1. The riboflavin metabolite, 7,8-dimethyl-10-formylmethylisoalloxazine, has been shown to be reduced to the corresponding alcohol, 7,8-dimethyl-10-(2′-hydroxyethyl)isoalloxazine, by an enzyme present in the soluble fraction of liver and kidney.

2. The enzyme is present in these organs in a number of species but is especially prevalent in the tissues of ruminants. It appears to be different from the normal hepatic alcohol dehydrogenase in that it uses NADPH rather than NADH as cofactor.

1. The ovulation rate of forty-eight Scottish half-bred ewes was increased by using pregnant mare's serum gonadotrophin thus inducing litters of one to four foetuses.

2. The effects of increased litter size upon the foetal growth rate and upon the rate of transfer of calcium and phosphorus across the placenta were studied at 108–112, 122–126 and 136–140 d gestation.

3. The number of foetuses had little effect upon foetal weight at 112 d, the mean weights of a singleton, twin, triplet or quadruplet being similar. However, by 140 d mean foetal weight decreased markedly as litter size increased.

4. Failure of individual quadruplets to grow as fast as a singleton was associated with a limitation in the capacity of the placenta for transferring minerals. The maximum rates of transfer of Ca and P, whatever the number of foetuses, were approximately 2·8 and 1·4 g/d respectively. These rates were attained by 112 d when quadruplets were being carried, by 126 d for triplets, and by 140 d for twins.

1. Groups of rats were maintained from weaning on magnesium-deficient (30 mg Mg/kg) and control (460 mg Mg/kg) diets.

2. Mg deficiency for a period of more than 3 months resulted in sterility of both males and females.

3. A Mg deficiency of less than 3 months caused abortions or resorptions in utero of foetuses in pregnant females before other physical signs appeared.

4. Mg deficiency during lactation rendered the survival of young rats uncertain. The mother rat died of exhaustion if she did not devour her litter.

5. The growth of surviving young rats born of Mg-deficient mothers was noticeably retarded when they were nursed by mothers receiving the Mg-deficient diet.

1. Details of a chemical method, using acetic acid and sodium nitrite, for determining ‘available lysine’ in plant materials are given. An analytical procedure was used which distinguished lysine from ornithine; the latter was liable to arise in the course of the deamination and hydrolysis procedure.

2. The experimentally determined ‘available lysine’ contents of various samples of leaf-protein concentrates showed significant positive correlations with previously reported values for their biological value and true digestibility. ‘Available lysine’correlated significantly with total lysine liberated by direct acid hydrolysis.

1. The butterfat in a whole-milk diet was replaced by either beef tallow, coconut oil or soya-bean oil. The diets contained 280 g fat and 720 g dried skim milk per kg and were supplemented with vitamins A, D, E and K.

2. These diets were offered as a milk, containing 200 g solids/Kg, to pigs weaned at 2 d of age during a 26 d experiment. The pigs were fed at hourly intervals to a scale based on live weight (scale E).

3. The performance of the pigs and the apparent digestibility of the dietary fats indicated that soya-bean oil was equal to butterfat. Butterfat was slightly superior to coconut oil and markedly superior to beef tallow.

4. The amount and composition of the fatty acids were studied in the proximal, mid and distal portions of the small intestine. When the beef tallow diet was given there was an increased amount of total fatty acids in the digesta of the small intestine, mainly in the distal portion. The digesta contained the smallest quantity of fatty acids when the soya-bean oil diet was given. The fatty acid composition of the digesta indicated that the short- and medium chain fatty acids from all the diets were well utilized, but an increasing proportion of stearic acid occurred in the distal portion of the small intestine. The interpretation of changes in fatty acid composition in the digesta in relation to absorption is discussed.

1. The method of Sukhatme (1970b), which takes into account the interrelationship between dietary protein and energy, has been applied to the dietary survey results collected during the nation-wide Nutrition Survey of West Pakistan. It was found that most of the protein deficiency that occurs in Pakistan is conditioned by energy deficiency. The incidence rises from 13 to 40% when cases conditioned by energy deficiency are taken into account. Protein deficiency as such exists in only 2% of families compared with 11% of families which are deficient in both protein and energy. These findings indicate the magnitude of the protein problem in Pakistan.

2. In view of these findings, it is obvious that, unless the energy need is met, increased protein production will not help much to improve the situation and may be a costly approach to the solution of the protein problem in Pakistan.

1. There were statistically-significant relationships between the concentrations of vitamin B12 in the livers of rats and their urinary excretion of methylmalonic acid, both before and after the intraperitoneal injection of sodium propionate.

2. The effects of diets based on raw and heated soya-bean flour (SBF) on the growth rates, urinary excretion of methylmalonate and hepatic vitamin B12 were compared in normal and vitamin B12-depleted rats.

3. When female weanling vitamin B12-deficient rats were put on to the raw SBF diet they lost weight and became moribund after 3 weeks, even when the diet was supplemented with vitamin B12. Male adult vitamin B12-deficient rats lost weight but showed no other signs of severe vitamin B12 deficiency.

4. Stock weanling male rats were fed on raw SBF diets with or without added vitamin B12. The diets were given alone and supplemented with either methionine or a mixture of methionine, valine, threonine and tyrosine. The rats still did not grow as well as those fed on diets containing heated SBF. However, there was some evidence of increased methylmalonate excretion and lower hepatic concentrations of vitamin B12 in the rats fed on the raw SBF diets.

1. The vitamin B12 content of items of diet and of meals was measured after they had been prepared for consumption.

2. There was poor agreement between the vitamin B12 contents of meals estimated by measurements on meal homogenates and the contents estimated by calculations involving the weights and vitamin B12 contents of items.

3. The average amount of vitamin B12 absorbed per d from a hospital diet was found to be 1.7 μg.

1. Techniques were devised for the operation of a new small-scale gnotobiotic rat unit.

2. The unit was then used to compare the cariogenicity of sucrose and glucose under carefully controlled conditions in the presence of a single strain of a streptococcus, as gnotobiotic experiments by other workers had given conflicting results.

3. Streptococcus IB-1600 was implanted into thirty-four rats, which were then fed on high-sugar diets under gnotobiotic conditions for 5 or 8 weeks from weaning. The level of caries was significantly higher on the sucrose than on the glucose diet, but there was no significant difference in the extent of soft coronal dental plaque.

1. Two experiments were conducted to compare the effect on nitrogen retention of three dietary levels of N given either as groundnut or as urea to growing heifers. Additions of maize starch or dextrose were made to the diets to equalize the inputs of digestible energy within and between experiments.

2. In the first experiment, in which the maximum level of N supplementation was 69·0 g/d, the response to additional N was linear, and was identical for both sources of N. Differences in faecal N between treatments were small; differences in urinary N were large and were entirely attributable to level of N intake.

3. In the second experiment, the maximum level of N supplementation was raised to 103·3 g/d. The response to additional N was again linear and identical for both sources of N; however, for a given level of N input, the amount of N retained was 4·6 g less than in Expt 1. This reduction in N retention may have been due to the change in the proportion of digestible energy derived from the fibrous components of the ration.

4. Live-weight changes calculated from the observed N retentions have been compared with published responses to the inputs of N and energy used in these experiments.

1. Purine or pyrimidine bases, nucleosides or nucleotides were incubated, in vitro, with whole rumen contents, or with a cell-free filtrate prepared from rumen contents of calves fed on diets of flaked maize and hay.

2. During incubations with whole rumen contents, all derivatives bearing a side amino group were deaminated to varying extents.

3. All nucleotides and nucleosides were rapidly degraded to the parent base or its desamino counterpart.

4. Evidence suggests that guanosine was degraded to guanine before deamination occurred whereas deamination preceded ribosidic cleavage for adenosine.

5. Xanthine, uracil, hypoxanthine and thymine resisted further degradation to varying degrees.

6. Little or no breakdown was observed when any derivative was incubated, in vitro, with cell-free preparations.

1. The effect of dietary copper deficiency on the distribution of Cu, zinc and iron between plasma, various soft tissues and bone was investigated in weanling male rats.

2. The concentration of Cu decreased in plasma, liver, kidney and femur, and the concentration in plasma correlated with that in all three organs. The total amount of Cu in the liver was reduced over the whole depletion period and a net loss from kidney also occurred over a shorter period, indicating that liver and, to a lesser extent, kidney both provide a mobilizable reserve of Cu.

3. Animals in galvanized cages developed Cu deficiency more rapidly than similar rats in stainless-steel cages owing to Zn aggravating the depletion. Zn accumulated in the liver and femur of Cu deficient rats, particularly when they were housed in galvanized cages.

4. Cu-deficient animals accumulated Fe in the liver, but had reduced concentrations in plasma, kidney and spleen. The hypertrophy of the heart and bone-marrow observed in Cu-deficient rats appeared to be secondary to the anaemia resulting from this impaired mobilization of hepatic Fe.

1. The haematological status of Ayrshire bull calves reared on fat-supplemented skim milk from about 17 d of age has been examined. The calves were moderately anaemic after an 11-week experiment and it was shown that their performance was related to their blood haemoglobin concentration.

2. The relative availabilities of iron from FeSO4, ferric citrate, ferric-ethylenediaminetetra-acetate and iron phytate were compared at a supplementary dietary concentration of 30 μg Fe/g. No significant differences were noted between the three soluble Fe sources but the Fe of the insoluble iron phytate was less available.

3. The decreases in blood haemoglobin concentrations in all calves were greatest in the early weeks of the experiment. In calves given supplementary Fe, however, there was generally an improvement in haematological status after 6 weeks. Plasma Fe concentrations fell to 0·20 μg/ml in the most deficient animals. Total Fe binding capacities averaged about 10 μg Fe/ml in the later stages of the experiment.

4. Some of the calves were copper-deficient, and in some animals the effects of dietary Cu supplementation on both Cu and Fe metabolism were studied. About 50% of the supplementary Cu was retained in the livers of the calves.

5. A dietary intake of 40 μg Fe/g milk powder appears to be sufficient to prevent all but a very mild anaemia, provided the Fe is presented in soluble form.

1. Young female Wistar rats were fed for 18 d on diets containing dextrose, 43 dextrose equivalent (DE) glucose syrup, fractions of 43 DE glucose syrup of high and low molecular weight or sucrose.

2. All rats gained weight and showed no gross external abnormalities or significant dental caries scores.

3. The concentrations of cholesterol, triglycerides, free fatty acids and glucose were determined in samples of liver and serum. Generally, these values tended to increase with increasing molecular weight of dietary carbohydrate in the order dextrose, glucose syrup fraction of low molecular weight, and glucose syrup fraction of high molecular weight.

4. Rats given the high-molecular weight glucose syrup fraction were found to have caecums twice the normal size.

1. The pool size, space and rate of irreversible loss of glucose were estimated with primed infusions of [U-14C]glucose in reindeer cows within 6 h of being taken from outdoor pens or from free grazing in the field.

2. In conjunction with primed infusions of [U-14C]glucose, single injections of [3-3H]glucose were also used to estimate pool size, space, transfer rate, and turnover time of glucose.

3. Except in a period of severe undernutrition, the concentration of glucose in plasma was higher (range 0·76–1·40 mg/ml) than that recorded for other ruminants.

4. The size of the glucose pool (range 8–35 g) varied in parallel with plasma glucose concentration and was generally distributed in a space in excess of the extracellular fluid volume.

5. The lowest rates of irreversible loss of glucose (approximately 1·7 mg/min per kg0·75) were measured when cows were in mid pregnancy and when available food was scarce; the highest rate (5·5 mg/min per kg0·75) was found in cows during mid summer.

6. Changes in irreversible loss and transfer rate of glucose are interpreted in relation to changes in body composition (estimated in a parallel study), subjective assessment of available food and factors known to control glucose metabolism in other ruminants.

7. The difference between glucose transfer rate and rate of irreversible loss of glucose was used as an index of the rate of resynthesis of glucose from products of glucose catabolism. The rates of glucose resynthesis were highest during a period of rapid growth (4·52 mg/min per kg0·75 or 45% of the glucose transfer rate) and in mid and late pregnancy (respectively 4·14 and 4·28 mg/min per kg0·75 or 71 and 59% of the transfer rate).

1. Three groups of rats of different mean weights were given a diet of milk treated with hydrogen sulphide and supplemented with copper-free minerals and vitamins. Also divided into three groups of similar weights were rats given the same diet supplemented with 500 μg Cu/week and stock rats which were given a commercial diet.

2. In a second experiment eight adult female rats were given the Cu-deficient diet for 2 weeks before mating and during pregnancy, and in a third experiment were mated and immediately after mating were given the Cu-deficient diet or the Cu-supplemented diet.

3. Cu deficiency reduced the growth rate of younger rats but had a much less marked effect on the weight of more mature rats. Achromotrichia appeared at 5 weeks; diarrhoea, with the faeces frequently containing undigested blood, and subcutaneous oedema were terminal changes. Deaths occurred in the youngest group of rats after 9 weeks and later in heavier, older rats.

4. Histological changes were seen in livers, spleens, testes and epididymes but not in blood vessels or bones.

5. Pups were not born to mothers given the deficient diet before mating, and the pups from mothers given the deficient diet only during pregnancy were born dead or showed congenital abnormalities.

6. Foetal and liver Cu concentrations for the various groups of animals are given.

7. Maintenance of the foetus appears to be the biological process most susceptible to Cu deficiency in the rat.

1. A group of ten Ugandan children were given, ad lib., under supervision, the traditional home diet and their intakes of energy and protein and changes in body-weight and concentrations of serum albumin compared with those of a similar group of nine children fed on a milk-based diet with the same protein concentration.

2. The energy and protein intakes of the children fed on the home diet were significantly lower than those of the children fed on the milk-based diet, as was their rate of weight gain and serum albumin regeneration.

3. The significance of the findings is discussed in relation to the low intakes of energy and protein and the hypoalbuminaemia found in Ugandan preschool children.