Showing papers in "British Journal of Nutrition in 1970"

Calorie conversion factors. An experimental reassessment of the factors used in the calculation of the energy value of human diets

Abstract: 1. The intake and excretion of total nitrogen, fat and the various forms of carbohydrate, and the heats of combustion of the diet, urine and faeces were measured in groups of young men, young women, elderly men and elderly women. 2. Each group was studied while the subjects were eating two diets in turn, which differed in their contents of unavailable carbohydrate; the young women were also studied on a third diet which was rich in unavailable carbohydrate. 3. Increasing the intake of unavailable carbohydrate resulted in a greater faecal loss of energy, and in most instances of nitrogen and fat. 4. There was no significant effect of sex or age on the apparent digestibility of protein, fat or available carbohydrate. 5. The results are used to evaluate the use of calorie conversion factors for calculating the metabolizable energy content of mixed diets. 6. These show that for practical purposes the classical Atwater factors can be used to calculate the metabolizable energy of a diet with reasonable accuracy, provided that when available carbohydrate (as monosaccharides) values are used in the calculation a factor of 3.75 kcal/g (15.7 kJ/g) is used. 7. The studies demonstrate that the accuracy of any method for calculating the metabolizable energy of a diet is largely determined by the accuracy with which the method is capable of predicting the gross energy of the diet.

Blood urea measurement as a technique for assessing protein quality.

Abstract: 1. Three factors were investigated which influence blood urea content, namely the protein content in the diet, the time after feeding and the protein quality of the diet.2. To investigate the relationship between the protein content in the diet and the blood urea content, seventeen experiments with rats given increasing amounts of protein in the diet were carried out. The experimental results show that there is a positive correlation (r = 0.95) between the protein content in the diet and the blood urea content.3. For investigation of the influence of time after feeding on the urea content in the blood, a pig was used having a catheter in the portal vein for blood sampling at intervals. The results from this experiment showed that the blood urea content increases for the first 3–4 h after feeding and thereafter reaches a plateau.4. To use blood urea measurement as a technique for assessing protein quality it is necessary to work under standardized conditions, especially in regard to the two factors just discussed.5. Forty-two feeding-stuffs of widely differing quality were used in nitrogen balance trials with rats. The results showed that there is an inverse relation between the blood urea content and the biological value of the diet which is sufficiently accurate (coefficient of variation = 53%) to provide ausefulmethod for the predictionof protein quality from measurement of urea levels.

The experimental production of zinc deficiency in the rat.

Abstract: 1. Techniques for the preparation of a semi-synthetic basal diet suitable for the rapid production of zinc deficiency in the rat are described. The complete diet usually contains between 0.6 and 0.9 ppm Zn.2. When the unsupplemented diet was fed to weanling rats, growth arrest occurred after 4–5 d; when supplemented with ZnSO4 to provide 12 or 20 ppm Zn, the rate of growth of rats was similar to that attained in animals given a conventional stock colony diet providing 83 ppm Zn. A study of relationships between dietary Zn concentration and weight gain in 21 d suggested that the Zn requirement of male and female rats for growth on this diet is approximately 12 ppm.3. The development of Zn deficiency on diets providing < 1 or 3 ppm Zn was accompanied by poor food consumption and the development of a characteristic cyclic pattern of intake. A significant decline in the variability of daily food intake was observed when the diet was supplemented with Zn to provide 6, 9 or 12 ppm.4. Studies of the influence of dietary Zn content upon changes in the Zn content of a range of tissues and upon whole-body Zn retention are reported.5. The above findings are discussed in relation to the problem of defining the severity and duration of Zn deficiency in animals used for studies on the nature of the metabolic role of Zn.

Effects of zinc deficiency on food intake and feeding patterns of rats.

Abstract: 1. The effects of alterations of the protein and zinc concentrations of a semi-synthetic diet on the food intake and dietary preferences of Zn-deficient and normal rats have beencompared.2. The voluntary food intake of Zn-deficient rats fell to 70% 96 of that of the controls. The day-to-day variation of intake increased markedly and was associated with a cyclical pattern of food consumption. When the food intake of deficient rats was slightly restricted the troughs of the cycles disappeared.3. Concurrent with the fall in food intake, Zn-deficient rats ceased to gain weight, but a similar change was found with pair-fed controls.4. Force-feeding Zn-deficient rats with 140 % of their voluntary intake rapidly induced signs of ill-health.5. Reduction of the protein content of the diet from 20 to 5 % resulted in an increased food intake and the disappearance of the cyclical pattern of intake. Growth, however, was not renewed.6. Zn-deficient rats responded to a Zn-supplemented diet within 1–2 h by an increased food intake.7. Zn-deficient rats were able to discriminate between diets containing 6 and I ppm Zn when both diets were offered simultaneously.8. The responses of Zn-deficient rats to Zn-containing diets did not occur if the diets did not contain protein.

The protein quality of cassava leaves.

Abstract: 1. A chemical and biological evaluation of the protein content of some leaves and leaf extracts from the eastern region of Nigeria (Biafra) has been made: most were from cassava ( Munihot utilissima ). 2. The protein content of the leaves was from 3 0 to 40% (expressed as percentage of leaf dry matter). The concentrations of essential amino acids were adequate, except for methionine. The biological criteria, true digestibility (TD) and biological value (BV), showed that the digestibility was from 70 to 80%, whereas BV varied from 44 to 57%, depending on the methionine content. 3. Adding methionine to a diet of cassava leaves raised BV from 49 for the leaves alone to 80 for the mixture. This relationship clearly shows that cassava leaves contain too little available methionine. An investigation into the true availability of the amino acids showed that this is somewhat variable, and only 60% of the methionine is available. 4. The BV of cassava leaves combined with Norwegian dried cod showed a mutual supplementation effect.

Mechanisms of heat damage in proteins. 2. Chemical changes in pure proteins.

Abstract: 1 Bovine plasma albumin (BPA) containing approximately 14% moisture, when heated for 27 h at 115° suffered an appreciable loss of cystine and a small loss of lysine; at 145° all the amino acids except glutamic acid and those with paraffin side-chains, showed considerable losses Isoleucine also showed some loss through racemization to alloisoleucine2 BPA heated at 115° evolved H2S; at 145° other sulphur compounds were released as well, all coming from the breakdown of cystine Possible mechanisms for this are discussed3 Ammonia was also liberated from BPA heated at 115° The degree of correlation of lysine binding in different proteins with ammonia liberation and amide changes has led us to suggest that the main reaction of e-amino lysine groups is with amide groups of asparagine and glutamine Reaction of e-amino groups with carboxylic groups is thought to be less important4 Model experiments have shown that a reaction between amide groups and the e-amino group of lysine in proteins can occur at practical drying temperatures5 Reactions of the e-amino group of lysine with destruction products of cystine is also considered to be partially responsible for the lysine binding in heated proteins

Influence of starch digestion in the large intestine of sheep on caecal fermentation, caecal microflora and faecal nitrogen excretion.

Abstract: 1. The concentrations of volatile fatty acids (VFA) in the rumen and caecum were compared when sheep were given barley or dried grass. The molar proportions of VFA in the caecum resembled those in the rumen except that the proportions of isobutyric and isovaleric acids were higher in caecal than in rumen fluid indicating an extensive breakdown of protein during fermentation in the caecum.2. The capacity for starch digestion in the large intestine was studied in two sheep receiving dried grass. Starch was infused into the caecum, the amount given increasing by daily increments of 20 g until 300 g daily were infused. Infused starch in excess of 138 g daily largely appeared in the faeces, indicating a limited but substantial capacity for starch fermentation in the large intestine. The infusion caused a marked increase in the molar proportion of butyric acid.3. Determinations made with a single sheep showed that the infusion of starch into the caecum caused large changes in the microflora, and species similar to Butyrivibrio became prevalent. The viable count on a starch medium was increased by 83 % by starch infusion.4. The infusions of starch increased the excretion of nitrogen in the faeces from 5.8 to 9.0 g daily. Using a fractionation procedure it was shown that when 100 g of starch were fermented in the large intestine the 'bacterial and endogenous debris' nitrogen increased by about 1.0 g. When starch was given orally to two sheep the increase in this fraction was about 0.4g nitrogen/100 g starch digested.5. It is suggested that dietary factors that cause changes in the site of fermentation from the rumen to the caecum will render less microbial nitrogen available to the host animal per unit of carbohydrate fermented and decrease the apparent digestibility of nitrogen.

Observations on the microbiology and biochemistry of the rumen in cattle given different quantities of a pelleted barley ration.

Abstract: 1. Three heifers were changed from a diet of equal parts of hay and barley cubes (50:50 diet) to one entirely of barley cubes given in three equal feeds throughout the day. Feed intake was restricted to 80% of calculated appetite at the time of change and this percentage progressively decreased as the live weights of the animals increased.2. The change of diet had no significant effect on the volume of rumen fluid but the rate of outflow from the rumen was significantly lower on the barley diet than on the 50:50 diet.3. Animals on the restricted barley diet developed an exceptionally high rumen ciliate population and the bacterial population was shown by Gram films to include a number of organisms typical of roughage-fed animals. In culture, organisms of the genus Bacteroides were predominant but these appeared largely as cocco-bacilli in the Gram films. This microbial population was associated with a higher proportion of butyric acid than of propionic acid in the rumen fluid.4. Occasional fluctuations in ciliate populations occurred in all three heifers. Decreases in ciliate number were paralleled by increases in propionic acid and decreases in butyric acid but not necessarily by a fall in pH. Under these conditions Gram films showed increases in bacteriodes-type rods and in certain curved Gram-negative rods.5. Rumen ammonia concentrations were on average lower and showed a different diurnal pattern when ciliate numbers were reduced. Lactic acid concentrations were low and were not affected by the size of the ciliate population.6. When the three heifers were given the barley diet ad lib. there was a decrease in rumen pH and a complete loss of rumen ciliates. The rumen bacterial population and the volatile fatty acid proportions were similar to those seen during decreases in ciliate number at the restricted level of intake. These changes also occurred in a fourth heifer which was changed fairly rapidly from the 50:50 diet to a restricted amount of the barley diet.7. Two steers which had never had access to roughage were changed from ad lib. to restricted intake of the barley diet and were later given an inoculum of rumen ciliates. The rumen microbial population and the pattern of fermentation so produced were similar to those found in the heifers on the restricted barley diet.8. Anomalous values were noted for total counts of rumen bacteria when free starch grains were present in the rumen fluid.9. It is concluded that large ciliate populations and high proportions of butyric acid can be produced in animals fed exclusively on a barley diet by suitable adjustment of the intake and the method of feeding. It is postulated that the ciliate population may be largely responsible for the high butyric acid concentrations.

Food intake and energy expenditure of army recruits.

Abstract: 1. The food intake of sixty-four infantry recruits was measured at six centres during 3 weeks of initial training. The daily energy expenditure was measured in thirty-five of these men.2. The mean daily consumption of the sixty-four subjects provided them with 3850 kcal (16110 kJ); the energy expenditure of the thirty-five subjects averaged 3750 kcal (15690 kJ).3. Serial auto- and cross-correlations of intake and expenditure were very small and there was no significant relationship between food intake and energy expenditure on the same day.4. The intakes and expenditures of different subjects at the same centre were not independent.5. There was a significant relationship between intake and expenditure for the whole period of the survey when results for all subjects were included. In three centres the correlation was high, +0.788 (P < 0.001), but was only + 0.083 (P < 0.5) in the remaining three centres.6. There was a positive but not significant correlation between body-weight and the average food intake of 6 d.7. There was a negative correlation between body-weight and calorie balance.8. Weight change and calorie balance over 1 week were related, the correlation averaging 0.40. There was a correlation of 0.32 between daily weight changes and calorie balance. A rather small amount of variation in calorie balance can be explained by contemporary changes in weight.

Nucleic acid metabolism in the ruminant. 2. Formation of microbial nucleic acids in the rumen in relation to the digestion of food nitrogen, and the fate of dietary nucleic acids.

Abstract: 1. Concentrations of nucleic acid nitrogen (NA-N) and other nitrogenous constituents were estimated in samples of rumen fluid taken from calves and cows which were either given stall diets of varying nitrogen content or were allowed to graze pasture. Concentrations of NA-N ranged from 1.5 to 27.5 mg/100 g water.2. Ratios of RNA: DNA in rumen fluid were similar to those in rumen bacteria and were not related to those in the diets. Pure nucleic acids added to the rumen were rapidly degraded. It was therefore concluded that NA-N in rumen fluid was largely of microbial origin and provided an index of total microbial nitrogen.3. In most experiments, with an individual animal consuming diets of various nitrogen contents, NA-N formed a fairly constant percentage (8-15 for different animals) of the total non-ammonia nitrogen in rumen fluid. This suggested that nitrogen entering the rumen fluid limited microbial growth. Consumption of a diet containing extracted decorticated groundnut meal (diet B), however, led to lower values for this percentage than did the other diets. Diet B was also exceptional in leading to marked diurnal variations in NA-N concentrations in rumen fluid, suggesting a cyclic fluctuation in the size of the microbial population.4. Comparison of NA-N:total nitrogen ratios in rumen fluid and bacteria suggested that, for all the diets except diet B, 55–80 and 40–50% of the non-ammonia nitrogen in rumen fluid was of microbial origin for the calves and cows respectively.

Synthesis of microbial protein from ammonia in the sheep's rumen and the proportion of dietary nitrogen converted into microbial nitrogen

Abstract: 1. The extent to which ammonia-N (NH3-N) serves as a starting point for synthesis of microbial nitrogenous compounds was assessed when 15N as (15NH4)2SO4 was continuously infused into the rumen of a sheep for periods of 78–98 h. Steady states were reached in the composition of the rumen contents because the animal was fed equal parts of its ration at hourly intervals. Concentrations of 15N in bacterial-N, protozoal-N and rumen NH3-N were compared.2. In two trials with a low-N diet consisting largely of wheaten hay the 15N concentration in bacterial N was 76 and 78% of that in the NH3-N. For protozoa the values were more variable —64 and 43%.In two trials with a higher-N diet (lucerne hay), the corresponding values were lower—bacterial-N 62 and 64%, protozoal-N 41 and 35%.It was concluded that synthesis of microbial protein was more dependent on ammonia as a starting point with the low-N diet than with the higher-N diet.3. Entry and exit rates for ammonia into and out of the rumen system were determined, and the results, in combination with those obtained for bacterial-N in the first part of the work, allowed calculations to be made of the production of microbial-N/d formed from NH3-N, and this in turn allowed calculation of minimal values for conversion of plant-N to microbial-N in the lumen. Minimal extent of conversion was 68% for the low-N diet and 53–55% for the higher-N diet.4. Total production of microbial-N in relation to the amount of N given was also calculated by using previously reported values for the relative proportions of protozoal-N and bacterial-N in sheep given diets similar to those used here. These values for extent of conversion were 73% for the low-N diet and 58–59% for the higher-N diet.

The digestion and absorption of protein in man. 1. The site of absorption.

Abstract: 1. The absorption of the amino acid components of two protein-containing test meals has been studied in six healthy volunteers. One meal contained 15 g of milk protein and the other contained 15 g of gelatin. In a control experiment a meal was given which contained a negligible amount of protein. 2. The subjects were intubated with a single lumen tube; then each meal was swallowed and intestinal residues were obtained from known levels. The amino acid composition of the intestinal contents was compared with that of the original meal. Correction was made for net water shifts by reference to a non-absorbable marker compound (polyethylene glycol 4000). 3. The results showed that at least 70–75% of the milk protein test meal had been absorbed when the sampling holes were 230 cm from the nose. It is suggested, however, that most, if not all, of the meal had been absorbed when the sampling holes were 140 cm from the nose. 4. Amino acids were absorbed at rates proportional to their concentrations in the meal. 5. Gelatin, a protein known to be relatively resistant to enzymic hydrolysis, was poorly absorbed from the region of the small intestine under study. 6. Estimates of the amount of endogenous protein secreted in response to the test meals ranged from z to 8 g, equivalent to 13–53% of the protein containing test meals. 7. The absorption of certain amino acids, e.g. the dicarboxylic amino acids, was more rapid than was expected; glutamic and aspartic acids are absorbed slowly from a mixture of amino acids, both in vitro and in vivo.

The digestion and absorption of protein in man. 2. The form in which digested protein is absorbed.

Abstract: 1. Intestinal contents, collected from the human jejunum after a test meal (milk-protein, gelatin or low-protein) were fractionated by centrifugation and gel filtration on G-75Sephadex. The fractions were hydrolysed and the proportion of the total amino acid in each fraction was determined. The amino acids were measured with an EEL Amino Acid Analyser.2. The free amino acid concentrations were determined in samples of the contents of the small intestine collected from various levels after the three types of test meal.3. Intestinal contents collected from two levels of the jejunum after a milk-protein meal, were incubated in vitro at 37° for periods up to 80 min and the rates of release of the individual free amino acids were determined.4. There was a rapid breakdown of the proteins of the test meals to fragments of molecular weight under 5000. The further breakdown (during incubation in vitro) to free amino acids was sufficiently rapid to account for the absorption in the free form of arginine, lysine, tyrosine, valine, phenylalanine, methionine and leucine. It was not rapid enough to account for the absorption of glycine, threonine, serine, the imino acids or the dicarboxylic amino acids in the free form.5. The free amino acid concentrations in the intestinal lumen bore very little relationship to the concentrations in hydrolysates of the test meals or to those in hydrolysates of the intestinal contents. Many of the free amino acids in the intestinal samples were present in approximately equimolar concentrations.6. It is suggested that experiments in which amino acid mixtures, simulating a dietary protein, are fed to experimental animals to determine the rates of amino acid absorption do not present a true picture of the events in the small intestine following the ingestion of a protein meal.

The effects of early zinc deficiency on DNA and protein synthesis in the rat.

Abstract: 1. The effects of early zinc deficiency on DNA and protein metabolism of the liver, kidneys, testes and spleen of the young rat were studied. The investigations were carried out in two phases: before food consumption and growth were affected, and afterwards. 2. The incorporation of [ 3 H]thymidine into DNA was markedly affected by differences of less than a week in the age of the rats. 3. Zn deficiency significantly reduced the incorporation of [ 3 H]thymidine into DNA of liver, kidneys and spleen before growth and food consumption were affected. The degree of inhibition was of the order of 50% in the first 5 d. A similar but non-significant trend was observed for the testes. 4. The incorporation of [ 3 C]lysine into protein was not significantly affected in liver and testes during the initial period of Zn deficiency; the incorporation into kidneys and spleen was significantly inhibited but the magnitude of the effect was only of the order of 20% in 5d. 5. One week after the start of the second phase, the concentration of DNA in liver, testes, and spleen of Zn-deficient animals was not significantly different from that in pair-fed controls. The DNA content of the kidneys was significantly reduced by the deficiency hut only to 97% of that in pair-fed animalsgiven the Zn-supplcmenteddiet. The incorporation of [ 3 H]thymidine into DNA was not significantly different between deficient and control groups in any of the four organs investigated.

Studies on intestinal digestion in the sheep. 3. Net movement of certain inorganic elements in the digestive tract on rations containing different proportions of hay and rolled barley.

Abstract: 1. In each of three experiments, two sheep were given diets consisting of hay, or two parts hay to one part barley or one part hay to two parts barley. Each sheep was equipped with a cannula into the rumen and re-entrant cannulas into the proximal duodenum and the terminal ileum. The rations containing barley were supplemented to adjust the intake of calcium, phosphorus, magnesium, sodium and potassium to a level similar to that in the all-hay ration. Paper impregnated with chromic oxide (Cr2O3) was given twice daily by rumen fistula.2. Amounts of crude ash and the five minerals entering and leaving the small intestine and excreted in the faeces were measured. The amounts passing through the re-entrant cannulas were adjusted to give 100% recovery of chromic oxide. The values were used to calculate the direction and net movements of the elements through the walls of the three main parts of the alimentary tract.3. In all instances there was an extensive net secretion of Na and P between mouth and small intestine, net absorption of K and P from the small intestine and of Na from the large intestine.4. The net movements of Ca and Mg were small and rather variable. In five of the six observations there was a small net secretion of Ca and small net absorption of Mg during passage of the digesta through the reticulo-rurnen, omasurn and abomasurn. Net secretion of Ca and Mg apparently occurred in the small intestine and net absorption of Mg in the large intestine.5. The only between-diet differences were small differences in net movements of Na and K.

Production, absorption, distribution and excretion of vitamin B12 in sheep.

Abstract: 1. The efficiency of production and utilization of vitamin B12 was studied with sheep given a cobalt-deficient diet with and without supplementary Co (1 mg/d). Vitamin B12 to lignin ratios in rumen contents were used to estimate minimum rates of production and these were related to faecal and urinary excretion. Tissue distribution and excretion of vitamin B12 were studied with [58Co]cyanocobalamin and 5′-deoxyadenosyl[60Co]cobalamin.2. Labelled Co was rapidly sequestered by particulate material in the rumen and was largely excreted in the faeces. Most of the vitamin B12 in whole rumen contents was contained in micro-organisms, but was released on incubation at pH 2. Added cyanocobalamin was partly degraded in the rumen.3. The vitamin B12 to lignin ratio in rumen contents began to decline 1–3 d after cessation of a daily Co drench. Estimated ruminal production of vitamin B12 on full feed was not less than 400–700 μg/d with supplementary Co and 50–110 μg/d from the Co (0.01–0.05 μg/g dry weight) in the basal diet. Production of vitamin B12 appeared to be limited by food intake with or without additional Co.4. At full feed the efficiency of production of vitamin B12 from Co in the basal diet was about 13% while that from added Co was about 3%. Part of the vitamin B12 produced in the rumen was degraded before reaching the faeces and about 5% was absorbed. The minimum total requirements of sheep for vitamin B12 are assessed at about 11 μg/d.5. Injected 5′-deoxyadenosylcobalamin was better retained than injected cyanocobalamin, faecal excretion exceeded urinary excretion with both. Labelled cobalamin was selectively retained by liver (particularly by the mitochondria), kidneys and the walls of parts of the alimentary tract. Vitamin B12 was secreted into the duodenum and reabsorbed in the ileum, but little secretion occurred above the duodenum and little absorption below the small intestine.

Calcium metabolism in pregnant ewes.

Abstract: 1. A combination of balance and isotope techniques has been used to study calcium metabolism in ten sheep at different stages of pregnancy, and the results have been combined with earlier results obtained during lactation to show the variations in Ca metabolism which occur during the whole reproductive cycle. 2. Transfer of Ca to the foetuses during pregnancy and to the milk after parturition rose rapidly from the 65th day of gestation and reached a maximum at parturition or shortly afterwards. 3. Although the rate of absorption of Ca from the intestine increased steadily throughout pregnancy it was insufficient to meet the full requirements of late pregnancy and early lactation. During this period, the extra Ca was supplied by increased bone resorption. 4. The maternal Ca balance became negative during pregnancy, the net daily loss of Ca reaching a maximum in early lactation. 5. In late lactation the maternal Ca balance became positive enabling the animals to replenish their skeletal stores. 6. There was no marked change in the demands for Ca at parturition and the connexion between this observation and the pathogenesis of milk fever is discussed. 7. Rates of transfer of Ca to the foetus during pregnancy are compared with estimated values of other workers.

The effects of feeding procedure on closure of the oesophageal groove in young sheep.

Abstract: 1. Barium sulphate suspensions were given to young sheep by mouth or by injection via an oesophageal catheter. Closure of the oesophageal groove was assessed by observing radiographically whether the suspension passed to the ruminoreticulum or to the abomasum.2. Complete closure of the groove took place in lambs that were trained to drink small meals from a trough after being weaned from their dams, a finding similar to that for lambs weaned on to a teat-bottle.3. When barium was injected into the oesophagus of lambs that were excited by being offered their bottle or trough beyond their reach, the barium passed direct to the abomasum if the normal feeding routine was closely imitated. When the lambs were able to discriminate between this teasing procedure and the normal routine, the barium frequently passed to the ruminoreticulum. If the lambs were not teased the barium passed invariably to the ruminoreticulum.4. It is concluded that the reflex closure of the groove can be conditioned by the feeding procedure adopted at weaning so that it no longer depends on the stimuli associated with sucking and swallowing.

The effect of trypsin inhibitors on pancreatopeptidase E, trypsin, chymotrypsin and amylase in the pancreas and intestinal tract of chicks receiving raw and heated soya-bean diets.

Abstract: 1. Feeding on a raw soya-bean diet (RSD) increased the levels of trypsin, chymotrypsin and pancreatopeptidase E but decreased the level of amylase in the pancreas of chicks as compared to a heated soya-bean diet (HSD), while supplementation of HSD with soya-bean trypsin inhibitors increased the activity of all four enzymes. HSD + trypsin inhibitors caused significant enlargement of the pancreas but only a slight depression in growth rate.2. Fasting for 24 h of chicks previously given RSD and HSD increased the activity of all four enzymes but the increase was much greater in chicks previously given RSD than in those previously given HSD.3. Feeding RSD for 4 d to chicks previously adapted to HSD resulted in a dramatic inhibition in growth rate, a small increase in pancreas weight, and an increase in the activity of all proteolytic enzymes, while no change in the amylase was detectable.4. Trypsin, chymotrypsin and pancreatopeptidase E activities were assayed in the contents of the small intestine and caecum of chicks fed on RSD or HSD over a period of 35 d. Trypsin and chymotrypsin activities in the small intestine were lower in chicks fed on RSD while pancreatopeptidase E activity was almost equal or even higher in RSD-fed chicks, especially at the age of 35 d. Trypsin activity in the caecum of RSD-fed chicks was lower at all stages of the experiment, while the pancreatopeptidase E and chymotrypsin activities in the caecum of RSD-fed chicks exceeded the levels in the HSD group at the age of 21 and 35 d respectively. It would appear therefore that pancreatopeptidase E may play an important part in overcoming the inhibition of the proteolytic activity in the intestine of chicks fed on RSD.

The energy cost of human lactation

Abstract: A total of 55 diet surveys were made on 49 women in Scotland within about 2 months of parturition some of whom were fully breast-feeding and some of whom were fully bottle-feeding their babies in an attempt to measure the effect of lactation on energy exchanges in the mother. 23 women were breast-feeding and 32 were bottle-feeding their babies; the lactating mothers took 591 kcal per day more than those who were not lactating. Both groups of mothers were losing weight and the estimated contribution of such losses to the total energy supply was added to and the amounts expended on basal metabolism deducted from the dietary energy intakes. The activity of each group was fairly similar; hence it was concluded that the average amount of energy available to support lactation was 618 kcal daily. The average energy value of the milk produced was estimated from the weights of the babies to be 597 kcal daily. From these data it was concluded that the energy exchanges in human lactation have an efficiency of 90% or more with the lower limit being 80%. Therefore an additional supply of 600 kcal in a daily diet should support lactation and 500 kcal is offered as the official recommended allowance.

Volatile fatty acid production in the rumen of cattle given an all-concentrate diet.

Abstract: 1. Short-term in vitro incubations of whole rumen contents have been used to measure the rate of production of volatile fatty acids (VFA) in two heifers given a diet containing 85% barley and 15% protein-mineral-vitamin supplement. Daily intake of the diet was restricted to 5.1 kg which was given in three equal feeds. In one heifer (no. 794), VFA production was measured over a 24 h feeding cycle; in the other (no. 832), a single 6 h feeding period was examined.2. The feeding schedule outlined above was found in previous work to result in a major alteration in the rumen environment and in the end-products of rumen fermentation relative to findings in animals given the same diet ad lib. Some of these earlier observations have been confirmed and extended in the present work.3. In heifer 794, the rate of VFA production reached a maximum (52–62 m-moles/l. h) 15 minafter each feed and then declined steadily throughout the remainder of the feeding period. Consistent changes with time were observed in rumen pH and in the concentration of VFA and dry matter in rumen contents during each feeding period.4. Simultaneous measurements of rumen fluid volume and outflow allowed estimates to be made of VFA production and absorption in the entire rumen during each feeding period. In heifer 794, total VFA production amounted to 18.2 moles/day of which approximately 85 % was absorbed directly from the reticulo-rumen. On a caloric basis, total daily production accounted for 36. 5% of the digestible energy intake.5. In heifer 832 there were significant differences in the rate of VFA production and in rumen pH and VFA concentration between two sets of observations made some 8 weeks apart. These differences appeared to be related to changes in the rumen microbial population and particular to a marked alteration in the numbers of ciliate protozoa. The possible role of rumen ciliates in modifying both the rate of VFA production and the environment within the rumen is discussed.

Artificial rearing of pigs. 1. Effect of frequency and level of feeding on performance and digestion of milk proteins.

Abstract: 1. Pigs were weaned from the sow at 2 d of age and reared on a diet of cow's milk supplemented with vitamin D, and antibiotics. The effects of four levels and two frequencies of feeding, and the temperature of the environment were studied in relation to the performance of the pigs and the digestion of the milk protein. Pigs fed at the two lower levels receivedadiet of cow's milk, but at the two higher levels cow's milk was spray-dried and reconstituted to 20% total solids. A comparison was also made between cow's milk and spray-dried reconstituted milk, both fed hourly with 12.5% total solids. The pigs were slaughtered at 28 d of age. 2. No differences in the nutritive value or digestion of the milk protein were found when cow's milk and reconstituted milk were fed with a total solids content of 12.5 yo. 3. Increasing the level of feeding resulted in a faster growth rate, and some deterioration in the feed conversion efficiency. The growth rate of the pigs from 2to 28 d of age when fed at a high level greatly exceeded that of sucking pigs reared on the sow. The retention of the dietary nitrogen also improved with increased feed intake. A highly significant inverse linear correlation of N retention with age was found at all levels of feeding. The milk protein was efficiently digested at all levels of feeding. 4. The mortality rate was very low but there appeared to be some association of losses with a high level of feeding during the first few days of life. 5. Feeding hourly compared with feeding twice daily improved the feed conversion efficiency, although the effect on growth rate and N retention was small. The retention of digesta in the stomach appeared to be an important factor in the regulation of the amount of digesta in the small intestine and in the maintenance of digestive efficiency. The stomachs of pigs fed twice daily contained considerably greater amounts of digesta than those of pigs fed at hourly intervals. There was little difference in the amount and composition of digesta in the small intestine and caecum at either frequency of feeding. 6. No differences were found in the performance of the pigs, N retention or the efficiency of digestion of the milk protein when the environmental temperature was maintained either at zoo throughout the experiment, or at 30' gradually reducing to zoo during the first 14d.

The requirement of sheep for cobalt or for vitamin B12

Abstract: 1. Sheep confined topens and given a cobalt-deficient ration which supplied about 30μgCo/d required for maintenance of normal growth rate a Co supplement approaching 40 μg administered per os daily; for maintenance of what appeared, under the conditions of the experiments described, to be the maximum vitamin B12 status of a sheep, namely 3 ng vitamin B12/ml serum and 1.4 μg vitamin B12/g liver tissue, a supplement of between 0.5 and 1.0 mg Co/d per os was necessary.2. For maintenance of normal growth rate the minimum daily requirement for vitamin B12 of sheep given the Co-deficient diet was about 11μg: about 5 μg absorbed from the gut and about 6 μg injected parenterally.3. Extrapolation of the linear regression obtained by plotting the amount of vitamin B12injected/d against concentration of vitamin B12 in the liver tissue of a sheep indicated that to attain a concentration of 1.4 μg vitamin B12/g liver (wet weight) injection of 34 μg vitamin B12/d was necessary.4. Comparison of the relative effects on body-weight of the administration of 100 μg vitamin B12/dper os and 3.12 μg vitamin B12/d by injection to sheep given the Co-deficient diet indicated that the efficiency of absorption of the vitamin from the gut was < 3%.5. Loss of appetite, the first symptom of vitamin B12 deficiency to appear in the sheep, occurred when the concentration of vitamin B12 in the liver was reduced to about 0.1 μg/g wet weight.6. In sheep given a supplement of 1 mg Co/d per os neither production in the rumen nor absorption from the gut but rather capacity for storage limited the concentration of vitamin B12 in the liver.7. Following treatment to restore the vitamin B12 status of a sheep whose stores of the vitamin had been depleted, there was a linear negative correlation between the increase in the concentration of vitamin B12 in the liver and the concentration prior to treatment.8. Following withdrawal of treatment from a sheep whose stores of vitamin B12 were adequate, there was a linear positive correlation between the rate of depletion of vitamin B12 from the liver and the concentration prior to cessation of treatment.9. The concentrations of vitamin B12 in the serums of sheep given the Co-deficient diet, and given a supplement of 1 mg Co/d per os 0.5 h after feeding, remained relatively stable over the period 0–7 h after feeding; maximum concentration occurred 7–8 h after feeding.10. Under the conditions of the experiments described a significant linear regression existed between concentration of vitamin B12 in the liver of a sheep and the logarithm of the concentration in the serum.

Lipid transport in kwashiorkor.

Abstract: 1. In an attempt to elucidate the pathogenic mechanism of the fatty liver of kwashiorkor some aspects of lipid metabolism were studied in ten patients with kwashiorkor and nine with marasmus, so classified according to the clinical and laboratory findings.2. Plasma lipid levels, especially those of triglycerides, were low in patients with kwashiorkor; they showed a marked rise very early during treatment.3. The changes in the plasma lipid levels occurred mainly in the serum lipoprotein fraction of density < 1.063. The elevation of plasma lipid levels during treatment coincided with a loss of liver lipids and a marked rise in serum protein concentration.4. The findings support the suggestion that the primary mechanism in the production of the fatty liver of kwashiorkor is an impairment in the synthesis of lipoprotein of very low density, probably due to the rate-limiting synthesis of its protein moiety.5. In patients with marasmus no modifications in lipid metabolism were detected by the methods used.

Growth retardation in a New Guinea boarding school and its response to supplementary feeding.

Abstract: 1. Children attending a boarding school in the New Guinea highlands, and receiving a protein-deficient diet of sweet potato and taro showed, when compared with village children, a progressive retardation of growth which was related to the number of years at school.2. Feeding of supplementary protein resulted in a dramatic acceleration of growth in both height and weight, whereas the feeding of extra calories produced an increase in only weight and skinfold thickness.3. This response to protein feeding appears to be greater than previously reported in the literature.

Voluntary intake, digestion, rate of passage, amount of material in the alimentary tract and behaviour in cows receiving complete diets containing straw and concentrates in different proportions.

Abstract: 1. Pelleted diets containing concentrates and 0, 20, 40 or 60% chopped straw were fed ad lib. for 5 h daily to four cows. Voluntary intake, digestion and rate of passage of these diets were examined, and also the behaviour of the cows and the amount of material in the rumen before and after feeding.2. Least dry matter (7.5 kg) was consumed when there was no roughage in the diet. When roughage was present, its level had no effect on dry-matter intakes, which were 10.7, 11.3and 10.7kg for 20, 40 and 60% roughage respectively. Digestible energy intakes were greatest with diets containing 20 or 40% roughage.3. The digestibilities of the dry matter of the four diets were 81, 69, 59 and 55% in increasing order of roughage content. The proportion of total digestion which occurred in the rumen decreased as the roughage content of the ration increased. The rate of breakdown of cotton threads in the rumen increased as the roughage content of the diet increased.4. Rates of passage varied greatly between cows and there were no differences between treatments in passage rates through the entire alimentary tract. The diets on which the cows consumed the largest amounts of digestible energy (20 and 40% roughage) passed through the rumen more slowly, and through the hind gut more quickly, than the other diets.5. The times spent daily eating and ruminating both increased as the proportion of roughage in the diet was increased, but in relation to the amount of dry matter eaten, eating times were lowest with diets containing 20 or 40% roughage. Time spent ruminating per kg straw eaten decreased with increasing straw content of the diet. Rumen contraction rate during eating was greatest when dry-matter intake was greatest, but during rumination it was similar with all three levels of roughage.6. Before and after feeding, the amount of digesta and digesta dry matter in the rumen increased as the proportion of roughage in the diet increased. After feeding, there was a highly significant linear relationship between the amount of digesta in the rumen and the digestibility of the diet.7. In a second experiment, similar diets containing 0 or 50% roughage were given to two cows for 5 or 24 h daily. The 24 h intake expressed as a percentage of 5 h intake was 148% for the 0% roughage diet, but only 105% when the diet contained 50% roughage.8. The results of these experiments are interpreted as indicating a declining importance of physical factors in the regulation of the intake by cows of a range of diets of increasing digestibility.

Vitamin E and hepatotoxic agents: 3.* Vitamin E, synthetic antioxidants and carbon tetrachloride toxicity in the rat

Abstract: 1. The acute toxicity of orally administered CCl4 and its subacute toxicity (liver necrosis and hepatic fat accumulation) were studied in young adult male and female rats. CCl4 was more toxic in males than in females. The protective effects of vitamin E (D-α-tocopheryl acetate) and three synthetic antioxidants, DPPD (N,N'-diphenyl-p-phenylenediamine), ethoxyquin (6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline) and BHT (butylated hydroxytoluene) were studied.2. Three daily oral doses (450 mg/kg) of vitamin E given before CCl4 increased survival in male rats but not consistently in females. Single oral doses (450 mg/kg) given previously at times between 24 and 72 h were also protective in males, but slightly decreased survival in females. Single intraperitoneal doses (500 mg/kg) given to female rats 1–48 h before CCl4 had no effect on survival. None of these treatments with vitamin E significantly decreased CC14-induced hepatic triglyceride accumulation. A large oral dose (2000 mg/kg) 6 h before CCl4 not only significantly increased hepatic fat accumulation but also increased mortality.3. Three daily doses (600 mg/kg) of DPPD or a single oral dose given 72 h before CCl4 increased survival in male and female rats. When single doses of DPPD were given 6–48 h before CCl4 they had no effect on survival. In contrast, DPPD usually significantly decreased the CC14-induced hepatic triglyceride rise when given orally 6–72 h before CCl4. Single intra-peritoneal doses (100–1500 mg/kg) of DPPD, given 1–48 h before CCl4, decreased the hepatic triglyceride rise. Multiple doses of DPPD decreased CC14-induced liver necrosis, but single doses were generally less effective.4. Three daily oral doses (300–500 mg/kg) of ethoxyquin given before CCl4 were highly effective in preventing mortality, liver necrosis and the rise in hepatic triglycerides. Single oral doses (500 mg/kg) given 72 or 48 h before CCl4 produced the same effect, but these single doses 24 or 6 h before CCl4 were without effect. The effective treatments usually increased liver weight markedly. Intraperitoneal treatment with ethoxyquin also substantially reduced the toxicity of CC14. Ethoxyquin was the most effective of all four treatments studied, and livers from animals given this substance were often nearly normal in histological appearance.5. The activity of oral doses (400–600 mg/kg) of BHT, given 48 h or more before CCl4 was, in general, similar to that of ethoxyquin, but less marked. This substance also caused a large increase in liver weight after 48 h. Oral doses given 6–24 h before CC14 increased the CC14-induced triglyceride rise still further. Intraperitoneal doses of BHT were ineffective against acute toxicity, liver necrosis or the triglyceride rise.6. Concentrations of a-tocopherol and the three synthetic antioxidants were measured in liver in many of the experiments. Very high hepatic concentrations of a-tocopherol could be obtained without affecting either the acute or subacute toxicity of CCl4. Ethoxyquin and BHT were rapidly eliminated from the liver after oral dosage, and when maximum concentrations were reached (24 h or less after administration) they were without protective effect. In contrast, when ethoxyquin and BHT were most active (48–96 h after administration) they could not be found in appreciable concentration in the liver.

The absorption of α-tocopherol in man

Abstract: 1. Physiological oral doses of DL [5-Me-3H]α-tocopherol were administered to fasting subjects with various disease states, with and without steatorrhoea, and net absorption was calculated by measurement of faecal unabsorbed radioactivity. In each subject studied more than 70% of the faecal radioactivity was excreted as unchanged α-tocopherol.2. α-Tocopherol absorption was significantly less in subjects with steatorrhoea (mean 59.4%, range 31–83%) than in those without steatorrhoea (mean 72.4%, range 51–86%). Nineteen out of twenty-four subjects with steatorrhoea absorbed less than 65% of the α-tocopherol dose, while twenty-two out of twenty-six subjects without steatorrhoea absorbed more than 65%. There was a significant correlation between the severity of steatorrhoea and α-tocopherol absorption. In a wide range of diseases steatorrhoea appeared to be the common factor associated with a decrease in α-tocopherol absorption; however, in subjects after gastric surgery α-tocopherol absorption was often low even in the absence of steatorrhoea, and this may be an important factor in explaining the high incidence of vitamin E deficiency in such patients.3. Radioactivity in the plasma was maximal 6–12 h after dosing. Plasma radioactivity curves were significantly lower in patients with steatorrhoea than in those without steatorrhoea, but there was considerable overlap. In some patients with severe deficiency and severe steatorrhoea there was no detectable plasma response even with considerable absorption of up to 40% of the administered dose. Three patients with severe dietary deficiency of the vitamin and no steatorrhoea also showed a decreased plasma radioactivity.4. Three subjects were studied twice, initially when deficient in α-tocopherol and a second time after repletion with α-tocopherol acetate. There was no evidence for a compensatory mechanism to increase α-tocopherol absorption in α-tocopherol deficiency.5. A small quantity of the administered dose (almost always less than 6%) was excreted in the urine.

Concentrations and metabolism of volatile fatty acids in the fermentative organs of two species of kangaroo and the guinea-pig.

Abstract: 1. Contents from the fermentative organs of the kangaroo and guinea-pig were found to have concentrations of total volatile fatty acids ranging from 50 to 140 mM.2. In each instance acetic was the most abundant acid, followed by propionic, then n-butyric, Trace amounts of isobutyric, n-valeric and isovaleric acids were present.3. When studiedin vitro, tissue from the wall of each fermentative organ was shown to metabolize butyrate to ketone bodies. Acetoacetate was the major ketone body. The presence of acetate and propionate did not affect ketogenesis from butyrate.4. In the guinea-pig caecum most of the ketogenic activity resided in the mucosa.5. The upper colon of the guinea-pig was as active as the caecum in metabolizing butyrate to ketone bodies.6. For both the guinea-pig caecum and the kangaroo fermentative stomach, incubations with 14C-labelled butyrate showed that the proportion oxidized to CO2 was considerably less than that metabolized to ketone bodies.

Digestion and nitrogen metabolism in sheep and red deer given large or small amounts of water and protein.

Abstract: I. The interaction between nitrogen and water intake was studied in two ewes and two red deer hinds. They were given pelleted diets, at maintenance level, containing equal amounts of roughage but either rich or poor in nitrogen. The deer received 50 yo more food than the sheep. Water was given either in large amounts (sheep 5.0 1, deer 7.0 1 daily) or in small amounts (sheep 1.1 1, deer 2.4 1 daily). 2. Nearly three-quarters of the nitrogen of the high-nitrogen rations but less than half of that of the low-nitrogen rations was excreted in the urine. Restriction of water intake reduced urinary nitrogen excretion by only about I g daily, mainly as a result of decreases in the excretion of urea and ammonia, but did not affect the excretion of nitrogen in the faeces. 3. The urinary excretions of creatinine, creatine, hippuric acid, uric acid and allantoin were also examined. The excretion of creatinine was not related to either nitrogen or water intake. The excretion of uric acid and of allantoin was greater in the sheep than in the deer. 4. The concentrations of urea in the plasma and of ammonia in the rumen fluid were measured before and after feeding. The plasma urea value was related to dietary nitrogen intake and was higher on the low- than on the high-water regime. The rumen ammonia value also was related to the nitrogen intake but, while it generally increased after feeding when the high-nitrogen diet was given, it fell almost to zero z h after feeding when the low-nitrogen diet was given. 5. The sheep digested dry matter, cellulose and nitrogen a little more fully than the deer. The high-water regime slightly increased the digestibility of dry matter and cellulose but did not affect the digestibility of nitrogen.