bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth and development of rats artificially reared on a high or a low plane of nutrition
Authors: Smart J. L. , Stephens D. N. , Katz H. B.
Published: September 2005

1. In order to exclude the possibility of differences in maternal care which are known to result from typical methods of undernutrition during the suckling period, rat pups were reared artificially on different planes of nutrition away from their mothers.

2. Artificial rearing was accomplished by fitting infant rats with a gastric cannula through which a milk substitute was infused intermittently. Rats were fed thus from 4 to 21 d on a high (ARHI) or a low (ARLO; 44% of ARHI level) plane of nutrition. Underfeeding of the ARLO group was continued till 25 d, after which all rats were given a good-quality pelleted diet ad lib.

3. Compared with mother-reared (MR) litter-mates, ARHI rats showed advanced eye-opening and, at 21 and 25 d, they resisted restraint more strongly.

4. Growth in body-weight of ARHI and MR rats was similar but, when autopsied at 32 weeks, the ARHI rats were shorter (nose–rump length) and had lighter gastrocnemius muscles, adrenals and brains, but heavier epididymal-fat pads.

5. ARLO rats had deficits at 32 weeks compared with ARHI rats in whole body, kidney and epididymal-fat-pad weights, and in tibia length.

6. In a second experiment, ARHI and MR rats were killed at 21 d. All the differences found at 32 weeks were already present at 21 d. In addition, the ARHI pups had enlarged livers and intestines but shorter tibias.

7. The milk substitute, which is one commonly used in such studies, has a low protein and high carbohydrate content compared with rats' milk. This difference probably caused the abnormal organ growth of ARHI rats.
Dependence of 24 h energy expenditure in man on the composition of the nutrient intake
Authors: Dauncey M. J. , Bingham S. A.
Published: September 2005

1. The influence of the nutrient composition of food on energy expenditure during a 24 h period was investigated in adult volunteers. The maximum probable effect was determined using iso-energetic diets high in either protein or in glucose.

2. Two men and four women took part in the study. Their body-weights and body composition were within the normal range. Each subject lived for 28 h in a whole-body calorimeterset at 26°, on two separate occasions. During each session they ate one of the following iso-energetic diets: high-protein–low-carbohydrate or high-glucose–low-protein.Energy expenditure was determined while the subject followed a pre-set pattern of activity. A 24 h collection of urine was made and total nitrogen, creatinine and urea excretions were determined, so that heat production could be corrected for protein metabolism.

3. Two independent measures of energy expenditure were made: direct calorimetry was used to obtain heat loss partitioned into its sensible and evaporative components, while indirect calorimetry was used to estimate heat production from oxygen consumption, carbon dioxide production and N excretion. There was good agreement between the two estimates of 24 h energy expenditure: for the twelve sessions in the calorimeter the mean difference between heat production and heat loss was only 0·4 (SEM 0·39)%.

4. The results showed that nutrient composition can have a marked influence on 24 h energy expenditure in adult humans. Mean values of 8659 (SEM 230) kJ and 7735 (SEM 250) kJ were obtained for the high-protein and high-glucose diets respectively. This 12% increasein energy expenditure on the high-protein intake was significant (P< 0·001). On the high-glucose intake, total heat loss comprised 22 and 78% evaporative and sensible heat losses respectively. The increase in heat loss onthe high-protein intake was accounted for by a 39% increase in evaporative heat loss and a 7% increase in sensible heat loss.

5. It is concluded that the composition of the nutrient intake has a greater influenceon the metabolic rate of adult humans than has been suggested by some groups of workers in recent years.
Studies on the availability of iron in potatoes
Authors: Fairweather-Tait Susan J.
Published: September 2005

1. Iron availability in potatoes and ferrous sulphate was measured in rats in a 10 d balance study and from a single meal using59Fe and55Fe as extrinsic labels.

2. Dried potato samples were incubated in gastric juice in vitro and the amount solubilized was compared with other foods. The relationship between ascorbic acid content of dried potato and Fe solubilization was examined in vitro.

3. In the balance study, the rats absorbed (mean with SE) 15·2 (2·7)% Fe from the diet containing 660 g dried potato/kg and 32·1 (2·8)% Fe from the semi-synthetic diet containing FeSO4. Absorption was higher from the extrinsically-labelled single meal: 49·6 (1·1)% Fe from59Fe-labelled potato and 62·4 (1·2)% Fe from59FeSO4.

4. The in vitro experiments showed a much greater solubilization of Fe from potato than from the other foods examined. There was a correlation between Fe solubilization and ascorbic acid content of potatoes (rs0·76,P< 0·00).

5. It appears that potatoes contain Fe of moderate availability, possibly higher than most vegetables. They also provide ascorbic acid which may enhance Fe absorption from a meal if present in sufficient quantities. Thus potatoes may make a useful contribution towards the Fe nutriture of the UK population.
Simultaneous determination of absorption of selenium from poultry meat and selenite in young men: application of a triple stable-isotope method
Authors: Christensen Merrill J. , Janghorbani Morteza , Steinke Fred H. , Istfan Nawfal , Young Vernon R.
Published: September 2005

1. A triple stable-isotope method was used to estimat simultaneously selenium absorption from poultry meat intrinsically labelled with74Se and from an extrinsic tracer of76SeO32−in four young adult men. The subjects received an experimental diet based on chicken meat as the source of protein. Two diet periods, lasting from 5 to 10 d, depending on the frequency of stool output for each subject, were conducted to allow duplicate determinations within each subject of Se absorption from both sources.

2. Absorption of Se was determined by the faecal isotope balance procedure through monitoring the stable isotopes74Se,76Se and80Se by means of radiochemical neutron activation analysis.

3. For the separate periods, mean (with SEM) absorption of74Se from the intrinsically-labelled poultry meat was 70·9 (1·5)% and 72·0 (2·5)%. The absorption of Se from76SeO32−was 34·7 (5·5)% and 37·6 (3·2)% during the same periods.

4. From these results it is concluded that, under the present experimental conditions, the intrinsic and extrinsic Se isotopes did not form a common pool before absorption. Possible reasons for this are discussed.
The effect of body condition on metabolic changes associated with intake of food by the cow
Authors: Bines J. A. , Morant S. V.
Published: September 2005

1. Changes in concentrations of metabolites in blood and rumen fluid were measured in cows when fat and when thin and when given hay and concentrates at a restricted level or ad lib.

2. When fed ad lib., cows consumed 24% more food when thin than when fat.

3. Concentrations in rumen fluid of acetate and propionate after feeding at both levels did not differ significantly between fat and thin cows.

4. Concentrations in blood of the lipogenic substrates acetate and 3-hydroxybutyrate did not differ between fat and thin cows after feeding, but glucose concentration fell more rapidly in thin cows especially when fed ad lib. Propionate rose more in thin cows than in fat cows when fed ad lib. Non-esterified fatty acids were higher in fat cows before feeding, but fell to similar levels to those in thin cows after feeding.

5. The results are interpreted as indicating a more rapid rate of fatty acid synthesis in adipose tissue of thin cows. This in turn tends to lower blood levels of fatty acid precursors and so enhance the rate of their absorption from the rumen. This in turn permits higher intake of food before short-term chemical regulators of intake start to operate.
Effects of addition of kaolin or cellulose to an elemental diet on intestinal cell proliferation in the mouse
Authors: Goodlad R. A. , Wright N. A.
Published: September 2005

1. Various methods of estimating intestinal mass and cell proliferation were used to compare the effects of a pelleted laboratory diet (diet A), an elemental diet (Flexical; diet B), Flexical plus kaolin (diet C) and Flexical plus cellulose (diet D) on the mucosa and other tissues of the mouse small intestine and colon.

2. The weight of the distal third of the small intestine was significantly decreased in mice given diets B, C and D (P< 0·001). The length of the colon was significantly decreased in the mice given diets B (P< 0·001), C (P< 0·01) and D (P< 0·05); however, the weight of the colon was only decreased in the mice given diet B or diet C (P< 0·001).

Similar changes were noted in the weights of the intestinal muscle and serosa layers; however, no such changes were noted in the weight or DNA content of the mucosa.

3. No changes were observed in the crypt cell production rate in the small intestine, apart from an increase in the mid-region (P< 0·01) of mice given diet C, which was associated with a similar increase in the mucosal content of DNA.

Crypt-cell production was significantly decreased (P< 0·01, 0·001) in the two sites of the colon studied in the mice given diets B or C, but the crypt-cell production rates were not significantly different from control levels at either site in the mice given diet D.

4. The length of the colonic crypts was significantly decreased (P< 0·05, 0·02) in mice given diets B and C, but not in those given diet D; total cell number showed a similar change (P< 0·01, 0·05).

The correlation coefficient between the length of the colonic crypts and absolute cell number was 0·513.

5. The conclusion of the present study was that dietary fibre (cellulose), but not inert bulk (kaolin), prevents mucosal atrophy of the colon of mice given a fibre-free diet, and that many of the observed changes in intestinal weight are due to reduction in the bulk of the muscle layer.
Investigation of nitrogen balance in dairy cows and steers nourished by intragastric infusion
Authors: Ørskov E. R. , MacLeod N. A. , Fahmy S. T. M. , Istasse L. , Hovell F. D. DeB.
Published: September 2005

1. Two dairy cows were maintained by intragastric infusion of volatile fatty acids and casein. Except when fasting, the casein-nitrogen was held constant, while total gross energy supply was varied from zero during fasting to 650 kJ/kg body-weight (W)0·75.

2. One cow was estimated to attain zero N balance at an energy intake of 255 kJ/kg W0·75and the other at 307 kJ/kg W0·75, which was calculated to be substantially below the estimated energy required for zero energy balance.

3. When the cows were later given an N-free infusion for a period preceding the trial, N balance occurred at 98 kJ/kg W0·75for one cow and 115 kJ/kg W0·75for the other.

4. Four steers were similarly nourished by intragastric infusion and the energy nutrient increased from 0 at fasting to 450 kJ/kg W0·75. The protein was held constant at 1 g N/kg W0·75except at fasting. The energy level at which N balance occurred was 154 (SE 38) kJ/kg W0·75or approximately equal to the energy content of the protein. The practical implications of these findings are discussed.
The effect of high-protein and high-carbohydrate diets on [125I]iodoinsulin binding in skeletal muscle plasma membranes and isolated hepatocytes of rainbow trout (Salmo gairdneri)
Authors: Ablett Richard F. , Taylor Matthew J. , Selivonchick Daniel P.
Published: September 2005

1. [125I]iodoinsulin-binding studies in the presence of a concentration range of bovine insulin were conducted to establish specific insulin-binding levels in skeletal muscle plasma membranes and isolated hepatocytes of rainbow trout (Salmo gairdneri) reared on control, high-protein or high-carbohydrate diets.

2. Negative co-operativity was observed and receptor concentrations and apparent dissociation constants established for each preparation.

3. No differences of specific binding attributed to diet were detected in skeletal muscle plasma membrane preparations; however, the receptor concentration of isolated hepatocytes from high-carbohydrate-reared trout was increased. This contrasted to comparable mammalian studies.
The intake of milk by suckled, newborn lambs and the effects of twinning and cold exposure
Authors: Thompson G. E.
Published: September 2005

1. Clun Forest ewes with single and twin lambs were exposed to neutral (20°) or cold (−1°) environmental temperatures, beginning soon after parturition, for 4 d. The intakes of milk, lactose and glycerides by the lambs were calculated from measurements of the rate of displacement of tritiated water (injected into the lambs) by non-radioactive water in milk from the ewes, and measurements of the concentration of lactose and glyceride glycerol in small samples of milk.

2. The yield of milk from ewes bearing twin lambs was greater than the yield from single-bearing ewes in the neutral environment but, in both environments, twin lambs had lower intakes of milk and milk lactose and glycerides, and gained body-weight more slowly, than single lambs. Milk from twin-bearing ewes had a lower lactose concentration than milk from single-bearing ewes.

3. Cold exposure reduced the intake of milk and milk lactose, and reduced the rate of weight gain, of single and twin lambs. Glyceride intake was not different in the two environments.

4. There appears to be a conflict between reduced supply of milk by the ewe and increased demand for milk by the lamb in cold temperatures. Such a conflict is sharpened when twin lambs are born.
Rate of endogenous methionine oxidation in rats at different levels of methionine intake
Authors: Neale R. J. , Waterlow J. C.
Published: September 2005

1. The fractional rates of loss of 14C and body-weight were measured in growing female rats after a single dose of [1-14C]methionine. After the dose, the rats were maintained for 30 d on diets containing graded amounts of methionine and killed at 30 d.

2. By 20 d after the dose the level of labelling of body proteins was fairly uniform. From 20 to 30 d, 14CO2 was collected at intervals. The rats were killed at 30 d and the total radioactivity remaining in the body was measured.

3. The fractional loss of 14CO2 between days 20 and 30 was constant regardless of methionine intake except at the highest intake level.

4. After correcting the fractional loss of 14CO2 for urinary 14C loss, a value of 35 mg/kg body-weight (20 mg/kg body-weight0·75) was obtained for the rate of endogenous methionine oxidation.
Losses in weight and body water in sows after weaning
Authors: Zoiopoulos P. E. , Topps J. H. , English P. R.
Published: September 2005

1. The loss of body water of eight sows in the 7 d following weaning was determined using the deuterium oxide dilution technique. Four of the sows had received a concentrate diet in restricted amounts while the other four had been given the same diet mixed with two-thirds its weight of oat husksad lib. during the whole of the preceding lactation. Certain blood and urine constituents were also measured.

2. Loss of body water was significantly less (P < 0·05) than weight loss of fasted animals, but body water losses were considerable in six of the eight animals.

3. Excretion of urinary nitrogen, urea and creatinine and levels of plasma urea were higher, while levels of plasma non-esterified fatty acids and the hydroxyproline index were lower 1 week after weaning compared with values obtained on the day following weaning.

4. These results indicate that in addition to water loss, depletion of body tissue, including protein, occurs in the newly-weaned sow.
Basal urinary nitrogen excretion and growth response to supplemental protein by lambs close to energy equilibrium
Authors: Hovell F. D. DeB. , Ørskov E. R. , Grubb D. A. , MacLeod N. A.
Published: September 2005

1. Two experiments are reported. In Expt 1, five male lambs of 26–33 kg were used to measure basal nitrogen excretion when the lambs were entirely sustained by an intraruminal infusion of 450 kJ/kg body-weight0·75 per d of volatile fatty acid (VFA) and were receiving no protein. In Expt 2, which was a conventional growth trial, the response to fish meal (66 or 132 g dry matter/d) of lambs given a control diet of sodium-hydroxide-treated barley straw was measured.

2. In Expt 1 the mean basal N excretion of the lambs was 429 (SE 21) mg N/kg body-weight0·75 per d. This exceeds current UK standards for the amino acid N of microbial origin which would be made available to the normally-fed host animal at a maintenance level of metabolizable energy intake.

3. In Expt 2 there was a clear growth response to the fish meal, which was greater (P < 0·05, single-tailed test) than that to be predicted from the energy content of the fish meal. There was no effect of fish meal on the voluntary intake of the basal diet, but there was a suggestion that the digestibility of the basal diet was improved.

4. It is concluded from Expt 1 that the basal requirement for amino acid N by lambs is three- to fourfold that currently recommended in the UK. This higher basal requirement should have resulted in a marked response to supplemental protein in Expt 2. The fact that the growth response in Expt 2 was less than anticipated may have been due to a combination of a slightly lower basal N excretion than that found in Expt 1, a higher yield of amino acids of microbial origin than current UK standards predict, and possibly to a change in the body composition of the lambs.
Differing effects of pectin, cellulose and lignin on stool pH, transit time and weight
Authors: Hillman Lybus , Peters Sue , Fisher Anne , Pomare E. W.
Published: September 2005

1. Randomized cross-over studies were undertaken to determine the effects of daily dietary supplements of pectin (12 g/d), cellulose (15 g/d) and lignin (12 g/d) on stool characteristics of healthy volunteers.

2. Detailed dietary records were kept throughout the study. Stool collections over 48 h were used to determine mean stool pH and weight. The single stool transit time was measured using radio-opaque markers.

3. Pectin did not significantly alter the mean stool pH, transit time or 24 h wet weight.

4. Cellulose lowered the mean stool pH from 6·38 to 6·12, decreased mean stool transit time by 27% and increased mean wet stool weight by 57%.

5. Lignin lowered the mean pH from 6·34 to 6·25, decreased the stool transit time by 20% and increased stool weight by 27% but these changes were not statisticallysignificant.

6. These findings have shown that individual fibre components have different colonic metabolic effects and support the view that associations between dietary fibre intakes anddiseases such as colorectal cancer should be evaluated with regard to the type of fibrecomponents consumed.
The influence of dietary tea, coffee and cocoa on protein and energy utilization of soya-bean meal and barley in rats
Authors: Eggum B. O. , Pedersen Birthe , Jacobsen Ingeborg
Published: September 2005

1. Two series of balance experiments were performed with growing rats to test the effect of black tea, green tea, coffee and cocoa on protein and energy utilization. In Expt 1 soya-bean meal was fed as a basal diet and supplemented with freeze-dried materials from 11 black tea, green tea or coffee/500 g dry matter. Cocoa powder, corresponding to 11 of the beverage, was also added to the basal diet. In Expt 2 the procedure was repeated with a barley-based diet.

2. In both experiments both tea varieties and coffee had significantly negative effects on true protein digestibility and biological value, while digestible energy was only slightly affected in the barley-based diet. Cocoa had no effect on protein or energy utilization in either soya-bean meal or barley diets, although the protein in cocoa powder was completely indigestible.

3. As the tannin concentration in both tea varieties and coffee was very high it is assumed that the observed deleterious effects might, in part, be explained by anti-nutritional effects of tannin.

4. The strongest deleterious effect was recorded for black tea.
A survey of the nutritional and haemagglutination properties of legume seeds generally available in the UK
Authors: Grant George , More Linda J. , McKenzie Norma H. , Stewart James C. , Pusztai Arpad
Published: September 2005

1. Eighty-five samples from fifteen different legume seed lines generally available inthe UK were examined by measurements of their net protein utilization by rats and by haemagglutination tests with erythrocytes from a number of different animal species. From these results the seeds were classified into four broad groups.

2. Group a seeds from most varieties of kidney (Phaseolus vulgaris), runner (Phaseolus coccineus) and tepary (Phaseolus acutifolius) beans showed high reactivity with all cell types and were also highly toxic.

3. Group b, which contained seeds from lima or butter beans (Phaseolus lunatus) and winged bean (Psophocarpus tetragonolobus), agglutinated only human and pronase-treated rat erythrocytes. These seeds did not support proper growth of the ratsalthough the animals survived the 10 d experimental period.

4. Group c consisted of seeds from lentils (Lens culinaris), peas (Pisum sativum), chick-peas (Cicer arietinum), blackeyed peas (Vigna sinensis), pigeon peas (Cajanus cajan), mung beans (Phaseolus aureus), field orbroad beans (Vicia faba) and aduki beans (Phaseolus angularis). These generally had low reactivity with all cells and were non-toxic.

5. Group d, represented by soya (Glycine max) and pinto (Phaseolus vulgaris) beans, generally had low reactivity with all cells but caused growth depression atcertain dietary concentrations. This growth depression was probably mainly due to antinutritional factors other than lectins.

6. Lectins from group a seeds showed many structural and immunological similarities. However the subunit composition of the lectin from the tepary bean samples was different from that of the other bean lectins in this or any other groups.
Retinol homeostasis in lambs given low and high intakes of vitamin A
Authors: Donoghue Susan , Kronfeld David S. , Sklan David
Published: September 2005

1. Four groups of lambs were fed on a low-carotene basal diet. One group received no supplemental vitamin A (mildly deficient). Remaining groups were supplemented daily with vitamin A acetate equivalent to 100 (control) 9000 (mildly intoxicated) and 18000 (severely intoxicated) μg retinol/kg body-weight. After 16 weeks lambs received a bolus of[15−3H]retinol intravenously; blood, urine and faeces were sampled for 48 h.

2. Plasma retinol was complexed to a protein of 20000 molecular weight (MW), which in turn was complexed to a protein of 65000 MW; these proteins correspond respectively to retinol-binding protein and prealbumin. Plasma retinol concentration reached plateau values in intoxicated lambs, but plasma retinyl ester concentrations increased rapidly when liver contents of both retinol and retinyl esters exceeded approximately 10 and 100 mg respectively and kidney contents of both retinol and retinyl esters exceeded 30 μg. Labelled compounds, more polar than retinol, were found in plasma; their concentration increased tenfold in intoxicated lambs within 48 h.

3. Plasma retinol transport rates were 0·1, 10·5 and 11·8 times control values, and clearance rates were 0·3, 14·1 and 14·3 times control values in mildly-deficient, and mildly- or severely-intoxicated lambs respectively. Turnover of retinol increased rapidly when liver contents of retinol and retinyl esters exceeded approximately 10 and 100 mg respectively and kidney contents of both retinol and retinyl esters exceeded approximately 30 μg. Plasma clearance of retinyl esters was unchanged with intake. Faecal excretion of tracer increased linearly with plasma retinol clearance.

4. Our findings identify, several variables that appear to be involved in retinol homeostasis, including plasma retinol clearance and excretion.
Whole-body metabolism of glucose and lactate in productive sheep and cows
Authors: Baird G. D. , Van Der Walt J. G. , Bergman E. N.
Published: September 2005

1. Constant infusions of D-[U-14C]glucose, D-[6−3H]glucose and L-[U-14C]lactate were used to determine rates of apparent turnover,de novoproduction, disposal and interconversions of glucose and lactate, together with total recycling of glucose-C, in ewes and dairy cows during late pregnancy and early lactation. The cows were also examined while being fasted. In the fed animals, infusions were made within 5 h after the morning meal when steady-state conditions appeared to exist.

2. In the ewes, circulating concentrations of glucose and lactate, and magnitudes of apparent turnovers of glucose and lactate, tended to be higher during lactation than during pregnancy, while the extent of interconversions of glucose and lactate tended to be lower.

3. Although the metabolic pattern seen in the cows appeared to be similar to that of the ewes during pregnancy, there were clear differences during lactation. Thus, in the lactating cows, as compared with the lactating ewes, circulating concentrations of glucose and lactate were lower, as was apparent lactate turnover related to metabolic body-weight. Furthermore, the percentage of lactate turnover converted to glucose was higher.

4. In the cows, fasting was characterized by low rates of apparent turnover of glucose and lactate and relatively high rates of interconversion of the two compounds.

5. The results indicated that, under the conditions used in this study and when feeding is to recommended levels, carbohydrate metabolism in ewes is more precarious during late pregnancy than during early lactation, while in dairy cows it is more or less equally precarious in both physiological states.

6. A further conclusion is that the extent of glucose–lactate interconversions, and thus Cori cycle activity, seems to be lower in ruminants than in other species.
The effect of biotin deficiency and dietary protein content on lipogenesis, gluconeogenesis and related enzyme activities in chick liver
Authors: Bannister D. W. , O'Neill Iris E. , Whitehead C. C.
Published: September 2005

1. Chicks were given biotin-deficient diets containing either suboptimal (low) or supraoptimal (high) concentrations of protein from 1-d-old until they were used during their fourth week of life. The low-protein diet predisposed chicks to develop fatty liver and kidney syndrome and the high-protein diet to develop classical biotin deficiency signs. Two other groups, as controls, received biotin-supplemented rations.

2. Low dietary protein increased lipogenesis by isolated hepatocytes but had little effect on gluconeogenesis compared to high dietary protein.

3. Low dietary protein decreased activities of hepatic isocitrate dehydrogenase (EC1.1.1.42), fructose-1,6-bisphosphatase (EC3.1.3.11) and glucose-6-phosphatase (EC3.1.3.9; GP) and increased activities of fatty acid synthase (FAS), citrate cleavage enzyme (EC4.1.3.8; CCE) and malate dehydrogenase (decarboxylating) (EC1.1.1.39).

4. When biotin deficiency was superimposed, the rate of lipogenesis by isolated hepatocytes (from fed birds) was decreased. Gluconeogenesis from lactate and glycerol was also depressed.

5. Activity of GP was further decreased by biotin deficiency on the low-protein regimen and FAS and CCE were further increased. PK activity was increased by biotin deficiency.
Chemical factors affecting the intestinal absorption of zinc in vitro and in vivo
Authors: Seal C. J. , Heaton F. W.
Published: September 2005

1. Everted sacs of rat duodenum and ileum were used to study the effect of anions and organic ligands on the absorption of zinc. The uptake per unit weight of tissue was greater in duodenum than ileum, and it was influenced by the Zn concentration and pH of the incubation medium.

2. The Zn uptake from inorganic salts in simple buffered medium varied in the order zinc sulphate > zinc chloride > zinc phosphate. Zinc acetate was more effective and zinc citrate less effective than ZnCl2. Addition of aspartic acid or histidine to ZnCl2increased the uptake but galactose or lactose decreased it. 2-Picolinic acid greatly increased the Zn uptake but 4-picolinic acid reduced it.

3. When incubated with intestinal sacs after incorporation into a synthetic rat diet, only ZnSO4and 2-picolinic acid increased Zn uptake compared with ZnCl2, but zinc citrate and 4-picolinic acid still tended to decrease it.

4. Metabolic balance studies showed no significant differences in the faecal excretion, total excretion or retention of Zn between rats receiving diets containing different forms of Zn. ZnSO4, zinc citrate and particularly 2-picolinic acid increased the urinary excretion of Zn.

5. The significance of these results is discussed in relation to the suitability of methods for investigating Zn absorption and the importance of Zn-binding ligands.
The effect of changes in the amount of energy infused as volatile fatty acids on the nitrogen retention and creatinine excretion of lambs wholly nourished by intragastric infusion
Authors: Hovell F. D. DeB. , Ørskov E. R. , MacLeod N. A. , McDonald I.
Published: September 2005

1. The nitrogen balance and creatinine excretion of wether lambs of 30–48 kg, wholly nourished by the intragastric infusion of nutrients, were measured in two experiments. Four lambs were used in each experiment. In Expt 1 a constant amount of casein was infused into the abomasum (640 mg N/kg body-weight (W)0·75 per d) and the amount of volatile fatty acids (VFA) infused into the rumen ranged from 0 to 670 kJ/kg W0·75 per d as six increments. Expt 2 was of similar design but two levels of casein were infused (530 and 1060 mg N/kg W0·75 per d) and, with each level of casein, VFA infused ranged from 0 to 700 kJ/kg W0·75 per d as seven increments.

2. Daily creatinine excretion was not constant, but varied between 2-d means with standard deviations of between 7·1 and 16·5% (average 13·1%) of the over-all means. There was an apparent correlation between creatinine excretion and the amount of energy infused in six out of eight lambs. There was no effect of the amount of casein infused.

3. In both experiments N balance was negative only when the amount of energy infused was substantially below published values for energy maintenance. In Expt 1, N equilibrium was calculated to be achieved at a gross (VFA plus protein) energy infusion level of 162 (SE 29) kJ/kg W0·75 per d. In Expt 2 it was observed that, at a given level of energy infusion, N retention was greater when the amount of energy had been increased from the previous level, than when it had been decreased.

4. It is concluded that the animal appears to allocate available amino acids to protein synthesis, rather than to oxidation, even when in negative energy balance. It is also concluded that the enhanced N retention observed when the amount of energy infused had been increased represented compensation after a period of energy restriction.
Hydrolysis of14C-labelled proteins by rumen micro-organisms and by proteolytic enzymes prepared from rumen bacteria
Authors: Wallace R. J.
Published: September 2005

1. Proteins were labelled with14C in a limited reductive methylation using [14C]formaldehyde and sodium borohydride.

2. The rate of hydrolysis of purified proteins was little (< 10%) affected by methylation and the14C-labelled digestion products were not incorporated into microbial protein during a 5 h incubation with rumen fluid in vitro. It was therefore concluded that proteins labelled with14C in this way are valid substrates for study with rumen micro-organisms.

3. The patterns of digestion of14C-labelled fish meal, linseed meal and groundnut-protein meal by rumen micro-organisms in vitro were similar to those found in vivo.

4. The rates of hydrolysis of a number of14C-labelled proteins, including glycoprotein II and lectin from kidney beans (Phaseolus vulgaris), were determined with mixed rumen micro-organisms and with proteases extracted from rumen bacteria. Different soluble proteins were digested at quite different rates, with casein being most readily hydrolysed.

5. Proteins modified by performic acid oxidation, by cross-linking using 1,6-di-iso-cyanatohexane or by diazotization were labelled with14C. Performic acid treatment generally increased the susceptibility of proteins to digestion, so that the rates of hydrolysis of performic acid-treated proteins were more comparable than those of the unmodified proteins. Cross-linking resulted in a decreased rate of hydrolysis except with the insoluble proteins, hide powder azure and elastin congo red. Diazotization had little effect on the rate of hydrolysis of lactoglobulin and albumin, but inhibited casein hydrolysis and stimulated the breakdown of γ-globulin.
Rates of proteolysis in the rumen of the soluble proteins casein, Fraction I (18S) leaf protein, bovine serum albumin and bovine submaxillary mucoprotein
Authors: Nugent J. H. A. , Jones W. T. , Jordan D. J. , Mangan J. L.
Published: September 2005

1. The rate of proteolysis in the rumen was dependent on the soluble protein used. With a sheep on a hay + concentrate diet the rates (approximatelyVmax) for casein, Fraction I leaf protein and bovine serum albumin were 16·5, 3·4 and 0·9 mg protein nitrogen/l per min respectively.

2. Change of diet from hay + concentrate to fresh lucerne (Medicago sativa) increased the proteolytic rates for all three proteins.

3. Bovine submaxillary mucoprotein degraded extremely slowly in the rumen at approximately 0·5–0·6 mg N/l per min and its sialic acid component was degraded at a similar rate to that of the protein chain.

4. Uniformly14C-labelled Fraction I leaf protein was used to demonstrate that in the presence of a second protein, competition for enzymic sites occurred. In Fraction I and bovine serum albumin mixtures, reduced rates for the individual proteins of the mixture were observed compared with the proteins treated separately.

5. Treatment of bovine serum albumin with dithiothreitol (0·2 g/l) to cleave disulphide bridges increased the rates of proteolysis by as much as 8·5-fold.
Carotene-cleavage activity in chick intestinal mucosa cytosol: association with a high-molecular-weight lipid-protein aggregate fraction and partial characterization of the activity
Authors: Sklan David
Published: September 2005

1. A fluorescent high-molecular weight lipid–protein aggregate was isolated from the cytosol of chick intestinal mucosa or liver by gel filtration on columns of Sepharose 4B or 6B.

2. This aggregate exhibited carotene-cleavage activity.

3. On incubation of this aggregate, dissociation occurred and low-molecular weight fractions containing Cu and Zn and exhibiting carotene-cleavage activity were found. This fraction appeared on sodium dodecyl sulphate polyacrylamide electrophoresis to have a molecular weight of 7000–11000 and resembled the previously described Cu chelatins in amino acid composition.

4. Carotene cleavage may be effected by a copper–zinc metalloprotein of low-molecular weight, associated in intestinal cytosol with a lipid–protein aggregate.
Factors affecting the capture of dietary nitrogen by micro-organisms in the forestomachs of the young steer. Experiments with [15N]urea
Authors: Salter D. N. , Smith R. H. , Hewitt D.
Published: September 2005

1. For a period of at least 2 weeks before an experimental collection each of four young steers received total daily intakes consisting of approximately (g/kg) 600 straw and 400 concentrates with the nitrogen provided mainly as urea and in which the main energy source was starch (tapioca) for diet 1 and glucose for diet 2. Concentrates were given twice daily at about 09·00 and 17·00 hours, straw at 17·00 hours only. The value for the ratio, rumen-degradable N: metabolisable energy (g/MJ) in the daily intake was estimated to be approximately 1·2.

2. On the day that an experimental collection was to be made the urea normally given in the feed at 09·00 hours was labelled with 15N. This urea and sometimes the appropriate energy source were added either as a single dose (SD) at 09·00 hours or in three equally-divided doses (DD) at 09·00, 11·00 and 13·00 hours. Treatments, given in a Latin-square design, were: (A), starch (SD)+ urea (SD); (B), starch (SD) + urea (DD); (C), glucose (SD) + urea (DD); (D), glucose (DD) + urea (DD). Doses of polyethylene glycol (PEG) and 144Ce (as cerous chloride) were given as markers with the urea.

3. After these doses were given, samples of abomasal and duodenal digesta were taken periodically for 72 h. It appeared that virtually all the PEG had left the rumen by this time and mean recovery of 144Ce relative to PEG was approximately 90%. From recoveries of non-ammonia-15N (microbial 15N) at the abomasum, estimated relative to PEG, values for mean fractional efficiencies of conversion of urea-N to microbial-N were calculated to be 0·59, 0·59, 0·40 and 0·41 for treatments A, B, C and D respectively. Values for treatments A and B were significantly greater than those for treatments C and D but no other differences were significant. Examination of duodenal samples led to similar conclusions.

4. It was concluded that starch was a more suitable energy source than glucose for maximal capture of ammonia-N for microbial synthesis but that spreading the urea and glucose doses in an attempt to match energy and ammonia release rates had no significant effect on capture efficiency.
Glutathione peroxidase (EC1.11.1.9), glutathione-S-transferase (EC2.5.1.13), superoxide dismutase (EC1.15.1.1) and catalase (EC1.11.1.6) activities in tissues of ducklings deprived of vitamin E and selenium
Authors: Xu Guang-Lu , Diplock Anthony T.
Published: September 2005

1. Vitamin E and selenium deficiencies were produced in the Pekin duckling (Anser cinerens) and were characterized by the development of lesions after 14 d in gizzard, intestine, heart and skeletal muscle.

2. The activities of glutathione peroxidase (EC1.11.1.9), using hydrogen peroxide and cumene hydroperoxide as substrates, glutathione-S-transferase (EC2.5.1.13), superoxide dismutase (EC1.15.1.1) and catalase (EC1.11.1.6) were measured in homogenate supernatant fractions of liver, heart, intestine, gizzard and skeletal muscle of deficient ducklings and of control birds given vitamin E or Se or both.

3. Glutathione peroxidase activities were dramatically lower in tissues of Se-deficient ducklings, and this was unaffected by vitamin E. No adaptive changes were seen in the activity of the other enzymes, even after 21 d when the deficiency was severe.

4. It appeared likely that the variability of the enzyme activities, other than glutathione peroxidase, in the different tissues studied might explain differences among the tissues in susceptibility to peroxidative damage.
The nutritive value of rumen micro-organisms in ruminants
Authors: Storm E. , Brown D. S. , Ørskov E. R.
Published: September 2005

1. An experiment was conducted with three sheep maintained entirely by intragastric nutrition to estimate the digestibility of isolated individual constituents and amino acids (AA) of rumen micro-organisms (RMO) in the small intestine.

2. Five levels of RMO were infused into the abomasum. The apparent and true disappearance of the individual components were measured by regression of abomasal input on the passage at the ileum.

3. The true digestibility values of N, AA-N, DNA and RNA were 0·82, 0·85, 0·81 and 0·87, respectively.

4. The digestibility of individual AA varied between 0·80 and 0·88, the only exceptions being diaminopimelic acid (0·37), histidine (0·68) and cystine (0·73), which were significantly lower than the average (0·847).

5. The endogenous components in the ileal fluid in sheep given protein-free infusions, expressed in mg/kg live weight0·75 per d, were total N 42 and AA-N 20.
The tryptophan requirement of the kitten
Authors: Hargrove Diane M. , Rogers Quinton R. , Morris James G.
Published: September 2005

1. To estimate the tryptophan requirement of the kitten, six male and six female kittens were presented diets containing 0·7, 0·9, 1·1, 1·3, 1·5 and 3·0 g tryptophan/kg diet for six experimental periods lasting 10 d in accordance with a 6 × 6 balanced Latin-square design.

2. Mean daily weight gain and nitrogen retention (N intake minus urinary and faecal N) plateaued at 1·1 g tryptophan/kg diet indicating that the minimal tryptophan requirement of the kitten was 1·1 g/kg diet.

3. Plasma tryptophan concentration exhibited a marked increase at dietary tryptophan concentrations above 1·3 g/kg diet.
Human energy metabolism below, near and above energy equilibrium
Authors: Van Es A. J. H. , Vogt J. E. , Niessen CH. , Veth J. , Rodenburg L. , Teeuwse V. , Dhuyvetter J. , Deurenberg P. , Hautvast J. G. A. J. , Van Der Beek E.
Published: September 2005

1. Complete 24 h energy and nitrogen balances were measured for fifteen subjects at three levels of energy intake and for two other subjects at two levels of intake.

2. At each level, the fifteen subjects ate diets consisting of fifteen to twenty separate foods for 7 or 8 d. Faeces and urine were collected for the final 4 d. Respiratory gas exchange was measured during the final 72 h while the subjects stayed in an 11 m3open-circuit respiration chamber, and simulated office or light household work. The energy balance of the other two subjects was determined initially in a similar way when they consumed a diet which was sufficient for energy equilibrium. Subsequently, the measurements were repeated twice at the same high level of metabolizable energy (ME) intake after 4 and 18 d on that diet.

3. Neither energy nor N digestibilities were significantly affected by intake level or subject. Due to relatively small urinary energy losses the ME content of the gross energy increased slightly at the higher intake.

4. Respiratory quotient increased with intake level from 0.78 to 0.87.

5. The efficiencies of utilization of ME were approximately 1.0 for maintenance (from the low to the intermediate intake level) and decreased to about 0.9 for maintenance and energy deposition (from the intermediate to the high intake level).

6. Estimates of daily ME requirements at energy equilibrium were 149 (SD 13) kJ ME/kg body-weight, 432 (SD 33) kJ ME/kg body-weight0.75and 204 (SD 22) kJ/kg lean body mass. The former two values were negatively correlated with percentage body fat although not significantly so.

7. ME utilization and heat production of the other two subjects were nearly equal after 6 and 20 d on a diet supplying 1.5–1.7 times the ME needed for energy equilibrium.
Effect of dietary supplements of guar gum and cellulose on intestinal cell proliferation, enzyme levels and sugar transport in the rat
Authors: Johnson I. T. , Gee J. M. , Mahoney R. R.
Published: September 2005

1. Male Wistar rats (approximately 200 g) were given fibre-free semi-synthetic diets containing either sucrose (S) or a sucrose-starch mixture (SS) as the carbohydrate component, or a diet similar to SS containing 40 g guar gum/kg (G), or 100 g cellulose/kg (C). The animals remained healthy, and weight gain after 30 d was similar in all groups.

2. The small intestines of the animals given diet G were significantly longer than those of the other groups, and showed signs of increased mitotic activity and mucosal growth.

3. No significant differences in mucosal enzyme activity were detected between the two fibre-free control groups. Lactase (EC3.2.1.23) and alkaline phosphatase (EC3.1.3.1) activities were significantly lower than controls in group G, but were higher in group C.

4. Kinetic analysis of 3-O-methyl glucose uptake by isolated intestine indicated that the maximum transport rate (Vmax) of tissue from group G tended to be lower than from the fibre-free group SS and group C.

5. It is concluded that materials which are classed as dietary fibre but which differ markedly in their physical properties may also differ in the functional changes to which they give rise in the small intestine. These changes may be at least partially mediated by effects on mucosal cell proliferation.
Effect of guar gum on glucose and water absorption from isolated loops of jejunum in conscious growing pigs
Authors: Rainbird Anna L. , Low A. G. , Zebrowska Teresa
Published: September 2005

1. Four pigs initially of 30 kg live weight were surgically prepared with two re-entrant cannulas in the jejunum 1.0 m apart which allowed an isolated loop to be formed through which solutions were perfused. 51Cr-EDTA was used as a marker for measuring net secretion or absorption.

2. A new Ringer solution was made, the ionic content of which resembled more closely that found in the jejunum of pigs given similar diets, than Krebs-Ringer solution.

3. The absorption of glucose and water from Krebs-Ringer and new Ringer solutions was compared.

4. The effect of guar gum on the absorption of glucose and water from solutions of glucose and maltose was studied.

5. There was a trend (not significant) for greater absorption of glucose and water from the new Ringer solution than from the Κ rebs-Ringer solution.

6. Guar gum significantly reduced the net absorption of glucose from glucose or maltose solutions from 74.2 to 41.4% (P < 0.001) and 71.1 to 35.0% (P < 0.001) respectively.

7. Guar gum significantly reduced the net absorption of water from the glucose solution from 42.7 to 8.3% (P < 0.01) and from the maltose solution from 49.2 to 5.1% (P < 0.001).

8. The lack of differences between the absorption of glucose from solutions of glucose or maltose suggested that maltase (EC 3.2.1.20) activity was not inhibited to the extent that this limited the rate of glucose absorption.
Digestibility of proteins of the histological components of cooked and raw rice
Authors: Bradbury J. Howard , Collins J. Grant , Pyliotis N. A.
Published: September 2005

1. The aleurone layer, grain coat and embryo which constitute rice bran are rich in vitamins, lipids, protein and lysine compared with the endosperm (milled rice).

2. A method was developed to measure the in vitro protein digestibility of raw and cooked brown rice and their histological components.

3. The protein digestibility of cooked endosperm by the in vitro method agreed with that of other workers using in vivo techniques.

4. The protein digestibility of the aleurone layer and grain coat from raw rice was only 25% but increased to 65% from cooked rice, due to disruption of the cellulosic cell walls at 100°, which was shown by electron microscopy.

5. The decreased protein digestibility due to cooking was not the result of formation of ε-lysyl–γ-glutamyl isopeptide cross-links, but may be due to formation of a cystine-rich core that is resistant to proteases.

6. The protein digestibility of cooked brown rice was approximately the same as that of cooked milled rice, hence it is advantageous for those for whom rice is a staple food to consume brown rather than milled rice.
The mode of action of anabolic agents: the effect of testosterone on muscle protein metabolism in the female rat
Authors: Martinez J. A. , Buttery P. J. , Pearson J. T.
Published: September 2005

1. Testosterone (1 mg/kg body-weight per d) given subcutaneously to female rats increased their growth rate and food conversion efficiency but not their food intake compared with that of the placebo-oil controls. A higher dose of testosterone (10 mg/kg body-weight per d) failed to increase the daily weight gain.

2. The increased growth rate of the testosterone-treated rats appeared to occur in the whole body and not specifically in muscle. There were no significant changes in body composition.

3. The fractional synthetic rate of gastrocnemius muscle protein was higher in the hormone-treated rats than in controls. This contrasts with previous results for the anabolic agent trenbolone acetate and reflects differences in the mode of action of these two different steroids, both with androgenic properties.