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. 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. 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. 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. 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 fatty-acid composition of the plasma total lipids of children with kwashiorkor and of healthy infants was determined by gas–liquid chromatography. Breast milk from Yoruba mothers, and traditional weaning foods, were also analysed for fatty acids, and for protein, fat and carbohydrate.

2. Evidence of essential fatty acid (EFA) deficiency was obtained in the children with kwashiorkor. The proportions of linoleic and arachidonic acids were reduced in the plasma lipids, whereas the endogenous eicosatrienoic acid showed a marked increase. The triene:tetraene ratio had the abnormally high value of 1·08. These changes were consistent with the prolonged ingestion of suboptimal amounts of linoleic acid.

3. Breast milk was of good quality, with a particularly high concentration of retinol. The milk was also rich in linoleic acid, and was thus discounted as a factor in the development of EFA deficiency, but the weaning foods were found to provide substantially less than the minimum recommended intake of 1% of the total energy as linoleic acid.

4. The maize pap with which the children with kwashiorkor had been fed for several months before the appearance of acute symptoms provided almost 7% of the energy as protein, but only 1·21 MJ (290 kcal)/kg. To satisfy energy requirements, it would have been necessary to consume 3–4 kg of the pap each day.

5. It is concluded that the protein deficiency which leads to the development of kwashiorkor in the Yoruba community arises from a very severe restriction in energy intake rather than from the consumption of foods very low in protein at adequate or excessive levels of energy intake.

1. The availability of iron added to dried skim milk and to maize–soya-bean–milk mixture (CSM) was measured by whole-body counting in thirty clinically healthy children and compared with the availability of Fe from ferrous ascorbate alone.

2. The mean absorption of Fe added as ferrous sulphate to a test meal of dried skim milk was 9·5% when the test meal was given as a sweetened drink. When maize meal was added to the dried skim milk to produce a porridge the mean absorption of the supplementary Fe was reduced to 6·3%. The mean absorption of Fe given as ferrous ascorbate alone was 59·6%.

3. These results differed from those reported for indirect tests done with animals in which the absorption of inorganic Fe added to milk-based feed preparations for infants was substantially greater than that of dietary Fe.

4. The mean absorption of Fe added as ferrous fumarate to a test meal of maize–soya-bean–milk mixture was 6·0%, whereas that of Fe given as ferrous ascorbate alone was 63·5%.

5. The amount of supplementary Fe added to maize–soya-bean–milk mixture (USA Department of Agriculture specification) was considered to be adequate.

1. Eleven obese subjects fasted for 24 d, by which time their serum albumin concentration had fallen significantly. 125I-labelled albumin was injected on day 7 of fasting to allow study of albumin metabolism.

2. Although no significant alteration occurred in either the intravascular content or the absolute catabolic rate of albumin between days 7 and 24 of fasting, the mean values for both content and catabolic rate were significantly lower than values determined in eight normal subjects.

3. A corresponding fall occurred in the absolute ‘synthesis+transfer’rate.