1. Three experiments involving sixty-two growing-finishing pigs from 28 to 90 kg body-weight were conducted to investigate the effect of environmental temperature on the thiamin requirement of growing-finishing pigs. Three temperatures (20°, 30° and 35°) were used.

2. Under these experimental conditions, average daily weight gain indicated no effect of environmental temperature on thiamin requirement. By using erythrocyte transketolase (EC 2.2.1.1) activity and its percentage stimulation by thiamin pyrophosphate (TPP stimulation per cent) as criteria, there was a significant effect of environmental temperature on the thiamin requirement of growing-finishing pigs. At 20°, the thiamin requirement for maintaining maximum transketolase activity or minimum TPP stimulation per cent was found to be approximately 3·3 mg/kg diet; at 30°, the requirement was between 3·7 and 4·0 mg/kg diet. As estimated from erythrocyte transketolase activity, and the rate of TPP stimulation per cent increase, the thiamin requirement might be higher than 4·0 mg/kg diet at 35°.

3. There was a significant effect of environmental temperature on daily weight gain and food intake. The rate of weight gain and food intake decreased with increasing temperature. The efficiency of food utilization generally showed no significant differences among temperatures.

1. Six 45 kg pigs with re-entrant ileal cannulas were used in two 3 × 3 Latin-square design experiments to study the site of absorption of protein and amino acids. Semi-purified diets containing soya-bean meal (SBM), rapeseed meal (RSM) or no protein source (protein-free) were offered at the rate of 1 kg dry matter/d.

2. Flow-rates of ileal contents for 24 h collection periods, corrected for recovery of marker, were 3135, 3127 and 1243 ml (SE 390) for SBM, RSM and protein-free diets respectively.

3. Amounts of dry matter digested in the small intestine were 730, 669 and 809 g/d for SBM, RSM and protein-free diets respectively, all values being significantly different (P < 0·001).

4. Nitrogen intakes were 32·6, 29·9 and 5·9 g/d, and amounts digested in the small intestine were 25·7, 20·2 and 1·6 g/d for SBM, RSM and protein-free diets respectively, all values being significantly different (P < 0·001). Amounts digested in the large intestine were 2·6, 3·7 and 0·7 g/d.

5. Total amino acid intakes and amounts collected at the ileum and in the faeces were (g/d): SBM, 177, 24 and 18; RSM, 149, 28 and 22; protein-free 3, 9 and 12. Digestibility in the small intestine was higher for SBM than RSM for seventeen of the eighteen amino acids estimated. Greater quantities of arginine, methionine, cystine and tyrosine were voided in the faeces than passed through the ileal cannulas for pigs receiving the SBM and RSM diets. For those receiving the protein-free diet this was true for each amino acid except proline.

6. Significant differences were found between all diets in the concentration of some amino acids in ileal and faecal amino-N, and endogenous protein secretions did not mask the differences between diets.

7. Differences in digestibility between SBM and RSM were greater at the ileum than in the faeces. Amino acid fermentation in the large intestine obscured or reduced differences between SBM and RSM.

1. Total lysosomal hydrolase activities were measured in liver, gastrocnemius muscle and plasma of malnourished and normal rats between 3 and 8 weeks of age.

2. Concurrently, the DNA and protein contents of the livers and muscles were determined.

3. Increased amounts of acid hydrolase activities were found to be associated with subnormal protein: DNA ratios in the tissues of malnourished rats.

4. It was concluded that lysosomal enzymes may be involved in protein catabolism during malnutrition.

1. The response to cyanocobalamin and folic acid therapy was studied in forty-seven subjects with severe nutritional megaloblastic anaemia; twenty-five were vitamin B12 deficient and, of these, ten were also folic acid deficient.

2. In twenty-four of the subjects, absorption of orally administered cyanocobalamin was normal, and there was a haematological response to small doses of orally administered cyanocobalamin, indicating adequate absorption. In one subject there was impaired cyanocobalamin absorption although free gastric hydrochloric acid was present.

3. The findings indicate that the absorptive function of the small intestine was unimpaired, with one exception, although there was a possible defect in nucleoprotein synthesis associated with a lack of vitamin B12 and folic acid. Addisonian pernicious anaemia was not found in any of the subjects.

1. Leucine, lysine, valine and phenylalanine uniformly labelled with 14C were given by intragastric or intravenous infusion for 4 h, after an overnight fast, to rats which had been fed on normal or protein-free diets for 20 d. Expired CO2 was collected during the infusion. At the end of the infusion the rats were killed and radioactivity was measured in liver, muscle, skin, gastrointestinal tract and the remaining carcass.

2. There were no significant differences between the results obtained with different amino acids.

3. When the two routes of infusion were compared, there was no difference in the output of 14CO2, expressed as a proportion of the administered radioactivity. With intragastric infusion a slightly larger proportion of radioactivity was recovered from liver and gastrointestinal tract and significantly less from the skin.

4. When the rats adapted to a protein-free diet were compared with those on the control diet, there was again no difference in the proportion of dose oxidized to CO2. In the rats on the protein-free diet significantly more of the dose was recovered in the liver and gastrointestinal tract, and less in the skin.

5. The rats on the protein-free diet excreted more CO2 per kg body-weight, with a lower specific radioactivity.

6. The results show no indication of adaptive changes in the oxidation of essential amino acids, but the evidence is not conclusive. Under these experimental conditions the output of 14CO2 is not a valid measure of the extent of amino acid oxidation. The difficulties of interpretation are discussed.

1. The effect of ammonia concentration on microbial protein production was determined in continuous-culture fermentors charged with ruminal contents obtained from steers fed on either a protein-free purified diet, a maize-based all-concentrate diet, or a forage–concentrate (23:77) diet. Urea was infused into the fermentors to maintain various concentrations of ammonia in the incubating mixtures.

2. Under nitrogen-limiting conditions, microbial protein yield measured as tungstic acid-precipitable N (TAPN) increased linearly with supplementary urea until ammonia started to accumulate in the incubating ingesta. Increasing the ammonia concentration beyond 50 mg NH3-N/l had no effect on microbial protein production.

3. The molar proportions of volatile acids produced were not affected by the level of urea supplementation. Total acid production was decreased slightly under N-limiting conditions, but not to the same extent as microbial protein production.

4. Estimated yield of microbial dry matter/mol ATP produced averaged 15·6 when non-limiting N as urea was provided with the purified diet.

5. These results suggest that addition of non-protein N supplements to ruminant rations are warranted only if the prevailing concentration of ruminal ammonia is less than 50 mg NH3-N/l ruminal fluid.

1. Absorption rates of glucose (from a 200 mM solution), glycine (from a 100 mM solution), and glycylglycine (from a 50 mM solution) have been estimated in six Zambian African adults with clinical evidence of malnutrition. A double-lumen tube technique was used to determine absorption rates from a 300 mm section of jejunum in vivo.

2. Two of the subjects had ileal tuberculosis and Kaposi's sarcoma respectively. A third probably had abdominal tuberculosis. Three of them had pellagra. Mean serum albumin concentration was 24 (14–43) g/l. Absorption rates have been compared with those in Zambian Africans (control subjects), previously studied, who had no clinical evidence of malnutrition, systemic infection or of gastrointestinal disease.

3. Mean glucose, glycine and glycylglycine absorption rates in the malnourished subjects were not significantly different from those in the control subjects. Mean net water absorption rate from the glucose solution was similar in the malnourished subjects and controls; during the glycine and glycylglycine perfusions the mean net absorption rate was, however, significantly lower in the malnourished subjects (P < 0.01 and P < 0.05 respectively); mean net water transfer during the glycine perfusions was towards the jejunal lumen in the malnourished subjects. One subject with pellagra had an abnormal excretion of D-xylose after a 25 g oral load; all other tests were normal.

4. It seems probable that malnutrition must be very severe, with jejunal mucosal abnormalities, before absorption rates of glucose, glycine and glycylglycine are significantly altered. The present study does not support the view that subclinical malnutrition is important in producing malabsorption of dietary components in Zambian African subjects. Systemic bacterial infections, and raised serum γ-globulin and immunoglobulin IgG concentrations have previously been associated with an impairment of glucose absorption rate in Zambian African subjects; those factors seem much more likely than subclinical malnutrition to be relevant, in the context of absorption, in the pathogenesis of overt malnutrition.

1. The proximate composition, amino acid composition and the quality of the protein of the African locust-bean (Parkia filicoidea Welw.) seed, seed with pulp, and various processed forms, with or without amino acid supplementation, were assessed.

2. The crude protein content of the locust-bean seed was 303 g/kg and the crude fibre content was 121 g/kg.

3. The seeds contained (mg/g protein): 67 lysine, 6.1 methionine and 8.9 tryptophan.

4. Diets containing 100 g protein/kg supplied by the seed did not support growth in rats, demonstrating that the protein was of poor quality.

5. Utilization of the protein of locust-bean seeds was improved by cooking, and by removal of the tough leathery outer testa of the seeds.

6. Supplementation with methionine alone resulted in positive growth and a very substantial increase in protein values.

7. Supplements of methionine and tryptophan caused further improvement in protein quality and increased the growth of rats to almost that obtained with whole egg.

1. Experiments were conducted to determine the effects of the supplementation of carbohydrate-deficient fatty acid-based (FA) diets with 18·7, 37·5, 75, 150 and 300 g maize starch (MS)/kg on the growth and metabolism of the growing rat. Further, the effects of fasting on rats given the FA diet were compared with those given the high-carbohydrate (CHO) diet. Due to the significant decrease in food consumption of rats given the FA diet, the effects of pair-feeding the CHO and the FA diet were also investigated.

2. The isoenergetic replacement of fatty acids with increasing amounts of MS in the FA diet given to rats increased their weight gain and concentration of glucose in their plasma. These increases, however, tended to level off for weight gain and glucose concentration, respectively, at about 18·7 g and 75 g MS/kg diet. The same type of replacement decreased the concentration of ketones in the plasma but the decrease levelled off at the high concentration of 300 g MS/kg diet. Activities of liver glucose-6-phosphatase (EC 3.1.3.9) and glucokinase (EC 2.7.1.2) decreased and increased respectively with increasing concentration of maize starch in the diet. These changes tended to level off at concentrations of about 75–150 g MS/kg diet.

3. Fasting for 18 h decreased the concentration of glucose in plasma of both the FA- and the CHO-fed rats, while fasting of the CHO-fed rats depressed the concentration of glycogen in the liver but did not influence that of the FA-fed rats. Pair-feeding the CHO diet to the FA diet produced similar weight increases during the 8-week experimental period.

1. A study of the effects of four dietary treatments on body-weight and the water, protein, fat and energy content of the empty bodies of forty-three Suffolk ewes is reported. The treatments were as follows: T1, ad lib. food intake from a full-body-weight (FBW) of 40 kg to 71 kg; T2, partial fasting with a resulting weight loss from 71 kg to 50 kg FBW; T3, realimentation and regrowth from 50 kg to 71 kg FBW; T4, a slight food restriction producing a reduced growth rate from 40 kg to 50 kg FBW followed by ad lib. food intake from 50 kg to 71 kg FBW. On all treatments sheep were slaughtered in groups of three at 7 kg intervals between 50 kg and 71 kg FBW.

2. The whole body, with the exception of several body organs and glands, wool and the contents of the gastrointestinal tract, was minced and analysed for water, protein, fat and energy. Adipose tissue samples were removed at slaughter from subcutaneous and internal fat depots for histological examination. Regression analysis was used in comparing treatment effects on body composition.

3. No significant differences were observed between the results of T1 and T4. In consequence these results were pooled and are referred to as T1. At 40 kg FBW the empty (ingesta-free) bodies of the lambs contained approximately 52% water, 14 % protein and 29% fat. Through normal growth to 71 kg FBW on T1 these values had changed to 40, 11.5 and 45 %, respectively. Following weight loss to 50 kg FBW on T2 the water, protein and fat contents of the empty bodies were 47, 13.5 and 35 %, respectively. Regrowth on T3 to 71 kg FBW resulted in little change in these components, the respective values being 46, 13 and 36 %. The sheep which had undergone weight loss and regrowth retained significantly more water and less energy than normally grown controls and tended to deposit less fat and more protein.

4. Gastrointestinal tract contents accounted for 11 % of FBW at 71 kg in T3 animals. In T1, the value was 7.1 % at a similar FBW. Thus there was an average increase of over 56 % in contents in the realimented animals.

5. Mean adipocyte diameter at 50 kg FBW on T1 was 134 ± 3 μm. At 71 kg FBW the mean diameter had increased to 152 ± 9 μm. Weight reduction (T2) and regrowth (T3) resulted in mean diameters of 122 ± 4 μm and 143 ± 4 μm at 50 kg and 71 kg FBW, respectively.

1. The development of vitamin B12 deficiency, as indicated by the serum and liver vitamin B12 levels and the excretion of methylmalonic acid, was studied over a 2-year period in baboons (Papio cynocephalus) given a diet deficient in vitamin B12. The effects of partial hepatectomy and the inclusion of either ampicillin or sodium propionate in the diet on the rate of development of the deficiency were also studied.

2. The baboons had previously been fed on a mainly vegetarian diet. Their serum vitamin B12 levels were less than 100 ng/l and the mean liver vitamin B12 concentration was 0·56 μ/g. Similar serum and liver vitamin B12 levels were found in baboons given a purified diet supplemented with 1 μg vitamin B12/d, and marked increases in the serum and liver vitamin B12 levels occurred when the daily intake was increased to 2 μg.

3. The serum vitamin B12 levels decreased to less than 20 ng/l in all baboons given a vitamin B12-deficient diet.

4. The liver vitamin B12 concentration also decreased in all baboons given a deficient diet. At 9 months the lowest levels (0·20 μ/g) were found in partially hepatectomized baboons but subsequently baboons given the diet containing ampicillin had the lowest levels (0·11 μ/g).

5. The excretion of methylmalonic acid after a valine load was found to be inversely related to the liver vitamin B12 concentration. In the early part of the study, partially hepatectomized baboons excreted the highest amount but subsequently baboons given a diet containing ampicillin excreted the highest amount.

6. Increased formiminoglutamic acid excretion after a histidine load was observed in two baboons given a vitamin B12-deficient diet and in both baboons the liver folic acid concentration was low.

7. No haematological or neurological symptoms of the vitamin B12 deficiency were observed.

1. Apparent digestibility, apparent absorption and nutrient-balance studies were made with two Ayrshire and three Friesian calves given milk-substitute diets. Cannulas were inserted into the duodenum of the calves at about 21 d old, so that the quantity of pancreatic secretion entering the duodenum could be varied.

2. After cannulation, there was a significant reduction in the apparent digestibility of the dry matter, organic matter, crude protein and fat, and in the apparent absorption of calcium and phosphorus from a milk-substitute diet containing ‘mildly’ pre-heated, spray-dried skim-milk powder. The amounts of nitrogen and P retained by the calves were also significantly reduced.

3. Collection and removal of the pancreatic secretion for a period of 12 h/d resulted in a further significant reduction in the apparent digestibility of the dry matter, organic matter and crude protein of the milk-substitute diet.

4. At 77 d of age, there was no significant effect on the nutrient balance or on the digestibility of a diet containing a ‘severely’ pre-heated, spray-dried skim-milk powder when the normal secretion of the pancreas was supplemented for 12 h/d with additional pancreatic secretion collected from the same calf.

5. Friesian calves, in comparison with Ayrshires, tended to have a higher digestibility of dry matter, organic matter and fat, apparent absorption of Ca and P and retention of N, Ca and P. These differences were apparent both before and after the calves were cannulated.

1. Excessive amounts of food (70% greater than ad lib. intake) introduced into the gastrointestinal tract of young chicks were efficiently digested and caused increased growth resulting mainly from lean body substance and partially from fat deposition, more efficient energy utilization than the ad lib.-fed controls, increased relative weights of the crop, proventriculus, intestine, liver and abdominal adipose tissue. Pancreas relative weight was not changed and that of the gizzard was reduced.

2. The treatment also caused changes in blood plasma composition. Free fatty acid, trigly-ceride, α2-, β- and γ-globulin and pre-β-lipoprotein concentrations increased.

3. Fasting for 30 h caused higher body fat losses and lower body protein losses in the force-fed chicks than in the ad lib.-fed chicks.

4. The effects of over-feeding on body and blood plasma composition and differences found in these measurements during starvation are discussed.

1. The long-term fate of an oral dose of [75Se]selenite was studied in three young women.

2. Urinary and faecal excretion, respiratory and dermal losses and whole-body retention of 75Se were measured, and also 75Se turnover in whole body, blood and tissues during a period of 16–20 weeks.

3. Intestinal absorption of [75Se]selenite by the three subjects was 70, 64 and 44% of the dose.

4. Urinary excretion accounted for 14–20% of absorbed 75Se in the 1st week. There were only trace amounts of radioactivity in expired air and no dermal loss was detected.

5. After an initial phase in which radioactivity decreased rapidly, whole-body retention of 75Se diminished exponentially with a half-time of 96–144 d. Radioactivity in the liver, heart and plasma decreased more rapidly than that in the whole body, but radioactivity in skeletal muscle and bone decreased more slowly.

1. Escherichia coli and mixed cultures of rumen bacteria were grown with [8-14C]adenine to label their nucleic acids specifically.

2. The labelled bacteria were injected into the rumen of sheep and the radioactivity incorporated into tissue nucleic acids and that excreted in the urine and faeces was determined.

3. The radioactivity was present in the cold trichloroacetic acid-soluble fraction and the RNA and DNA fractions of all tissues examined. Liver, kidney, spleen, and blood had the highest levels of radioactivity.

4. The radioactivity of the RNA was present only in adenosine monophosphate and guanosine monophosphate.

1. The effects of processing cereals on aspects of rumen metabolism, physiology and pathology were investigated in five experiments with lambs. Three experiments studied the effects of diets containing loose whole, pelleted whole or pelleted rolled barley on rumen volatile fatty acid ratios, rumen pH and digestibility. In a 4th experiment the effects, on the same measurements, of pelleting whole barley, maize, oats or wheat compared to feeding the whole grains in the loose form were studied. The firmness of subcutaneous fat was measured in two of these experiments when injections of cyanocobalamin or hydroxycobalamin were given and in one experiment when the diets were supplemented with two levels of cobalt. In a 5th experiment, the effect on rumination time of pelleting whole barley compared to feeding loose whole grain was assessed.

2. When the diet contained whole barley in a loose mix and also when it contained whole maize, oats or wheat, the proportion of acetic acid in the rumen fluid was significantly increased and that of propionic acid decreased in comparison with the proportions observed when the pelleted diets were offered.

3. The pH of the rumen liquor was not significantly changed by feeding pellets based on rolled or whole barley, but when barley, maize, oats or wheat was given in loose form, there was an increase in the pH by about 1 unit in comparison with the pelleted diets. This increase in pH was, for all cereals, associated with complete elimination of ruminitis which, except for the oat diet, was always apparent with the pelleted feeds.

4. In general the digestibilities were not affected greatly by processing and in two experiments there were no significant differences. In one experiment pelleted whole barley was better digested than pelleted rolled barley. In another experiment the digestibility of barley was slightly greater when it was fed whole and loose compared to pelleted, while the digestibility of whole wheat was less than that of pelleted wheat. The mean digestibilities of organic matter for barley, maize, oats and wheat were 0.791, 0.832, 0.687 and 0.846 respectively.

5. Neither injections of vitamin B12 nor cobalt supplementation of the diet had any effect on the firmness of subcutaneous fat. Feeding diets containing loose whole barley increased the firmness of the subcutaneous fat, and this was associated with a decrease in the proportion of propionic acid in the rumen fluid.

6. The feeding of loose whole barley instead of pelleted whole barley caused an increase in time of rumination from 3.6 to 6.6 h/24 h.

1. The purine nucleotide cycle has been proposed (Lowenstein, 1972) as an alternative scheme for amino acid deamination in tissues, such as skeletal muscle, having low concentrations of glutamate dehydrogenase (EC 1.4.1.2).

2. Activities of AMP deaminase (EC 3.5.4.6), one of the enzymes of the cycle, have been measured in soleus, plantaris and extensor digitorum longus muscles of rats maintained for 18 d on diets providing 0, 0·035 or 0·10 net dietary protein energy (energy supplied by utilizable protein: total metabolizable energy, NDp:E), and in rats given the 0·10 NDp:E diet for 3 d after the 0 or 0·035 NDp:E regimens.

3. Concentration of AMP deaminase in the different muscles from the control (0·10 NDp:E diet) rats appeared to bear an inverse relationship to the proportion of mitochondria-rich fibres (i.e. rich in glutamate dehydrogenase) in each muscle.

4. Dietary protein deprivation (0 or 0·035 NDp:E) led to adaptive reductions in AMP-deaminase activity in the soleus and plantaris muscles, but in the extensor muscle the 0·035 NDp:E diet produced no change, while the 0 NDp:E diet caused an increase in activity.

5. Refeeding the 0·10 NDp:E diet to the protein-deprived rats caused reductions of AMP-deaminase activity to lower levels in all three muscles, except in the instance of soleus in rats refed after the 0·035 NPp:E diet.

6. In view of the different responses shown by the three muscles to the dietary treatments, the importance of specifying the particular muscles used in future nutritional studies is emphasized.

7. The adaptive changes in AMP deaminase are discussed in terms of operation of the purine nucleotide cycle for amino acid deamination responding to the changes in amino acid catabolism known to be caused in muscle by these protein-deficient diets.