1. The capacity of the Chilean mixed diet to meet the daily protein and energy needs was tested in eight subjects aged from 20 to 31 years using the nitrogen balance method. This diet was tested at the protein levels of 0.40. 0.55 and 0.70 g/kg body-weight per d.

2. An egg reference diet providing 0.30, 0.45 and 0.60 g protein/kg per d was also assayed.

3. The mean daily energy intake was 207 kJ/kg per d according to subjects’previous intake and activity pattern.

4. The N balance response to each dietary protein level was taken as a measure of adequacy of protein intake, and regression analyses of N balance (Y) v. N intake (X) were calculated to estimate protein needs. The equations found were Y = 0.70X–68.7 for the egg diet, and Y = 0.74–92 for the mixed diet.

5. From these equations the mean protein requirements for equilibrium were estimated to be 0.61 g/kg for egg and 0.78 g/kg for the mixed diet.

6. If the coefficient of variation is 15, the protein requirement for N equilibrium of 97.5% of the population would be 0.8 g/kg per d for egg and 1.0 g/kg per d for the mixed diet.

1. The obligatory nitrogen losses were measured in young adult males of the low socio-economic group, consuming an N-free diet at 192 kJ (46 kcal)/kg per d from day 1 to 10 and 243 kJ (58 kcal)/kg per d from day 11 to 18.

2. All subjects, except one, lost weight compatible with N loss.

3. A kinetic evaluation of the results showed that the asymptotically derived urinary N loss after stability had been reached was 35·8 mg N/kg per d. The mean time to stability was 6·5 d. The subjects showed a trend toward decline in N loss while consuming the high-energy N-free diet.

4. The obligatory faecal N loss for days 1–10 was 16·1 mg N/kg per d and 8 mg N/kg per d for days 11–18.

5. Based on the factorial approach the total obligatory N loss of our subjects, for the initial 10 d, was 57·5 mg N/kg per d.

1. Sixteen adult male volunteers were selected on the basis of body size and customary food intake: half could be described as‘lean’and habitually consuming large amounts of food (group mean ± SEM: 15·03± 1·13 MJ/d), the high-energy-intake group (HEI group), and half though‘lean’admitted to a weight problem and regularly consumed a lower than average food intake (group mean ± SEM: 6·90 ± 0·39 MJ/d), the low-energy-intake group (LEI group).

2. Energy expenditure was measured by open-circuit indirect calorimetry. Resting metabolic rate (RMR) was recorded. A meal (Complan, either 2·1 MJ or 4·2 MJ), ephedrine hydrochloride (0·25 mg and 0·50 mg/kg body-weight) or a water control were then administered and metabolic rate (MR) was measured for 4 h. Blood was collected before and 1 h after the meal or drug, and the serum analysed for various hormones and blood metabolites.

3. The size of the thermic response to feeding but not the time-course was related to meal size in both groups. MR increased by 21·6 and 28·6% in the HEI group and by 8·2 and 20·0% in the LEI group in response to the 2·1 and 4·2 MJ Complan meals respectively. Fasting insulin levels were similar in both groups but showed a significantly higher level in the LEI than HEI group after the Complan meals.

4. The mean RMR increased by 5·2 and 10·3% in the LEI in response to ephedrine and by 15·7 and 11·2% in the HEI groups after 0·25 mg and 0·50 mg ephedrine/kg respectively. The rise in serum-free fatty acids in response to ephedrine was significantly higher in the HEI group than in the LEI group.

5. These results suggest (1) the meal size required to promote a maximum thermic effect is smaller in energetically inefficient individuals (2) the sensitivity to a sympathomimetic drug is also increased in energetically-inefficient individuals.

6. We conclude that in energetically-efficient individuals both the thermic response to a meal and the sympathetic-mediated thermogenesis are lower than in energetically-inefficient ones.

1. The relation between dietary carbohydrate:lipid ratio and the fuel mixture oxidized during 24 h was investigated in eleven healthy volunteers (six females, and five males) in a respiration chamber. Values of the fuel mixture oxidized were estimated by continuous indirect calorimetry and urinary nitrogen measurements.

2. The subjects were first given a mixed diet for 7 d and spent the last 24 h of the 7 d period in a respiration chamber for continuous gas-exchange measurement. The fuels oxidized during 2·5 h of moderate exercise were also measured in the respiration chamber. After an interval of 2 weeks from the end of the mixed-diet period, the same subjects were given an isoenergetic high-carbohydrate low-fat diet for 7 d, and the same experimental regimen was repeated.

3. Dietary composition markedly influenced the fuel mixture oxidized during 24 h and this effect was still present 12 h after the last meal in the postabsorptive state. However, the diets had no influence on the substrates oxidized above resting levels during exercise. With both diets, the 24 h energy balance was slightly negative and the energy deficit was covered by lipid oxidation.

4. With the high-carbohydrate low-fat diet, the energy expenditure during sleep was found to be higher than that with the mixed diet.

5. It is concluded that: (a) the composition of the diet did not influence the fuel mixture utilized for moderate exercise, (b) the energy deficit calculated for a 24 h period was compensated by lipid oxidation irrespective of the carbohydrate content of the diet, (c) energy expenditure during sleep was found to be higher with the high-carbohydrate low-fat diet than with the mixed diet.

1. The adsorption of bile salts from aqueous solution on to soya-bean flour, wheat bran, fine dry sawdust and lucerne (Medicago sativa) wasmeasured. Adsorption on to the residuum after the first three of these substances had been extracted with organic solvents, pronase or solvents, pronase and acid (to produce lignin) was also measured.

2. The removal of saponins from soya-bean flour did not affect bile salt adsorption, and bile salts were adsorbed on to lignin and on to wheat bran (deficient in saponins). Although our methods differed from Oakenfull & Fenwick (1978) we were unable to substantiate their conclusions that saponins are responsible for most bile salt binding to fibrous substances in vitro.

1. Experiments were conducted to study the effects of dietary vicine (2, 6-diamino-4, 5 dihydroxy pyrimidine-5 (β-D-glucopyranoside)) and supplemental vitamin E on the performance of laying hens and growing chicks.

2. Chicks fed on diets that contained vicine had similar growth rates but slightly higher levels of spontaneous haemolysis of erythrocytes than birds fed on a control diet.

3. Vicine when fed to laying hens had a very dramatic effect. It depressed food consumption, egg weight, fertility and hatchability of eggs, packed cell volume and erythrocyte haemoglobin levels and led to increased liver weights, liver glutathione levels, liver and plasma lipid levels, plasma lipid peroxide levels and erythrocyte haemolysis in vitro. Liver protein and plasma vitamin E:lipid levels were not altered. Vitamin E supplementation slightly increased egg weights, markedly improved fertility and hatchability of eggs and lowered liver weights and lipid levels but did not affect the other factors examined.

4. It is concluded that vicine which was isolated from faba beans (Vicia faba L.) has a marked influence on the metabolism of the laying hen and only a slight effect on the growing chick. Vicine or its metabolites or both cause peroxidation of cellular components which result in abnormal lipid transport or synthesis or both, increased fragility of erythrocytes, and reduced fertility. These effects are overcome to varying extents by supplemental vitamin E.

1. Rats were fed to appetite on a stock laboratory diet or on diets consisting of the stock diet and in addition 50 or 200 g triolein/kg, 50 g palmitic acid/kg or 50 g/kg of a concentrate mixture of methyl branched-chain fatty acids (Me-BCFA) which had been prepared from sheep adipose triacylglycerols.

2. No differences could be detected in the Δ9-desaturase activity or fatty acid synthetase activity of liver preparations from rats which had been fed on either the stock diet, the 50 g palmitic acid/kg or the 50 and 200 g triolein/kg diet; the palmitic acid diet was therefore taken as the control diet in subsequent experiments.

3. Rats consuming the 50 g Me-BCFA/kg diet exhibited a marked reduction in the capacity of their liver microsomes for Δ9-desaturation when compared with animals receiving the control diet. The Δ6-desaturase activity also showed an inhibitory trend with the Me-BCFA diet.

4. Microsomal ω-oxidation of fatty acids, mitochondrial succinate oxidation and the activity of cytosolic fatty acid synthetase (FAS) were unaffected by the ingestion of the Me-BCFA mixture compared with the diet which included palmitic acid.

5. There were no differences in the plasma concentrations of thyroxin, insulin and glucagon between animals fed on the diets containing palmitic acid or the Me-BCFA.

6. For a given concentration of fatty acids the Me-BCFA had a greater inhibitory effect when added to incubations of liver microsomes from rats fed on the standard diet than did the addition of palmitic acid.

7. The observations in vivo and in vitro strongly suggested that the Me-BCFA were having a specific inhibitory effect on the desaturation reaction.

1. Wether sheep were used, some of which were prepared with a Thiry-Vella loop of jejunum. The long-term use of these loops was ensured by regular perfusion with fresh nutrient solution.

2. The net calcium absorption rale from a Thiry-Vella loop of jejunum increased with increasing intraluminal Ca concentration and was increased by the addition of 1 α-hydroxy-cholecalciferol (3μg/l) to the loop fluid.

3. When the diet of sheep was changed from one which was normal in Ca to a diet low in Ca there was an increase in the efficiency of net Ca absorption from the jejunal loop. This dietary change was accompanied by an increase in the circulating concentration of 1,25-dihydroxy-cholecalciferol (1.25(OH)2D3).

4. An intravenous infusion of the Ca chelating agent EDTA increased the efficiency of net Ca absorption from the jejunal loop. The use of 47Ca demonstrated that this reflected an increase in the true absorption rate of Ca.

5. Dietary phosphorus deficiency reduced the efficiency of intestinal Ca absorption and was associated with a reduction in the plasma concentration of 1,25(OH)2D3.

1. Sheep were fed on different diets of juice-extracted herbage to determine what effect juice-extraction had on reticulo-rumen motility.

2. The frequency of A and B sequences of contraction of the reticulo-rumen were recorded during eating, rumination and inactivity for continuous periods of 24–72 h by using integrated electromyograms obtained from electrodes implanted in the musculature of the reticulum and cranial dorsal rumen.

3. Animals were fed on herbage in which approximately 200 g/kg dry matter had been removed in juice extracted from ryegrass (Lolium perenne), white clover (Trifolium repens), mixed ryegrass–white clover and lucerne (Medicago saliva).

4. Over all the frequency of A sequences of contraction did not differ in animals fed on pressed herbage or the unpressed material from which it was derived, although it was slower during rumination on some of the pressed material. In contrast, the frequency of B sequences was higher on the pressed material. The frequencies of contraction of A and B sequences in animals fed on pressed herbage was related to the activity of the animals in the order eating > rumination > inactivity.

5. Changes in reticulo-rumen motility due to juice extraction were small and the frequencies of A and B sequences of contraction in sheep fed on pressed herbage were in the range encountered in ruminants consuming more conventional foods.

1. Glucose turnover (i.e. glucose entry and utilization rates) in fed and 48 h starved goats during pregnancy and lactation was determined using a continuous infusion of [U-14C]- and [3-3H]glucose.

2. Glucose synthesis and utilization increased during pregnancy and lactation in fed but not in starved goats.

3. Recycling of giucosc-C was approximately 10% in fed animals and 15–20% in starved animals and was unaffected by the stage of pregnancy or lactation.

4. Plasma glucose concentrations were maintained during pregnancy and lactation in fed goats but decreased during 48 h starvation in pregnant goats. Little change was seen in the plasma concentration of lipids and their metabolites during pregnancy and lactation in fed goats, but increases were observed after 48 h starvation.

5. The control of glucose metabolism in ruminants during pregnancy and lactation is discussed.

1. The frequency of association between methanogenic bacteria and ovine rumen ciliates was studied in the rumen fluid of a fistulated sheep.

2. A period of fasting and flushing of the rumen content with nitrogen resulted in a relatively high association, whereas the intake of food and flushing with hydrogen caused a detachment of the methanogenic bacteria from the ciliates.

3. The changes in the frequency of association can be correlated with the relative attribution to the H2 production by hydrogenogenic bacteria and rumen ciliates.

1. Restriction of food to ewes bearing twin lambs showed a trend to decrease the level of ω6 fatty acids in muscle phospholipids of the foetus though this was not significant statistically (P < 0·05).

2. There was a significant increase in the fatty acid ratio, 20:3ω9:20:4ω6 in the twin lambs as compared with single lambs.

3. There were no symptoms of polyunsaturated fatty acid deficiency.

1. Four pairs of Scottish Blackface ewes were given a basal diet of hay, providing 8 mg zinc/d, and one of four levels of supplementary Zn (0, 75, 150 or 225 mg/d) continuously by intraruminal infusion.

2. 65Zn (59 μCi) was given intravenously after stabilization for 14 d and the changes in specific radioactivity (SR) of plasma and faeces were monitored for a further 10 and 13 d respectiveiy. The faecal endogenous losses and absorption of Zn were estimated, using the principle of isotope dilution, by two methods using the whole or latter parts of SR: time curves.

3. Faecal endogenous losses were estimated by the part area method to be 4·9, 6·4, 5·1 and 6·3 ± 0·35 mg/d at 0, 75, 150 and 225 mg supplemental Zn/d i.e. largely unaffected by Zn intake and averaging 0·11 mg/kg live weight (LW). The whole area method gave similar results.

4. Urinary excretion was negligible (probably < 0·2 mg/d) for all sheep.

5. The amount of Zn absorbed was assumed to equal the irreversible loss of Zn under steady-state conditions and found to remain constant at 7·6±0·39 and 10·3±0·6 mg/d when calculated by ‘whole’ and ‘part area’ methods. Zn retention did not increase with Zn intake and homoeostasis was achieved primarily by control of Zn absorption which fell from 0·75 to 0·03 or from 0·96 to 0·05 of intake, depending on method of calculation, as intakes increased.

1. Two sows were housed in farrowing crates with slotted floors and fed daily with approximately 200 μCi 198Au from 3 d before farrowing until their piglets were 21 d old.

2. The sows' faeces became radioactive but their milk remained free of radioactivity. The piglets' mean (±SE) whole-body radioactivity was equivalent to 8·5 ± 0·9 g (range 3·8–15·5 g) of faeces. This is probably a measure of their daily intake of faeces.

3. The possibility of using this natural coprophagia to prevent piglet anaemia has been demonstrated on two commercial piggeries by feeding the sows a diet containing 2000 mg Fe/kg.

1. Pancreatic growth was measured in rats by changes in pancreatic weight, nucleic acid content and protein content after feeding diets of heated soya-bean flour (HSF), raw soya-bean flour (RSF), 200 g raw soya-bean flour+800 g heated soya-bean flour/kg (80 HSF) and 400 g raw soya-bean flour+600 g heated soya-bean flour/kg (60 HSF) for periodsup to 36 weeks. Control rats of comparable age to soya-bean flour-fed rats were continuedon rat cubes during the 36-week study.

2. Cube-fed rats remained significantly heavier than rats fed on soya-bean flour diets. Analysis of variance showed rats fed on HSF were significantly heavier than RSF-fed rats and rats fed on 80 HSF significantly heavier than those fed on 60 RSF.

3. Pancreatic indices in HSF-fed rats were similar to comparable control rats.

4. Hypertrophy was found in rats fed on the RSF-containing diets with the extent of enlargement corresponding to the RSF content. Hyperplasia was also found in rats fed on RSFand 60 HSF.

5. The greatest pancreatic growth was seen in RSF-fed rats with all the indices peaking at 8 weeks followed by a decline and then a rise again at 36 weeks.

6. The fall in pancreatic indices in rats fed on RSF for 12 and 24 weeks is most likely an effect of general malnutrition due to the multiple deficiences in amino acids which occur in animals fed on RSF. The rise at 36 weeks may reflect increased body growth or the beginning of adenornatous changes.

1. The content of total pantothenic acid (PaA) in two foodstuffs of microbial origin was measured by standard microbiological and chick biological assays.

2. Substantially and consistently higher values were found by the chick assay than by the microbiological determination, indicating that PaA-containing compounds were present that were not utilized by the test micro-organisms but were available for chicks. Attempts to identify these compounds did not explain the source of excess PaA activity for the chick.

3. It is suggested that forms of PaA that are undetected by standard methods of microbiological assay differ from one food to another and require different treatments to make the vitamin available to the assay organism.

1. The contribution of dietary constituents to the large urinary output of benzoic acid characteristic of ruminants and some herbivores is not well understood.

2. Methods for the analysis of quinic, cyclohexanecarboxylic, benzoic, phenylacetic, 3-phenylpropionic and cinnamic acids in urine and in rumen fluids were developed.

3. The urinary output of aromatic acids by sheep given seven rations was determined: benzoic acid output varied between 2·8 and 7·8 g/d; phenylacetic acid output between 0·16 and 1·3 g/d; cinnamic acid between 0·08 and 0·25 g/d and small amounts of 3-phenylpropionic acid were found in some samples.

4. Increments in urinary aromatic acid excretion were determined when the acids listed in paragraph 2 were infused via rumen or abomasal cannulas.

5. When cyclohexanecarboxylic acid was infused 40% of the dose was excreted as urinary benzoic acid after either route of infusion. Quinic acid was completely metabolized in the rumen: following rumen infusion between 16 and 53% of the infused acid was recovered as urinary benzoic acid; none was so recovered after abomasal infusion.

6. Urinary recoveries of rumen- and abomasally-infused aromatic acids were: benzoic acid 90 and 88% respectively as benzoic acid, phenylacetic acid 78 and 83% respectively as phenylacetic acid, 3-phenylpropionic acid 96 and 105% respectively as benzoic acid and cinnamic acid, 70 and 70% respectively as benzoic acid.

7. The concentration of aromatic acids in rumen fluid varied with time after feeding: cyclohexanecarboxylic acid was maximal (7 mg/l) 1 h after feeding, benzoic acid was always a minor component (0·5 ± 0·5 mg/l), phenylacetic acid varied between 0 and 35 mg/1 and 3-phenylpropionic acid between 25 and 47 mg/l. Cinnamic acid was not found in rumen fluid but on rumen infusion of this acid the concentration of 3-phenylpropionic acid in rumen fluid increased by 10 mg/l rumen fluid per g infused per d.

8. The incomplete metabolism of quinic and cyclohexanecarboxylic acids to urinary benzoic acid is discussed. It is concluded that the principal dietary precursors of urinary benzoic acid in ruminants are compounds yielding 3-phenylpropionic acid on microbial fermentation in the rumen. The small amount of cinnamic acid characteristic of ruminant urine arises as an intermediate in the β-oxidation of 3-phenylpropionic acid in the body tissues.

1. The extent to which phenolic derivatives of benzoic acid (seven); of phenylacetic acid (one); of 3-phenylpropionic acid (one) and of cinnamic acid (six) served as precursors of the urinary benzoic acid excreted by sheep was determined after administration as continuous drips via rumen or abomasal cannulas.

2. Phenolic derivatives of benzoic or of phenylacetic acid were not dehydroxylated to yield aromatic acids following administration via either route.

3. Rumen infusion of phenolic derivatives of both 3-phenylpropionic and cinnamic acids gave enhanced rumen concentrations of 3-phenylpropionic acid with negligible amounts of benzoic acid. Between 63 and 106% of the 2-, 3- or 4-hydroxy acids, of the 3,4-dihydroxy acids or of the 3-methoxy, 4-hydroxy acids infused were excreted in the urine as benzoic acid and a variable proportion, characteristic of the individual animal, of up to 20% of the dose as cinnamic acid.

4. Abomasal infusion of monohydroxy 3-phenylpropionic and cinnamic acids did not yield urinary benzoic acid increments. However, between 11 and 34% of abomasally-infused disubstituted phenolic cinnamic acids infused were excreted in the urine as benzoic acid due, it is postulated, to entero-hepatic circulation and microbial metabolism of the infused acids in the large intestine.

5. It is concluded that rumen microbial metabolism of dietary phenolic cinnamic acids to 3-phenylpropionic acid followed by its absorption and oxidation in the body tissues is responsible for the greater part of the benzoic and cinnamic acids found in ruminant urine.