1. The ingestion of cassava (Manihot esculenta Crantz) by rats increased the plasma thiocyanate concentration and reduced the thyroid iodine content and the plasma protein-bound iodine.

2. Administration of increasing doses of thiocyanate raised the plasma thiocyanate concentration and reduced the thyroid iodine content and the plasma protein-bound iodine.

3. In producing these effects, the daily ingestion of 10 g cassava root containing 1·6 mg cyanide was approximately equivalent to a daily intake of about 1–2 mg thiocyanate.

4. These results suggest that the antithyroid action of cassava is the result of the production of thiocyanate by the rat from cyanide arising from the cyanogenic glucosides present in this food.

1. The vitamin A content of Saccobranchus fossilis kept on a diet of rice and meat gradually decreased and became negligible at the end of 3–5 months.

2. S. fossilis initially contained more dehydroretinol than retinol; administration of β-carotene or zeaxanthin to the vitamin A-depleted fish did not result in an accumulation of dehydroretinol in the liver. On the other hand, when lutein was administered by mouth or subcutaneous injection, it was converted into dehydroretinol.

1. Using a double-lumen tube perfusion system, solutions of lactose (50, 125 and 250 mmol/l) were introduced into the upper jejunum of six Zambian African subjects. By reference to a non-absorbable marker, polyethylene glycol, mol. wt 4000, the rates of absorption of lactose from each solution were calculated for a 300 mm jejunal segment.

2. In three subjects total lactase activity of the jejunal mucosa and brush-border lactase and other disaccharidase activities were estimated. The jejunal total and brush-border lactase activities were low. Jejunal morphology was normal for African subjects.

3. All subjects suffered abdominal colic and diarrhoea during and after the lactose perfusions. The kinetic curves for lactose were very shallow, and with all perfused solutions, there was a net movement of water into the jejunal lumen. The limited number of subjects, and the low and narrow range of enzyme activity, did not permit correlation between lactose absorption rate and lactase activity.

4. In Zambian African subjects with adult hypolactasia, the jejunal mucosa absorbs a very small proportion of the perfused lactose.

1. Studies were performed with female rats to examine the effect of various levels of orally administered oxytetracycline on body-weight, weight of various portions of the intestinal tract, weight of mesenteric lymph nodes, distribution pattern of the tissue elements in the terminal portion of the ileum, and on the susceptibility to invasion by Salmonella typhi-murium.

2. There was no growth promotion resulting from any antibiotic treatment. A consistent finding was the decrease in the wet weight of mesenteric lymph nodes in the rats given antibiotic.

3. In the bacteriological test, no differences between antibiotic-fed and control groups were observed in isolations from the liver, spleen or intestinal tissue. It was concluded that there were no effects of oxytetracycline administration on invasive capacity of orally administered S. typhi-murium.

1. Faecal and urinary sulphur excretions of Merino sheep given fifty-one forage diets were measured in 205 balance experiments to derive estimates of the dietary requirements of Merino sheep for S.

2. Faecal S excretion varied with the S, organic matter and digestible organic matter intakes. Non-dietary faecal S excretion was estimated by regression analysis and was approximately 0·7 g S/kg organic-matter intake. Apparent S digestibility declined linearly with the reciprocal of dietary S content, and was predicted to be zero when the dietary S content was 0·81 g S/kg organic matter.

3. Both urinary S excretion and S retention varied with the digestible S and digestible organic-matter intakes. Endogenous urinary S excretion was taken to be the urinary S excretion when digestible S intake was zero, and the sheep was at zero energy balance. It was estimated by regression analysis to be 38 mg S/d.

4. The S and digestible S intakes necessary to maintain the fleece-free tissues in S equilibrium can be calculated from the equations derived in this study. An example is presented.

1. Rates of absorption of glycine and glycylglycine from a 300 mm jejunal segment were compared in vivo when those compounds were given alone or together to six Zambian African subjects who had no clinical evidence of malnutrition or of gastro-intestinal disease. Solutions containing (A) glycine (100 mmol/1), (B) glycine (100 mmol/l)+glycylglycine (50 mmol/l), and (C) glycylglycine (50 mmol/l) were infused into the upper jejunum by means of a double-lumen tube perfusion system.

2. Rate of absorption of glycine was significantly higher from the glycylglycine solution (C) than from the glycine solution (A). Glycine absorption rate from solution B (glycine+glycylglycine) was very similar to the sum of absorption rates of glycine from solutions A and C in each subject. Luminal disappearance rate of glycylglycine from solutions C and B were very similar; however, the rate was significantly greater than the total glycine absorption rate from solution C and indicates back-diffusion of glycine into the lumen after glycylglycine hydrolysis.

3. The results are interpreted as indicating that the transport mechanisms for glycine and glycylglycine in man are partly, and possibly wholly, separate.

1. Eight groups each of four castrated male pigs, 25–30 kg initial body-weight, were kept for periods of 3 weeks in a calorimeter equipped as a pig pen and maintained at either 8° or 20°. At each temperature two feeding levels (g food/kg body-weight per d) were used, 45 and 52 at 8°, and 39 and 45 at 20°. Metabolizable energy, heat loss and nitrogen balance were measured.

2. Heat loss was higher at 8° than at 20° and was independent of plane of nutrition, whereas at 20° the higher heat loss occurred at the higher plane of nutrition. Energy retention depended on both temperature and feeding level, and was highest at the 52 g feeding level at 8°.

3. N retention was not influenced by environmental temperature but varied with plane of nutrition (correlation coefficient = 0·94), the increase being 9·98 (± 0·8) mg N per g food increase. The correlation coefficient between N retention and body-weight gain was also 0·94; body-weight gain was correlated with N retention rather than with fat deposition. Fat gain was reduced at the lower feeding levels and at the lower environmental temperature at the feeding level of 45 g/kg.

4. The partial efficiency of energy retention at 20° was 66·5%. From this efficiency the maintenance requirement (at zero energy retention) at 20° was calculated to be 418 kJ/kg0·75. At 8° the partial efficiency of energy retention was 99·4%.

1. Newborn infants of low birth weight absorb both pteroylmonoglutamic acid and pteroylpolyglutamate.

2. There was a significant fall in serum folate concentrations during the first 14 d of life in these infants, but a daily supplement of 50 μg pteroylmonoglutamic acid or pteroylpolyglutamate was sufficient to prevent the development of subnormal serum folate concentrations.

1. Estimates of sulphur retention by Merino sheep during growth, pregnancy and wool production, and of S excretion during lactation were obtained to derive estimates of the S requirements of Merino sheep.

2. The S content of fifty Merino sheep was related by weighted regression analysis to age, live weight and (age × live weight). The quantity of S stored was calculated for varying rates of live-weight gain in sheep differing in age and live weight.

3. The S contents of twenty-five samples of foetus, foetal membranes and uteruses were determined. Relationships between S content and days from mating were calculated, and differentiated to give daily net changes in S content during pregnancy.

4. Milk production of twenty-seven Merino ewes was estimated on eight to ten occasions at approximately weekly intervals to the 84th day of lactation. The average S content was 472 mg/l; it increased on average by 1·0 mg/l per d of lactation. The mean S content of ninety-seven samples of wool averaged 34 g S/kg clean dry wool.

5. It was concluded that wool represented the major demand for S by the Merino since approximately 70 g S were secreted in producing 2 kg clean wool, 50 g S in a lactation yielding 100 l milk and 8 g S in giving birth to a single lamb.

1. Interrelationships between the level of dietary fat and the metabolism of palmitate, stearate, oleate and linoleate in the broiler chicken have been studied by means of isotope dilution techniques.

2. The composition of the free fatty acid (FFA) and triglyceride fractions of plasma lipids was influenced by the level of dietary fat, but the only effect of diet on plasma concentration was the higher FFA levels after feeding in birds given the high-fat diet.

3. The rates of entry and oxidation of the individual fatty acids were correlated with their concentrations in plasma, but were unrelated to the level of dietary fat. Slight differences in the metabolism of the individual fatty acids were observed.

4. Acetyl-CoA carboxylase (EC 6.4.1.2) and desaturase activities were higher in the livers of birds given the low-fat diet.

1. Liver biopsies were performed through laparotomy wounds in six baby baboons during the development of a kwashiorkor-like illness induced by low-protein, high-carbohydrate diets similar to those consumed by many East African children. Up to six biopsies have been performed successfully in one animal within a period of 1 year. This material has been studied by light and electron microscopy.

2. A similar study was carried out in two healthy animals fed on an adequate diet. A description is given of liver ultrastructure in normal baby baboons, based on examination of these biopsies.

3. The hepatocytes of the malnourished animals contained excessive amounts of glycogen and showed a reduction in rough and smooth endoplasmic reticulum. Even at the height of an illness indistinguishable clinically from marasmic kwashiorkor, there was no excess of liver fat except in those animals whose diet contained sucrose. This may have been the result of stimulation of hepatic triglyceride synthesis by fructose.

4. In no specimen from the experimental group were there signs of serious progressive and irreversible liver cell damage which might have been expected if liver dysfunction were an important component of kwashiorkor.

5. Biopsies performed in one malnourished animal during recovery showed a return of liver ultrastructure to normal.

1. Experiments were conducted to investigate the effects of feeding rats on a diet based on a mixture of maize oil fatty acids as the only source of non-protein energy (fatty acid diet) and the influence on these effects of giving such a diet in a single daily meal lasting 2 h.

2. In comparison with a triglyceride diet in which the non-protein energy was in the form of maize oil, feeding ad lib. with the fatty acid diet produced no significant changes in body-weight gain, plasma glucose and plasma ketones concentrations, liver glycogen concentration and protein efficiency ratio.

3. In comparison with the triglyceride diet, meal-feeding with the fatty acid diet produced significantly lower body-weight gain and protein efficiency ratio; moreover, it significantly lowered plasma glucose and liver glycogen concentrations.

4. Rats meal-fed on the fatty acid diet synthesized glucose from protein, as evidenced by the significantly higher liver glycogen concentration detected 6 h after the meal had been eaten, but the increase was significantly lower than in the animals fed on the triglyceride diet. Also, 6 h after the meal had been eaten, the amount of meal remaining in the stomach of rats meal-fed on the fatty acid diet was significantly higher than in those fed on the triglyceride diet.

1. Male hooded Lister rats given a diet containing 40 mg zinc/kg were described as Zn-adequate. Other rats were subsequently given diets containing less than 1 mg Zn/kg. After a period of approximately 5 d these animals ceased to grow and were described as Zn-deficient.

2. Zn-deficient rats offered ad lib. a Zn-deficient diet containing 200 g egg albumen/kg ate only 55% of the weight eaten by Zn-adequate rats given a similar diet supplemented with Zn. The intake of the deficient rats increased when the metabolizable energy content of the diet was decreased and also when the environmental temperature was lowered.

3. Zn-deficient rats offered Zn-deficient diets containing 200 g egg albumen/kg showed a high day-to-day variability of intake. When the albumen content was raised to 400 g/kg, neither the mean food intake of the rats nor the variability of food intake changed, but with diets containing only 50 g albumen/kg the quantity eaten increased and the variability of food intake decreased. Results obtained when the low-protein diet was supplemented with essential and non-essential amino acids indicated that increased variability of intake was associated with the essential amino acid content of the diet. The effect on variability of intake was greatest when the supplements contained methionine, phenylalanine, threonine and tryptophan; addition of this group of amino acids to a Zn-supplemented, low-protein diet produced the largest increase in the growth rate of Zn-adequate rats.

4. When the food intake of the rats was examined for periods of 2 h throughtout the day, the Zn-deficient rats were found to eat on fewer occasions than the control rats. However, in those periods when the Zn-deficient rats did eat, the quantities eaten in 2 h showed the same distribution of weights as did those for the Zn-adequate rats.

5. There were significant relationships between food intake and plasma Zn concentration; the most significant was the negative correlation between food intake in 24 h and plasma Zn concentration at the end of the 24 h period.

6. Zn deficiency resulted in a failure of growth in the young rat and therefore in a reduction in its rate of energy expenditure but did not appear to cause directly a loss of appetite. It is suggested that cyclical patterns of food intake associated with Zn deficiency in young rats resulted from the slow but effective control of food intake by the energy balance of the animals.

1. The protein requirements of lambs were established by measuring nitrogen balance in seventy-four animals given liquid diets which passed direct to the abomasum. Four groups of lambs weighing approximately 8 kg (group 1), 13 kg (group 2), 21 kg (group 3) and 30 kg (group 4) received diets in which 0·10, 0·15, 0·20, 0·25, 0·30, 0·35 or 0·40 of the digestible energy was provided as protein (DPE:DE ratio) and a gross energy intake of from 1·30 to 1·42 MJ/kg0·73 per d.

2. When the protein requirements were taken to correspond to the protein intake at the point of intersection of the line describing the increase in N balance with increase in protein intake and the line representing the maximum N balance, values of 0·25, 0·23, 0·17 and 0·12 DPE:DE ratio were obtained for groups 1–4 respectively. The requirements expressed in these terms can be applied only to lambs fed on liquid diets which contain milk proteins and escape fermentation in the rumen. To enable the results to be applied to lambs given other diets, the requirements were expressed as g reference-protein (defined as a theoretical protein with the ideal pattern of amino acids) per MJ net energy and were 11·6, 10·4, 8·0 and 6·2 for groups 1–4 respectively. The relationship between protein requirement (Y, g reference protein/MJ net energy) and live weight (X, kg) was: Y = 13·4–0·242X.

3. The influence of energy intake on protein requirements in lambs is discussed and it is concluded that the results obtained are applicable to lambs given a metabolizable energy intake of more than about 1·75 times their maintenance requirement.

4. Application of the estimated requirements to ruminant lambs and methods of formulating diets to supply the required quantity of reference protein/MJ net energy are discussed.

1. Loaves of conventional white bread and of bread made by the Chorleywood Bread Process (CBP) were bought from bakers’shops in Britain over a 10-month period and were bulked to give samples representative of each type of bread produced for consumption in the country as a whole. These were analysed for moisture, protein and amino acids, fats and fatty acids, carbohydrate (by difference), sodium, potassium, iron, thiamin, riboflavin, total and available nicotinic acid, vitamin B6, and free folic acid.

2. There were no great differences between the nutrient contents of the two types of bread. The mean moisture contents differed by only 5 g/kg but a variation was found between some selected nutrients in paired loaves of the same type. CBP bread could not be distinguished from conventional bread in its content of fat, ash, calcium, sodium, potassium, thiamin, total and available nicotinic acid and vitamin B6. The content of riboflavin was slightly higher, and of protein and carbohydrate slightly lower in CBP bread than in conventional bread. Differences in fatty acid composition of the two types of bread and in their content of total sulphur-containing amino acids were slight.

1. The iron requirements of eighteen Ayrshire bull calves reared on fat-supplemented skim milk for 14 weeks from c. 16 d of age have been studied. There was a highly significant relationship between dietary Fe intake (10, 40 and 100 mg/kg dry diet) and blood haemoglobin concentration, packed cell volume and plasma Fe concentration.

2. A microcytic normochromic anaemia developed in the calves given a diet containing 10 mg Fe/kg diet, but not in the other calves.

3. Plasma Fe concentrations increased to > 5 μg Fe/ml in calves receiving 100 mg Fe/kg diet but there were no effects of Fe treatment on plasma Fe-binding capacity, which rose from 4·9 to 8·4 μg Fe/ml during the experiment. Saturation of plasma transferrin was only 3% in the Fe-deficient calves.

4. There were some significant effects of Fe treatment on tissue concentrations of Fe and cytochrome c.

5. Dietary supplementation with 5 mg copper/kg dry diet had little effect on the growth or haematological status of the calves, although there were significant Cu × Fe interactions for mean corpuscular haemoglobin and mean corpuscular volume. There was no evidence of Cu deficiency in the calves, as measured by blood and liver Cu concentrations and by ceruloplasmin and cytochrome oxidase activities.

1. Pooled samples of eggs from White Leghorn and New Hampshire hens given diets containing 110 and 200 g protein/kg were analysed for their content of essential amino acids.

2. The amino acid composition of the hen's egg protein was not significantly affected by variations in breed and diet.

3. The estimated values for lysine, total sulphur-containing amino acids and tryptophan in egg protein were higher by 8·9, 2·0 and 8%, respectively than those adopted for hen's egg by the FAO/WHO Expert Committee (FAO, 1965).

4. The isoleucine content of egg protein was found to be much lower (338 mg/g nitrogen) than that reported by other workers.