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.

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.

1. 64Cu as copper chloride in aqueous solution was given by intraperitoneal injection to rats varying in age from a few hours to 14 weeks. The isotope was allowed to circulate in the body for 24 h.

2. The amount of gamma radioactivity present in the brain and blood was measured and the percentage of the initial dose present was calculated. It was shown that the brain 64Cu activity reached a maximum around the 16th day of life and that the blood showed a steady decrease in the 64Cu activity per g from birth to maturity. Measurements were also made on the liver and kidney.

3. The excretion of 64Cu in the urine and faeces in 24 h was also studied. Approximately 30% of the isotope was excreted in that time, mostly in the faeces.

4. A limited number of experiments in three different age groups were carried out to discover whether changes in specific activity of the isotope given to rats had a significant effect on the percentage of 64Cu taken up by the brain and blood. No such effect was seen.

1. Bacillus subtilis and Escherichia coli were grown on 14C-labelled glucose and used for the preparation of labelled whole cells, cell walls, cell contents and peptidoglycan.

2. The radioactive samples were injected into the abomasum of sheep and the 14C appearing in expired air, plasma glucose, urine and faeces was determined. Whole cells were also injected into the rumen and the incorporation of 14C into volatile fatty acids was measured.

3. All the bacterial preparations, including cell walls, were extensively digested and absorbed, Less than 15% of the radioactivity was recovered in the faeces.

4. Up to 20% of the radioactivity injected was recovered in expired carbon dioxide with only 2.4–8.1% passing through the glucose pool.

5. It has been calculated that under the conditions of the experiment 18.5 % of the total glucose entering the body pool of glucose in 24 h was derived from bacterial carbon.

1. The concentrations of individual free serum amino acids have been studied during the course of chronic protein malnutrition in experimentally malnourished pigs.

2. Until growth was markedly impaired, reducing the protein content of the diet had no significant effect on serum amino acid composition.

3. During the period when growth had practically ceased but kcal intake per kg body-weight was normal the concentrations of valine, leucine, isoleucine, threonine and eventually tyrosine fell, the levels of alanine and serine were above control levels and aspartic acid, glycine, methionine, phenylalanine, proline, arginine, histidine and lysine remained unaltered.

4. When the kcal intake per kg fell below control levels, owing to anorexia, and the animals began to lose weight, the levels of alanine, glycine, serine and methionine fell and valine, leucine, isoleucine, threonine and tyrosine remained well below control levels.

5. The physiological, nutritional and metabolic significance of these findings is considered. The changes in alanine and glycine concentration are discussed in terms of the regulation of gluconeogenesis. The reduction of the branched-chain amino acids is interpreted on the basis of their availability for synthetic and catabolic needs.

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.

1. An apparatus is described for supplying small amounts of food to rats uniformly and continuously.

2. The apparatus consists of a Perspex disc carrying a groove containing food, which is rotated once each day by an electric motor. Access of rats to the food is restricted by suitably placed baffles.

1. Young rats were fed on diets containing heated or unheated soya-bean flour.

2. Feeding unheated soya-bean flour decreased concentrations of vitamin B12 in liver, kidneys and blood serum, urinary excretion of sulphate and concentration of reduced glutathione in liver. Blood glutathione level and urinary excretion of methylmalonic acid and formimino-glutamic acid following loads of propionate and histidine, respectively, were increased.

3. Supplementing a diet of unheated soya-bean flour with vitamin B12, had no effect on the level of reduced glutathione in the liver. Adding methionine to this diet decreased excretion of methylmalonic acid and the level of glutathione in blood.

4. The activity of liver methyl-tetrahydrofolate: L-homocysteine S-methyltransferase was not affected by the nature of dietary soya-bean flour nor by supplementation with vitamin B12

5. It is concluded that heat-labile substances present in soya-bean flour induce metabolic changes which can bring about an increased requirement for vitamin B12, and a deficiency of sulphur-containing amino acids.

1. The energy values of the diets of twenty-three women who were breast-feeding and thirty-two who were bottle-feeding their babies were determined by 7 d weighed surveys. All the subjects were healthy and living at home, and their babies were thriving. The lactating mothers took, on average, 591 kcal (2.5 MJ)/d more than those who were not lactating.

2. Both groups were losing weight, on average. 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. Since the activity of each group was fairly similar, it was possible to conclude that the average amount of energy available to support lactation was 618 kcal (2.6 MJ) daily. The average energy value of the milk produced was estimated from the weights of the babies to be 597 kcal (2.5 MJ) daily.

3. Critical evaluation of those averages, and of the assumptions on which they were based, led to the conclusion that the energy exchanges in human lactation have an efficiency of 90% or more, with a lower limit of about 80%.

4. The additional supply of 600 kcal (2.5 MJ) in the daily diet should suffice to support lactation and a ‘round figure’ of 500 kcal (2.1MJ) daily may be regarded as reasonable in official recommended allowances.

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.

1. The effect of addition of a mixture of two non-essential amino acids (NEA), namely alanine and glutamic acid, to milk proteins on nitrogen retention and the biological value of the proteins was determined in a group of six girls aged 10–11 years.

2. The mean daily intakes of milk protein by the children on three diets (1, 3 and 5 ) were 1.41, 1.10 and 0.70 g/kg body-weight. The quantities of NEA added daily to the three diets were 0.97, 0.49 and 0.97 g/kg body-weight respectively.

3. Addition of NEA did not bring about any significant increase in N retention in the children. The addition of NEA to milk proteins significantly decreased the biological value of the proteins.

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 [3H]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 [3H]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 [3C]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 [3H]thymidine into DNA was not significantly different between deficient and control groups in any of the four organs investigated.

1. The effects of the introduction into the diet of natural fats rich in individual fatty acids or of simple triglycerides on the composition of blood lipids and of milk fat in the sow were investigated.

2. Replacement in the diet of a mixture of animal, vegetable and marine oils by a single natural fat had varying effects on the concentrations of plasma lipid fractions, whereas replacement of tallow by simple triglycerides, with few exceptions, increased the concentrations of all fractions.

3. When butyric or caprylic acids were present in the diet there was no detectable transfer of those acids to plasma triglycerides, and there was only a limited transfer of dietary erucic acid. An increase in the dietary concentration of other acids (ranging from capric to linolenic) was associated with an increase in the content of the acids in the plasma triglycerides. For saturated fatty acids the response to dietary changes was at a maximum for myristic acid.

4. The effects on the composition of milk fat reflected the changes in the composition of the plasma triglycerides, except during the feeding of cottonseed oil when there were marked decreases in milk fat of palmitoleic and oleic acids and corresponding increases in palmitic and stearic acids which were not observed in the plasma triglycerides. Also, during the feeding of coconut oil, capric acid was present in the plasma triglycerides but not in milk fat, and the increases in the plasma triglycerides of lauric and myristic acids were much more marked than the corresponding increases in milk fat.

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.

1. Hypertryptophanaemia, hypertryptophanuria and to a lesser degree a generalized hyperaminoaciduria were observed in phenylketonuric patients receiving certain commercial low-phenylalanine diets containing DL-tryptophan.

2. The generalized hyperaminoaciduria was associated with the ingestion of acid hydro-lysates of protein, but not with the ingestion of enzymic hydrolysates or D-tryptophan.

3. Alanine recovered from the urine of these treated patients had a D-isomer content of approx. 50%. This amount of urinary D-alanine could be derived from the ingestion of an acid hydrolysate of protein in which the amino acids had racemized to the extent of 2–3%.

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.

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.

1. Groups of female albino rats were given 12–20 mg of one of the eight known toco-chromanols in 0.2 ml arachis oil by stomach tube, and were killed 2, 4, 8, 16 or 24 h afterwards. The liver, spleen, heart, kidneys, brain, small intestine and a portion of striated muscle were removed from each rat and analysed for the tocochromanol given.

3. Maximum levels of the tocochromanols occurred in most tissues 4–8 h after dosing. In the liver the tocopherols were more efficiently absorbed than were the corresponding toco-trienols. In kidney, heart and muscle the percentage uptake of the tocotrienols was often greater than that of the corresponding tocopherols.

1. The changes occurring in the free amino acids of the plasma of laying hens in relation to egg formation have been investigated in fed and starved hens in three experiments, each with eight birds.

2. The mean concentrations of most amino acids and of the totals were higher at night than in the morning.

3. In general, egg formation was associated with increases in the concentrations of non- essential and decreases in the concentrations of essential amino acids. Cystine and glutamic acid tended to behave like the essential amino acids.

4. After 40 h starvation seven amino acids, particularly serine, histidine and lysine, in- creased in concentration and only three, proline, ornithine and arginine, decreased significantly.

5. When eight cocks were injected with oestrogen most of the amino acids increased in con-centration. The essential amino acids (with the exception of phenylalanine), serine, proline, cystine and ornithine showed the greatest increases.

6. The results are discussed in relation to the possibility that the voluntary food intake of hens may be influenced by changes in the plasma levels of one or more essential amino acids associated with the synthesis of egg albumen. Arginine appeared to be the only amino acid that might possibly fulfil this role.

7. It was concluded that investigations of changes in the free amino acids of hen plasma are unlikely to provide a useful approach to a study of the amino acid requirements or the nutritive value of particular proteins for egg production.

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.