1. Force-feeding of young chicks for 15 d increased kidney arginase (EC 3·5·3·1) activity threefold. Fasting for 30 h decreased this activity by 50%.

2. Liver xanthine dehydrogenase was slightly increased after force-feeding and decreased following fasting.

3. The specific activities of two pentose-phosphate-cycle enzymes were not significantly affected by force-feeding, but glucose-6-phosphate dehydrogenase (EC 1.1.1.49) decreased following fasting.

4. The over-all secretion of digestive enzymes increased parallel to the increase in food consumption. Therefore, despite an increased absolute weight of the pancreas and intestinal chyme, specific activities were the same in the force-fed and ad lib.-fed groups, except for a higher activity in intestinal amylase.

5. Fasting did not affect the pancreatic enzymic activities.

1. Parenteral administration of pyridoxal 5′-phosphate (PALP) to riboflavin-deficient rats increased the non-FAD component of erythrocyte riboflavin.

2. Pyridoxaminephosphate oxidase (EC 1.4.3.5) activity in the livers of riboflavin-deficient animals was only 15% of that of controls. PALP concentration in blood, liver and brain was not affected. Deficient animals had higher levels of pyridoxine in liver.

3. Human subjects with lesions of the mouth responded to treatment with either riboflavin or pyridoxine.

4. PALP concentration of human blood was not affected by administration of riboflavin but was markedly increased by pyridoxine.

5. Erythrocyte glutathione reductase activity (EC 1.6.4.2) in humans was increased and in vitro stimulation of the enzyme with FAD was decreased by treatment with riboflavin, but not by treatment with pyridoxine.

1. The possibility that, when lambs are fed on barley-rich diets, vitamin B12 might limit hepatic utilization of propionate and result in the formation of branched-chain fatty acids was investigated with thirty-six animals allocated to twelve treatments according to a 3 × 2 × 2 factorial design.

2. From 13 kg live weight to slaughter at 35 kg the lambs were given diets containing barley in one of three physical forms, and one of two levels of cobalt (0.1 and 0.9 mg/kg diet). In addition, half the lambs received twice-weekly injections of cyanocobalamin (40 μg/kg body-weight).

3. The fatty acid composition of triglycerides from subcutaneous and perinephric adipose tissue was determined at slaughter.

4. Neither additional dietary Co nor the administration of cyanocobalamin (alone or in combination with additional Co) influenced the proportions of branched-chain acids in the triglycerides. The possibility is discussed that the ability of the lamb to respond to the increased supply of propionate which is provided by a high-barley diet is not restricted by the availability of cyanocobalamin, but by hepatic capacity to utilize it for the production of methylmalonyl-CoA mutase (EC 5.4.99.2).

5. Regardless of diet, subcutaneous triglycerides contained greater proportions of propionate-derived fatty acids than did perinephric triglycerides which contained greater proportions of exogenously-derived C18 unsaturated acids. Lambs given whole barley in loose mix produced triglycerides containing relatively less odd-numbered n-acids and branched-chain acids than did lambs fed on either of two pelleted diets containing rolled or whole barley.

1. The plasma concentration of retinol-binding holoprotein (holo-RBP) in rats given retinol-sufficient diets containing 50 g soya-bean protein/kg was 90 % of the concentration found in controls given 200 g soya-bean protein/kg, whereas in rats given 50 g rice protein/kg it was only 68 % of the control value. Plasma albumin concentrations in the low-protein groups were lower by 20–25 %.

2. The rats given retinol-deficient diets, whose plasma levels of holo-RBP were reduced almost to zero after 5–8 weeks, were given 1·5 mg retinol/kg body-weight. Changes in plasma holo-RBP were measured for 7 d. The rapid rise in the latter to a peak above normal control levels within 1·5–2 h indicated that a pool of the apoprotein had accumulated in the liver during the period of deficiency and that retinol was necessary for its release.

3. The maximum value reached in the groups of rats given the rice-protein diet was smaller than the values for the groups given the soya-bean-protein diets, reflecting a reduced rate of synthesis of the carrier protein in the livers of those groups.

4. The administration of 100 g casein/kg diet to the rats receiving only 50 g rice-protein/kg immediately stimulated the synthesis of the carrier protein which was released into plasma, reaching a peak after 24 h before settling down after 3–4 d to the steady-state level expected for normal well-nourished controls.

5. The half-life for excess holo-RBP released into plasma of rats receiving a normal level of good-quality protein was 7 h, where it was 14 h for the groups of low-protein diets.

1. Skinfold thicknesses at four sites – biceps, triceps, subscapular and supra-iliac – and total body density (by underwater weighing) were measured on 209 males and 272 females aged from 16 to 72 years. The fat content varied from 5 to 50% of body-weight in the men and from 10 to 61% in the women.

2. When the results were plotted it was found necessary to use the logarithm of skinfold measurements in order to achieve a linear relationship with body density.

3. Linear regression equations were calculated for the estimation of body density, and hence body fat, using single skinfolds and all possible sums of two or more skinfolds. Separate equations for the different age-groupings are given. A table is derived where percentage body fat can be read off corresponding to differing values for the total of the four standard skinfolds. This table is subdivided for sex and for age.

4. The possible reasons for the altered position of the regression lines with sex and age, and the validation of the use of body density measurements, are discussed.

1. The effects of dietary sulphur on the availability of dietary copper were estimated by means of a repletion technique. The responses of initially hypocupraemic ewes to repletion with Cu-supplemented diets containing supplements of organic S, as methionine, and of inorganic S, as Na2SO4, were compared with those obtained with a diet low in S.

2. The two forms of S had similar effects. Responses in plasma Cu were reduced by 39–56 % when S was increased from 1.0 to 3.0 or 4.0 g/kg diet and the availability of dietary Cu was estimated to have decreased from 0.062 to 0.041. Both S supplements produced marked increases in rumen sulphide concentrations.

3. Dietary S had no effect on plasma Cu when added to the low-Cu diet of hypocupraemic ewes being repleted by a continuous intravenous infusion of Cu.

4. The addition of CuS, providing 5 mg Cu/kg, to the diet of hypocupraemic ewes produced no response in plasma Cu or haemoglobin. The same amount of Cu, given as CuSO4, increased plasma Cu by 0.46±0.15 mg/l and haemoglobin by 33±3.8 g/l after 36 d: the subsequent replacement of CuSO4 by CuS induced hypocupraemia again but had no effect on haemoglobin.

5. It was concluded that variations in dietary S within the normal range for herbage exert an independent effect on Cu metabolism, possibly through the formation of insoluble CuS at sites beyond the rumen.

1. The object of the experiments was to estimate the maintenance requirements for lysine and leucine by a radioactive method. Rats were given a single dose of 14C-labelled lysine or leucine and groups of animals were killed after 15, 20 and 30 d.

2. After 20 d the specific radioactivity (SR) of protein was approximately the same in liver, muscle and viscera; it was somewhat lower in skin. Once uniform SR is achieved, the rate of loss of radioactivity is a measure of the rate of endogenous loss of the amino acid.

3. The rate of loss between 20 and 30 d was measured in two ways: from the daily output of expired 14CO2, and from the decrease, over the 10 d interval, of the total amount of radioactivity retained in the body.

4. For the first 15 d after administration of the labelled amino acid, all rats were given a low-protein or low-amino acid diet on which body-weight was maintained constant. For the second 15 d period some rats were kept on this diet; others were transferred either to a protein-free diet or to a diet lacking the specific amino acid (lysine or leucine) which had been administered in the labelled form.

5. The fractional rate of amino acid loss in the different experiments ranged from 1.5 to 3.5%/d, being greatest with the protein-free diet. The absolute rates of loss were calculated from measurements of the total lysine and leucine content of rats.

6. The best estimates of the rate of endogenous amino acid loss obtained in this way, expressed as mg/kg0.75 per d were: lysine 136, leucine 80. These estimates are higher than most estimates of maintenance requirements obtained by growth or nitrogen balance methods and possible reasons for these discrepancies are discussed.

1. Fifteen ‘constitutionally’ obese subjects, eleven hyperlipidaemic subjects of mixed-type and fourteen normal subjects were studied.

2. With a reduction in energy intake (range 3.3–4.2 MJ) for 21 d, there was no change in the levels of plasma total cholesterol (TC) and triglyceride (TG) of obese subjects, but the free fatty acid levels increased. However, in hyperlipidaemic subjects there was a reduction in levels of TC and TG with no increase in levels of free fatty acids.

3. There was a significant increase in the serum ketone levels of obese subjects but not in those of hyperlipidaemic subjects. The reduction of the respiratory quotient to a value of 0.7 was more rapid in the obese than in hyperlipidaemic subjects.

4. After administration of a fat load (0.5 g/kg gross body-weight) there was no change in plasma TG levels in obese subjects but there was an increase in those of normal subjects.

5. After administration of a glucose load (1 g/kg ideal body-weight) there was a significant reduction in plasma TG levels in obese subjects but no change in those of hyperlipidaemic subjects.

6. Hyperlipidaemic subjects eating their normal diet were found to have a hydroxybutyrate: acetoacetate ratio three- to fivefold that of obese and normal subjects.

7. These results suggest that obese subjects have an increased ability to store fatty acids, to mobilize them quickly and to generate fatty acid metabolites in the form of ketone bodies, while these same metabolic functions are reduced in hyperlipidaemic subjects.

1. Intestinal and renal vitamin D-dependent calcium-binding protein (CaBP) activity and cholecalciferol metabolism were investigated in the protein-deficient rat (40 g casein/kg diet) and in control animals (200 g casein/kg diet). Compared to control animals, 3 weeks of protein deprivation resulted in consistently reduced intestinal CaBP activity, while renal CaBP activity was not significantly altered.

2. Intestinal CaBP activity was greatly reduced in rats fed on diets deficient in both protein and vitamin D. CaBP activity was doubled by cholecalciferol administration, but did not reach control values. The rate of conversion of intravenously injected [3H]cholecalciferol to 25-hydroxycholecalciferol (25-HCC) and the disappearance rates of plasma 25-HCC were similar in the two groups of animals.

3. It is concluded that in the protein-deficient rat: (a) intestinal CaBP activity is reduced; (b) coexistent vitamin D deficiency reduces intestinal CaBP activity still further, but the intestinal mucosa retains the potential to respond to administered cholecalciferol: (c) hepatic and probably renal metabolism of cholecalciferol appear to be normal; (d) reduced CaBP is likely to be the result of reduced CaBP synthesis as a consequence of deficient amino acid substrate.

1. A method is described for the estimation of the microbial and dietary protein entering the small intestine of sheep, based on an intraruminal infusion of [35S]sulphate, and isolation of the labelled microbial protein.

2. Samples of the microbial fraction contained in duodenal digesta were isolated by highspeed centrifugation and a scheme of analysis was devised for the determination of the specific activity of the methionine in the microbial fraction and the duodenal digesta.

3. In the absence of dietary methionine in duodenal digesta, it was postulated that the ratio of the specific activities of microbial methionine (M) and digesta methionine (D) should equal 1. Using two purified diets containing urea as the sole source of nitrogen, the M:D ratio was found to vary from 0·94 to 1·08 (mean 1·01 ± 0·01).

4. Addition of known quantities of dietary protein to labelled duodenal digesta obtained from one sheep fed on a non-protein diet increased the M:D ratio. Prediction of the dietary protein present from changes in the M:D ratio gave satisfactory agreement with the amounts of dietary protein known to be present (96–101% of known value, mean 98·4 ± 1·24%).

5. When animals were fed hourly the M:D ratio remained reasonably constant throughout 24 h. In contrast, with twice-daily feeding the M:D ratio varied markedly throughout the 24 h. However, summation of the estimates made of the flow of microbial and dietary protein into the duodenum in each 2 h period throughout 24 h agreed closely with the estimates made from samples withdrawn from the accumulated flow of digesta over the whole 24 h period.

6. The method was finally adapted to situations with either frequent or infrequent feeding patterns, and the need for a priming infusion period of 16 h before the collection and sampling of duodenal digesta was established.

1. Folate deficiency was produced in baboons by feeding them on a diet which was deficient in folic acid.

2. Loss of body-weight, anorexia, asthenia, gingivitis and diarrhoea were common features of the deficiency.

3. Haematologically, the deficiency was characterized by leucopenia with a greater proportional decrease in the polymorphonuclear neutrophils, thrombocytopenia and in some baboons macrocytic anaemia.

4. Deficient baboons had low serum, erythrocyte and liver folate levels and excreted increased amounts of formiminoglutamic acid. The fall in the serum folate level was more rapid than that of the erythrocytes, occurring mainly during the 1st month of deficiency, while erythrocyte levels decreased gradually over a 5-month period.

5. Serum and liver vitamin B12 levels and methylmalonic acid excretion were normal in deficient baboons.

1. A comparison was made of the efficiency of food conversion and body composition of the preruminant lamb and young pig when offered cow's milk supplemented with minerals and vitamins from 2 to 10 weeks of age.

2. The daily voluntary intake of gross energy/kg live weight0·75 of the pigs was significantly greater than that of the lambs. The daily voluntary intake of the lambs decreased from 1895 to 1573 kJ/kg live weight0·75 (453 to 376 kcal/kg0·75) over the experimental period and that for the pigs increased from 2063 to 2519 kJ/kg live weight0·75 (493 to 602 kcal/kg0·75).

3. Of the organic matter of the milk, 0·97–0·98 was digested by both species. Food conversion ratio (kg dry matter milk/kg live-weight gain) did not differ between the species when food was given ad lib. but pigs restricted to 80% of voluntary food intake or to 1255 kJ/kg live weight0·75 (300 kcal/kg0·75) had a lower food conversion ratio than lambs similarly restricted in intake.

4. A 20% reduction in the voluntary intake of gross energy decreased daily protein deposition in the lambs only but decreased daily fat deposition in both species.

1. A metal-binding fraction with a molecular weight of about 12000 in calf and sheep liver has been characterized as a metallothionein-like protein.

2. The combined concentrations of copper and zinc in the fraction (as μg/g liver) are a direct function of liver Zn concentration.

3. The relative proportions of Cu and Zn in the fraction are dependent on the Cu: Zn ratio in the liver.

4. These findings may be relevant to the mutual interaction between Cu and Zn.

1. A study has been made by gel-filtration techniques of the soluble copper- and zinc-binding proteins in livers from calves and sheep of widely differing Cu and Zn status.

2. Cu and Zn generally occurred together in three main fractions, with approximate molecular weights of > 75000, 35000 and 12000, and Zn also in one other fraction with molecular weight about 65000. The distribution of the metals between these fractions was variable and dependent on both the Cu and Zn status of the animals.

3. Zn was usually absent from the low-molecular-weight fraction in Zn-deficient or high-Cu livers, with Cu also being absent in the former instance.

4. The fraction with molecular weight of 35000 was tentatively identified as hepatocuprein. It generally accounted for only 4% of the total hepatic Cu except in Cu-deficient livers.

5. The possible relationship of these findings to the mutual antagonism between Cu and Zn is discussed.

1. Analyses have been made of materials in which proteins were caused to react with sugars so as to cause a severe fall in their nutritionally available lysine content as assayed with both rats and chicks.

2. With materials in which the reactions had proceeded under mild conditions (37°), the direct use of either fluorodinitrobenzene (FDNB), o-methylisourea or sodium borohydride to measure selectively those lysine units which had not engaged in Maillard reactions gave similar values which, in turn, appeared to reflect the full extent of the nutritional damage.

3. Analysis by a procedure using trinitrobenzenesulphonic acid (TNBS), or the use of FDNB indirectly to measure ‘bound lysine’ failed to indicate the full extent of the Maillard reaction in mildly heated materials, although the same procedures did appear to do so when applied to materials in which sugar and proteins had been allowed to react at a higher temperature.

4. With a pure protein and with fat-extracted, dried muscle that had been severely heated, all the procedures for measuring reactive lysine gave similar results, with the exception of the procedure using sodium borohydride which proved ineffective in measuring the type of damage that had occurred in these materials.

5. The findings are discussed in relation to the nature of the reactions believed to take place in different types of heat damage.

6. Suggestions are made of the types of materials with which different procedures can be satisfactorily used. The direct FDNB procedure and that using o-methylisourea appeared to be applicable to all our samples.

1. This study set out to measure the sensitivity of muscle RNA content to food intake and food restriction, and to relate this to plasma insulin and intracellular amino acid concentrations.

2. Young rats were trained for 2 weeks to consume their daily food ration in a single 4 h period. After this time they had resumed normal growth. The rats were killed at intervals over 24 h and subsequently at daily intervals. One group was given a protein-free meal in place of the stock diet and a similar procedure was followed. Measurements were made of plasma insulin, concentration of nucleic acids and protein in liver, heart and skeletal muscle, and free amino acids in the gastrocnemius muscle.

3. Following the meal there was a fivefold increase in plasma insulin, which was accompanied by small increases in the concentrations of the intracellular amino acids in muscle. In all the tissues, after feeding, the RNA:DNA ratio increased by (%) 20, 19 and 12 in liver, skeletal and heart muscle respectively.

4. During the fasting period the plasma insulin decreased, and this decrease was accompanied by rapid losses of RNA from liver, muscle and heart at similar rates. There were increases in the concentrations of the essential amino acids, especially methionine and the branched-chain amino acids, but decreases, in general, in those of the non-essential amino acids. When the protein-free meal was given, there was a small increase in the plasma insulin, but the RNA was lost from the three tissues at the same rate as in the starved rats. There was, however, a transient fall in the concentrations of the essential amino acids.

5. The rapid changes in muscle RNA concentrations following food intake demonstrate that the minimum turnover rate of RNA in this tissue must be considerably faster than has been previously reported, and must be similar to that in liver. There is a direct correlation between tissue RNA concentration and that of plasma insulin, but little correlation between tissue RNA concentration and that of the intracellular essential amino acids.

1. Drinks of milk, lactose and casein were given to children who, though suspected of having malabsorption, were subsequently found to have normal gastrointestinal tracts. The plasma concentrations of glucose, amino acids, urea and insulin following these drinks were measured. The results can probably be taken to represent control values when investigating children with gastrointestinal or metabolic disorders.

2. The rise in plasma amino acids after giving casein and the rise in plasma glucose after giving lactose were greater than those after giving equivalent amounts of milk.

3. The absorption of an individual food constituent and its uptake by the tissues are influenced by the presence of other food constituents so that ‘tolerance tests’ with individual nutrients may not be truly physiological.

1. Weanling (24-d-old) male rats were maintained at their body-weight for 1 month by restricting the intake of their normal diet. The animals were then rehabilitated for 0, 3, 7, 10 or 16 d. Control animals were given an unrestricted diet and some killed at the same body-weight as the experimental animals and others at the same age.

2. The forebrain, cerebellum, brain stem, heart, lungs, liver, spleen, kidneys, testes, and three sections of the alimentary tract were weighed, and DNA, RNA and protein contents were determined in the brain parts and liver.

3. During rehabilitation the weight of the body, corrected for the weight of the gut contents, showed a rapid gain between 7 and 10 d, which was synchronous with a rapid gain in weight of the testes.

4. The weight of the majority of organs relative to body-weight was maintained during both undernutrition and rehabilitation, the most marked exceptions being the stomach, which increased in relative weight during undernutrition, and maintained a high relative weight during rehabilitation, and the spleen, which lost weight during undernutrition, and on rehabilitation gained weight very rapidly to achieve a high relative weight.

5. The weight of the forebrain fell during undernutrition, due to a loss of water, and the weight of the brain stem rose. In the forebrain, DNA and the protein: DNA ratio were unchanged throughout, whereas a marked loss of RNA occurred during undernutrition, which was restored during rehabilitation.

6. The weight of the liver remained unchanged during undernutrition, despite increases in the amounts of DNA and protein. The amount of liver RNA decreased during undernutrition, but on rehabilitation showed an immediate and rapid increase. The variables measured in the liver were normal relative to body-weight, within 10 d of rehabilitation.

7. It is suggested that the growth occurring on rehabilitation is a balanced response to a single stimulus, partly mediated at the cellular level by RNA.

1. A solution of gelled maize starch and Cr-EDTA was continuously infused for 4 weeks via the abomasum into sheep of different ages. The proportions of infused α-glucoside passing the terminal ileum as glucan (ethanol-precipitable α-glucoside), dextrins (ethanol-soluble glucose polymers) and glucose, and the glucan and over-all α-glucoside disappearances in the small intestine were determined. Ethanol-soluble α-glucoside compounds in ileal digesta were further separated by paper chromatography.

2. Glucan was efficiently degraded, since little reached the terminal ileum. Most of the α-glucoside in ileal digesta consisted of glucose and dextrins (mainly short chain length oligosaccharides), suggesting that α-amylase activity was not limiting over-all starch utilization.

3. No adaptation of intestinal starch utilization was evident except that the proportion of infused α-glucoside passing the terminal ileum as glucose decreased with time.

4. A negative correlation existed between the pH and the total α-glucoside content of the ileal digesta, possibly relating to changes in the microbial activity.

5. The advantages and disadvantages of feeding with starch so as to by-pass rumen fermentation are discussed.

1. Twelve sheep were offered a diet of hay and molassed sugar-beet pulp for 18 weeks, and from the 3rd to the 16th week the sheep were divided into four groups of three; one of each of the groups received daily 170 mg trichloroacetamide, 140 mg chloroform, 30 g linseed oil or no additive.

2. The additives had no significant effect on the apparent digestibility of the dry matter, organic matter, nitrogen or energy of the diet.

3. When either trichloroacetamide or chloroform was added to the diet, methane production was almost totally suppressed and some hydrogen was produced but, although these changes persisted with chloroform, they were much reduced after 28 d of trichloroacetamide administration. When linseed oil was added to the diet the methane production was reduced by almost 15%.

4. Each additive caused a significant reduction in the concentration of total volatile fatty acids in the rumen liquor and in the molar proportion of acetic acid in the total volatile fatty acids, with a corresponding increase in the molar proportion of propionic acid. The effect was greatest immediately after the introduction of the compound into the diet but it diminished and appeared to attain a stable value within the experimental period of 98 d.

5. All the effects disappeared within 14 d of the withdrawal of the compounds from the diet.

6. It is suggested that these effects may be the result of selective effects on the rumen microflora and that further work is needed to find an additive whose effects are persistent.