1. Doses of L-[35S]methionine (2 g) and [35S]casein (20 g) were given to sheep in the diet or via the abomasum, and the patterns of 35S-labelling in blood, wool and excreta were studied during the 7 d following administration of the dose.

2. Doses given via the abomasum resulted in substantial labelling of the plasma proteins and wool; only small amounts of the dose were recovered in the urine and faeces. In contrast, doses given in the diet resulted in much less labelling of plasma proteins and wool and ingreater losses in excreta. These results provide the basis of a rapid system for testing the effectiveness of various methods of protecting methionine and casein from degradation in the rumen.

3. From the patterns obtained with N-formyl-DL-[35S]methionine and [35S]polymethionine (mol. wt 7–8 × 104) it appears unlikely that these compounds would stimulate wool growth if given as dietary supplements.

4. [35S]Casein which had been treated with an 8 % aqueous solution of formaldehyde gave results which showed that the casein had been protected from destruction in the rumen without markedly reducing its subsequent digestibility. Treatment of [35S]casein with excess, formalde-hyde (a 40 % aqueous solution) gave a product which was completely indigestible.

5. It is concluded that the radioisotope technique could be applied to other [35S]amino acids or their derivatives and to other [35S]proteins, and should also be applicable to larger ruminants such as cattle.

1. The changes in the concentrations and solubilities of zinc, manganese and copper in the rumen, abomasum and along the small intestine of cannulated sheep, maintained on dried grass, have been determined. Relationships between the solubilities of the metals and the pH values of the samples were observed.

2. The pattern of change of solubilities could be reproduced in vitro by adjustment of the pH of rumen and abomasal samples.

3. By a combination of gel filtration and continuous-flow high-voltage electrophoretic techniques it was shown that soluble complexes of Zn and Mn occur in the rumen and lower regions of the small intestine. The soluble Zn and Mn in the abomasum, duodenum and upper jejunum appeared to exist in ionic form. The charge and molecular size of these complexes were found to be dependent on the pH of the samples.

4. From detergent treatment of rumen samples it appeared that much of the insoluble metal, particularly Cu, might be associated with microbial matter.

5. The significance of these findings and their relationship to the differences noted in the apparent requirements for trace elements of ruminants on different diets is discussed.

1. Serial measurements of total body potassium were made in children while they were malnourished and as they recovered. Initially, there was a low total body potassium which rose slowly and reached the normal levels of 45 m-equiv./kg at 3–4 weeks after admission to hospital.

2. The early stages of recovery were divided into three phases. In the first 5 days of treatment, retention of potassium served to correct a true potassium deficiency and the amount of potassium retained during this phase was related to the initial level of total body potassium. There was no relationship between serum potassium and total body potassium. There was indirect evidence that antecedent diarrhoea was an important factor in the production of potassium depletion.

3. In the next phase—the lag phase—potassium was retained in relation to deposition of new body tissue.

4. In the phase of rapid growth, potassium was also retained in the amount appropriate for deposition of new tissue.

5. After the repair of the acute potassium depletion, potassium retention was always correlated with the protein intake.

1. The extent to which ammonia-N (NH3-N) serves as a starting point for synthesis of microbial nitrogenous compounds was assessed when 15N as (15NH4)2SO4 was continuously infused into the rumen of a sheep for periods of 78–98 h. Steady states were reached in the composition of the rumen contents because the animal was fed equal parts of its ration at hourly intervals. Concentrations of 15N in bacterial-N, protozoal-N and rumen NH3-N were compared.

2. In two trials with a low-N diet consisting largely of wheaten hay the 15N concentration in bacterial N was 76 and 78% of that in the NH3-N. For protozoa the values were more variable —64 and 43%.

In two trials with a higher-N diet (lucerne hay), the corresponding values were lower—bacterial-N 62 and 64%, protozoal-N 41 and 35%.It was concluded that synthesis of microbial protein was more dependent on ammonia as a starting point with the low-N diet than with the higher-N diet.

3. Entry and exit rates for ammonia into and out of the rumen system were determined, and the results, in combination with those obtained for bacterial-N in the first part of the work, allowed calculations to be made of the production of microbial-N/d formed from NH3-N, and this in turn allowed calculation of minimal values for conversion of plant-N to microbial-N in the lumen. Minimal extent of conversion was 68% for the low-N diet and 53–55% for the higher-N diet.

4. Total production of microbial-N in relation to the amount of N given was also calculated by using previously reported values for the relative proportions of protozoal-N and bacterial-N in sheep given diets similar to those used here. These values for extent of conversion were 73% for the low-N diet and 58–59% for the higher-N diet.

1. Barium sulphate suspensions were given to young sheep by mouth or by injection via an oesophageal catheter. Closure of the oesophageal groove was assessed by observing radiographically whether the suspension passed to the ruminoreticulum or to the abomasum.

2. Complete closure of the groove took place in lambs that were trained to drink small meals from a trough after being weaned from their dams, a finding similar to that for lambs weaned on to a teat-bottle.

3. When barium was injected into the oesophagus of lambs that were excited by being offered their bottle or trough beyond their reach, the barium passed direct to the abomasum if the normal feeding routine was closely imitated. When the lambs were able to discriminate between this teasing procedure and the normal routine, the barium frequently passed to the ruminoreticulum. If the lambs were not teased the barium passed invariably to the ruminoreticulum.

4. It is concluded that the reflex closure of the groove can be conditioned by the feeding procedure adopted at weaning so that it no longer depends on the stimuli associated with sucking and swallowing.

1. The food intake of sixty-four infantry recruits was measured at six centres during 3 weeks of initial training. The daily energy expenditure was measured in thirty-five of these men.

2. The mean daily consumption of the sixty-four subjects provided them with 3850 kcal (16110 kJ); the energy expenditure of the thirty-five subjects averaged 3750 kcal (15690 kJ).

3. Serial auto- and cross-correlations of intake and expenditure were very small and there was no significant relationship between food intake and energy expenditure on the same day.

4. The intakes and expenditures of different subjects at the same centre were not independent.

5. There was a significant relationship between intake and expenditure for the whole period of the survey when results for all subjects were included. In three centres the correlation was high, +0.788 (P < 0.001), but was only + 0.083 (P < 0.5) in the remaining three centres.

6. There was a positive but not significant correlation between body-weight and the average food intake of 6 d.

7. There was a negative correlation between body-weight and calorie balance.

8. Weight change and calorie balance over 1 week were related, the correlation averaging 0.40. There was a correlation of 0.32 between daily weight changes and calorie balance. A rather small amount of variation in calorie balance can be explained by contemporary changes in weight.

1. Chicks were reared to 3 weeks in a germ-free or conventional environment on diets containing 50% raw or heated soya-bean meal. Body-weights and pancreas weights were determined and the proteolytic and amylolytic enzymes in the pancreas were measured. In one experiment the contents of the intestinal tract were analysed for their content of nitrogenous compounds.

2. The growth of chicks given raw soya was depressed below that of controls given heated soya, and the growth depression was significantly greater in the conventional compared with the germ-free environment.

3. The pancreases of chicks given raw soya were significantly larger than those given heated soya. The degree of enlargement was similar in both environments. The concentration of α-amylase was lower in the enlarged pancreases, but the total amount per pancreas was similar to that in the normal pancreases. Conversely, the concentration of proteolytic enzymes was the same or greater in the enlarged pancreases, which had significantly greater total content of proteases than did the normal pancreases.

4. There was evidence of impaired protein digestion in the birds given the raw soya diets. Their gut contents contained larger amounts of insoluble matter, with higher nitrogen content, and the soluble fraction contained more nitrogen present as ‘protein’, with correspondingly less ‘peptide’ and ‘amino acid’, than did similar samples from birds given heated soya. No differences were observed in this respect between germ-free and conventional birds.

5. It was concluded that the gut microflora exacerbated the growth-depressing effect on chicks of raw soya meal. Possible explanations are advanced.

1. The absorption of the amino acid components of two protein-containing test meals has been studied in six healthy volunteers. One meal contained 15 g of milk protein and the other contained 15 g of gelatin. In a control experiment a meal was given which contained a negligible amount of protein.

2. The subjects were intubated with a single lumen tube; then each meal was swallowed and intestinal residues were obtained from known levels. The amino acid composition of the intestinal contents was compared with that of the original meal. Correction was made for net water shifts by reference to a non-absorbable marker compound (polyethylene glycol 4000).

3. The results showed that at least 70–75% of the milk protein test meal had been absorbed when the sampling holes were 230 cm from the nose. It is suggested, however, that most, if not all, of the meal had been absorbed when the sampling holes were 140 cm from the nose.

4. Amino acids were absorbed at rates proportional to their concentrations in the meal.

5. Gelatin, a protein known to be relatively resistant to enzymic hydrolysis, was poorly absorbed from the region of the small intestine under study.

6. Estimates of the amount of endogenous protein secreted in response to the test meals ranged from z to 8 g, equivalent to 13–53% of the protein containing test meals.

7. The absorption of certain amino acids, e.g. the dicarboxylic amino acids, was more rapid than was expected; glutamic and aspartic acids are absorbed slowly from a mixture of amino acids, both in vitro and in vivo.

1. In the aetiopathogenesis, in Nigerians, of a degenerative neuropathy known as tropical ataxic neuropathy, chronic cyanide intoxication is believed to be the most important factor. The source of the cyanide is cassava (Manihot) and in Nigerian patients, plasma concentration of thiocyanate, a major detoxication product of cyanide, is high.

2. Since there is considerable doubt as to whether cyanide is readily released from cassava diet after ingestion, rats were fed on 80 and 100% purupuru (a cassava derivative) diets for periods varying between 6 and 18 months and their plasma thiocyanate levels were studied. Control rats were fed on a normal diet for the same periods.

3. Rats fed on the 100% purupuru diet were malnourished. Rats fed on the 80 % purupuru diet appeared normal, although their mean weight was less than the mean weight of rats fed on the normal diet.

4. Plasma thiocyanate was significantly higher in rats fed the purupuru diets than in the rats fed on the normal rat diet.

5. The concentration of thiosulphate Sulphurtransferase, the enzyme that catalyses the conversion of cyanide into thiocyanate was the same in rats fed on the purupuru diets as in the control rats.

6. The results suggest that raised plasma thiocyanate levels found in Nigerian patients with ataxic neuropathy, as in rats fed cassava diet, is the result of detoxication of cyanide, as the concentration of thiocyanate in cassava and most food products eaten by Nigerians is low.

1. Intestinal contents, collected from the human jejunum after a test meal (milk-protein, gelatin or low-protein) were fractionated by centrifugation and gel filtration on G-75Sephadex. The fractions were hydrolysed and the proportion of the total amino acid in each fraction was determined. The amino acids were measured with an EEL Amino Acid Analyser.

2. The free amino acid concentrations were determined in samples of the contents of the small intestine collected from various levels after the three types of test meal.

3. Intestinal contents collected from two levels of the jejunum after a milk-protein meal, were incubated in vitro at 37° for periods up to 80 min and the rates of release of the individual free amino acids were determined.

4. There was a rapid breakdown of the proteins of the test meals to fragments of molecular weight under 5000. The further breakdown (during incubation in vitro) to free amino acids was sufficiently rapid to account for the absorption in the free form of arginine, lysine, tyrosine, valine, phenylalanine, methionine and leucine. It was not rapid enough to account for the absorption of glycine, threonine, serine, the imino acids or the dicarboxylic amino acids in the free form.

5. The free amino acid concentrations in the intestinal lumen bore very little relationship to the concentrations in hydrolysates of the test meals or to those in hydrolysates of the intestinal contents. Many of the free amino acids in the intestinal samples were present in approximately equimolar concentrations.

6. It is suggested that experiments in which amino acid mixtures, simulating a dietary protein, are fed to experimental animals to determine the rates of amino acid absorption do not present a true picture of the events in the small intestine following the ingestion of a protein meal.

1. A survey was made of ascorbic acid concentrations in white blood cells of apparently healthy European men and women living in the tropical climate of Singapore.

2. The survey showed that there was a significant fall in these concentrations in men who had been resident for more than 4 months. Levels in women did not show a significant decrease.

1. Sixteen lambs were used to compare two methods of administering various protein supplements to weaned lambs. In one method the protein supplement was mixed with the dry feed, consisting mainly of rolled barley, so that it passed to the rumen. In the second method the supplement was suspended in water which the lambs were trained to suck from a bottle; the suspension then passed directly to the abomasum by way of the oesophageal groove and so escaped rumen fermentation.

2. When the protein supplements were given in amounts that provided less than the estimated protein requirement of the animals, giving the liquid suspension led to significantly lower urinary nitrogen excretion (P < 0.001), greater nitrogen retention (P<0.05) and greater live-weight gain (0.05<P<0.1) than giving the feed in the dry form.

3. The body-weight gain was greater with white fish meal than with casein (P<0.05) and soya-bean meal (P<0.001), whichever method of feeding was adopted. There was no significant interaction between method of feeding and protein source, but the faecal nitrogen excretion was highest when soya-bean meal was given in liquid suspension.

4. From a regression of nitrogen retention on nitrogen intake with lambs receiving the basal ration only, it was calculated that the improvement in retention of the protein supplement effected by giving it in liquid suspension was 31 % for casein, 27 % for fish meal and 24 % for soya-bean meal.

1. Isoalloxazines were characterized and measured in the caecum of two conventional rabbits kept on an adequate diet, two rabbits on the same diet from which vitamin B2 (ribo-flavine) had been omitted and five germ-free rabbits which were also on the adequate diet.

2. Riboflavine (up to 12mg) unaccompanied by any of its degradation products was found in the caecum of germ-free rabbits and 8–9 μg per ml were found in their urine.

3. Hydroxyethylflavine (4–5 mg) accompanied only by traces of riboflavine was found in the caecum of conventional rabbits.

4. There was about 1% ash in the contents of each of five germ-free and two conventional caecums.

5. The five germ-free caecal contents averaged 22.4% of the animal's body-weight. For four conventional animals this figure was only 10.5%.

6. In the caecum of each of two conventional rabbits kept on a diet deficient in riboflavine neither riboflavine nor hydroxyethylflavine was found but there was somewhat less than 1 mg of a yellow-fluorescing material of low RF value in each caecum.

7. The results are discussed in relation to the authors' previous reports on metabolites of riboflavine.

1. Emulsions with egg phosphatides of nine synthetic triglycerides (tributyrin, tricaprylin, tripelargonin, tricaprin, trilaurin, trimyristin, tripahitin, triisostearin, triolein) and of rapeseed oil and a proprietary emulsion of cottonseed oil were given as continuous infusions into the jugular vein of lactating sows. The effects of the infusions on the concentration and composition of blood plasma lipids and on the composition of milk fat were determined.

2. The infusions did not affect the concentrations in blood plasma of cholesterol, phospholipid or cholesterol esters, but there was a tendency for the concentration of plasma triglycerides to be increased which was most pronounced for the infusions of longer-chain triglycerides. The fatty acid composition of the plasma triglycerides was not altered by the infusion of tributyrin, except that there was an increase in the content of oleic and a decrease in that of linoleic acid. With other infusions the composition of the plasma triglycerides was altered towards that of the infused material and the effect was more marked for the longer-chain triglycerides, with the exception of triisostearin.

3. The changes in the composition of the milk fat reflected those in the composition of plasma triglycerides, with two exceptions. The infusion of tripalmitin was associated with an increase not only in the palmitic acid content of milk fat but also in the palmitoleic acid content. Also, the changes in the content in milk fat of eicosenoic acid and, more especially of erucic acid during the infusion of rapeseed oil were much less than the corresponding changes in the plasma triglycerides.