1. Rats were given diets containing different amounts of calcium, phosphorus and lead.

2. Pb retention was greatly increased when the diets contained less Ca or P than the minimum estimated requirement of the rat.

3. The release of Pb already incorporated into the skeleton was inhibited by diets low in Ca but was not affected by diets low in P.

4. The retention of Pb given intraperitoneally was not affected by dietary Ca or P.

5. It can be concluded that dietary Ca and P influence the absorption of Pb by the gut and dietary Ca influences the metabolism of Pb in the bone.

6. There were changes in the distribution of Pb among the tissues due to changes of dietary Ca.

7. At low body concentrations, Pb probably affected skeletal growth.

1. Three growth trials were done using male broiler chicks. In the first two trials, groundnut meal was used, with and without supplementary methionine and lysine. In the third trial, soya-bean meal was used with and without supplementary methionine. Protein levels ranged in the first trial from 120 to 420 g/kg diet and in the third trial from 120 to 300 g/kg diet. Thus the assumed minimal amino acid requirements of the chick were supplied by high levels of low-quality dietary protein.

2. Diets based on cereals and groundnut meal did not support maximum live-weight gain or maximum efficiency of food utilization at any level of dietary protein. When the principal deficiencies of lysine and methionine were corrected, this protein mixture was capable of supporting the same growth rate as a control diet of cereals and herring meal.

3. Diets based on maize and soya-bean meal did not support quite the same growth rate as similar diets supplemented with methionine, even though the protein level in the unsupplemented diets was sufficient to meet the assumed methionine requirements.

4. These results are interpreted as examples of amino acid imbalance in diets composed of familiar feeding-stuffs. It is concluded that one cannot assume that the poor quality of a protein source can always be offset by increasing the concentration of dietary protein.

1. Glucose in solution in saline, or saline alone, was administered to a group of twenty ewes during late pregnancy and again after lambing. Sequential blood samples were taken before and after the infusion and the concentration of plasma free amino acids was determined.

2. The effect of glucose was to reduce the concentrations of all amino acids except alanine. The reduction was greatest for tryptophan in the pregnant sheep, but this amino acid showed no significant change in the lactating animals.

3. An attempt to rank the amino acids on the basis of their response to glucose infusion indicated that, with the exception of tryptophan for the preparturient ewes, groups of essential amino acids could not be distinguished from each other. These groups were, for the preparturient sheep, valine, leucine, phenylalanine and isoleucine, and for the postparturient animals, isoleucine, lysine, methionine, valine and phenylalanine.

1. Seven groups of young turbot (Scophthalmus maximus) were given diets containing graded levels of thiamin (0.19–50 mg/kg) for 16 weeks and their growth rate was measured during this period.

2. Good growth was obtained on all these treatments except in the group given the lowest dietary thiamin level (0.19 mg/kg). These fish grew normally until the 12th week but thereafter their weight did not increase.

3. Measurements of erythrocyte transketolase (sedoheptulose-7-phosphate: D-glyceraldehyde-3-phosphate glycolaldehydetransferase; EC 2.2.1.1) activity at the end of the experiment and of percentage stimulation of erythrocyte transketolase by thiamin pyrophosphate indicated that the apoenzyme was saturated with coenzyme at a dietary thiamin level of 2.6 mg/kg, but not at 1.1 mg/kg.

4. An 8th group of turbot given the thiamin antagonist pyrithiamin (40 mg/kg diet) grew normally for 6 weeks. Thereafter mortalities began to occur and all fish died by the 10th week. No clear-cut signs of thiamin deficiency were observed.

5. The dietary thiamin requirement of turbot is much lower than published requirements of freshwater fish other than carp (Cyprinus carpio) and appears to be between 0.6 and 2.6 mg/kg diet.

1. Successive portions of boiled and mashed potatoes, roast pork, cooked, freeze-dried peas and ice-cream were taken in order to determine the total (sampling and experimental) error involved in the ‘duplicate analysis’ method of dietary survey.

2. These samples were analysed for water, nitrogen, fat, iron and energy.

3. The experimental error of the methods was also studied separately.

4. The sampling and experimental errors ranged from 0.3% for water in potatoes, to 23% for Fe in ice-cream. Sampling error was significantly greater than experimental error for all nutrients studied.

5. It is concluded that in reporting the results from dietary surveys, it is necessary to take account of the errors inherent even in the most precise methods.

1. Vitamin B12 metabolism was studied in bats of the species Rousettus aegyptiacus, which live on an all-fruit diet in the wild.

2. There was a wide range in values for the serum vitamin B12 concentration of newly captured bats, but bats captured in the early spring had significantly higher mean serum vitamin B12 levels than bats captured in the early autumn.

3. There was an exponential decrease in serum vitamin B12 concentration with time in captivity for bats fed on a vitamin B12-deficient, all-fruit diet; the biological half-life was 80 d in serum, 109 d in liver and 164 d in kidney.

4. The main storage organ for vitamin B12 in the bat was the liver, mean content 1067 ng vitamin B12. After 50 d, injected [57Co]cyanocobalamin had equilibrated with body vitamin B12 stores, and 17% of the retained radioactivity was present in the liver. From these results it was calculated that the total body vitamin B12 content of the bat was c. 6500 ng.

5. The biological half-life of injected [57Co]cyanocobalamin was 70–88 d and the calculated daily requirement was 50–60 ng (0.2 μg/kg body-weight per d).

6. As serum vitamin B12 levels decreased, serum folate levels increased. The erythrocyte folate concentration increased significantly after 130 d on the all-fruit diet and then decreased to the initial values after 190 d.

7. Vitamin B12 metabolism in the fruit bat is similar in many respects to that of man, but on a ‘weight-for-weight’ basis the bat has a 5- to 15-fold greater requirement for this vitamin.

8. Vitamin B12 deficiency may be induced fairly rapidly in fruit bats fed on an all-fruit diet.

1. The ability of organic and inorganic sulphur to influence the copper and molybdenum metabolism of sheep was compared in a series of three 2 × 2 factorial design experiments. In each experiment, four groups of five to seven hypocupraemic ewes were repleted with a basal diet supplemented with 6 mg Cu/kg and containing S and Mo at one of two concentrations, 1 or 4 g S and 0.5 or 4.5 mg Mo/kg respectively. Sodium sulphate (Expt 1), methionine (Expt 2) or cysteine (Expt 3) were used as the S sources. Cu and Mo concentrations in plasma were estimated in each experiment and in Expt 3 the concentrations of Cu in liver and Mo in urine were also estimated.

2. The effects of the three S sources on Cu and Mo metabolism were similar. Repletion of the plasma Cu pool was unaffected by Mo alone, reduced by S alone and totally inhibited by Mo + S. Plasma Mo was greatly increased by Mo supplements, slightly decreased by S supplements and unaffected by Mo and S supplements given together.

3. In Expt 3 the treatments were found to affect urinary Mo and plasma Mo in a similar manner; S prevented dietary Mo from increasing Mo excretion. The only group to show a significant repletion of the liver Cu pool was that given Mo alone.

4. Supplementation of the diet with organic S significantly reduced the within-treatment variation in plasma Cu and Mo, liver Cu and urinary Mo.

5. It is suggested that variations in dietary S and Mo within the normal range for herbage affect the Cu and Mo metabolism of the grazing animal, and that total S rather than inorganic S is the more useful measurement in the context of the Cu–Mo–S interrelationship.

1. Measurements have been made of the size and number of muscle fibres and number of nuclei in a small indicator muscle (m. flexor digiti V brevis) in the fore-foot of the pig. Wellnourished, 10-d-old and 1-year-old animals were studied, as well as 1- and 2-year-old animals that were severely energy-deficient and protein-deficient.

2. The normal 1-year-old animals had much larger muscle fibres, with more nuclei, than the pigs in any of the other groups.

3. There were no significant differences between the numbers of fibres in the muscles of pigs in any of the four groups.

4. There was a significant difference between the number of fibres in the muscles of pigs coming from different litters, irrespective of their dietary history after birth. This suggests that the number of fibres is determined genetically before birth, and all that can take place after birth is an alteration in size.

1. A procedure is described for assaying in vitro the activity of various inhibitors of methane production by rumen micro-organisms.

2. Methods of preparation of various inhibitors are described together with attempts to characterize these compounds by determining their physical properties (physical state, density, chromatographic behaviour), their hydrolysis by rumen contents and their relative potency as inhibitors.

3. The results of preliminary studies with trichloroethanol and its ester with pivalic acid are given.

4. The inhibitory activities of several groups of related compounds are reported. These include the polyhalogenated alcohols and their esters with pivalic acid, the esters of trihalogenated alcohols and monobasic fatty acids from C2 to C16 and the trihalogenated alcohol esters of dibasic acids. The results of experiments with esters of alcohols and polyhalogenated carboxylic and sulphonic acids are also given.

5. It is concluded that the mechanism of action of the inhibitors might be similar to that of known polyhalogenated methane analogues (e.g. chloroform). The relative activity of various compounds might be partly governed by the ease of their absorption into the microbial cells and by the extent to which the esters can be hydrolysed by rumen contents.

6. The results show that some substances are very poor inhibitors, unless they are esterified (e.g. trichloroacetic acid) but on the whole the esters in which the polyhalogen grouping is on the alcohol portion of the molecule are better inhibitors than those in which it is on the acid portion of the molecule.

1. Two inhibitors of rumen methane production were given to sheep and their effects were measured using an in vitro technique.

2. The substances used were trichloroethyl pivalate (TCE-P) and trichloroethyl adipate (TCE-A). In one experiment with two sheep TCE-P was injected into the rumen and in another experiment with two sheep the same inhibitor was mixed with the food just before feeding. In another experiment, TCE-A was given to two sheep at two dose levels, and in an experiment with four sheep two levels of inhibitor and two levels of diet were used.

3. In general the inhibition of methane production was greater with samples of rumen contents taken after feeding than with those taken before feeding. When sheep were given 120–300 mg TCE-P/d the inhibition of methane production ranged from 21 to 81%. When sheep given maintenance rations were given 125–300 mg TCE-A/d there was 28–90% inhibition of methane production. When sheep were given twice maintenance rations 150 mg TCE-A/d gave no inhibition and 300 mg TCE-A/d gave very low inhibition of methane production (about 16%).

4. In most experiments there was a significant increase in the propionic acid:acetic acid concentration ratio in the rumen when methane production was inhibited.

5. The possible practical use of inhibitors is discussed.

1. Serum colloidal osmotic pressure was measured in children ‘at risk’ to kwashiorkor, in others with frank signs of the disease and during recovery. Simultaneous estimations of serum albumin and globulin concentrations and assessments of the extent of oedema were also made.

2. During the development of kwashiorkor, serum colloidal osmotic pressure did not decrease significantly until albumin concentration was 25.1–27.5 g/l. Above 30.0 g/l, colloidal osmotic pressure was maintained at normal levels during which time a significant reciprocal relationship existed between albumin and globulin concentrations. These findings provide support for suggestions that there may be an oncotic regulation of albumin synthesis.

3. Low albumin concentrations were mainly responsible for the low colloidal osmotic pressures found in children with kwashiorkor and in agreement with previous findings the threshold for the formation of oncotic oedema was found to be about 2.35–2.65 kN/m2.

4. Values for colloidal osmotic pressure calculated from serum albumin and gobulin concentrations using empirical formulas did not agree well with measured values and no constant correction factor suitable over the whole range of albumin concentrations found in rural Ugandan children could be devised. In many hypoalbuminaemic children only direct measurement of serum colloidal osmotic pressure will indicate the true extent of risk to an episode of oedema.

1. A study was made of the absorption of [58Co]cyanocobalamin in suckling piglets. Cyanocobalamin given at birth and at 7 d of age was efficiently absorbed from the intestine and retained within the body, mostly in the liver. A 10 μg test dose was absorbed no less efficiently than 0.5 μg, despite the virtual absence of intrinsic factor in the gut. In piglets given a 10 μg test dose at different ages between 0.5 and 56 d, there was a marked decrease in the efficiency of retention between about 7 and 21 d of age.

2. Vitamin B12-binding capacity in the gastric mucosa increased with age, from 40 ng at birth to about 2000 ng at 14 d and 7000 ng at 35 d. This binder-protein was largely endogenous, whereas much of the unsaturated binder-protein in intestinal mucosa was apparently derived from milk.

3. The chyme in the stomach and small intestine contained unsaturated binder-protein, partly endogenous and partly deriving from milk, which prevented uptake of added [G-3H]-cyanocobalamin into the ‘solids’ phase of the intestinal contents. The intestinal chyme contained large numbers (log10 7.0–9.1/ml) of bacteria, some of which were isolated and shown to take up cyanocobalamin or folic acid or both.

4. The findings are discussed in relation to the concept that for some days or weeks after the cessation of transport of intact protein across the neonatal gut epithelium (‘closure’), protein-bound vitamins may continue to be taken up into the epithelial cells and there released for transport into the circulation. It is concluded that unsaturated vitamin-binders may strongly influence the ecology of the intestinal microflora.

1. In one experiment the effect on rumen pH of feeding with restricted amounts of whole or pelleted barley was studied. With whole barley there was little variation in rumen pH associated with feeding time, but with pelleted barley the pH decreased from about 7.0 before feeding to about 5.3, 2–3 h after feeding.

2. The rate of disappearance of dried grass during incubation in the rumens of sheep receiving either whole or pelleted barley was studied in a second experiment. After 24 h incubation only 423 mg/g incubated had disappeared in the rumen of sheep receiving pelleted barley while 625 mg/g incubated had disappeared when it was incubated in the rumen of sheep receiving whole barley.

3. The voluntary intake of dried grass by lambs was studied in a third experiment when they received supplements of either 25 or 50 g whole or pelleted barley/kg live weight0.75. At the high level, pelleted barley reduced intake of dried grass by 534 g/kg but whole barley reduced it by only 352 g/kg. The digestibility of acid-detergent fibre was reduced more by pelleted barley than by whole barley but there was a tendency for a small increase in digestibility of the barley due to processing.

4. The implications of these findings on supplementation of roughages with cereals are discussed.

1. The long-term fate in rats of an oral dose of [75Se]selenocystine was compared with that of an oral dose of [75Se]selenomethionine.

2. Urinary and faecal radioactivities were measured during the 1st week and whole-body radioactivity was determined for 10 weeks. Rats were killed at weekly intervals for 4 weeks and at weeks 6 and 10 for analysis of tissue distribution of 75Se.

3. Intestinal absorption of [75Se]selenocystine was 81% of the administered dose; that of [75Se]selenomethionine was 86%. Urinary excretion of absorbed [75Se]selenocystine was 13.9% and that of [75Se]selenomethionine was 5.8%, in the 1st week.

4. Whole-body retention of 75Se was greater for [75Se]selenomethionine than for [75Se]-selenocystine but after the 1st week it decreased at a similar rate in both groups. Tissue distribution of retained 75Se was also similar in both groups.

5. The initial utilization of [75Se]selenocystine was different from that of [75Se]selenomethionine. However, after the 1st week 75Se from both sources appeared to be metabolized similarly, suggesting that dietary Se of both forms is ultimately incorporated into the same metabolic pool.

6. When these findings were compared with those of earlier studies with [75Se]selenite and 75Se incorporated in vivo into rabbit kidney (RK-75Se) (Thomson, Stewart & Robinson, 1975) the metabolism of [75Se]selenocystine resembled that of [75Se]selenite and RK-75Se, rather than that of [75Se]selenomethionine.

1. Rats were undernourished in early life by feeding their mothers a restricted quantity of a good-quality diet during pregnancy and lactation. All offspring were fed ad lib. from weaning. Behavioural tests were done using adult males.

2. Thresholds of aversion to electric shock were determined in a rectangular box, one side of which was designated ‘live’ and the other ‘safe’ (o V side) for any particular shock level. Three 15 min sessions were given at each of five shock levels. Previously undernourished rats had a lower aversion threshold than controls. They spent more time than controls on the o V side at two intermediate levels of shock.

3. Other male rats were subjected to six graded series of brief, unavoidable shocks. Previously undernourished rats responded to a greater total number of shocks than controls.

4. These results support the hypothesis that previously undernourished rats have a lowered threshold of arousal.

1. Dietary histories covering I week were obtained from 212 men and 263 women, aged 62–90 years, who formed a random sample of the older people living in a defined area of Edinburgh. The histories were validated by 2 d weighed-diet records for 219 of the subjects.

2. Nutrient intakes are given as mean values and standard deviations, and as percentage distributions of intake relative to the recommended intakes of nutrients. Intakes are also related to factors which might affect diet adversely.

3. Mean values obtained suggested that intakes were less than recommended intakes for more nutrients for women than for men, particularly values for energy and vitamin D. Values for percentage distributions indicated that a substantial proportion of all subjects had low intakes of ascorbic acid and vitamin D, that the energy intake of many women was low and that for most nutrients a greater proportion of men than of women had the recommended intake. Factors associated with significant proportions of subjects with less than the recommended intakes were mental illness in women and deafness and severe dyspnoea in men.

4. Possible action to improve the diet of the elderly is discussed.