ground, maize-based diets

Sheep fitted with re-entrant canulas in the proximal duodenum and terminal ileum were used to determine the amount of alpha-glucoside entering, and apparently disappearing from, the small intestine when either dried-grass or ground maize-based diets were fed. The fate of any alpha-glucoside entering the small intestine was studied by comparing the net disappearance of such alpha-glucoside from the small intestine with the absorption of glucose into the mesenteric venous blood. Glucose absorption from the small intestine was measured in sheep equipped with catheters in the mesenteric vein and carotid artery. A continuous infusion of [6-3H]glucose was used to determine glucose utilization by the mesenteric-drained viscera and the whole-body glucose turnover rate (GTR). The amounts of alpha-glucoside entering the small intestine when the dried-grass and maize-based diets were given were 13.9 (SE 1.5) and 95.4 (SE 16.2) g/24 h respectively; apparent digestibilities of such alpha-glucoside in the small intestine were 60 and 90% respectively. The net absorption of glucose into the mesenteric venous blood was -2.03 (SE 1.20) and 19.28 (SE 0.75) mmol/h for the dried-grass and maize-based diets respectively. Similarly, total glucose absorption amounted to 1.52 (SE 1.35) and 23.33 (SE 1.86) mmol/h (equivalent to 7 and 101 g/24 h respectively). These values represented 83 and 111% of the alpha-glucoside apparently disappearing from the small intestine, determined using the re-entrant cannulated sheep. Total glucose absorption represented 8 and 61% of the whole-body GTR for the dried-grass and maize-based diets respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Net absorption of glucose and nitrogenous compounds by lactating Holstein cows

Net absorptions from portal-drained viscera of glucose, ammonia nitrogen, alpha-amino nitrogen, and urea nitrogen were measured in four Holstein cows in first lactations. Cows were fed for ad libitum consumption a completely mixed, 60:40 corn silage:supplement diet (dry basis) in two equal feedings at 12-h intervals daily. Portal blood flow (dye dilution) and net absorption (portal-arterial difference times portal blood flow) were measured at hourly intervals for 12 h for all cows 4 and 8 wk postpartum and for two cows 4, 8, 12, 16, and 20 wk postpartum. Apparent digestibilities of dry matter and nitrogen were measured immediately after net absorption. Milk yield and composition were measured with absorption and digestion. Mean daily dry matter intake and milk yield were 14.1 +/- .6 and 23.8 +/- 1.8 kg. Portal blood flow was not affected by time of day or weeks postpartum; mean was 1371 +/- 123 liters/h. Net absorption of glucose was negative, indicating no uptake of glucose from dietary sources. Means (g/day) for nitrogenous sources were: nitrogen intake 387, fecal nitrogen 121, urinary nitrogen 146, milk nitrogen 116, net ammonia nitrogen absorption 149, net alpha-amino nitrogen absorption 137, and net loss of urea nitrogen from blood to the gut 93. Net absorption of amino nitrogen and alpha-amino nitrogen in blood was greater than in plasma; corresponding losses of urea nitrogen and glucose to the gut were greater from blood than plasma.

Net absorption and ruminal concentrations of metabolites in nonpregnant dry Holstein cows before and after intraruminal acetic acid infusion

Objectives were to define daily patterns of net absorption of various nutrients and to assess effects of intraruminal infusion of acetic acid on concentrations of ruminal fluid and net absorption of various metabolites. These characteristics were measured in three nonpregnant, dry Holstein cows (491 kg) at hourly intervals for 24 h before and after 5 days of intraruminal infusion of acetic acid to provide energy equal to 10% of daily intake of metabolizable energy. Cows were fed a completely mixed, 60% corn silage, 40% grain supplement diet at maintenance intake; daily rations were split into two feedings. Net rates of absorption were greatest after feeding and least during early morning. Net absorption of all metabolites measured was similar for the two daily feeding intervals, indicating daily net absorption could be calculated from either feeding interval. Intraruminal infusion of acetic acid caused increased ruminal and plasma concentrations of acetate, increased net absorption of acetate, and almost a twofold increased loss of urea-nitrogen from plasma to the gut. Sixty-nine percent of acetic acid infused was accounted for by increased net absorption of acetate. Ruminal fluid concentrations and net absorption of other volatile fatty acids were not affected by infusion of acetic acid. Net absorptions of ammonia-nitrogen, L-lactate, and glucose likewise were not affected. Net absorption of volatile fatty acid and L-lactate was 43% of daily intake of metabolizable energy.

Net volatile fatty acid absorption in nonlactating holstein cows

Net absorption of volatile fatty acids was measured in four nonlactating Holstein cows fed orchardgrass-clover silage ad libitum and 50 g trace mineralized salt daily. Cows ranged in age from 2 to 4 yr and in body weight from 326 to 525 kg. Portal blood flow and volatile fatty acid concentrations of portal and arterial plasma were determined at 30-min (three cows) or 90-min (one cow) intervals for about 12 h. Mean portal blood flow was 836 liters/h. Mean volatile fatty acid concentrations of portal plasma and differences of portal-arterial concentrations were (mM): acetate 2.00, .67; propionate .264, .228; isobutyrate .022, .017; n-butyrate .057, .038; 2-methylbutyrate .017, .014; 3-methylbutyrate .007, .005; and n-valerate .012, .008. Mean net volatile fatty acid absorption was 682 mmol/h. Acetate and propionate accounted for 91% of net volatile fatty acid absorption on a molar basis and 85% on an energy basis. Net energy absorbed as volatile fatty acid was 5.43 Mcal/cow per day, which was about 35% of calculated metabolizable energy intake. Portal blood flow was maximal 1.5 h postfeeding, and net volatile fatty acid absorption was maximal 2.5 h postfeeding.