1. Adult rats were subjected to a brief period of diethyl ether anaesthesia and were given diets with 200 or 100 g casein/kg with or without arginine plus glycine supplementation in the post-anaesthesia period. Nitrogen retention was measured as well as liver protein content and liver and muscle transaminase activities (l-aspartate aminotransferase (GOT), (EC 2.6.1.1), and l-alanine aminotransferase (GPT) (EC 2.6.1.2)).

2. Results demonstrated that anaesthesia-stressed rats consuming the high-protein diet with supplemental arginine and glycine retained twice as much N as did rats given the diet with 200 g casein/kg alone, for the first 5 d post-anaesthesia.

3. Anaesthesia-stressed animals consuming the diets with 100 g casein/kg with or without arginine plus glycine supplementation did not differ from each other in N retention.

4. Liver protein content increased after anaesthesia in rats given the high-protein diets; liver transaminase activity increased, whereas muscle transaminase activity decreased, in animals consuming the high protein diets.

5. Possible mechanisms to account for these results are discussed.

1. Measurements were made of energy balance by direct calorimetry, and of nitrogen balance in groups of lean and congenitally obese (‘fatty’) Zucker rats at body-weights of 200 and 350 g given a highly digestible semisynthetic diet at 14.0 or 18.4 g/rat per 24 h.

2. Losses of food energy and N in faeces were very small. The fatty rats lost much more N in urine than did lean rats. Despite this the proportion of gross energy that was metabolized was 0.92 for both fatty and lean rats.

3. In all trials, fatty rats lost a smaller proportion of metabolizable energy (ME) as heat and deposited less as protein than thin rats but deposited much more as fat.

4. The amounts of ME required to deposit 1 kJ of protein and 1 kJ of fat respectively were shown by regression analysis to be 2.25 (±0.16) and 1.36 (±0.06) kJ respectively. These values agree extremely closely with recent, more tentative, estimates based on assumptions as to maintenance requirement which the present experiments were able to circumvent. It may be concluded with confidence that the energy costs of depositing 1 g of protein or fat are almost identical at 53 kJ ME/g.

1. The comparative effects of raw soya beans on food intake, growth, digestive organ weight, and enzyme activities in goslings and chicks were studied.

2. Goslings were more affected than chicks by the ingestion of a raw soya-bean diet (RSD) in the following ways: reduction in food intake and growth rate; increase in relative weight of the digestive organs; reduction in specific activities of lipase (EC 3.1.1.3), amylase (EC 3.2.1.1) and chymotrypsin (EC 3.4.4.5) in the pancreas (not affected in chicks); greater inhibition of trypsin (EC 3.4.4.4), chymotrypsin and amylase in the intestinal contents of goslings than of chicks.

3. Addition of methionine to the RSD improved food intake and growth rate more in goslings than in chicks.

4. The interrelationships between enzyme activities, food passage rate, nutrient absorption and food intake regulation are discussed.

1. Eighteen crossbred wethers were allotted at random (six per treatment) to each of the following diets: (1) maize-silage; (2) grass-silage; and (3) chopped hay. After 6 months a single oral dose of D-α-[5-Me-3H]tocopherol was given to each sheep on these three treatments.

2. Blood plasma, rumen liquor and urine radioactivity were measured for 4 d and, at the end of this period, the animals were killed and tissue distribution of 3H was determined.

3. Maize-silage generally contained less α-tocopherol than grass-silage or hay. Tissue uptake of 3H was greater on maize-silage than other diets.

4. In muscle, spleen and liver, tocopherol concentrations were lower in the maize-silage than the grass-silage fed animals.

5. A tendency to higher uptake of radioactivity was recorded at all times in the plasma and its lipid extract of sheep fed on maize-silage than those fed on grass-silage or hay.

6. Urine clearance of radioactivity tended to be higher in animals fed on the maize-silage than those fed on grass-silage or hay. This difference of magnitude in urinary excretion was probably related to the rate of metabolism of the ingested radiotocopherol.

1. Young male rats were used in five experiments to study the utilization for growth of methionine sulphoxide, and the relationship between the sulphoxide content in the diet and the level of microbiologically determined methionine activity in blood or blood plasma. In one nitrogen-balance experiment methionine and methionine sulphoxide were compared as supplements to a casein diet and a fish-meal diet.

2. Methionine sulphoxide was poorly utilized for growth when tested as the sole sulphur amino acid in an amino acid diet. Substitution of one-third of the sulphoxide with cystine improved utilization so that it approached that of methionine.

3. Methionine alone and in combination with methionine sulphoxide were added to a soya-bean-meal diet. The sulphoxide showed no adverse effect on growth.

4. Fish meal in which methionine had been oxidized to methionine sulphoxide was tested alone and in combinations with unoxidized fish meal. Only when the oxidized meal was given alone was there an appreciable effect on growth. The fish meals used were low in cystine.

5. Whereas both methionine and methionine sulphoxide improved the N balance when a casein diet was given, there was no effect when a fish-meal diet was given.

6. There was a linear relationship between methionine sulphoxide content in the amino acid diets and the methionine activity in the blood plasma. Methionine sulphoxide added to a soya-bean-meal diet or present in oxidized fish meal gave a curvilinear relationship, and the observed activities were lower than with the amino acid diets. Methionine activity in blood could not be used as an indicator of moderate amounts of methionine sulphoxide in protein-containing diets.

1. The effect of isoenergetic substitution of bran and wholemeal bread for white flour and white bread was investigated in six healthy volunteers in a metabolic unit.

2. A 21 d high-fibre experimental period was preceded and followed by a 14 d control period, so that each experiment lasted 7 weeks. Blood samples were taken on each of the last 3 d and faeces collected (using carmine markers) for the last 6 d of each diet period.

3. Plasma cholesterol, triglycerides and serum calcium concentrations were not altered by the addition of wheat fibre.

4. Wheat fibre caused a significant increase in faecal bulk and frequency. Faecal steroid excretion was the same in the last week of the first control and the high-fibre periods but increased in the subsequent control period.

1. Three experiments were conducted on the ability of cats to utilize dietary carbohydrates. In two experiments, the digestibilities of carbohydrates were measured by the chromic oxide-marker technique using a balanced Latin-Square allocation of treatments: in the third experiment, the effect of age and diet on the activity of intestinal β-galactosidase (lactase) (EC 3.2.1.23) and β-fructofuranosidase (sucrase) (EC 3.2.1.26) of kittens was measured.

2. In Expt 1 the digestibilities of six individual carbohydrates, glucose, sucrose, lactose, dextrin, raw maize starch and wood cellulose added to a meat-based basal diet were measured.

3. In Expt 2, a similar meat-based basal diet was used and the effect of three processing methods (fine and coarse grinding, and cooking) on the apparent digestibility of the starch in maize and wheat grain was measured.

4. In Expt 3 the effects of the inclusion of either 200 g lactose or 200 g sucrose/kg in an all-meat diet and of age on the β-galactosidase and β-fructofuranosidase activities of the small intestine of weanling kittens were measured.

5. Adult cats efficiently (> 0.94) digested all six individual carbohydrates added to the diet with the exception of cellulose, which was indigestible. The digestibility coefficients of glucose, sucrose and lactose were significantly (P < 0.01) greater than that of starch. The inclusion of lactose caused diarrhoea in some cats and significantly (P < 0.01) reduced apparent digestibility of crude protein (nitrogen × 6.25) in the total ration.

6. Fine grinding significantly enhanced the digestion of starch in wheat and maize grain, but the effect was greatest for maize grain. Cooking had a similar effect to fine grinding for wheat grain, but an effect intermediate between coarse and fine grinding for maize grain.

7. Intestinal β-galactosidase activity decreased with age in kittens (71-106 d). Neither β-fructofuranosidase nor β-galactosidase activities were significantly affected by the addition of sucrose and lactose to the all-meat diet.

1. The first part of this study was designed to determine the increase in the amount of iron absorbed by hypothetical groups of subjects on the border-line of Fe deficiency when they were given meals fortified with ferrous sulphate. Two levels of Fe fortification were used (1.6 and 8.9 mg/meal) and the increase in the amount of Fe absorbed by the ‘border-line’ groups was 0.13 and 0.7 mg respectively.

2. Subjects which are on the border-line of Fe deficiency may be considered the target group of an Fe-fortification programme. Therefore the experimental model used can provide valuable information on the effects on the prevalence of Fe deficiency which can be expected when such a programme is introduced.

3. In the second part of the study, the bioavailability in man of reduced Fe with different physico-chemical properties was measured. Special emphasis was given to the relationship between the values obtained in vitro and in vivo.

4. The bioavailability was expressed as absorbability relative to that of ferrous sulphate. In four samples of hydrogen-reduced Fe the bioavailability ranged from 90 to 13%. The reduced-Fe products differed considerably with respect to solubility in hydrochloric acid (8–94% dissolved after 30 min), particle size distribution (91–1% < 7 μm) and reactive surface area (< 0.1–2.7 m2/g).

5. The relationships found between physico-chemical information and bioavailability indicated that reactive surface area and dissolution rate were better predictors of the bioavailability than the particle size.

1. The effects of giving milk once or twice daily (Expt 1) and of weaning (Expt 2) on the flow rate of digesta through the duodenum and on pancreatic secretion were studied in four and two Ayrshire calves respectively. The calves were prepared with duodenal re-entrant and pancreatic sac cannulas.

2. In Expt 1, when whole milk was offered ad lib. once daily, the calves ingested 141 g/kg live weight (46 g dry matter (dm)/kg live weight 0.75) at a single meal. The subsequent pattern of flow and total recovery of polyethylene glycol from the duodenum suggested that none of the ingested milk passed into the rumeno-reticulum. As the total daily quantity of milk ingested when the calves were fed once and twice daily was similar, it was concluded that abomasal distension is unlikely to be the sole factor limiting milk intake in the preruminant calf.

3. With twice-daily feeding, there were no differences in the pattern or total flow of fluid, electrolytes, nitrogen or fat through the duodenum of the calves following the 09.00 and 21.00 hours meals. The pattern of flow of duodenal and pancreatic fluids and the concentration of electrolytes, N and fat were markedly different when the calves were fed once or twice daily. The patterns of flow of fluid and the concentration of electrolytes in the duodenal digesta reflected the frequency of feeding and the size of the meal and the consequent balance between feed and endogenous components of the digesta. The quantity of the apparent endogenous secretion and pancreatic secretion was markedly less when the calves were fed once daily.

4. In Expt 2, the two Ayshire calves were given whole milk twice daily (diet MM), whole milk once daily with concentrates (diet MC), concentrates alone (diet CC) or dried grass alone (diet DG). The calves consumed 46, 49, 45 and 51 g dm/kg live weight 0.75 when given diets MM, MC, CC and DG respectively.

5. The twice-daily fluctuations in the flow and concentration of fluid, electrolytes, N and fat in the duodenal digesta and the pancreatic fluid observed when diet MM was given were replaced by relatively constant flow rates and composition when diet CC or DG was given.

6. Over the 24 h experimental period 97, 70, 50 and 58% of the DM and 112, 98, 99 and 84% of the N in the feed passed through the duodenum of calves when given diets MM, MC, CC and DG respectively.

7. When dry food was given, the rate of pancreatic fluid secretion was markedly lower (11.3 and 13.5 ml/kg live weight for diets CC and DG respectively) than when diet MM (19.7 ml/kg live weight) was given.

1. Balances of twenty trace elements (silver, arsenic, gold, bromine, cadmium, cobalt, chromium, caesium, copper, iron, mercury, lanthanum, molybdenum, rubidium, antimony, scandium, selenium, samarium, tungsten and zinc) have been determined in four male patients during total parenteral nutrition including fat emulsion and a special solution for addition of Fe, Zn, manganese, Cu, fluorine and iodine, besides calcium and magnesium, to the infusion solutions.

2. The analyses for trace elements were made with the aid of an ion-exchange technique based on neutron activation, and combined with subsequent gamma spectrometry.

3. The intended intravenous supply of trace elements corresponded approximately to the analysed supply. However, all the other trace elements determined were found to be unintentionally administered in small amounts.

4. There was a substantial retention of Fe. Other elements retained were Ag, Co, Cr, Cu, Sb, Sc and W.

5. Particularly Br and Rb were lost by the patients, but negative balances were also found for As, Au, Cd, Cs, Mo, Se and Zn. However, Zn was retained by one patient with short bowel syndrome.

6. The serum concentrations of thirteen (Ag, Br, Co, Cs, Cu, Fe, Hg, Mo, Rb, Sc, Se, W and Zn) of the trace elements were found to have some decrease during the period of total parenteral nutrition, mostly in accordance with the corresponding balance values. Fe, in particular, was found to have the directional change in concentration.

7. The administration of trace elements is recommended in long-term total parenteral nutrition.

1. In an experiment in which a high-fat supplement was given in the dry form to lambs offered dried grass ad lib., both the voluntary intake and digestibility of the dried grass were reduced. When the high-fat supplement was given in a liquid suspension so that the rumen was by-passed, the voluntary intake and digestibility of the dried grass were not significantly altered.

2. The effect of injecting an emulsion of tallow into the rumen of sheep on rumen metabolism was studied in another experiment. Increasing the fat supplementation lowered the rate of digestion of both dried grass and cotton thread, lowered markedly the concentration of rumen ammonia, and raised the proportion of propionic acid in the rumen.

1. From 5 weeks of age, control and experimental rats were given diets containing 210 and 31 g protein/kg respectively, and killed for analysis at 0, 2, 5, 8, 12 and 20 d after the start of the experiment. At these times estimates were made of plasma albumin concentration, plasma volume and total vascular and extravascular albumin mass.

2. Plasma albumin concentrations were significantly lower in the experimental animals when compared to controls at 8, 12 and 20 d but plasma volumes (ml/kg body-weight) tended to be greater in the former animals. Total vascular albumin mass (g/kg body-weight) was significantly less in experimental animals compared to controls at 8 and 20 d, but was significantly reduced below values at 0 d only at 20 d.

3. Extravascular albumin mass (g/kg body-weight) was significantly lower in experimental animals in comparison with controls at 2, 5, 8, 12 and 20 d and significantly reduced below values at 0 d at 5, 8, 12 and 20 d.

4. Whole-body albumin mass was significantly reduced at 5, 8, 12 and 20 d when compared both with controls killed at the same time and animals killed at 0 d. Measurement of the ratio, extravascular albumin mass: vascular albumin mass indicated a significant redistribution of whole-body albumin mass at 5 and 20 d and mean values for this ratio were always lower in experimental animals than in controls.

5. It was concluded that measurement of plasma albumin concentration does not indicate the true extent of whole-body albumin losses in protein deficiency since total vascular albumin mass is, to some extent, maintained at the expense of extravascular albumin mass.

1. Mixed rumen bacteria were grown in vitro in a medium containing [U-14C]adenine. Radioactivity was incorporated into the purine bases of the nucleic acids.

2. Labelled bacteria were incubated with a nitrogen-deficient cell-free medium (medium A), a protozoa-free supernatant suspension from a slow-speed centrifuging of a steer's rumen contents (medium B) and whole rumen contents of a steer (medium C). Mean (six experiments) proportional rates of release of radioactivity(/h) were significantly greater for medium A (0.140) than for media B or C (0.055 and 0.043 respectively). Some of the radioactivity accumulated in the cell-free media; some was lost, partially as carbon dioxide.

3. Calculation from this and other information indicated that about 30% of bacterial nucleic acids may turn over in the rumen even in the absence of protozoa.

1. The incidence of colchicine-induced lesions in the germinal epithelium of the rat duodenum was studied in young rats in an early stage of zinc deficiency and in their pair-fed controls. At both dose levels of colchicine used, a marked increase in the amount of cell damage was observed in the duodenum of Zn-deficient rats as compared with the pair-fed, control (Zn-supplemented) rats.

2. No statistical interaction between Zn and colchicine was demonstrable, and no lesions were found in the duodenum of animals that had not been treated with colchicine.

3. The results are discussed in relation to the effects of Zn deficiency in animals and the possible involvement of Zn in the maintenance of the integrity of microtubular structures.

1. The fractional rate of loss of 14C and body-weight was measured in adult male rats after giving 14C-labelled methionine or leucine and maintaining rats for 30 d on a low-protein or a specific methionine+cystine-free diet: carcasses were then analysed for protein and fat 14C radioactivity.

2. The fractional loss of 14CO2 from [14C]methionine or [14C]leucine between day 20 and day 30 was always greater than the fractional loss of body-weight.

3. Carcass protein 14C radioactivity after giving [14C]leucine was higher than after giving [14C]methionine, but fat 14C radioactivity after either 14C-labelled amino acid was only a small proportion of the total body 14C radioactivity.

4. After correction of the fractional loss of 14CO2 for urinary 14C loss, but not body-weight loss, absolute amino acid loss was calculated using published values for methionine and leucine content of rats.

5. The best estimates of endogenous amino acid loss obtained using 1-14C-labelled amino acids, expressed as mg/kg body-weight0.75 per day were leucine 79, methionine 38.

1. A study was made in goats of the response in terms of milk production, nitrogen utilization, plasma amino acids and glucose kinetics to postruminal infusions of glucose and casein. Goats in mid-lactation, housed in metabolism cages, were fed on 2 kg basal ration (containing 112 g crude protein (N × 6.25)/kg)/d alone (control) and with daily infusions into the abomasum of 45 g casein or 45 g glucose.

2. Milk production increased with casein infusion (P < 0.01), but not with glucose infusion, being 1.59, 1.86 and 1.62 kg/d with the control, casein and glucose infusions respectively. Milk composition was unaffected except for milk fat, which was decreased by the glucose infusion.

3. The goats were in positive N balance on the basal ration. Milk N output increased with casein infusion, by an amount equivalent to 27% of the infused N.

4. The concentration of dispensable amino acids in arterial plasma was decreased with casein infusion and increased with glucose infusion.

5. Glucose kinetic measurements with control, casein and glucose infusions indicated that pool sizes were 247, 279 and 302 mg/kg live weight0.75, and irreversible losses were 5.5, 6.7 and 7.0 mg/kg live weight0.75 per min respectively. The differences between the results obtained from the glucose and casein infusions were not significant (P < 0.05).

6. The results of the experiment indicate that the increased milk production obtained when casein was infused was not due to enhanced gluconeogenesis.

1. Six Caucasian male Massachusetts Institute of Technology students participated in a 77–87 d metabolic balance study to determine the adequacy of the 1973 FAO/WHO egg protein allowance for men (0.57 g/kg body-weight per d). Each subject was given an initial energy allowance calculated to meet his particular requirements, and these intakes were raised by increments of 10% approximately every 2 weeks until a slightly positive balance was achieved. Each individual's energy intake was maintained at this final level for the remainder of the study.

2. At energy intakes sufficient to meet their estimated requirements, five of six subjects were in negative nitrogen balance. In five subjects, N balance improved with increased energy intake until N balance was achieved. The mean change in N balance was 0.335 mg N/additional kJ consumed. All of the subjects gained weight at the higher energy intakes.

3. Serum aspartate aminotransferase and alanine aminotransferase activities increased with continued intake of the experimental diet and reached abnormal levels in five of the six subjects. In the two subjects showing the earliest increases in serum transferase activity, the levels returned towards normal when protein intake was raised to 0.73–1.0 g/kg body-weight per d. All subjects showed normal serum transferase values on an ad lib. diet 2–3 weeks after termination of the study.

4. The findings indicate that at energy intakes necessary to bring subjects into slightly positive N balance at the level of 0.57 g egg protein/kg per d, a significant proportion of young adults continue to gain weight for as long as 70 d.

5. These findings suggest that the 1973 FAO/WHO safe allowance of 0.57 g egg protein/kg per d is not sufficient for most healthy young men receiving dietary energy intakes appropriate for long-term maintenance of body-weight.

1. No difference in health was observed between men on megadosage of ascorbic acid and controls during the year of an Antarctic expedition.

2. All men appeared to have a satisfactory intake of ascorbic acid throughout the year.

3. There was a statistically significant decrease in excretion of ascorbic acid by men on megadosage over the year, and by the controls.

4. The decline in excretion by the control group may be explained by dietary change, but the decline in those on megadosage may be due to altered handling of ascorbic acid by the body.

5. No complications due to megadosage of ascorbic acid were observed.