bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparison of methods for the estimation of the proportion of microbial nitrogen in duodenal digesta, and of correction for microbial contamination in nylon bags incubated in the rumen of sheep
Authors: Kennedy P. M. , Hazlewood G. P. , Milligan L. P.
Published: June 2005

1. Four sheep, each fitted with cannulas in the rumen and proximal duodenum, were given two diets (1390 g dry matter (DM)/d) consisting of lucerne (Medicago sutiva) pellets (24.2 g nitrogen/kg DM) plus pelleted reed canary grass (Phaluris arundinacea; 14.1 g N/kg DM) or chopped hay (11.8 g N/kg DM) at intervals of 2 h. Flow of duodenal digesta measured by reference to the markers51Cr-EDTA and103Ru-phenanthroline indicated a net gain of 5.8–7.5 g non-ammonia-N (NAN) between mouth and duodenum.

2. The proportion of microbial N in duodenal digesta N was estimated using15N and35S incorporation into bacteria and digesta. Two methods of analysis for35S content, the Bird & Fountain (1970; B&F method) and the Mathers & Miller (1980; M&M method), were used. (15NH4)2S04and Na235S04were infused into the rumen for 3.5 d before and 4.0 d during sampling. A bacterial fraction was prepared from the fluid phases of sampled duodenal digesta and rumen contents by differential centrifugation. In addition, samples of ground canary grass and of lucerne were incubated in nylon bags in the rumen for 3–48 h during the infusion.

3. Each of the35S analytical methods yielded similar values of35S content of isolated rumen or duodenal bacteria, but there was more (P< 0.05) incorporation of15N into rumen than into duodenal bacteria. Relative to values obtained using the M&M method and15N incorporation, the B&F method for S analysis yielded higher (P< 0.05) estimates of microbial content of duodenal digesta from sheep given chopped reed canary grass.

4.35S activity associated with washed nylon-bag residues increased rapidly with time-period of incubation and was substantially greater (P< 0.05) when analysed by the B&F method compared with the M&M method. The35S content (/g DM) of adherent bacteria removed from nylon-bag residues by homogenization in a second experiment vaned from 0.65 to 1.88 that of free-living bacteria isolated from rumen fluid by differential centrifugation.

5. The difference in35S content in digesta and nylon-bag residues as measured using the two analytical methods was considered in relation to35S-labelled extracellular material postulated to be produced by bacteria adherent to plant residues. Estimates of disappearance of dietary N from nylon bags after correction for microbial contamination indicated a disparity with estimates based on in vivo information.
Energy balances of eight volunteers fed on diets supplemented with either lac ti to1 or saccharose
Authors: Van Es A. J. H. , De Groot Lisette , Vogt J. E.
Published: June 2005

1. Complete 24 h energy and nitrogen balances were measured for eight subjects both while consuming a basal diet supplemented with 49 g saccharose/d (diet S) and while consuming the same basal diet but supplemented with 50 g lactitol monohydrate/d (diet L).

2. The subjects ate the two diets for 8 d. Faeces and urine were collected for the final 4 d. Exchange of respiratory gases (oxygen, carbon dioxide, hydrogen and methane) was measured during the final 72 h while the subjects stayed in an open-circuit respiration chamber, 11 m3, and simulated office work. Before eating diet L, subjects ate 50 g lactitol daily for 10 d.

3. On diets L and S, faecal moisture content averaged 0.787 and 0.753 g/g respectively, the difference being significant (P < 0.05). On diet L, energy and nitrogen digestibilities and energy metabolizability averaged 0, 922, 0.836 and 0-881 respectively, and on diet S 0.935, 0.869 and 0.896 respectively; the differences were also significant (P < 0.05). Urinary energy losses and N balances were not significantly different for the two diets.

4. In all subjects only traces of methane were produced but hydrogen production differed significantly (P < 0.05) for diets L and S, being 2.3 and 0.4 litres (normal temperature and pressure)/d respectively.

5. Intakes of metabolizable energy (ME) were corrected, within subjects, to energy equilibrium and equal metabolic body-weight. The corrected ME intakes did not show differences between diets. However, when on diet L the subjects were probably less active than when on diet S because differences within subjects of ankle actometer counts between diets showed a high correlation with the corresponding differences in corrected ME intakes (r 0.92). Further correction of ME intake toward equal actometer activity showed a significant (P < 0.05) difference between diets: for maintaining energy equilibrium 5.6 (SE 0.8; P < 0.05) % more ME from diet L was needed than from diet S. The reliability of this 5.6% difference depends on whether or not one ankle actometer gives an accurate picture of the subject's physical activity.

6. The energy contribution to the body is clearly smaller from lactitol than from saccharose, certainly due to the effect of lactitol on digestion, and probably also due to the effect on the utilization of ME.
The passage of protozoa from the reticulo-rumen through the omasum of sheep
Authors: Michalowski T. , Harmeyer J. , Breves G.
Published: June 2005

1. Protozoa in rumen contents and omasal effluent of growing wethers were counted. The wethers were equipped with rumen and abomasal cannulas, and omasal sleeves attached to the omasal-abomasal orifice. Rumen fluid dilution rates were elevated by continuous infusions of hypertonic mineral solutions (34 litres/d) for 24 d. Rumen contents and omasal effluent were sampled between 9 and 21 h during the last 10 d of each experiment.

2. Protozoa1 concentrations in omasal effluent were only 0.24.3 those found in the rumen under normal conditions. The ratio of protozoal concentrations in rumen: those in omasal effluent was for small Diplodinium spp. 4.6 (SD 0.9), forOphryoscolexspp. 4.3 (SD 1.0), forDasytricha ruminantium4.0 (SD 0.5), forIsotrichaspp. 3.8 (SD 0.8), forEntodiniumspp. 3.6 (SD 0.9) and forPolyplastron multivesiculatum2.6 (SD 0.5).

3. Elevation of rumen fluid dilution rate by 20 and 55% respectively, increased protozoal concentrations in omasal effluents from 22 to 33% and from 31 to 47% those in rumen contents. The apparent residence times of protozoa in the rumen were decreased 50% by the infusion of a mineral-salt solution. The increase in rumen fluid dilution rate had no significant effect on concentrations of protozoa in the rumen or on the differences of the apparent residence times between different species. The apparent residence time of holotrichs remained the same before and after infusion of the mineral-salt solution.

4. Apparent residence times of individual species of protozoa in the rumen were, under normal feeding conditions, 2.55 d, and were four to six times longer than the mean residence time of CrEDTA in the rumen.
Effects of vitamin D on calcium regulation in vitamin-D-deficient pigs given a phytate-phosphorus diet
Authors: Pointillart A. , Fontaine Nicole , Thomasset Monique
Published: June 2005

1.Vitamin-D-deficient pigs were fed on a phytate-phosphorus diet and treated with vitamin D, (+D) to examine the time-course of adaptative changes in plasma minerals, vitamin D metabolites, parathyroid hormone (PTH) and calcium balance and intestinal Ca-binding protein (CaBP).

2. The 5-week vitamin D repletion (25 μg cholecalciferol/kg diet) regimen restored plasma Ca, P and alkaline phosphatase (EC3.1.3.1) to normal, decreased PTH and markedly and rapidly increased plasma 25- hydroxycholecalciferol (25-OHD, sevenfold after 4 d) and 1, 25-dihydroxycholecalciferol ( 1, 25(OH)2D3, 1.8-fold after 4 d).

3. CaBP concentrations were markedly elevated all along the digestive tract, especially in the distal regions.

4. Ca absorption and retention were enhanced (fourfold and sixfold respectively) by the +D diet.

5. The improved Ca absorption, coupled with increased CaBP and 1, 25(OH)2D3 levels, suggest that vitamin D metabolism in phytate-P-fed pigs is sensitive to the depressed Ca availability due to phytate feeding. It also indicates that CaBP may play an important role in the adaptation of Ca absorption.

6. Persistent hypercalciuria indicates that mineral metabolism was still affected by the phytate nature of the dietary P in spite of the vitamin D treatment.
The effect of Intralipid®infusion on the human leucocyte sodium-pump in vivo
Authors: Ng L. L. , Hockaday T. D. R.
Published: June 2005

1. The effect of unsaturated long-chain non-esterified fatty acids (NEFA) on the human leucocyte sodium-pump was studied in vivo.

2. Plasma NEFA level was raised acutely from 0·28 (sd0·10) to 2·54 (sd0·48) mmol/l by infusion of ‘Intralipid 20%’ (trademark) at 90 ml/h with heparin, and the human leucocyte22Na efflux rate constants were studied in eight normal weight males.

3. After 3 h, there was a significant lowering of the total (from 3·97 (sd0·92) to 3·10 (sd0·71)/h;P< 0·01) and ouabain-sensitive22Na efflux rate constants (from 2·89 (sd0·55) to 2·37 (sd0·62)/h;P< 0·02). Ouabain-insensitive efflux rate constants showed a tendency to fall (from 1·08 (sd0·51) to 0·73 (sd0·23)/h). Leucocyte potassium content remained unchanged, but sodium content rose from 31 (sd12) to 38 (sd18) mmol/kg dry weight (P< 0·05). Total, ouabain-insensitive and ouabain-sensitive efflux rates did not change significantly during the Intralipid-heparin infusion.

4. Plasma insulin levels rose gradually throughout the 3 h infusion period.

5. In conclusion, NEFA, when raised to pathological levels, can inhibit the leucocyte Na-pump in vivo even in the presence of physiological levels of serum albumin, and may increase insulin secretion.
Contribution of liver, skin and skeletal muscle to whole-body protein synthesis in the young lamb
Authors: Attaix D. , Aurousseau E. , Manghebati A. , Arnal M.
Published: June 2005

1. Protein fractional synthesis rate (FSR) was measured in some major tissues and in the whole body of six 1-week-old sucking lambs by a large injection of L-[3H]valine.

2. Upper estimates of tissue protein FSR (%/d), assuming that the tissue-homogenate free-valine specific radioactivity defined that of valyl tRNA, were 115.0 in liver, 24.1 in skin, 22.9 in the white M. tensor fasciae latae, 21.6 in the red M. diaphragma and 19–6 in the remainder (exsanguinated whole body without liver and gastrointestinal tract) of lambs.

3. Absolute synthesis rates (ASR) of tissue protein were 17, 19 and 42 g/d in the liver, skin and skeletal muscle respectively, and 112 g/d in the remainder. The ASR of whole-body protein, derived from the tissue values, was 146 g/d, i.e. 33 g/d per kg body-weight. The calculated whole-body protein FSR was 23.9 %/d.

4. The relative percentage contribution of liver, skin and skeletal muscle to whole-body protein synthesis was 11.7, 13.1, and 29.0.

5. We concluded that tissue protein FSR in lambs were in exactly the same decreasing order, from visceral tissues to skeletal muscles, as observed in rats. The ovine FSR estimates and the partitioning of protein synthesis between tissues were in the same range as values recently obtained by flooding-dose experiments in immature rats, piglets, and even in chicks. These findings suggest that inter-species differences are rather limited.
Effects of the β-agonist, cimaterol, on growth, body composition and energy expenditure in rats
Authors: Sainz R. D. , Wolff J. E.
Published: June 2005

1. Male Sprague-Dawley rats weighing 146·5 (se 4·3)g were fed on a semi-synthetic diet containing 0, 25 or 150 mg cimaterol/kg for 12 d. Net changes in weight and composition of carcass, liver, heart, gastrointestinal tract, gastrocnemius plus plantaris muscles, skin and remainder were estimated by comparative slaughter.

2. Cimaterol increased protein gains in gastrocnemius plus plantaris muscles from 0·09 g in controls to 0·14 and 0·12 g in 25 and 150 mg cimaterol/kg groups respectively. Carcass protein gains increased from 6·27 g in controls to 8·00 and 7·05 g in 25 and 150 mg cimaterol/kg groups respectively.

3. Rats treated with cimaterol either gained less fat or actually lost fat from all tissues studied, whilst control rats gained fat. These changes were reflected in lower energy retention in cimaterol-fed rats.

4. Energy intake was not affected by treatment. Cimaterol increased heat production from 776 kJ/kg body-weight0·75 in controls to 863 kJ/kg body-weight0·75 in both treated groups. Gross efficiency was reduced from 17·4% in controls to 8·0 and 7·7% in rats fed on 25 and 150 mg cimaterol/kg diets respectively.

5. These results indicate that cimaterol increases protein gain at the expense of fat in rats. In addition, subcutaneous adipose tissue appears to be more sensitive than abdominal fat, whilst protein gains are particularly enhanced in skeletal muscle relative to other body tissues.
Amino acid absorption and production of pancreatic hormones in non-anaesthetized pigs after duodenal infusions of a milk enzymic hydrolysate or of free amino acids
Authors: Rérat A. , Nunes C. Simoes , Mendy F. , Roger L.
Published: June 2005

1. Six non-anaesthetized pigs (mean body-weight 57.0 kg) were used to study the intestinal absorption of amino acids (AA) from either an enzymic hydrolysate of milk (PEP) containing a large percentage of small peptides (about 50% with less than five AA residues) and very few free AA (8%), or from a mixture of free AA with an identical pattern (AAL) infused intraduodenally in one of two amounts (55 or 110 g). Concomitant insulin and glucagon production rates were estimated.

2. Each pig was previously fitted, under anaesthesia, with an electromagnetic flow probe. around the portal vein, with permanent catheters in the portal vein, the carotid artery and the duodenum. Each infusion was performed after an 18 h fasting period and each pig received each infusion. The observation period lasted for 5 h.

3. The absorption of AA was greater, more rapid and more homogeneous after PEP infusion than after AAL infusion, independent of the amount infused.

4. For the majority of AA considered individually, the absorption coefficient was higher after infusion of PEP than after that of AAL. The exceptions were methionine with a higher absorption coefficient after AAL infusion, and isoleucine, aspartic acid + asparagine and glutamic acid + glutamine with identical coefficients for both infusions.

5. Some AA, such as asparagine, ornithine, citrulline and taurine, while absent in the infusates, appeared in the portal vein in appreciable amounts after the infusion of both solutions. While a small proportion of taurine may arise from recycling of taurine-containing bile salts, it seems that the gut wall is able to synthesize all four AA.

6. Insulin production did not differ according to the nature or amount of solutions infused. Glucagon production was greater after PEP infusion.
An evaluation of the relation between food consumption rate and equilibrium body-weight in male rats
Authors: Gettys Tom W. , Mills Susan , Henrickst Donald M.
Published: June 2005

1. Two experimental approaches were employed to assess the relation between food consumption rate and maintenance requirements in male weanling rats. The first approach involved restricting food intake in rats previously given free access to food from weaning to 59 d of age. The second approach involved restriction of food intake to various levels after weaning. Maintenance requirements (g foodid per g body-weight (W)) were estimated by dividing the rate of food consumption by the resulting equilibrium W (EBW) for each animal. In addition, food consumption was partitioned into growth-independent (maintenance) and growth-dependent (gain) components by alternately setting W and specific growth rate (W') to zero in an equation relating food intake rate to W and W. Coupling coefficients representing maintenance consumption (g food/d per g W) and gain consumption (g food/g gain) were estimated for each animal by least squares.

2. Both techniques for estimating maintenance consumption provided similar estimates within and across experiments, and regardless of when food restriction was imposed or its severity, consumption for maintenance was about 5% W/d.

3. The EBW to which animals in each treatment group aspired was directly proportional to that group's food intake rate.

4. Coventional measures of growth efficiency were also related to food intake; efficiency decreased with decreasing food intake. Partitioning food consumption into maintenance and gain components revealed that as the rate of food intake decreased, the proportion of total intake consumed for maintenance increased. The results suggest that growth efficiency declines during food intake restriction because proportionately more of total intake is used for maintenance, leaving less available for gain.
Degradation of hemicellulose and pectin by horse caecum contents
Authors: Bonhomme-Florentin A.
Published: June 2005

1. Polysaccharide depolymerases and glycoside hydrolases involved in the breakdown of plant structural polysaccharides (hemicellulose and pectins) were monitored in three fractions of the liquid phase of horse caecum digesta: acellular fluid (AF), bacteria (B) and protozoa plus bacteria (PB).

2. Both bacteria and protozoa were found to be involved in the decomposition of pectic substances, with two enzymic activities: depolymerase (polygalacturonase,EC3.2.1.15; and pectin lyase,EC4.2.2.10) and esterase (pectinesterase,EC3.1.1.11). The activity of the PB fraction was higher than that of B.

3. With hemicellulosic substrates, all three fractions showed a significant xylan endo-1,3-β-xylosidase (EC3.2.1.32) activity. Mannan was hardly broken down.

4. Galactomannan and arabinogalactan were broken down more extensively by the PB fraction than by the B fraction. Glycosidase activities (xylan 1,4-β-xylosidase,EC3.2.1.37 and α-L-arabinofuranosidase,EC3.2.1.55) were also observed.
Distribution of retinol in rat liver cells: effect of age, sex and nutritional status
Authors: Blomhoff Rune , Berg Trond , Norum Kaare R.
Published: June 2005

1. We have recently shown that the stellate cells, under normal conditions, contain a majority (more than 80 %) of the total store of retinol in liver (Blomhoffet al.1985).

2. In the present work we have studied the role of the various liver cells in rats of different ages, sex and vitamin A status.

3. In most of these groups of rats, storage of retinol in parenchymal cells was proportional to the liver store of retinol, and less than 10% of total retinol in the liver could be recovered in the parenchymal cells. The only exception was parenchymal cells isolated from vitamin A-deficient rats. In rats containing 5 nmol retinol/g liver, about 16% of total retinol could be recovered in parenchymal cells, while in rats with only 1 nmol retinol/g liver, about 40% of total retinol could be recovered in parenchymal cells.

4. These results indicate that parenchymal cells played a minor role in liver storage of retinol, and that stellate cells stored more than 90% of liver retinol in most instances. Only in rats with a low retinol status did the percentage of retinol in parenchymal cells increase.
Glucose metabolism in shorn and unshorn pregnant sheep
Authors: Symonds M. E. , Bryant M. J. , Shepherd D. A. L. , Lomax M. A.
Published: June 2005

1. Whole-body, hind-limb and uterine tissue metabolism of glucose was studied using a combination of isotopic and arterio-venous difference techniques in shorn and unshorn pregnant sheep over the final 4 weeks of pregnancy. This was combined with the measurement of the concentrations of oxygen and carbon dioxide in arterial blood and plasma concentrations of lactate, acetate, non-esterified fatty acids, 3-hydroxybutyrate, glycerol, growth hormone (GH), insulin, glucagon, cortisol, thyroxine and 3, 5, 3'-triiodothyronine (T3).

2. Glucose entry rate was 28 % higher in shorn ewes compared with unshorn controls, even though there was no difference in the arterial plasma concentration of glucose. This effect may have been caused by a decrease in the molar rate, insulin: glucagon (I:G), which was 40% lower in shorn ewes as a result of a significant decrease in the plasma concentration of insulin. There was no difference in the plasma concentration of cortisol or GH.

3. Blood flow across the hind-limb or uterine tissues was not significantly different between shorn and unshorn groups, neither were the net glucose uptake, glucose oxidation rate or contribution of glucose to O2consumption across these tissues.

4. Insulin-tolerance tests performed on a separate group of shorn and unshorn ewes showed an increased sensitivity to the hypoglycaemic effects of insulin in the shorn group.

5. There was no significant difference between shorn and unshorn animals in the contribution of glucose to CO2output or in the proportion of glucose entry rate oxidized. CO2entry rate was 18% higher in shorn ewes compared with unshorn controls which resulted in a 26 % higher estimated value for heat production. There was a 47 % increase in glucose oxidation rate in shorn ewes but there was no significant difference in the proportion of total heat production which was derived from glucose. The arterial concentrations of O2and CO2were significantly higher in shorn ewes, which may be an indication of the higher metabolic rate in these animals. This effect may be mediated via a significant rise in plasma T3concentration in the shorn group.

6. It is concluded that as a result of long-term cold exposure there is a significant increase in whole-body glucose entry and oxidation rates in the shorn pregnant ewe. The increase in insulin sensitivity at the same time as a decrease in plasma insulin concentration may represent a mechanism to ensure continued glucose supply to insulinsensitive tissues while the concomitant decrease in plasma I:G stimulates hepatic gluconeogenesis.
Effect of tannin-rich leaves of oak (Quercus incana) on various microbial enzyme activities of the bovine rumen
Authors: Makkar H. P. S. , Singh B. , Dawra R. K.
Published: June 2005

1. The objective of the present experiment was to study the effects of oak (Quercus incana) leaves rich in tannins on various enzyme activities of the bovine rumen.

2. The procedure employed was incubation of tannin-rich, very-low-tannin or virtually tannin-free leaves in nylon-gauze bags in the rumen, and determination of enzyme activities in microbes tightly bound to the solid matrix and in microbes loosely plus tightly attached to the solid matrix.

3. The activities of urease (EC3.5.1.5), carboxymethylcellulase, glutamate dehydrogenase (EC1.4.1.2) and alanine aminotransferase (glutamic-pyruvic transaminase) (EC2.6.1.2) were significantly lower in the tannin-rich group, whereas the activities of glutamate ammonia ligase (glutamine synthetase) (EC6.3.1.2; both yγ- glutamyltransferase (EC2.3.2.2) and the forward reaction) were higher in the tannin-rich group. These changes were more marked in micro-organisms tightly bound to the solid matrix than in the more complex microbial compartment.

4. The protein, DNA and RNA contents, and protein: RNA ratio, were significantly lower in the tannin-rich group, whereas no difference was observed for protein: DNA between the groups.

5. Effects of tannin-containing extracts of oak leaves on various rumen enzymes in vitro showed a trend similar to that observed in nylon-gauze bags, suggesting that the changes observed in various compartments were due to the tannins of oak leaves.
The effect of lactulose, pectin, arabinogalactan and cellulose on the production of organic acids and metabolism of ammonia by intestinal bacteria in a faecal incubation system
Authors: Vince A. J. , Mcneil N. I. , Wager J. D. , Wrong O. M.
Published: June 2005

An in vitro faecal incubation system was used to study the metabolism of complex carbohydrates by intestinal bacteria. Homogenates of human faeces were incubated anaerobically with added lactulose, pectin, the hemicellulose arabinogalactan, and cellulose, both before and after subjects had been pre-fed each carbohydrate. Fermentation of added substrate was assessed by the production of short-chain fatty acids (SCFA) and suppression of net ammonia generation over 48 h of incubation. Control faecal homogenates to which carbohydrate was not added yielded an average increment of SCFA of 43 mmol/l, equivalent to 172 mmol/kg in the original stool. The addition of lactulose, pectin and arabinogalactan each increased the yield of SCFA by a similar amount, averaging 6·5 mmol/g carbohydrate or 1·05 mol/mol hexose equivalent; organic acid yield was not increased by pre-feeding these substances for up to 2 weeks. Acetate was the major SCFA in all samples at all times and, after pre-feeding with extra carbohydrate, butyrate concentrations exceeded propionate in all samples. Faecal homogenates incubated with cellulose showed no greater SCFA production than controls over the first 48 h, but there was a slight increase when samples from two subjects pre-fed cellulose were incubated for 14 d. Net ammonia generation was markedly suppressed by addition of lactulose to faecal incubates with an initial period of net bacterial uptake of ammonia. Pectin and arabinogalactan also decreased ammonia generation, but the reductions were not significant unless subjects were pre-fed these materials; cellulose had no effect on ammonia generation.
The effect of a 48 h fast on the physiological responses to food ingestion in normal-weight women
Authors: Gallen I. W. , Macdonald I. A. , Mansell P. I.
Published: June 2005

The thermogenic, cardiovascular and metabolic responses to a 30 kJ/kg body-weight test meal were studied in eight normal-weight, healthy female subjects after a 6 or 48 h fast. There was no significant change in metabolic rate following the 48 h fast, but plasma glucose, insulin, noradrenaline and respiratory exchange ratio were all reduced, and plasma β-hydroxybutyrate was increased. Forearm blood flow was increased, with reduction in diastolic blood pressure. After the 48 h fast, there was a reduction in the metabolic rate response 40–90 min after food (control+0·54 (se0·05), 48 h fast + 0·27 (se0·12) kJ/min,I< 0·01), and in forearm blood flow and diastolic blood pressure responses, but increases in heart rate, blood glucose and plasma insulin responses to the ingestion of the test meal. There was no significant relationship between plasma catecholamine concentration and food ingestion or metabolic rate. Fasting induced considerable adaptation in these subjects and altered some of the physiological responses to food ingestion.
Forms of soluble iron in mouse stomach and duodenal lumen: significance for mucosal uptake
Authors: Simpson Robert J. , Peters T. J.
Published: June 2005

Stomach contents of mice fed on a standard rodent breeding diet contained 29–733 pM-soluble non-haem-iron. A very variable percentage (3–100, mean 49·3 (se4·7),n37) of this Fe was rapidly (half-life < 1–2s) available for chelation by the strong Fe(II) chelator ferrozine, with little or no further Fe being available on addition of ascorbate. Ferrozine-available Fe could be detected in the duodenal lumen at concentrations up to 60 μM in vivo and after in vitro neutralization of stomach contents. No significant changes in quantity of stomach ferrozine-available Fe or soluble non-haem-Fe occurred in mice with adaptive enhancement of Fe absorption induced by chronic hypoxia. Electron paramagnetic resonance (e.p.r.) spectroscopy of the soluble portion of mouse stomach contents demonstrated ag= 4·3 signal (rhombic Fe(III)) equivalent to up to 20 % of soluble non-haem-Fe. The signal was unaffected by addition of excess ferrozine and increased on subsequent neutralization, suggesting redistribution of Fe from other e.p.r.-silent species. Solutions of Fe-nitrilotriacetate (NTA) (a synthetic Fe chelate used as a bioavailable, model Fe solution) were found to contain both rapidly and slowly ferrozine-available Fe (after addition of ascorbate) depending on pH, NTA:Fe ratio and the presence of Ca(II) ions. Fe-ascorbate mixtures (a model solution for Fe absorption studies) also contained ferrozine-available Fe. These results suggest the presence of Fe(II), rhombic Fe(III) and other e.p.r.-silent Fe species in the soluble fraction of mouse stomach contents. The ferrozine-available (Fe(II)) fraction is not limited by the reducing power in the diet, but by binding to ligands. Neutralization with bicarbonate leads to a loss of ferrozine-available Fe and increase in rhombic Fe(III) at the expense of both ferrozine-available and other e.p.r.-silent Fe species. The ferrozine-available Fe in mouse stomach and duodenal lumen can be related to Fe species present in model solutions used for in vitro studies of mucosal uptake mechanisms.
Excretion of purine derivatives by ruminants: effect of exogenous nucleic acid supply on purine derivative excretion by sheep
Authors: Chen X. B. , Hovell F. D. DeB. , Ørskov E. R. , Brown D. S.
Published: June 2005

The present study examined the relationship between the supply of exogenous nucleic acid (NA) purines and their recovery as the derivatives hypoxanthine, xanthine, uric acid and allantoin in urine. Six lambs, totally nourished by intragastric infusions of volatile fatty acids (VFA) and casein (i.e. no rumen fermentation), were given by abomasal infusion a microbial NA concentrate at six levels (from zero to 24·5 mmol purines/d). The true digestibility between the abomasum and terminal ileum of the NA purines was measured in a separate experiment using three lambs. The relative proportion of urinary allantoin increased, and that of other derivatives decreased, as the amount of NA infused was increased. The relationship between total excretion of purine derivatives (Y;mmol/d) and exogenous purines absorbed (X;mmol/d) wasY= 0·84X+ 0.150W0·75e-0.25X, where W is body-weight (kg). This implies that the endogenous contribution to the total excretion of derivative decreased as the supply of exogenous purines increased, with an associated progressive replacement ofde novosynthesis by exogenous purines. The model also implies that 0·16 of the purines were eliminated through routes other than derivative excretion in urine. Once excretion exceeded 0·6 mmol/kg W0·75per d, endogenous excretion was effectively zero and thusY= 0·84X.In normally fed sheep, derivative excretion should therefore relate to the microbial purines and, hence, microbial protein absorbed according to these models. The changing proportions of allantoin and other derivatives in urine were probably due to changes in the relative importance of endogenous and exogenous purines as precursors.
Protein and energy metabolism of lactating Granadina goats
Authors: Aguilera J. F. , Prieto C. , FonollÁ J.
Published: June 2005

Twelve goats of the Granadina breed in mid- and late lactation were used in two consecutive years to determine their protein and energy requirements for lactation. The animals were individually fed on diets based on pelleted lucerne (Medicago sativa) hay and barley. A total of six balance experiments were carried out. Gas exchange was measured using open-circuit respiration chambers. Milk yield ranged widely from 0.649 to 1.742 kg/d in the first year and from 0.222 to 1.989 kg/d in the second year, a steady decline in milk output being observed as lactation progressed. Milk composition remained rather constant during the midstage of lactation, with an average content (/kg milk) for total solids, total nitrogen, fat and gross energy of 149.7 g, 5.39 g, 58.8 g and 3.59 MJ respectively. Total endogenous N, endogenous urinary N and maintenance requirement for N in lactating goats were estimated to be 244, 218 mg N/kg body-weight (W)0.75 per d and 478 mg total N/kg W0.75 per d respectively from regression equations. A constant efficiency of use of dietary N for milk N plus retained N of 51.0 % was found. By regressing milk energy plus apparent body energy retention or loss on metabolizable energy (ME) intake, the maintenance energy requirement was estimated to be 401 kJ ME/kg W0.79 per d. When estimating the corrected milk yield as milk energy +(0.84 x negative energy retention) +(1.05 x positive energy retention), regression analysis indicated that the overall efficiency of use of ME for lactation was 66.7%. Also, from a plot of apparent body energy retention v milk energy yield, both expressed as a percentage of ME intake above maintenance, the efficiency with which ME was used to promote energy retention in the body during lactation was calculated to be 0.907 times that for milk secretion.
The effect of patterns of rumen fermentation on the response by dairy cows to dietary protein concentration
Authors: Lees J. A. , Oldham J. D. , Haresign W. , Garnsworthy P. C.
Published: June 2005

Four groups of seven dairy cows were given hay plus high-fibre concentrates based on sugar-beet feed (hay-concentrate, 40:60 w/w) or high-starch concentrates based on flaked maize (hay-concentrate, 20:80 w/w), with a crude protein (nitrogen x 6.25) content of either 160 or 220 g/kg dry matter, over weeks 4–18 of lactation. Performance during week 3 of lactation, when all cows were fed on a standard ration, was used as a covariate. For diets with a high-fibre content, higher protein concentrations led to increases in yields of milk and milk fat, with no effect on live-weight loss. For diets with a high-starch content, higher protein concentrations did not affect milk yield or composition but resulted in an increase in live weight rather than a decrease. Diets with a high-starch content led to increased proportions of propionic acid in the rumen and increased concentrations of insulin in the blood. It is concluded that the source of carbohydrate needs to be taken into account when predicting the response to protein supply by dairy cows.
Excretion of purine derivatives by ruminants: recycling of allantoin into the rumen via saliva and its fate in the gut
Authors: Chen X. B. , Hovell F. D. DeB. , ØRskov E. R.
Published: June 2005

The saliva of sheep was shown to contain significant concentrations of uric acid (16 (sd) 4.5) μmol/l) and allantoin (120 (sd 16.4) μmol/l), sufficient to recycle purine derivatives equivalent to about 0.10 of the normal urinary excretion. When allantoin was incubated in vitro in rumen fluid, it was degraded at a rate sufficient to ensure complete destruction of recycled allantoin. In a series of experiments in which allantoin was infused into the rumen of sheep fed normally, or into the rumen or abomasum of sheep and the rumen of cattle completely nourished by intragastric infusion of volatile fatty acids and casein, no additional allantoin was recovered in the urine. These losses were probably due to the degradation of allantoin by micro-organisms associated with the digestive tract. It is concluded that all allantoin and uric acid recycled to the rumen via saliva will be similarly degraded. Therefore, the use of urinary excretion of purine derivatives as an estimator of the rumen microbial biomass available to ruminants will need to be corrected for such losses.
Enterohepatic circulation of sulphur in female goats
Authors: Halais Christine , Moir R. J.
Published: June 2005

Sulphur flow through the gut was monitored in eight adult female goats at different stages in their reproductive cycle. The amount of S transferred from the body into digesta between the mouth and the transverse duodenum was directly proportional to the amount of nitrogen retained in the body and secreted in milk. S secretion into digesta was also a function of metabolic body-weight (body-weight0.75) in non-pregnant, non-lactating goats and in pregnant goats. During lactation there was an additional S input into digesta, and S gain was directly proportional to the yield of milk N. The S was conserved by intestinal absorption and was recycled to the gut predominantly as carbon-bound (neutral) S in bile. The enterohepatic circulation may act as a mobile reserve of S, particularly of taurine.
Undernutrition during the preweaning period changes calcium ATPase and ADPase activities of synaptosomal fractions of weanling rats
Authors: ROCHA J. B. T. , Mello C. F. , Sarkis J. J. F. , Dias R. D.
Published: June 2005

The presence of activities that hydrolyse externally added ATP to adenosine in synaptosomal preparations from various sources is well demonstrated. The hydrolysis of ATP to AMP can be mediated either by the concerted action of enzymes or by an ATP-diphosphohydrolase (EC3.6.1.5; apyrase). Undernutrition during the preweaning period can delay the development of several enzymes involved in the metabolism of neurotransmitters or neuronal function. In young rats, the presence of an apyrase in synaptosomal preparations from cerebral cortex was investigated. The results suggested that the hydrolysis of externally added ATP and ADP can be mediated by a single enzyme. The effects of preweaning undernutrition on the hydrolysis of ATP and ADP were also investigated. In weanling rats, previous undernutrition caused a decrease of about 20% in the hydrolysis of both substrates in synaptosomal fractions.
The effect of feeding frequency and meal size on amounts of total and parotid saliva secreted by sheep
Authors: Carter Richard R. , Allen O. Brian , Grovum W. Larry
Published: June 2005

Total and unilateral parotid saliva production during eating were measured in response to offering sheep a fixed amount of lucerne (Medicago sativa) hay as one, two, four or eight meals. Total saliva measurements were obtained using sham-fed oesophageal-fistulated sheep. Unilateral parotid saliva was collected from sheep fitted with reversible re-entrant cannulas. Dry matter intakes and eating times were measured for each meal but were not constrained to particular values. Total and unilateral parotid saliva production during eating increased linearly with the log of the number of meals (p = 0.0001). The amounts corresponding to one, two, four and eight meals of lucerne hay were 1553, 1737, 1851 and 2087 ml during total collections and 209, 248, 307 and 352 ml during unilateral parotid collections. The time-period spent eating and the amount of food consumed both increased as meal number increased. Total saliva collections when lucerne hay was sham-fed as one, two, four or eight meals were associated with eating times of 56.9, 57.4, 70.8 and 86.0 min and intakes of 562, 622, 629 and 638 g dry matter respectively. For unilateral parotid collections, eating times and dry matter intakes were 64.2, 71.3, 78.0, 82.1 min and 515, 579, 614 and 627 g for one, two, four and eight meals of lucerne hay respectively. The saliva production response appeared to be determined through the effects of the time-period spent eating and amounts consumed, but other undetermined effects of feeding frequency contributed to the response. The importance of meal duration on total saliva production was assessed by sham-feeding of 800 g lucerne as stem, leaf, hay, chopped hay or ground and pelleted hay. Increasing meal duration by feeding with stems resulted in the production of 1808 ml saliva, whereas the rapid consumption of pellets resulted in only 442 ml being produced.
Effects of food or nutrient restriction on milk vitamin A transfer and neonatal vitamin A stores in the rat
Authors: Maria Ana , Pasatiempo G. , Ross A. Catharine
Published: June 2005

We have investigated the effects of maternal diets low in fat or protein, or restricted in total food intake on vitamin A transfer from the dam to her pups. When animals were fed on diets moderately restricted in fat or protein, minimal differences in milk, serum, and liver vitamin A concentrations were observed compared with animals fed on a control diet. In a second study, dams were fed on diets more severely restricted in protein, or fat, or both, or were fed on a control diet equal to 50% of the intake of control rats but containing an equal amount of vitamin A. The quantity of milk obtained from these more severely restricted dams' nipples or the pups' stomachs was greatly reduced; however, there were no differences in milk vitamin A concentration. Body-weight, liver weight, and total liver vitamin A stores of undernourished pups were just half those measured for control pups, although serum vitamin A and serum retinol-binding protein were nearly normal in concentration. We conclude that (a) moderate restrictions in fat or protein in the maternal diet are insufficient to affect transfer of vitamin A to the suckling pup; (b) further dietary restrictions could cause decreased milk production with little change in milk vitamin A concentration and, hence, (c) the neonates' hepatic retinol accumulation during the suckling period is markedly reduced when maternal diets are severely deficient in fat or protein or of normal composition but restricted in amount.
The interaction of vitamin A deficiency and rotavirus infection in the mouse
Authors: Ahmed Faruk , Jones David B. , Jackson Alan A.
Published: June 2005

Weanling mice were fed on a control dietad lib., a vitamin A-deficient dietad lib.or pair-fed to the intake of the vitamin A-deficient group. Vitamin A deficiency was induced by 63–70 d of age. On day 77 mice were given 30 μl rotavirus/mouse orally and examined histologically 1 week later. There were no changes in relative liver weight in any of the groups, but following infection animals deficient in vitamin A showed a significant increase in spleen weight compared with the other groups. The relative weight of the thymus was reduced by vitamin A deficiency, in both non-infected and infected animals. The histology of the spleen, thymus and small intestine was similar in all three dietary groups before infection. The number of goblet cells per duodenal villus in vitamin A-deficient animals was significantly lower than that of control and pair-fed animals. In the small intestine of vitamin A-deficient animals, rotavirus infection caused dramatic changes to the mucosa, with almost complete destruction of the tips of the villi, but control and pair-fed animals had normal villi. It is concluded that although rotavirus infection and vitamin A-deficiency cause few changes alone, in their action together there is significant destruction of the mucosal barrier of the small intestine.
Measurement of milk intake: tracer-to-infant deuterium dilution method
Authors: Butte Nancy F. , Wong William W. , Klein Peter D. , Garza Cutberto
Published: June 2005

The tracer-to-infant deuterium dilution method for the measurement of milk intake was evaluated in twenty breast-fed and twenty formula-fed infants. The isotope method was compared with conventional direct-weighing techniques. Human milk intake was assessed by 5 d test-weighing. Intakes of formula, supplemental foods, and water were determined by pre- and post-weighing of feeding bottles. An oral dose of 200 mg 2H2O/kg body-weight was given to each infant, and urine was sampled daily for 14 d. 2H enrichment of the urine was measured by gas-isotope-ratio mass spectrometry. Milk intakes estimated from the deuterium dilution method were consistently higher than those from direct-weighing; the mean difference between methods was 106 (sd 47) g/d or 14% for the breast-fed group and 70 (sd 155) g/d or 8 % for the formula-fed group. Estimates of intake for some infants varied substantially between the two methods of measurement. When the estimated values of human milk intake were corrected for environmental water influx and insensible water loss during breast-feeding, the relative bias decreased to 5%. Correction of the estimated values of formula intake for environmental water influx decreased the relative bias to 1–2%. The acceptability of the deuterium dilution method to determine milk intake depends on the goals and the tolerance for error in group and individual intake estimates of a given study
Influence of low- and high-protein diets on insulin and insulin-like growth factor-1 binding to skeletal muscle and liver in the growing rat
Authors: Dardevet D. , Manin M. , Balage M. , Sornet C. , Grizard J.
Published: June 2005

The influence of protein content of the diet on the plasma concentrations and binding to skeletal muscle and liver of insulin and insulin-like growth factor-1 (IGF-1), was studied in growing rats. Animals with a starting body-weight of 80 g received for an 11 d period isoenergetic diets containing (g/kg dry matter) 155 protein as controls (MP), or 55 (LP) or 300 (HP) protein. Food was offered as six equal meals/d. Daily food intakes provided adequate amounts of energy. Total plasma IGF-1 increased linearly as a function of dietary protein intake. Plasma insulin was lower in the LP than in the MP and HP groups. Hormone binding was studied in wheat-germ agglutinin (WGA) partially purified skeletal muscle receptor preparations. Each125I-labelled hormone binding was competed for by increasing amounts of homologous and heterologous unlabelled hormone; this displacement needed lower concentrations of homologous than heterologous hormone. When compared with MP-diet feeding, the LP diet resulted in an increased ligand concentration for half-maximal binding. In addition the specific125I-labelled insulin and125I-labelled IGF-1 binding increased at all hormone concentrations and, as revealed by Scatchard analysis, the hormone binding capacity also rose (only significant for low-affinity insulin receptors and high-affinity IGF-1 receptors). The HP diet had little effect on hormone binding, except to increase insulin binding at very low insulin concentrations. Hormone binding was further studied in WGA partially purified liver receptor preparations. Those preparations did not exhibit any detectable specific125I-labelled IGF-1 binding. The specific125I-labelled insulin binding was not altered by dietary protein level. It is concluded that the increase in skeletal muscle insulin and IGF-1 binding along with a decrease in insulin and IGF-1 in the blood from rats fed on the LP diet, is consistent with the concept of an inverse relationship between plasma hormone and hormone binding. The physiological significance with respect to metabolic adaptation of muscle remains to be established
Effect of various levels of selenium in wheat and meat on blood Se status indices and on Se balance in Dutch men
Authors: Van Der Torre Hetty W. , Dokkum Wim Van , Schaafsma Gertjan , Wedel Michel , Ockhuizen Theo
Published: June 2005

After a 5-week period of low selenium intake, twenty-four Dutch men received 55, 135 or 215 μg Se/d as Se-rich meat or bread for a 9-week period. Four unsupplemented subjects served as controls. Plasma Se increased more rapidly than erythrocyte Se levels; the increases were significantly dependent (P< 0.001) on Se intake level. Glutathione peroxidase (EC1.11.1.9; GSH-Px) activity in platelets increased rapidly after supplementation and plateaued after 4–9 weeks. At 10 weeks after supplementation ended, plasma Se levels and platelet GSH-Px were still higher than the baseline values whereas erythrocyte Se levels continued to increase. Except for the higher erythrocyte Se levels after supplementation with high-Se meat, there were no differences in bioavailability of Se between meat and wheat products. Daily urinary and faecal Se excretions as well as Se retention increased with an increased Se intake irrespective of the form of the supplement. Regression of Se excretion ν. intake indicated that 33 μg Se/d is necessary to compensate for urinary and faecal losses