1. The vitamin A content of Saccobranchus fossilis kept on a diet of rice and meat gradually decreased and became negligible at the end of 3–5 months.

2. S. fossilis initially contained more dehydroretinol than retinol; administration of β-carotene or zeaxanthin to the vitamin A-depleted fish did not result in an accumulation of dehydroretinol in the liver. On the other hand, when lutein was administered by mouth or subcutaneous injection, it was converted into dehydroretinol.

1. Rates of absorption of glycine and glycylglycine from a 300 mm jejunal segment were compared in vivo when those compounds were given alone or together to six Zambian African subjects who had no clinical evidence of malnutrition or of gastro-intestinal disease. Solutions containing (A) glycine (100 mmol/1), (B) glycine (100 mmol/l)+glycylglycine (50 mmol/l), and (C) glycylglycine (50 mmol/l) were infused into the upper jejunum by means of a double-lumen tube perfusion system.

2. Rate of absorption of glycine was significantly higher from the glycylglycine solution (C) than from the glycine solution (A). Glycine absorption rate from solution B (glycine+glycylglycine) was very similar to the sum of absorption rates of glycine from solutions A and C in each subject. Luminal disappearance rate of glycylglycine from solutions C and B were very similar; however, the rate was significantly greater than the total glycine absorption rate from solution C and indicates back-diffusion of glycine into the lumen after glycylglycine hydrolysis.

3. The results are interpreted as indicating that the transport mechanisms for glycine and glycylglycine in man are partly, and possibly wholly, separate.

1. Eight groups each of four castrated male pigs, 25–30 kg initial body-weight, were kept for periods of 3 weeks in a calorimeter equipped as a pig pen and maintained at either 8° or 20°. At each temperature two feeding levels (g food/kg body-weight per d) were used, 45 and 52 at 8°, and 39 and 45 at 20°. Metabolizable energy, heat loss and nitrogen balance were measured.

2. Heat loss was higher at 8° than at 20° and was independent of plane of nutrition, whereas at 20° the higher heat loss occurred at the higher plane of nutrition. Energy retention depended on both temperature and feeding level, and was highest at the 52 g feeding level at 8°.

3. N retention was not influenced by environmental temperature but varied with plane of nutrition (correlation coefficient = 0·94), the increase being 9·98 (± 0·8) mg N per g food increase. The correlation coefficient between N retention and body-weight gain was also 0·94; body-weight gain was correlated with N retention rather than with fat deposition. Fat gain was reduced at the lower feeding levels and at the lower environmental temperature at the feeding level of 45 g/kg.

4. The partial efficiency of energy retention at 20° was 66·5%. From this efficiency the maintenance requirement (at zero energy retention) at 20° was calculated to be 418 kJ/kg0·75. At 8° the partial efficiency of energy retention was 99·4%.

1. Experiments were conducted to investigate the effects of feeding rats on a diet based on a mixture of maize oil fatty acids as the only source of non-protein energy (fatty acid diet) and the influence on these effects of giving such a diet in a single daily meal lasting 2 h.

2. In comparison with a triglyceride diet in which the non-protein energy was in the form of maize oil, feeding ad lib. with the fatty acid diet produced no significant changes in body-weight gain, plasma glucose and plasma ketones concentrations, liver glycogen concentration and protein efficiency ratio.

3. In comparison with the triglyceride diet, meal-feeding with the fatty acid diet produced significantly lower body-weight gain and protein efficiency ratio; moreover, it significantly lowered plasma glucose and liver glycogen concentrations.

4. Rats meal-fed on the fatty acid diet synthesized glucose from protein, as evidenced by the significantly higher liver glycogen concentration detected 6 h after the meal had been eaten, but the increase was significantly lower than in the animals fed on the triglyceride diet. Also, 6 h after the meal had been eaten, the amount of meal remaining in the stomach of rats meal-fed on the fatty acid diet was significantly higher than in those fed on the triglyceride diet.

1. The protein requirements of lambs were established by measuring nitrogen balance in seventy-four animals given liquid diets which passed direct to the abomasum. Four groups of lambs weighing approximately 8 kg (group 1), 13 kg (group 2), 21 kg (group 3) and 30 kg (group 4) received diets in which 0·10, 0·15, 0·20, 0·25, 0·30, 0·35 or 0·40 of the digestible energy was provided as protein (DPE:DE ratio) and a gross energy intake of from 1·30 to 1·42 MJ/kg0·73 per d.

2. When the protein requirements were taken to correspond to the protein intake at the point of intersection of the line describing the increase in N balance with increase in protein intake and the line representing the maximum N balance, values of 0·25, 0·23, 0·17 and 0·12 DPE:DE ratio were obtained for groups 1–4 respectively. The requirements expressed in these terms can be applied only to lambs fed on liquid diets which contain milk proteins and escape fermentation in the rumen. To enable the results to be applied to lambs given other diets, the requirements were expressed as g reference-protein (defined as a theoretical protein with the ideal pattern of amino acids) per MJ net energy and were 11·6, 10·4, 8·0 and 6·2 for groups 1–4 respectively. The relationship between protein requirement (Y, g reference protein/MJ net energy) and live weight (X, kg) was: Y = 13·4–0·242X.

3. The influence of energy intake on protein requirements in lambs is discussed and it is concluded that the results obtained are applicable to lambs given a metabolizable energy intake of more than about 1·75 times their maintenance requirement.

4. Application of the estimated requirements to ruminant lambs and methods of formulating diets to supply the required quantity of reference protein/MJ net energy are discussed.

1. The iron requirements of eighteen Ayrshire bull calves reared on fat-supplemented skim milk for 14 weeks from c. 16 d of age have been studied. There was a highly significant relationship between dietary Fe intake (10, 40 and 100 mg/kg dry diet) and blood haemoglobin concentration, packed cell volume and plasma Fe concentration.

2. A microcytic normochromic anaemia developed in the calves given a diet containing 10 mg Fe/kg diet, but not in the other calves.

3. Plasma Fe concentrations increased to > 5 μg Fe/ml in calves receiving 100 mg Fe/kg diet but there were no effects of Fe treatment on plasma Fe-binding capacity, which rose from 4·9 to 8·4 μg Fe/ml during the experiment. Saturation of plasma transferrin was only 3% in the Fe-deficient calves.

4. There were some significant effects of Fe treatment on tissue concentrations of Fe and cytochrome c.

5. Dietary supplementation with 5 mg copper/kg dry diet had little effect on the growth or haematological status of the calves, although there were significant Cu × Fe interactions for mean corpuscular haemoglobin and mean corpuscular volume. There was no evidence of Cu deficiency in the calves, as measured by blood and liver Cu concentrations and by ceruloplasmin and cytochrome oxidase activities.

1. Studies were made of the effects of food supplements varying in carotene and calcium content on the nutritional status of children aged 2–6 years. Three groups of children who were given a dietary supplement for 6 months and a fourth group of controls were investigated. The supplement was the fermented food dhokla, made of wheat and Bengal gram (Cicer arietinum L.) (group 1) or dhokla with added greens (group 2) or dhokla with added greens (fenugreek) and lime powder (a mixture of CaO, Ca(OH)2 and CaCO3) (group 3).

2. Studies were made of the effects of the above supplements on height, weight, skeletal status as judged by increments in bone age and cortical thickness of the second metacarpal bone and femur, and biochemical status as judged by the composition of blood (haemoglobin), serum (protein, albumin and vitamin A) and urine (creatinine, nitrogen, thiamin, riboflavin and vitamin C).

3. All the groups given the supplement were found to be superior to the controls as judged by these criteria. The size of the increment generally increased from group 1 to group 3 and the differences were most marked for bone age and cortical thickness.

4. The results suggested that (a) calcium deficiency is a crucial factor in the aetiology of skeletal retardation in young children and (b) that at the levels of calcium (560 mg) and phosphorus (980 mg) consumed, and with liberal exposure to sunlight, a dietary supply of vitamin D may not be a crucial factor for skeletal development in young children.

1. The effect of feeding sheep at two different frequencies (once hourly and once daily) on the flow of digesta, dry matter, and starch to the duodenum was assessed by fitting sheep with re-entrant cannulas in the proximal duodenum and giving them, at each feeding frequency, rations differing in the particle size of the roughage component.

2. Frequent feeding resulted in a less variable daily pattern of flow of digesta and a significant increase (P < 0·01) in the total daily volume flowing to the duodenum. Altering the particle size of the ration did not affect the flow of digesta at either feeding frequency.

3. The pattern of flow of dry matter followed very closely that of the flow of digesta, but there was a significant (P < 0·001) interaction between feeding frequency and particle size of the ration which affected the flow of starch to the duodenum. As a result, more starch entered the duodenum when both the frequency of feeding and the particle size of the ration were increased.

1. In the first of three experiments four sheep received chopped (C) and pelleted (P) hay by mouth (m) or rumen fistula (f) in the four combinations shown below. Feed eaten by mouth was offered ad lib. from 09·15 to 16·00 hours; feed was given by fistula at 09·00 hours in amounts equal to half of total intake (i.e. by mouth and by fistula) on the previous day. Daily dry-matter intake (g/kg metabolic live weight, W0·75) was as follows: treatment CmCf, 51·5; CmPf, 74·5; PmCf, 57·8; PmPf, 85·7. The corresponding dry-matter digestibility coefficients were 0·59, 0·56, 0·57 and 0·53.

2. The intention was that the difference in intake between CmPf and PmCf should provide a measure of palatability, since the animals digested the same composite diet but ate different components of it. For the comparison to be valid the two treatments had to promote equal rates of digestion, but measurements of rumen fill and of rate of passage of digesta suggested that Cf was digested more slowly than Cm.

3. In Expt 2, each form of hay was given entirely by mouth or partly by fistula. Daily dry-matter intake (g/kg W0·75) was as follows: Cm, 45·5; CmCf, 42·4; Pm, 80·4; PmPf, 79·2. In this experiment there was less evidence of Cf being digested more slowly and hence depressing intake.

4. The conclusion drawn from these two experiments is that fistula feeding in its present form is not a suitable technique for measuring the relative palatability of feeds differing considerably in physical structure. However, the technique might be improved if food given by rumen fistula to one animal was previously masticated by, and collected from the oesophageal fistula of, a second animal.

5. In Expt 3, the effects of sudden changes from a composite diet to either C or P, or from C to P or vice versa were measured in sheep receiving food by mouth only. The patterns of intake suggested that total intake might be partially determined by feed palatability.

1. Allantoin excretion was determined in forty-four rats; twenty-four rats were 21 d old and twenty were 90 d old. The animals received ad lib. for 11 d diets that contained varying amounts of protein from casein and from gluten. Urinary allantoin excretion was determined during the last 3 d of the period.

2. The amount of allantoin excreted in both young and adult animals was independent of the diet consumed and was related to metabolic weight (W in kg0·73) and rate of gain in body-weight (ΔW in g/d), also to body nitrogen content (N in g0·73) and rate of gain in body N (ΔN in mg/d), according to the equations allantoin (mg/d) = 60·54 W0·73 + 2·12ΔW, and allantoin (mg/d) = 5·45 N0·73 + 0·071ΔN.

1. Twelve Friesian bull calves were weaned at 5 weeks and reared to approximately 18 weeks of age on diets consisting mainly of concentrates containing 209 (HP), 169 (MP) or 130 (LP) g crude protein/kg dry matter. Hay was removed from the diet when the calves reached 10 weeks of age.

2. In relation to metabolic body size, daily dry-matter intake rose rapidly until the calves were about 9 weeks old and then tended to level off at between 80 and 100 g dry matter/kg0·73.

3. After adjustment for treatment differences in concentrate intake, the live-weight gains of calves given diets HP or MP were significantly greater, both from 1 to 12 weeks and from 1 to 16 weeks of age, than those of calves given diet LP.

4. Digestibility trials made twice on each calf, when given solely the concentrate diet and when live-weight gain was about 1 kg/d, showed no differences in dry-matter digestibility, but the apparent digestibility of crude protein increased with the protein content of the concentrate mixture. The true digestibility coefficient of dietary protein was estimated to be 0·880, with no difference between diets. Metabolic faecal nitrogen excretion was estimated to be 3·43 g N/kg dry matter ingested.

5. At the mean intake of digestible energy/kg0·73, N balance was significantly greater with diets HP and MP than with diet LP. Endogenous urinary N excretion was estimated to be 220 mg/kg0·73 and the apparent biological value of protein was 0·851 when diet LP was given.

6. The results confirm the importance of a balanced relationship between energy and protein intakes in the diet of the rapidly growing calf. It is concluded that the crude protein content of the diet can be reduced to below 172 g/kg dry matter, and possibly as low as 153 g/kg, for calves of 122 kg live weight to achieve weight gains of 1 kg/d, when given an all-concentrate diet. This lower protein level would be expected to result in the maximum efficiency of utilization of the dietary energy and protein.

1. The dietary intake, and urinary, cutaneous and faecal loss of water, sodium, potassium and iron have been studied in young men living and performing moderate work in a hot climate. The dietary intakes of K and Fe were lowered during part of the study.

2. The subjects were already somewhat acclimatized to heat; further acclimatization was achieved when they were performing work, and this was assessed in terms of the increase in their rate of sweating.

3. The subjects tended to be in marginally negative Na balance, partly owing to lowered Na intakes. Intakes and outputs of K were in balance. Losses of K in sweat amounted to 15% of intake when the dietary level was reduced.

4. The subjects were slow in adapting to changes in Fe intake, 8 d being an insufficient period for adaptation after their intake had been halved. Losses of Fe in sweat were approximately 0·3 mg/d, or one-third of the estimated requirement for absorbed Fe.

5. It is concluded that Fe losses in sweat could be a significant factor in Fe depletion if dietary Fe was low or unavailable, as there was no evidence that a low intake and absorption affected sweat losses.

1. Information was sought concerning the long-term fate of orally and intravenously administered [75Se]selenomethionine and [75Se]selenite in rats.

2. Urinary and faecal radioactivity was assayed during the 1st week and whole-body radio-activity was determined weekly for 16 weeks. Rats were killed at intervals for analysis of 75Se tissue distribution.

3. Intestinal absorption after oral administration was estimated to be 91–93% for selenite and 95–97% for selenomethionine.

4. Urinary excretion of absorbed [75Se]selenite was greater than that of [75Se]selenomethionine during the 1st week.

5. After the 1st week, whole-body retention diminished exponentially at a similar rate in rats given either selenomethionine or selenite. Except for the erythrocytes, 75Se content of individual tissues also decreased exponentially.

6. It appears that, after an initial period, 75Se from either selenomethionine or selenite is metabolized similarly, suggesting that Se from both potential dietary sources is ultimately incorporated into the same metabolic pool.

1. Deuterium oxide was used to estimate body water in twenty-four pigs of widely differing body composition and of average weight 83·9 kg.

2. After infusion of the isotope, blood samples were collected every 30 min for 4 h. The resulting plasma was purified by a heat-distillation procedure, after which it was analysed for D2O by infrared spectroscopy.

3. Approximately 24 h after infusion of the D2O each pig was killed, and its composition determined both by chemical analysis and physical dissection.

4. Equilibration of D2O in the body was found to be complete within 2 h of injection of the tracer.

5. The mean D2O space was found to be 8·6% greater than the mean empty body water space, but only 2·2% greater than the total body water space.

6. Empty body water and total body water were estimated from the regression lines with residual standard deviations of 2·7 and 1·9% respectively. Similarly, the residual standard deviations of the regressions involving the other fat-free components were 6·3% for dissectible lean, 3·2% for fat-free mass, and 5·6% for crude protein.

7. The residual standard deviations of the regressions in which the weights of dissectible fat and total body lipid were predicted were 6·0 and 6·7% respectively.