1. A number of folates labelled with 14C were administered orally to rats, at various doses, and urinary, faecal and hepatic folates examined.

2. 10-Formylpteroylmonoglutamic acid (10CHO—PGA) entered the folate pool very slowly, and is thought to be relatively ineffective in nutrition.

3. 10-Formyl[2-14C]tetrahydrofolic acid (10CHO—[2-14C]THF) entered the folate pool very rapidly. 5-Methyl[2-14C]tetrahydrofolate (5CH3—[2-14C]THF) was the major urinary folate.

4. 5-Formyl[2-14C]tetrahydrofolic acid (5CHO—[2-14C]THF) entered the folate pool only to a small extent. 5CHO—[2-14C]THF, given intravenously, produced no urinary 5CH3—[2-14C]THF in the first 6 h.

5. 10-Methylidyne[2-14C]tetrahydrofolic acid was metabolized to an extent which was dependant on the dose. At doses of 3 and 30 μg/kg body-weight, 5CH3—[2-14C]THF represented 5·4 and 20% respectively of urinary folates and for 10CHO—[2-14]PGA, the values were 16% of total urinary folates after the higher dose, and 78·5% after the lower dose.

6. Results obtained for the metabolism of 5CH3—THF varied depending on the position of the labelling: 514CH3–THF gave no labelled urinary folate, the methyl group being lost rapidly. When 5CH3—[2-14C]THF was given, it appeared as the major urinary folate.

7. Folates found in the liver after oral administration of labelled folates were identified by thin-layer chromatography; only folate monoglutamates were identified.

1. Sections of small intestine from rats given raw-soya-bean (RS) diets had a decreased capacity to actively accumulate L-methionine when compared to those taken from rats given heated soya bean (HS), and casein-fed controls. The extent of the reduction was small in comparison with pair-fed animals, but was statistically significant in comparison with rats restricted to the same weight gain as the RS group

2. The differences in the passive uptake of D-mannitol appear to be directly related to differences in gut thickness between the control and RS groups

3. Values for water movement and intestinal transmural potentials further support the results found in the active accumulation studies

4. From this study it was concluded that the degree of starvation directly affects the magnitude of the effect of RS diets when comparisons are made against adequately fed controls.

1. Rats were mated and at weekly intervals during pregnancy and lactation, and after weaning, the dipeptidase activity in the supernatant fraction from small intestinal mucosa extracts was determined for two dipeptides: glycyl–L-leucine dipeptidase (EC 3.4.3.2) and L-alanyl–L-glutamic acid dipeptidase.

2. Dipeptidase activity is found mainly in the soluble (supernantant) fraction of the mucosa homogenate.

3. Compared with those values obtained for unmated controls, the food consumption of the animals and the nitrogen content, total and specific activities of the dipeptidases (per unit quantity of N) in the soluble fraction of the small intestinal mucosa extracts increased slightly during pregnancy and markedly during lactation. After the pups were weaned, values for all these measurements fell rapidly.

4. Whether the increases found in enzyme activity were simply a response to increased food intake or were the result of hormonal stimulus is discussed.

1. An immunohistochemical method was used to study the effect of a low-protein diet on growth hormone (GH) cells in the pituitaries of developing rats. The deficient diet (80 g protein/kg) was administered during gestation and lactation, or during the time after weaning until 90 d of age, or during both periods.

2. GH-cell changes were much more striking in males than in females.

3. In males, GH-producing cells were usually reduced in size and number in all treatments. The effect was most intense when protein deprivation occurred throughout gestation and sucking, and continued until 90 d of age, but it was also evident in animals given the low protein diet only after weaning. Recuperation appeared to be almost complete when offspring of deprived dams were fed on a normal diet after weaning.

4. It is concluded that a low-protein diet reduces the amount of GH in the rat pituitary in a way similar to that with a protein-free diet.

1. Twenty-seven energy and protein balances were done using nine cross-bred (Brown Swiss × Sahiwal) mature bullocks in a series of three balance trials. The bullocks were fed 75, 100 and 125 % of the metabolizable energy (ME) and digestible crude protein standard values recommended by the (US) National Research Council (1966). Heat production was estimated by indirect calorimetry, by collection and analysis of respiratory gases

2. Utilization of energy for maintenance and fat production was estimated by computing regression of energy balance v. digestible energy (DE) and ME separately on a metabolic body size (kg body-weight (W)0·75) basis. Maintenance energy requirements and efficiency of utilization of ME for lipogenesis were estimated using multiple regression of ME intake, also. Heat production (and thus energy balance) was corrected for excess nitrogen intake

3. An attempt was made to measure basal heat production of bullocks so that the net energy requirements for maintenance could be estimated. Extrapolation of the regression line of energy balance v. ME intake below maintenance on a W0·75 basis gave a basal metabolism of 348·09 kJ/W0·75 per d

4. Energy requirements for maintenance were (kJ/kg W0·75 per d): 539·43 DE, 448·81 ME and 348·09 net energy. The results of multiple regression gave a requirement of 432·15 kJ ME/kg W0·75 per d for maintenance

5. The efficiency of utilization of ME for maintenance was 81·34% while for lipogenesis it was 54·5 %.

1. The effect of subcutaneous administration of bovine growth hormone on calcium metabolism of nearly mature wether sheep has been studied by a combination of a radioactive technique and a nutrient balance technique.

2. Administration of growth hormone resulted in a significant increase in the rates of absorption of Ca, accretion of Ca into bone, resorption of Ca from bone and skeletal retention of Ca, and also in the sizes of the exchangeable Ca pools.

3. Retention of phosphorus was also significantly increased.

4. These changes suggest that the effect of growth hormone was to alter the Ca metabolism of nearly mature wethers to resemble that of younger, more actively growing animals.

5. Results are consistent with the theory that oestrogens may alter Ca metabolism of wethers by increasing growth hormone production.

1. Forty-eight children, who were long-term hospital patients, were investigated to assess their leucocyte ascorbic acid status.

2. Twenty-nine children had been receiving long-term anticonvulsant therapy, and these children did not have a significantly lower level of ascorbic acid than the untreated group, which did not have epilepsy.

3. The ascorbic acid levels of all subjects were low and seventeen had levels between 7·3 and 16·0 μg/108 white blood cells.

1. Skinfold thicknesses, arm circumferences, heights, weights and serum cholesterol levels were determined in ninety-one university students, 207 soldiers and 102 out-patients, all male subjects. Some of these measurements were used to determine the amount of body fat, Quetelet's index and mid-arm muscle circumference

2. Quetelet's indices and body-fat values obtained were similar to previously reported values for lean or moderately built males

3. Serum cholesterol levels were generally low, with means ranging from 3·98 mmol/1 for 18- to 29-year-old students to 5·19 mmol/l for 40- to 69-year-old out-patients

4. The mean values for triceps skinfold thickness, the amount of body fat and serum cholesterol levels for healthy adults obtained in this study are probably normal for northern Nigerian populations

5. There was a significant correlation between the amount of body fat and values for triceps and subscapular skinfold thicknesses, Quetelet's index and body-weight for all adults. The correlation between muscle circumference and the amount of body fat was significant for all subjects except adult soldiers.

1. Food consumption, live weight, anatomical measurements on the gut organs and the absorptive capacity of the small intestine for L-leucine and D(+)-glucose were made on virgin (control), pregnant and lactating albino rats.

2. Food intake increased by approximately 60% during pregnancy and a further 250% during lactation.

3. Pregnancy did not markedly influence the gross anatomy of the gastrointestinal tract. There was evidence for increased villus height and percentage water in the small intestine and for increased length of the colon during pregnancy.

4. During lactation, the alimentary canal progressively increased in weight and size. It partially regressed following weaning.

5. All anatomical measurements, except the length of the small intestine, completely regressed to control values within 20 d of weaning. The increased intestinal length had not completely regressed by day 30 post-weaning.

6. No significant change was observed in absolute absorption of glucose or leucine during pregnancy.

7. Absolute absorption of leucine and of glucose was increased during lactation. Greatest absorption occurred on the 10th day of lactation.

8. Results for absorption of leucine and glucose per unit length indicated that the ability of the mucosal cells to absorb or the number of absorptive cells/mm had changed during lactation and the post-lactation periods.

1. A study was made of factors affecting the plasma concentrations of free amino acids (PAA) and urea (PU) in calves receiving liquid diets

2. When calves were given whole milk (approximately 0·05 kg/kg live weight) at 10·00 and 17·00 hours there were marked decreases in PAA and slight decreases in PU for about 3–4 h after the morning feed. Both PAA and PU thereafter increased slightly and then remained constant for the next 10 h. In subsequent comparative experiments samples were taken 3 h after the morning feed. The variation in plasma methionine, isoleucine, leucine, phenylalanine, tyrosine and total PAA was apparently greater between than within animals

3. In calves transferred from a diet of whole milk to one consisting of diluted whole milk supplemented with appropriate nutrients, including amino acids, but deficient in methionine, PU increased markedly and plasma methionine decreased

4. Two calves (50–60 kg live weight) given the latter diet supplemented to give an intake of more than 4·5 g L-methionine/d together with 0·3 g cystine/d showed marked increases in plasma methionine. This was considered to correspond with the point at which methionine requirements were met and that under these conditions the methionine requirement for these calves (mean value ± SE) was 4·5 ± 0·2 g/d. In the same two calves PU decreased markedly with increasing levels of methionine supplementation up to 3·9 g/d and the estimated methionine requirement (mean value ± SE) was 3·9 ± 0·4 g/d.

1. To determine the effect of diet and level of energy intake on glucose metabolism in sheep, four dietary treatments consisting of feeding a low-roughage (LR) and a high-roughage (HR) diet at each of two intake levels estimated to provide 586 and 1172 kJ (140 and 280 kcal) digestible energy (DE)/kg body-weight0·75 per d were given to each of eight yearling rams in four different time periods each of 4 weeks duration. Both diets contained 140 g crude protein/ kg using ground maize, mixed hay and soya-bean meal and were given in two meals/d. Estimated DE values of food were verified during the study and actual intakes of DE were within 9·5% of the estimated values.

2. To study glucose metabolism, a single intravenous injection of [2-3H]glucose and subsequent withdrawal of nine venous blood samples within 3 h were made in each experiment. Two experiments were conducted on consecutive days for each sheep on each dietary treatment.

3. Coefficients of determination (r2) for linear regressions to measure the effect of time after a single injection of [2-3H]glucose on log specific radioactivity of plasma glucose were calculated for fifty-eight experiments. In fifty-six of the experiments, r2 values exceeding 0·95 were obtained.

4. Compared to the HR diet, the LR diet increased (P < 0·05) the pool size and decreased (P < 0·05) the half-life of glucose. At both intake levels, the LR diet increased (P < 0·05) the plasma concentration and the entry rate of glucose compared to the HR diet but interaction (P < 0·05) between diet and intake level was attributed to a greater difference obtained between diets at the higher compared to the lower level of food intake. Increasing the level of intake caused a greater (P < 0·05) pool size and space, and a shorter (P < 0·05) half-life of glucose.

5. It was concluded that substitution of roughage by concentrate in a ruminant's diet may increase the rate of glucose entry during a short time period after eating.

1. Lutein and anhydrolutein have been isolated from liver oils of freshly caught Sacco-branchus fossilis.

2. S. fossilis initially contained more dehydroretinol than retinol; administration of anhydrolutein to the vitamin A-depleted fish resulted in the accumulation of dehydroretinol.

3. Anhydrolutein has also been isolated from the liver oils of lutein-treated, vitamin A-depleted fish.

4. The pathway of the conversion of lutein into dehydroretinol is discussed.

1. Leaf is eaten in greater quantities than stem of similar digestibility. To determine whether this difference is caused by physical or chemical factors, leaf and stem fractions from Digitaria decumbens, Chloris gayana and Setaria splendida were fed ad lib. to sheep in the chopped and pelleted forms. Pellets were made from leaf and stem which had been ground through a screen with 3 mm holes. All sheep received a protein and mineral supplement

2. Voluntary intake of chopped leaf was 34% higher than that of the chopped stem fraction (40·3 and 30·0 g/kg body-weight0·75 respectively, P < 0·01) although dry matter digestibility ratios were similar (0·478 and 0·450 respectively, P > 0·05). The higher intake of leaf was associated with a larger surface area (13400 and 5200 mm2/g for chopped leaf and stem respectively), lower bulk density (60 and 180 kg/m3 respectively) and lower neutral-detergent fibre (706 and 724 g/kg respectively), acid-detergent fibre (383 and 413 g/kg respectively) and lignin (42 and 59 g/kg respectively) contents. Chopped leaf was retained in the reticulo-rumen for a shorter time than the stem fraction (19·9 and 26·4 h respectively)

3. Grinding and pelleting increased the voluntary intake of the leaf fraction by 88% and the stem fraction by 60%. This increased voluntary intake caused by grinding and pelleting was not accompanied by any significant changes in the chemical composition of the diet. Grinding and pelleting reduced the time that the food was retained in the reticulo-rumen and this change appeared sufficient to account for the observed increases in voluntary intake

4. It was concluded that the higher intake of the leaf fraction of grasses is caused by differences in retention time of food in the reticulo-rumen. These differences in retention time are caused by differences in physical properties and not chemical composition.

1. The effects of various factors on rates of flow and composition of digesta leaving the abomasum of preruminant calves were studied. The possible relation of some of these effects to the development of serum antibodies to certain dietary constituents has also been examined. Two situations were distinguished: (a) unsensitized responses, shown by calves receiving milk protein or soya-bean products for the first one or two occasions; (b) sensitized responses, shown by calves receiving certain soya-bean products, after a number of these feeds had been given.

2. For unsensitized calves, the rate of flow of total digesta from the abomasum was greater in the first few hours after a feed consisting of a mineral solution was given, than after cow's milk was given. This difference was apparently due to differences in the composition of digesta entering the duodenum. Total digesta flows after giving synthetic milk feeds, prepared from different protein sources, were similar to those after cow's milk was given.

3. For sensitized calves, rates of flow of total digesta from the abomasum were greatly affected by the nature of the protein source used in the diet. Soya-bean flour (heated or unheated) generally caused inhibition of flow for some hours after feeding; a soya-bean protein isolate (isoelectric) had a similar but smaller effect, but a soya-bean concentrate (prepared by alcohol extraction of a soya-bean flour) and milk protein had little or no effect. The inhibition, believed to be a sign of more general disorders, appeared to be caused by a factor entering the duodenum which induced a change in the way in which the calf responded, probably as the result of a gastrointestinal allergy.

4. Calves given soya-bean flour or a soya-bean protein isolate (isoelectric) in their diets for several weeks, showed respectively high and low titres of serum antibodies to an antigen prepared from soya-bean flour. Calves given alcohol-extracted soya-bean concentrate had no similar antibodies.

5. In addition to variations in total digesta flow, dietary nitrogen compounds were held up in the abomasum to different extents after different feeds. After a whole-milk feed or a synthetic feed prepared from casein, a slow, steady release of N occurred over at least 9 h. N hold-up after giving soya-bean-containing feeds was slight for the soya-bean flour, but extremely marked for the soya-bean protein isolate (isoelectric). The latter hold-up was followed after several hours by a rapid outflow of N from the abomasum.

1. [75Se]selenomethionine was administered to four rabbits and after 4 d their kidneys were removed and homogenized. The long-term fate in rats of an oral dose of this kidney homogenate (RK-75Se) was compared with that of an oral dose of [75Se]selenomethionine mixed with unlabelled rabbit kidney homogenate.

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 for analysis of tissue distribution of 75Se.

3. Intestinal absorption of RK-75Se was 87%; that of [75Se]selenomethionine was 91%. Urinary excretion of absorbed RK-75Se was 13·3% and that of [75Se]selenomethionine was 7·6%, in the 1st week.

4. Whole-body retention of 75Se was greater for [75Se]selenomethione than for RK-75Se but after the 1st week 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 in rabbit kidney is different from that of [75Se]selenomethionine. However, after the 1st week 75Se from these sources appears to be metabolized similarly, suggesting that Se from both is ultimately incorporated into the same metabolic pool.

1. Weanling male rats were maintained at constant body-weight for 28 d by feeding them reduced amounts of their normal diet. They were rehabilitated for 0, 3, 7, 10 or 16 d, and compared with two sets of control groups, one set of the same body-weight and the other of the same age

2. The quadriceps, gastrocnemius and anterior tibialis muscles from the left hind-limb were weighed, and DNA, RNA, extracellular protein and intracellular protein estimated in the quadriceps and gastrocnemius muscles

3. Each muscle responded differently during undernutrition and rehabilitation if compared with ‘age controls’, but if compared with ‘body-weight controls’ there was a tendency for muscle weight to remain appropriate for body-weight

4. The amount of DNA did not change in the gastrocnemius or quadriceps muscles during undernutrition, and on rehabilitation did not begin to increase until after 7 d. RNA decreased during undernutrition, but increased rapidly on rehabilitation. The rate of increase in RNA was greatest in the quadriceps during the first 3 d, but in the gastrocnemius was greatest between 3 and 7 d. The peak values for the rate of RNA increase corresponded with the initiation of intracellular protein accretion in each muscle. Extracellular protein increased during undernutrition, and on rehabilitation, responded in the same way as DNA, that is, it increased only after 7 d

5. It is concluded that the differences found between muscles of the hind-limb during rehabilitation are due mainly to differences in the rates of DNA and intracellular protein accretion. It is suggested that these differences are the result of a differential response of RNA to rehabilitation.

1. Studies were done on the effect of ascorbic acid and five amino acids (histidine, cystine, cysteine, valine and glutamic acid) on intestinal iron absorption in a group of ninety Egyptian infants and young children, of which fifty-seven were healthy controls and thirty-three were suffering from Fe-deficiency anaemia.

2. Supplements tested promoted Fe absorption in healthy controls in the following order: valine > histidine > ascorbic acid. Cysteine, glutamic acid and cystine were found to have no significant effect.

3. Supplementation with valine, ascorbic acid and histidine also increased intestinal Fe absorption in anaemic subjects, but to a lesser extent than in controls.

4. Supplementation of haematinic therapy with these compounds is recommended. Their use is also suggested to improve the availability of the Fe content of everyday diets.