1. The excretion of magnesium in urine, milk and faeces and of faecal dry matter (DM) by grazing monozygotic twin cows has been determined at intervals throughout four grazing seasons.

2. In Expt 1 three sets of twins were used to study the within-pair variance in the excretion of Mg and faecal DM. It was found that the variation within pairs was non-significant and small, less than 5% of the overall mean for all but one of the measurements made. The variation in urinary excretion of Mg within pairs was significant (P <0.05) in 1962.

3. In Expt 2 the effects of lactation on the excretion of Mg and faecal DM were studied. Only one of each of the monozygotic twins was in milk at a time, each twin being in milk for one season.

4. There were no significant differences in faecal nitrogen within and between pairs. On average, lactation increased faecal DM by 30% in 1964 and 24% in 1965.

5. The effect of lactation on urinary Mg was not consistent. For faecal Mg the effect of lactation was a simple reflection of the increased faecal DM since lactation had no effect on the concentration of Mg in the faeces. There was no correlation between the Mg excretion in urine and milk, either singly or together, with faecal Mg excretion.

6. The concentration of Mg in milk differed between twins and increased with length of lactation.

7. Mean intakes of Mg by the cows have been calculated from the values for the intake of DM and the Mg content of cut herbage and compared with total excretion of Mg in urine, milk and faeces. There was a significant correlation (P <0.05) between the sets of values but estimated intakes were lower (P <0.05) than excretions. The differences between intake and excretion differed between periods (P <0.001), being greatest between July and September. Selective grazing was considered to be the main factor responsible for these differences.

1. A method is presented for estimating the incidence of protein deficiency which takes due note of the association of protein deficiency with inadequate calorie intake and is applied to the data from dietary surveys in India. It is concluded that in only about one out of ten cases does protein deficiency occur as a direct result of inadequate protein intake. In the vast majority of cases protein deficiency is the result of inadequate intake of total energy. Protein which does not bring calories with it is therefore unlikely to make any significant contribution to the solution of the protein problem in India.

2. It is shown that diets based on cereals and pulses normally consumed by the people can meet man's needs for proteinat all ages provided enough food is taken to satisfy his energy needs. It is, however, important to ensure for infants a smooth transition from breast milk to solid diets. Special care is also necessary in the case of pregnant and lactating women.

3. The nature of protein deficiency is discussed in relation to different dietary patterns. The continuity implied in the bivariate distributions of calorie and protein intake is seen to provide a possible explanation of the experimental results on the development of kwashiorkor observed in animals on a diet short of both calories and protein and ondietspredominantly short of protein.

1. Eighty-eight Nigerian village children aged 1–12 years were involved in this study.

2. A food consumption survey on each child was carried out for 7 consecutive d; iron, folic acid and calorie intakes were calculated from food composition tables.

3. Samples of the children's diets (cooked) were collected and analysed for moisture, total nitrogen and ascorbic acid content.

4. Blood samples were assessed for haemoglobin and haematocrit values.

5. Calorie, protein and folic acid intakes were low for all age groups; iron and ascorbic acid intakes were adequate.

6. There was no incidence of severe anaemia. Only 10% of all the eighty-eight children had a haemoglobin concentration below acceptable levels and only about 8 % of all the eighty-eight children had haematocrit values below acceptable level.

1. Three factors were investigated which influence blood urea content, namely the protein content in the diet, the time after feeding and the protein quality of the diet.

2. To investigate the relationship between the protein content in the diet and the blood urea content, seventeen experiments with rats given increasing amounts of protein in the diet were carried out. The experimental results show that there is a positive correlation (r = 0.95) between the protein content in the diet and the blood urea content.

3. For investigation of the influence of time after feeding on the urea content in the blood, a pig was used having a catheter in the portal vein for blood sampling at intervals. The results from this experiment showed that the blood urea content increases for the first 3–4 h after feeding and thereafter reaches a plateau.

4. To use blood urea measurement as a technique for assessing protein quality it is necessary to work under standardized conditions, especially in regard to the two factors just discussed.

5. Forty-two feeding-stuffs of widely differing quality were used in nitrogen balance trials with rats. The results showed that there is an inverse relation between the blood urea content and the biological value of the diet which is sufficiently accurate (coefficient of variation = 53%) to provide ausefulmethod for the predictionof protein quality from measurement of urea levels.

1 The continuous faecal marker chromic oxide, Cr2O3, and the intermittent marker brilliant blue were used together in metabolic balance studies of calcium and magnesium in two young women.

2. Faecal output was derived by four methods: no marker, brilliant blue, Cr2O3, or both brilliant blue and Cr2O3.

3. Balances of Ca and Mg derived by the four methods of obtaining faecal output were compared.

4. Recovery of ingested Cr2O3 in the faeces appeared complete in experiments on three further subjects, with only a negligible amount being excreted in the urine.

5. Simultaneous use of both types of marker is recommended for short-term balance studies of nutrients such as Ca and Mg which are not readily absorbed.

1. The excretion of calcium and potassium in urine, milk and faeces by grazing monozygotic twin cows has been determined at intervals throughout four grazing seasons.

2. In Expt I three sets of twins were used to study the variation within pairs in the excretion of Ca and K. It was found that the variation within pairs was non-significant and small, less than 5% of the overall mean, for all but one of the factors measured. The variation in urinary excretion of Ca within pairs was significant (P <0.05) in 1962.

3. In Expt 2 the effects of lactation on the excretion of Ca and K by three sets of twins were studied over two grazing seasons. Only one of each of the twins was in milk at a time, each twin being in milk for one season.

4. Lactation increased (P <0001) urinary and faecal Ca in 1964 but not in 1965. The concentrations of Cain the faeceswere lower (P <0.01) for lactatingthanfornon-lactating cows.

5. Lactation increased (P < 0.001) the excretion of K in urine and faeces. Differences within pairs in faecal concentration were significant in 1964 (P <0001) and 1965 (P < 0.01), but the effect was not attributable to lactation.

6. Significant differences between pairs were found for urinary Ca and K in 1964 (P < 0.05) and for the concentration of K in faeces in both years ( P < 001 or P < 0.001).

7. In 1964 greatest total excretions of Ca were found in June and July and of K in May, whereas in 1965, although the differences between periods for Ca and K were significant (P < 0.001), there were no obvious seasonal trends.

8. Mean intakes of Ca and K by the cows have been calculated from the estimated drymatter intake of herbage and the Ca and K content of the cut herbage and compared with total excretion in urine, milk and faeces. The differences between intake and excretion differed between periods (P < 0.001); for Ca, negative values were greatest in July and August in 1964 but not in 1965 and for K the values were small in July and large and positive in May, September and October in both years. The differences between lactating and non-lactating cows were significant for Ca(P < 0.001) and K (P < 0.01) in 1964. Selective grazing was considered to be the main factor responsible for these differences.

1. Fifty-two pregnant women in a village were divided into three groups, A, B and C, and were given the following supplements: A, iron in the form of 200 mg ferrous sulphate daily; B, Fe(as group A) and 5 mg of folic acid daily; C, Fe and folic acid (as group B) plus an antimalarial drug.

2. Blood samples were collected each week and assessed for haemoglobin and haematocrit values.

3. Dietary intakes of Fe and folic acid were calculated for both pregnant and non-pregnant women. Results revealed that Fe intake was adequate and Fe deficiency not common. The supplement of Fe increased the haemoglobin levels.

4. Folic acid intake was low and intake probably fluctuated during the year because of seasonal changes in the dietary folic acid.

5. About 28% of patients, during their first attendance, had haematocrit values below normal. Folic acid supplements increased these values.

1. Techniques for the preparation of a semi-synthetic basal diet suitable for the rapid production of zinc deficiency in the rat are described. The complete diet usually contains between 0.6 and 0.9 ppm Zn.

2. When the unsupplemented diet was fed to weanling rats, growth arrest occurred after 4–5 d; when supplemented with ZnSO4 to provide 12 or 20 ppm Zn, the rate of growth of rats was similar to that attained in animals given a conventional stock colony diet providing 83 ppm Zn. A study of relationships between dietary Zn concentration and weight gain in 21 d suggested that the Zn requirement of male and female rats for growth on this diet is approximately 12 ppm.

3. The development of Zn deficiency on diets providing < 1 or 3 ppm Zn was accompanied by poor food consumption and the development of a characteristic cyclic pattern of intake. A significant decline in the variability of daily food intake was observed when the diet was supplemented with Zn to provide 6, 9 or 12 ppm.

4. Studies of the influence of dietary Zn content upon changes in the Zn content of a range of tissues and upon whole-body Zn retention are reported.

5. The above findings are discussed in relation to the problem of defining the severity and duration of Zn deficiency in animals used for studies on the nature of the metabolic role of Zn.

1. Hydroxyproline was determined in urine, carcass, and skin of young rats fed on low-protein and low-calorie diets.

2. Protein and calorie deprivation in young rats resulted in a marked fall in the soluble as well as insoluble collagen content of the skin.

3. The collagen content of the carcass (excluding skin) was slightly greater in the deficient rats than in the weanling rats, but very much lower than in the well-fed rats.

4. In rats subjected to protein and calorie deficiency, urinary hydroxyproline was markedly reduced. In these rats, most of the reduction in urinary hydroxyproline was observed within 1 week of feeding the deficient diet. Protein deficiency had affected urinary excretion of hydroxyproline more severely than calorie deficiency.

5. The reduction of urinary hydroxyproline in the deficient animals can be attributed to decreased turnover rate of their body collagen. This apparent decrease in turnover rate is explained as being due to an increase in the proportion of collagen of slow turnover in these animals.

6. Protein and calorie deficiency had also resulted in the depletion of non-collagen nitrogen of both carcass and skin.

1. In an attempt to elucidate the pathogenic mechanism of the fatty liver of kwashiorkor some aspects of lipid metabolism were studied in ten patients with kwashiorkor and nine with marasmus, so classified according to the clinical and laboratory findings.

2. Plasma lipid levels, especially those of triglycerides, were low in patients with kwashiorkor; they showed a marked rise very early during treatment.

3. The changes in the plasma lipid levels occurred mainly in the serum lipoprotein fraction of density < 1.063. The elevation of plasma lipid levels during treatment coincided with a loss of liver lipids and a marked rise in serum protein concentration.

4. The findings support the suggestion that the primary mechanism in the production of the fatty liver of kwashiorkor is an impairment in the synthesis of lipoprotein of very low density, probably due to the rate-limiting synthesis of its protein moiety.

5. In patients with marasmus no modifications in lipid metabolism were detected by the methods used.

1. An experiment is reported in which groups of six lambs were fed two basal diets supplemented at three levels with a mixture of sodium and calcium acetates.

2. The basal diets were given in amounts that provided equal intakes of digestible organic matter and crude protein. One contained 85 % of concentrates (Hc), the other 40% of concentrates (Lc). Rumen contents from a sheep receiving diet Hc contained a lower molar proportion of acetate and higher proportions of propionate and butyrate than when diet Lc was given.

3. The calculated metabolizable energy of the basal Hc diet was utilized more efficiently than that of the basal Lc diet, for promoting empty body-weight and carcass-weight gains.

4. On both basal diets, lambs receiving the diets supplemented with acetate made greater live-weight, empty body-weight and carcass-weight gains than lambs given unsupplemented diets. The responses of weight gain to increasing levels of acetate were linear.

5. The responses to acetate were greater when it was given with the Hc diet than with the Lc diet. This effect was most marked for live-weight gain (P < 0.001), intermediate for empty body-weight gain (P < 0.05), but not significant for carcass-weight gain. This order of effects was in part due to a greater weight of alimentary tract tissue, and its contents, in lambs fed the Hc diet supplemented with acetate.

6. It is concluded that under certain circumstances the energy of acetate may be utilized less efficiently than energy from propionate or butyrate.

1. Pigs were weaned from the sow at 2 d of age and reared on a diet of cow's milk supplemented with vitamin D, and antibiotics. The effects of four levels and two frequencies of feeding, and the temperature of the environment were studied in relation to the performance of the pigs and the digestion of the milk protein. Pigs fed at the two lower levels receivedadiet of cow's milk, but at the two higher levels cow's milk was spray-dried and reconstituted to 20% total solids. A comparison was also made between cow's milk and spray-dried reconstituted milk, both fed hourly with 12.5% total solids. The pigs were slaughtered at 28 d of age.

2. No differences in the nutritive value or digestion of the milk protein were found when cow's milk and reconstituted milk were fed with a total solids content of 12.5 yo.

3. Increasing the level of feeding resulted in a faster growth rate, and some deterioration in the feed conversion efficiency. The growth rate of the pigs from 2to 28 d of age when fed at a high level greatly exceeded that of sucking pigs reared on the sow. The retention of the dietary nitrogen also improved with increased feed intake. A highly significant inverse linear correlation of N retention with age was found at all levels of feeding. The milk protein was efficiently digested at all levels of feeding.

4. The mortality rate was very low but there appeared to be some association of losses with a high level of feeding during the first few days of life.

5. Feeding hourly compared with feeding twice daily improved the feed conversion efficiency, although the effect on growth rate and N retention was small. The retention of digesta in the stomach appeared to be an important factor in the regulation of the amount of digesta in the small intestine and in the maintenance of digestive efficiency. The stomachs of pigs fed twice daily contained considerably greater amounts of digesta than those of pigs fed at hourly intervals. There was little difference in the amount and composition of digesta in the small intestine and caecum at either frequency of feeding.

6. No differences were found in the performance of the pigs, N retention or the efficiency of digestion of the milk protein when the environmental temperature was maintained either at zoo throughout the experiment, or at 30' gradually reducing to zoo during the first 14d.

1. The intake and excretion of total nitrogen, fat and the various forms of carbohydrate, and the heats of combustion of the diet, urine and faeces were measured in groups of young men, young women, elderly men and elderly women.

2. Each group was studied while the subjects were eating two diets in turn, which differed in their contents of unavailable carbohydrate; the young women were also studied on a third diet which was rich in unavailable carbohydrate.

3. Increasing the intake of unavailable carbohydrate resulted in a greater faecal loss of energy, and in most instances of nitrogen and fat.

4. There was no significant effect of sex or age on the apparent digestibility of protein, fat or available carbohydrate.

5. The results are used to evaluate the use of calorie conversion factors for calculating the metabolizable energy content of mixed diets.

6. These show that for practical purposes the classical Atwater factors can be used to calculate the metabolizable energy of a diet with reasonable accuracy, provided that when available carbohydrate (as monosaccharides) values are used in the calculation a factor of 3.75 kcal/g (15.7 kJ/g) is used.

7. The studies demonstrate that the accuracy of any method for calculating the metabolizable energy of a diet is largely determined by the accuracy with which the method is capable of predicting the gross energy of the diet.

1. Isotope dilution techniques were used to measure the rates of entry and oxidation of glucose, acetate, palmitate, stearate and oleate in fed and fasted (16 h) pigs.

2. Glucose entry rates measured in eight fed and five fasted (16 h) pigs were 20.6 and 8.0 mg/min per kg0.75 (mean values) respectively. The entry rates in fed pigs were lower than the calculated rates of glucose uptake from the alimentary tract, and the validity of glucose entry rates determined under these conditions is discussed.

3. Acetate entry rates were unrelated to the fibre content of the diet, and acetate produced from endogenous metabolism was the main contributor to total acetate production.

4. Increased rates of entry and oxidation of palmitate, stearate and oleate were observed in fasted pigs.

5. Glucose production in fasted pigs was inhibited by raising the concentration of blood glucose. Infusion of insulin in the fed pig caused a decrease in glucose production and a simultaneous reduction in the mobilization of free fatty acids. When blood glucose concentrations fell below about 55 mg/100 ml the release of free fatty acid into the circulation was restored.

1. Pelleted diets containing concentrates and 0, 20, 40 or 60% chopped straw were fed ad lib. for 5 h daily to four cows. Voluntary intake, digestion and rate of passage of these diets were examined, and also the behaviour of the cows and the amount of material in the rumen before and after feeding.

2. Least dry matter (7.5 kg) was consumed when there was no roughage in the diet. When roughage was present, its level had no effect on dry-matter intakes, which were 10.7, 11.3and 10.7kg for 20, 40 and 60% roughage respectively. Digestible energy intakes were greatest with diets containing 20 or 40% roughage.

3. The digestibilities of the dry matter of the four diets were 81, 69, 59 and 55% in increasing order of roughage content. The proportion of total digestion which occurred in the rumen decreased as the roughage content of the ration increased. The rate of breakdown of cotton threads in the rumen increased as the roughage content of the diet increased.

4. Rates of passage varied greatly between cows and there were no differences between treatments in passage rates through the entire alimentary tract. The diets on which the cows consumed the largest amounts of digestible energy (20 and 40% roughage) passed through the rumen more slowly, and through the hind gut more quickly, than the other diets.

5. The times spent daily eating and ruminating both increased as the proportion of roughage in the diet was increased, but in relation to the amount of dry matter eaten, eating times were lowest with diets containing 20 or 40% roughage. Time spent ruminating per kg straw eaten decreased with increasing straw content of the diet. Rumen contraction rate during eating was greatest when dry-matter intake was greatest, but during rumination it was similar with all three levels of roughage.

6. Before and after feeding, the amount of digesta and digesta dry matter in the rumen increased as the proportion of roughage in the diet increased. After feeding, there was a highly significant linear relationship between the amount of digesta in the rumen and the digestibility of the diet.

7. In a second experiment, similar diets containing 0 or 50% roughage were given to two cows for 5 or 24 h daily. The 24 h intake expressed as a percentage of 5 h intake was 148% for the 0% roughage diet, but only 105% when the diet contained 50% roughage.

8. The results of these experiments are interpreted as indicating a declining importance of physical factors in the regulation of the intake by cows of a range of diets of increasing digestibility.

1. Analyses have been made of milk collected from thirty wild African elephants immediately after they were shot.

2. The milk contained an average of 5.1% protein, 9.3% fat and 3.6% lactose. The concentration of lactose decreased and the concentration of protein and fat increased with advancing lactation. Inorganic constituents were present in approximately the same proportions as in bovine milk.

3. The contribution of capric acid to the total fatty acids, previously shown to be extremely high, increased with advancing lactation.

4. The significance of these findings to the preparation of a milk for rearing young elephants by hand is discussed.

1. The serum glycerides of men were raised 1–2.5 h after the ingestion of glycerol, whereas in young women given glycerol the serum glycerides were not raised. In men who had a supplementation of glycerol to their free-choice diet there was a rise in the concentration of fasting serum glycerides, a rise that was not found when a similar supplementation was given to young women.

2. These findings would support the tentative suggestion that dietary fructose does not follow the Emden-Meyerhof pathway to the same extent as glucose. The increased serum glyceride levels reported after high-fructose diets may be due to an increased availability of the glycerol moiety of glycerides.

1. The nutritive value of solubilized wool protein prepared by dissolving finely ground wool in sodium sulphide-sodium sulphite solution followed by precipitation with 40 % acetic acid has been tested by incorporating it into protein-free diets containing the amounts of vitamins and minerals required by weanling rats.

2. At the level of 10 % (w/w) of the diet, solubilized wool protein failed to support growth in weanling rats, but when the diet was fortified with histidine, methionine and lysine a protein efficiency ratio of up to 1.8 was obtained. The effect of the addition of lysine was marginal. Similar results were obtained with solubilized wool protein prepared from dyed wool suiting material.

3. Apart from the methionine content, which varied from 0.49 to 0.66 g/100 g protein, the contents of the essential amino acids in the solubilized wool protein generally met the requirement of the FA0 (1957) provisional pattern, although in many of the preparations the levels of isoleucine and lysine were marginal. The tryptophan content was not determined. Supplementation of the solubilized wool protein with lysine to the level of 6–10 g/100 g protein slightly enhanced the nutritive value.

1. Rumen bacteria were prepared in bulk from freshly killed sheep. They were exposed to ultrasonic disintegration and a preparation of cell walls was made by differential centrifugation.

2. The amino acid composition of acid hydrolysates of whole cells and cell walls was determined. Summation of these results shows that whole cells contained approximately 40% amino acids and cell walls approximately 30%.

3. A considerable proportion of the alanine content of cell walls was present as the D-isomer, partly ester linked as in teichoic acids and partly more tightly bound in ‘peptide linkage’ being released only after hydrolysis in constant boiling hydrochloric acid.

4. Cell walls were found to possess an alanine racemase which was inactivated only after incubation of the cell walls in 0.1 M-NaOH.

5. Whole cells contained approximately 8% carbohydrates and cell walls approximately 5%. The glucose and galactose contents of whole cells and cell walls were low, accounting for little more than 2% of the dry weight of the bacterial samples.

6. The amino sugar content of bacterial samples was approximately 3% and consisted mainly of glucosamine.

7. The total lipid content of rumen bacteria was approximately 25% and that of cell walls varied considerably between 10 and 23%.

1. In a double reversal experiment, diets containing either a normal or a large amount of lignin fibre were given to four patients with pruritus due to a liver disease.

2. Neither an improvement in symptoms nor a decrease in serum bile acid levels was found. The dose of fibre may have been insufficient, changes in intraluminal pH may have impaired adsorption of bile acids, or, less likely, the concentration of bile acids in the intestine may have been too low.