1. Published results have been used to study the relationships between nitrogen retention (NR), body-weight (W) and N intake in the pig.

2. The general decrease in maximal NR (g/d per kg W0.75) with increasing W (kg) was curvilinear for values of W from 1.5 to 45: NR = 3.324−0.098 W+0.001 W2; and rectilinear for values of W from 45 to 165: NR = 1.252−0.006 W. Values for protein requirements derived from these equations agreed closely with published estimates.

3. The slopes of the curves for NR (g/d per kg W0.75) v. N intake (g/d) decreased as W (kg) increased from about 2.5 to 190. After extrapolation to a proposed common intercept on the NR axis of -150 mg N/d per kg W0.75, regression analysis of the intercepts of these curves on the N-intake axis v. W gave an estimate of N requirements for maintenance of 246±19 mg/d per kg W0.75.

4. The results also indicated that at low N intakes net protein utilization (N retention+ total obligatory N losses ÷ N intake) was essentially independent of W, whereas the gross efficiency of N utilization (NR ÷ N intake) was influenced by both W and N intake.

The absorption, transport and distribution of α-[3H]tocopherol were greatly decreased in protein deficiency. This was reflected in the subcellular distribution of α-[3H]tocopherol in livers of protein-deficient rats. The ratio, bound: free for α-[3H]tocopherol, also decreased in both serum and liver cytosol. After protein refeeding, absorption, transport and distribution patterns of α-[3H]tocopherol for the protein-deficient rats were restored to patterns similar to those of control animals.

1. Two experiments were done with Pietrain and Large White pigs (about 50 kg body-weight) to determine whether fat mobilization is enhanced in the stress-sensitive Pietrains (which also produce pale, soft, exudative (PSE) meat).

2. In Expt 1, plasma glucose and insulin concentrations and free fatty acid (FFA) concentrations and composition were measured in five Pietrains and five Large Whites after feeding, during an infusion of norepinephrine (2.5 μg/kg body-weight per min), 16 and 21 h after the withdrawal of food and following insulin administration (0.3 IU/kg body-weight). The entry rate of oleic acid was measured 4 h after feeding. Body composition and longissimus dorsi pH measurements were made on killing the pigs 4 d after the experiment.

3. After feeding, the Pietrains tended to have lower concentrations of glucose and insulin in plasma compared with the Large Whites, and higher concentrations of FFA. The Pietrains also had a faster entry rate of oleic acid into body tissues. In fasting (16 h) these differences in hormone and metabolite concentrations were also present and relationships between them and body development could be detected. Pietrains had higher concentrations of FFA and lower concentrations of insulin than Large Whites at a particular stage of the development of fat and muscle (subcutaneous fat weight÷longissimus muscle weight).

4. The fatty acid composition of FFA resembled that of the backfat triglycerides in fasting and during norepinephrine infusion but not in the fed state. In particular the proportion of fatty acid 18:1 was low in the fed pigs and that of 18:2 was high. The contrast in FFA composition between the fed and stimulated state was greater in the Large Whites.

5. The Pietrains were less sensitive to the antilipolytic action of insulin. Glucose and FFA concentrations were similar in both breeds during the norepinephrine infusion although insulin concentrations were increased to a larger extent in the Large Whites at the termination of the infusion.

6. In Expt 2, anaesthetized Pietrain and Large White pigs were given constant infusions of norepinephrine alone (2.5 μg/kg body-weight per min) and norepinephrine+propranolol (2 and 10 μg/kg body-weight per min) or phentolamine (2 and 10 μg/kg body-weight per min). The aim was to determine whether the breeds differed in their sensitivity to norepinephrine when conscious responses to the hormone were prevented.

7. When norepinephrine alone was infused, fat mobilization was greater in the Pietrain pigs and glucose concentrations were greater in the Large Whites. Propranolol markedly reduced the lipolytic action of norepinephrine, particularly in the Pietrain pigs studied, and phentolamine reduced its glycogenolytic action, particularly in the Large White pig.

8. It seems that the leanness of stress-sensitive, PSE-susceptible Pietrain pigs may be due to an enhanced fat mobilization under various conditions, associated with an impairment in insulin metabolism and a greater sensitivity to the β-adrenergic action of catecholamines on body fat stores.

1. Protein and energy requirements of pigs weaned at 2 d of age were studied. In Expt 1, three diets with crude protein (CP; nitrogen × 6.38) and fat contents (g/kg dry matter (DM)) of 268, 260 (diet A); 216, 415 (diet B) and 264, 405 (diet C) were compared, with and without a supplement of 2 g DL-methionine/kg. Diets A and B contained skim milk and soya-bean oil only, in different proportions. Casein was added to diet C to equalize the CP content to that of diet A. In Expt 2, diets containing 290 or 315 g CP/kg DM were used with either 310 or 405 g fat/kg. The diets contained different proportions of skim milk, soya-bean oil and casein. The same diets as used in Expt 2 were used in Expt 3 but fed to a scale based on live weight which was 25% less than that used in Expts 1 and 2.

2. Methionine supplementation had no significant effect (P > 0.05) on the growth rate or feed: gain ratio of pigs from 2 to 28 d of age. The growth rate of the pigs from 2 to 28 d of age was significantly (P < 0.05) reduced when they were given the higher level of either CP or fat, with the exception that the effect of level of fat was not significant (P > 0.05) in Expt 3. The reduction in growth rate was associated with a decrease in feed intake. Feed: gain ratios were unaffected (P > 0.05) by the level of either CP or fat in the diet.

3. The higher protein level did increase the proportion of CP in the carcass DM (Expt 2 P < 0.01, Expt 3 P > 0.05) and gave an indication, which was not significant (P > 0.05), of improved N retention (g/d per kg live weight). The higher dietary fat level increased the proportion of lipid in the carcass DM, and this effect was significant (P < 0.05) in both Expts 2 and 3.

4. Diets containing additional casein were not fully consumed at the level of feeding used in Expt 2. This effect may be associated with the larger amounts of digesta in the stomachs of these pigs. Some differences in the composition of the digesta in the stomach were observed, but these did not affect the performance of the pigs.

5. It seems unlikely that either growth rate or feed:gain ratio (g DM consumed/g live-weight gain) can be improved by protein or energy levels exceeding those in a diet containing (g/kg DM) 730 skim milk (265–290 CP) and 310 fat. In this diet, containing (g/kg DM) 6.4 methionine and 3.5 cystine, sulphur amino acid requirements were satisfied.

1. Nitrogen retention was measured in adult rats (250–350 g) subjected to the trauma of hind-leg fracture and given diets with or without arginine plus glycine supplementation. Observations were also recorded on excretion of creatine, creatinine, allantoin, and orotic acid. Liver and skeletal muscle transaminase activities were also determined.

2. When traumatized rats weighing approximately 250 g were given a diet with 200 g casein/ kg, supplemented with 20 g arginine and 10 g glycine/kg (EC diet) or a casein diet made isonitrogenous with the EC diet by addition of aspartic acid (C diet), a 60–70% increase in N retention was observed for the first 5 d post-injury for animals consuming the EC diet. A soyabean (S) diet, isonitrogenous to the diet containing 20% casein, supplemented with arginine and glycine was as effective as the EC diet in promoting significantly better N retention of traumatized rats (350 g) in comparison to rats given the C diet.

3. When the dietary casein content was reduced to 100 g/kg, supplements of 10 g arginine and 5 g glycine or 20 g arginine and 10 g glycine/kg did not improve N retention. It is suggested that both protein quality and protein quantity are important following injury.

4. An increased excretion of creatine was observed in traumatized rats given the high-protein diets supplemented with arginine and glycine. No consistent changes were noted for urine creatinine.

5. Urine allantoin levels remained stable after leg-fracture in rats consuming either the C or EC diets. Differences in the levels of urine orotic acid were found during both the pre- and post-injury periods in rats given the C, EC or S diets.

6. The mechanisms responsible for the improved N retention of traumatized rats consuming the high-protein diets with supplements of arginine and glycine may be related to the role of arginine both as a constituent of muscle tissue and as an intermediate in the urea cycle.

7. In traumatized rats fed the C or EC diets, liver transaminase activity increased whereas the transaminase activity in skeletal muscle decreased. These results support the recent concept that the increased excretion of N following injury arises from diminished reutilization of amino acids by muscle tissue without an acute increase in the rate of muscle catabolism.

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. 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. 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. 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. 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. 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. 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.

1. The fat content of the skin and of the skin-free carcass was measured in young, growing hairless mice about 4-8 weeks old kept at either 22° (cool environment, i.e. below their critical temperature) or at 33° (warm environment; i.e. within their thermoneutral range). The food intake of groups of the mice reared at each temperature was restricted to between 77 and 89 % of that of a litter-mate fed ad lib.

2. In all the mice, whether fed ad lib. or on a restricted intake, those reared in the warm environment contained about 1.5 times as much fat as those reared in the cool environment. At both temperatures and feeding levels, approximately 25 % of the total body fat was present in the skin.

3. Each mouse reared at 33° on an ad lib. regimen reached about the same plateau weight in the same period as its litter-mate reared at 22°. However its food intake during this period of growth was only about half that of the mouse reared at the lower temperature, so its food conversion ratio (dry food intake: body-weight gain) was twice as efficient.

4. It is concluded that neither the growth rate nor the distribution of fat within the body of the growing mouse can be influenced by rearing the animals at these different environmental temperatures. Rearing at the higher temperature, however, both decreases food intake and also promotes deposition of more fat within the body.

1. Na234SO4 was infused into the rumen of a sheep fed a dried grass diet.

2. The digesta at the pylorus which contained 35S-labelled cyst(e)ine synthesized by the rumen microflora was collected and mixed with chromium EDTA. This material was infused into the duodenum of 35S free sheep.

3. Ileal digesta was subsequently collected and analysed for cyst(e)ine 35S and Cr.

4. The proportion of the labelled cyst(e)ine truly absorbed from the small intestine was 0.72±0.004.