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. 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. 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. 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. 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.

1. Metabolic balance studies of zinc, copper, cadmium, iron, molybdenum and selenium were made on four young New Zealand women, using brilliant blue and chromic oxide as faecal markers.

2. Zn, Cu, Cd and Fe concentrations in foods, faeces and urine were measured by atomic absorption spectrophotometry, whereas Mo was determined spectrophotometrically with dithiol and Se fluorimetrically with diaminonaphthalene.

3. The dietary intakes of Zn, Cu and Fe were similar to those reported in the USA and the UK, whereas those of Cd, Mo and Se were less. The subjects ate a diet consisting of foods normally consumed by New Zealand women.

4. For each subject there was little variation in the urinary output of each element for three 6 d periods. Day-to-day variation was small for each subject. The individual variation in urinary output of each element among the subjects was smaller when expressed as a ratio of intake, except for Mo.

Retentions were small for Zn, Cu and Fe, all elements which are poorly absorbed. Balances of Se, Mo and possibly Cd were in equilibrium.

1. Gas exchanges on eleven steers with a mean weight of 273 kg, fasted for 96 h, were obtained over time intervals of 5·76 min in a confinement-type respiration chamber, when the animals were either standing of lying, or engaged in the act of standing or lying.

2. In all, 751 observations were analysed and these included twenty-four associated with the act of standing, forty-eight with the act of lying and the remainder approximately equally divided between standing and lying.

3. When lying, the heat production was 72·2 kJ (17·2 kcal)/kg fasted weight per 24 h and when standing, 85·7 kJ (20·5 kcal)/kg fasted weight per 24 h; an increase when standing of 18·7%. The double act of standing and lying was associated with an increase in heat production of 11·3 kJ (2·7 kcal)/100 kg fasted weight and while the act of standing was energetically more costly than the act of lying, the difference between the two was not significant.

4. The results are discussed in relation to earlier estimates.

5. Confinement-type respiration chambers of the type described by Turner & Thornton (1966), which have a fast response time and monitor the changes in chamber air frequently, are ideally suited to the detection of short-term changes in metabolic rate such as occur with changes in posture.

1. The effects of chronically raised body temperature on lipid metabolism were studied in groups of 3-month-old British (Shorthorn × Hereford) and Zebu (Africander × British) bull calves. Calves in control groups at ambient temperature were pair-fed to calves housed in a climate room.

2. In control groups, concentrations of plasma cholesterol and phospholipid were significantly higher and the excretion of fatty acids 14:0, 16:0 and 18:0 was lower in the Zebu than in the British calves.

3. In the climate room the constant daily environmental temperature required to maintain an increase in rectal temperature of 1·3° was 33° for British and 38° for Zebu calves. Changes in respiration rate, water metabolism and nitrogen metabolism associated with hyperthermia were similar in both breeds.

4. Hyperthermia in all animals was associated with lowered plasma concentrations of cholesterol and phospholipid and increases in the ratio of free to total cholesterol. It was without effect on the circulating concentrations of non-esterified fatty acids and about twice the amount of fat was excreted without change in its fatty acid composition.

5. The results showed that, when control of normal body temperature was lost, increased rectal temperature led to similar metabolic changes in animals of both breeds.

1. A simple two-compartment physical model was assembled with the aim of simulating passage of marker through the reticulo-rumen, small intestine, and caecum and proximal colon of sheep. Passage of marker through the whole digestive tract and the hind-gut were also simulated with a computer and methods of describing such results were compared.

2. The same mathematical equation applied equally well to the passage of a single injection of marker through the model and whole digestive tract of sheep. The magnitude of a rate-constant, reflecting in theory the retention time of marker in the caecum and proximal colon, was accurate for the model but larger than expected for the sheep. Modifications of the model are discussed which might account for the greater complexity in the biological system.

3. The average time available for digestion in the entire gut can be described with R or t and that for the intestinal tract distal to the abomasum with Ri or with a similar measurement ti. The magnitudes of these values and of rate-constants and a transit time of marker in the intestines, derived from the concentration curve of marker excretion in faeces, are closely related. The times for peak concentration of marker in faeces, for 5 and 50% excretion and the 80–5 % excretion time were found to be of limited usefulness in describing the results of rate of passage experiments with sheep.

1. Three groups of sheep receiving 400, 800 and 1200 g lucerne chaff/d in equal hourly meals were killed. The large intestines were removed and divided into segments 15 cm long to provide information on the amounts and dry-matter contents of digesta and on the rates of passage of digesta and absorption of water along the large intestine.

2. With increasing intakes of food, increases were observed along the entire large intestine in the amounts of wet digesta present, in the transit rates of digesta and in the rates of absorption of water. The mean retention time of digesta in the large intestine decreased with increasing food intake, being 1737, 1056 and 692 min respectively.

3. Four patterns of sodium and potassium concentrations in digesta water along the large intestine were found.

1. The effect of fortification of rice with lysine and threonine (at levels of 2 g and 1 g/kg respectively) on the growth of preschool children was assessed in feeding trials at a residential orphanage and a village day-care centre.

2. In the first trial, the children at the orphanage were offered a diet based on rice, to provide the recommended allowances of protein and energy. For the children in the experimental group, the rice was fortified with lysine and threonine for the 6 months of the trial.

3. Statistically significant differences in final height and weight were not observed between the children in the control and in the experimental groups.

4. The children in the control group grew at optimal rates.

5. In the second trial, the diet provided approximately 80% of the daily energy and protein intakes from rice and was offered ab lib. at four meals a day in the orphanage and at three meals a day in the day-care centre.

6. In the orphanage, most children are enough of this high-bulk diet to ensure an adequate energy intake. The children given the fortified rice and those who served as controls grew at very satisfactory rates.

7. At the village centre most of the children were unable to eat enough food to achieve an adequate intake of energy. The children given the fortified rice did not grow taller than those given unfortified rice.

8. Fortification of rice with lysine and threonine did not improve rates of growth of preschool children.

1. Two adult wether sheep were maintained on a diet of hay and two on a diet of dried grass for 3 weeks before starvation for a period of 10 d. Urinary excretion of the following acids was determined when the animals were fed and when they were fasted: total diethyl ethersoluble acids of hydrolysed and unhydrolysed urine, hippuric acid, benzoic acid and phenylacetic acid. By the 5th day of fasting, urinary output of all acids had attained stable levels that did not change during the remaining starvation period. The output of all urine fractions except phenylacetic acid declined rapidly during the first 4 d of fasting: phenylacetic acid output by all sheep increased to a maximum during the first 4 d of fast and then declined to stable values (0·42–0·73 g/24 h) which were greater than those observed when the sheep were fed. It is concluded that prolonged retention of food and microbial residues in the digestive tract is responsible for the large output of phenylacetic acid in the urine of fasted sheep.

2. Solutions of casein which supplied between 6·3. and 26·5 g nitrogen/24 h were infused into the rumens (fifteen experiments) or abomasums (sixteen experiments) of eight adult wether sheep. Ruminal infusions of casein caused increments in the urinary excretion of diethyl ethersoluble acids and phenylacetic acid. Both these increments were described by linear regression equations (P < 0·001), the coefficients of which showed that 284 ± 44 and 220 ± 21 mg benzoic acid equivalent were excreted as diethyl ether-soluble acids and phenylacetic acid respectively per g casein N infused. The phenylacetic acid excreted was equivalent to 95% of the phenylalanine of the infused casein. No increments in urinary benzoic acid were observed. One sheep scoured when it was given an abomasal infusion of casein. This was the only animal to show any increment in urinary aromatic acids when casein was infused into the abomasum.

3. When four sheep were given two rations containing an excess of carbohydrate as sugarbeet pulp or rolled barley, 11 and 16% respectively of their phenylalanine intakes were excreted in the urine as phenylacetic acid. When the same sheep were given two rations containing an excess of N as linseed meal or field beans, 51 and 59% respectively of their phenylalanine intakes appeared in the urine as phenylacetic acid.

4. Methods for the determination of creatinine, and of benzoic, phenylacetic, 3-phenylpropionic, cinnamic, hippuric and phenaceturic acids are described.

5. It is suggested that the amount of phenylacetic acid excreted in the urine is a measure of the equilibrium occurring in the rumen between catabolism of phenylalanine and reutilization of the products of catabolism for phenylalanine synthesis.

1. Homogenates of mucosa from bovine small intestine hydrolysed isomaltose slowly.

2. The enzyme exhibited maximum activity at pH 6·0–6·2 and possessed a Km value of 9·1 mM.

3. Isomaltase and maltase activities showed a similar pattern of distribution along the small intestine; activity was higher in the jejunum than in the ileum, the lowest activity being in the duodenum.

4. Neither activity changed markedly with age.

5. The disaccharidase activities (maltase, isomaltase, trehalase, lactase and cellobiase) of the small intestine were found in the sediment when homogenates were centrifuged at 100000g.

6. Heat inactivation studies suggested that there was one enzyme which hydrolysed trehalose, one enzyme which hydrolysed isomaltose, one enzyme which hydrolysed lactose and cellobiose and that the hydrolysis of maltose was brought about by more than one enzyme.

1. Twenty-eight subjects complaining of tiredness completed a double-blind cross-over trial of injections of hydroxocobalamin (5 mg twice weekly for 2 weeks) followed by a rest period of 2 weeks and then a similar course of matching placebo injections. Symptoms were assessed by a daily self-rating method and included appetite, mood, energy, sleep and general feeling of well-being.

2. Those subjects who received the placebo in the first 2-week period showed a favourable response to hydroxocobalamin in the second period in all measurements made. The response achieved statistical significance (P = 0·006) in respect of general well-being; ‘happiness’ achieved a value of P = 0·032. Subjects who received hydroxocobalamin in the first period showed no difference between responses to active and placebo treatments, which suggests that the effects of the vitamin may persist for a period of at least 4 weeks.

1. Proteolytic activity was measured in the abomasal contents of five calves during the first 7 weeks of life and in the stomach contents of rabbits and guinea-pigs during the first 4 weeks of life.

2. The pattern of protease secretion in the abomasum varied considerably among individual calves; in addition to rennin, some pepsin activity was found in most animals from the first sampling at 9 d of age.

3. Only pepsin was secreted in the guinea-pig stomach from birth, at a consistently high level at all ages.

4. The main peak of proteolytic activity in the rabbit stomach during the 1st week post partum had an optimum at pH 3·5–4·0, corresponding to that for calf rennin. During the 3rd week of life the main pepsin peak, with an optimum at pH 1·6–2·0, developed.

5. Agarose gel electrophoresis of an extract of neonatal rabbit stomach mucosa showed the activity peak at pH 3·5–4·0 to be due to two slow-moving components of mobilities similar to that of crystalline rennin. At least one of these cross-reacted with antiserum to crystalline rennin.

6. At 10 d and 3 weeks of age, activity at pH 1·6–2·0 was due to two faster-moving proteases, one being the main pepsin of the adult rabbit, which moved at the same speed as crystalline porcine pepsin, with the antiserum of which it cross-reacted.

1. Preparations of bound nicotinic acid obtained from wheat bran by an acid extraction procedure (‘niacytin preparations’) were resolved into several nicotinic acid-containing components.

2. Extraction of wheat bran under neutral conditions yielded 62% of the bound nicotinic acid in solution; of this 90% was non-diffusible. Methods were developed which gave high yields of ‘non-diffusible nicotinic acid’ preparations.

3. The bound nicotinic acid in the latter preparation was linked to macromolecules of mol. wt about 1500 to 17000 daltons, approximately 60% of which were polysaccharide and 40% peptide or glycopeptide in character.

4. o-Aminophenol, and ferulic and sinapic acids, are also contained in macromolecules in wheat bran, but are not directly associated with the bound nicotinic acid.

5. The significance of these results in explaining the nutritional unavailability of bound nicotinic acid is discussed.

1. The rates of passage of markers of fluid and particulate digesta through the sheep alimentary tract have been described mathematically in single-injection experiments by analysing the concentration curves of marker excretion in faecal dry matter and then predicting these concentrations by means of an equation containing two exponential terms. Three components related to this equation are a transit time for digesta in the intestines, a half-time of marker in the reticulo-rumen and a half-time tentatively associated with the passage of marker through the caecum and proximal colon. With this approach no surgical interference with an animal is required to obtain meaningful information about gut function.

2. Abomasal cannulation did not affect the rate of passage of 51Cr EDTA through the gut.

3. The mean half-times (T1/2) for 51Cr EDTA in the reticulo-rumen and hind-gut, respectively, were 646 and 236 min for a roughage diet and 890 and 607 min for a diet consisting mainly of wheat grain, both diets providing approximately the same amounts of digestible dry matter. These results indicated that the changes in half-times were proportionately much greater in the caecum and proximal colon than in the reticulo-rumen. The mean transit time of marker through the digestive tract also increased from 721 to 1345 min when the concentrate diet was given.

4. The complex of chromium-51 with EDTA was excreted faster in faeces than cerium-144–praseodymium-144 when both were given together as a single injection into the reticulorumen. This was caused mainly by differential rates of elimination of water and particulate matter from the reticulo-rumen.

1. Uptakes of glucose, galactose, glucose+galactose and lactose from the intestine were studied in preruminant calves fitted with cannulas in the proximal small intestine, and in slaughtered calves. Responses in concentration of blood sugar to the presence of sugar in the small intestine were also investigated.

2. Glucose and galactose were absorbed at about the same rate when present in the intestine separately. The rate for each sugar approached a maximum with increasing sugar concentration in the lumen.

3. When glucose and galactose were present in the intestine together, the rate of galactose absorption was greatly depressed; that of glucose was virtually unaffected. Consequently, when calves were fed with mixtures of glucose and galactose, absorption of galactose in the proximal intestine, where the relative concentration of glucose was high, was depressed. In the more distal intestine where the glucose concentration had fallen, absorption of galactose was rapid. Both sugars were absorbed efficiently during their passage through the whole small intestine, but at different sites.

4. Galactose appeared in the blood after galactose alone was given but conversion of some galactose into glucose always occurred. Results of experiments in which [14C]galactose, together with glucose, was infused into the duodenum of a calf suggested that under these conditions the rate of galactose absorption was depressed to such an extent that nearly all the galactose entering the blood was converted into glucose.

5. Lactose hydrolysis occurred much more rapidly than the absorption of its constituent monosaccharides. Thus, after lactose was fed to the calves, glucose and galactose accumulated in the lumen of the proximal small intestine. A similar accumulation occurred when lactose was infused into loops of small intestine. The rate-limiting step in the total absorption of lactose in the young calf was not, therefore, the hydrolysis stage, as reported for other mammals. The absorption of the released glucose and galactose occurred in a manner similar to that described above for mixtures of glucose and galactose.