1. The decrease in specific radioactivity of individual volatile fatty acids (VFA) after a single injection of tracer was monitored. The results obtained indicated the occurrence of a first-order process.

2. Regression analysis indicated the high flux of VFA through the caecal pool, equivalent to 30% of the maintenance energy requirement of the animal.

3. Interconversion of VFA was monitored, and results indicated substantial synthesis of butyric acid from acetic acid.

4. Results were obtained from animals on two dietary regimens, and these were compared with results reported for other species.

1. The contribution to acidification of the stomach contents of pigs by hydrochloric acid secretion or by lactic acid produced by fermentation was studied in fifteen suckling pigs from six litters born and reared either in a ‘conventional’ environment or in an isolated ‘clean’ environment. Sequential samples of stomach contents obtained during periods of up to 24 h were analysed for their chloride and lactic acid contents, pH and total titratable acidity. These values gave a measure of organic and inorganic acids respectively.

2. Six pigs from two litters born and reared in a ‘clean’ environment had acid secretion in the stomach at 2 d of age, and the concentrations of lactic acid in stomach contents remained low (0-40 mmol/1) throughout the suckling period.

3. Eight pigs from three litters born and reared in a ‘conventional’ environment, and a ninth pig born in this environment but moved to the ‘clean’ environment at 24 h of age, had lactic acid in concentrations of up to 250 mmol/l in stomach contents within the 1st week of life. The pattern of lactic acid production (and hence the acidity of stomach contents) was governed by the frequency of suckling.

4. Both between- and within-litter variation in the age of onset of HCl secretion was evident in the group reared in a ‘conventional’ environment, and when HCl secretion did occur it was usually accompanied by a reduction in lactic acid production.

5. It is concluded: (I) that the environment at birth is important in determining the fermentative ability of the stomach flora; (2) that if lactic acid is produced in large amounts in the stomach, it may partly or completely inhibit acidification by HCl.

1. Fifty unselected consecutive cases of protein-energy malnutrition (PEM) presenting at the General Out-patient Clinic of the University College Hospital, Ibadan were classified as marasmus (twenty), kwashiorkor (nineteen) marasmic-kwashiorkor (seven) and undernutrition (four) according to the Wellcome Classification of PEM (Lancet, 1970; Waterlow, 1972).

2. The mean age of the children with marasmus (22.4 months) and of the children with kwashiorkor (25.4 months) were not significantly different. The children with marasmickwashiorkor (27.8 months) were significantly older than the children with marasmus.

3. The deficits in weight- and length-for-age were similar to values previously reported (Waterlow, 1972) even though the children with marasmus tended to be older and the children with kwashiorkor younger than has been reported. Values obtained for the deficit in length-for-age suggested that the children with marasmus had been undernourished from birth whereas the children with kwashiorkor had apparently grown normally until they were 10 months old. It is possible that the history of growth in the first year of life influences the final form of PEM in these two groups of children.

4. Forty-nine of the fifty children had been breast-fed for at least 9 months and nine children had been breast-fed for 2 years. Of the twenty children with marasmus nine were still receiving some breast milk. The diets fed to weaned children with marasmus and to children with kwashiorkor were identical and consisted solely of a maize-starch gruel with no supplementation of protein or vitamins. The similarity in the dietary histories of the two main groups of children suggests some uncertainty concerning a specific role for protein deficiency in the development of kwashiorkor.

5. All the children had had similar infections. The most common of these were measles (morbilli) (40% of all cases) and gastrointestinal infections. However the children with marasmus had a history of chronic diarrhoea whereas the children with kwashiorkor had had more acute diarrhoea.

6. The similar dietary histories but dissimilar histories of infection given by the mothers of the children with marasmus as opposed to those with kwashiorkor suggest that recurrent diarrhoea was at least partially responsible for the chronic undernutrition in the group of children with marasmus. Furthermore although the weaning diets were inadequate the final deterioration in nutritional status was precipitated by gastroenteritis, often following measles.

1. In order to study the ability of the ileum of the sheep to digest and absorb protein, casein or gluten were infused into the intestine of rams through cannulas inserted at distances of 0·05, 7, 9 and 15 m from the pylorus. Amounts of casein or gluten containing 10–20 g nitrogen were infused during 24 h, in animals given a low-N diet.

2. N balance was negative during the preliminary period when no infusion was given; infusion of casein or gluten increased the daily N retention to 5–15 g.

3. Infusion of proteins into the intestine did not induce an increased activity of pancreatic proteases in digesta withdrawn from the lower part of the intestine.

4. The increased N retention after the infusion of proteins into the lower part of the intestine indicates a considerable capacity of this section of the intestine to digest and absorb proteins.

1. 14C-labelled lysine, glutamic acid and methionine were each administered as single infusions through catheters in the jugular veins of pigs between 28 and 42 d old, receiving either a low-protein (LP) (140 g protein/kg), or a high-protein (HP) (200 g protein/kg) diet. The pigs received 40 g diet/kg body-weight per d.

2. l-[U-14C]lysine and l-[U-14C]glutamic acid were both rapidly removed from the plasma; 3 min after completion of the infusion less than 10% of the activity from the [14C]-lysine, and between 10 and 20 % of the activity from the [14C]glutamic acid remained in the plasma.

3. In pigs killed 15 min after infusion of either [14C]lysine or [14C]glutamic acid 26% of the activity from the dose of lysine was in the liver of those receiving the LP diet, whereas the corresponding value was only 16% for those which had received the HP diet. The uptake of activity from [14C]glutamic acid by the liver was unaffected by the level of protein in the diet. More activity from [14C]lysine than from [14C]glutamic acid was recovered in the spleen, heart and brain.

4. The recovery of the activity from [14C]lysine as 14CO2 in the 6 h after the infusion of the dose was lower for the pigs on the LP diet (2.7 %) than for those on the HP diet (4.8%). The corresponding values for [14C]glutamic acid infusion were 34 and 52% respectively.

5. Supplementing the LP diet with five successive increments of 1.5 g DL-methionine/kg resulted in an increase from 8 to 17% dose in the recovery of activity as 14CO2 from a dose of l-[I-14C]methionine, whereas with the same supplementation of the HP diet the recovery increased from 8 to 24 % dose.

1. Free amino acid concentrations in the plasma have been compared with those in liver and quadriceps muscle, in rats fed on diets containing 209 (control) and 31 (low-protein) g protein/kg. The effects of the low-protein diet on diurnal variations in these values were also measured.

2. In the plasma, the total amino acid concentration was significantly lower in animals given the low-protein diet, at all times of day except 12.00 hours. In the liver, and to a lesser extent the muscle, total amino acid concentration was maintained.

3. In the control animals, diurnal variation in the concentrations of both essential and non-essential amino acids was very similar in plasma, liver and muscle. In animals given the low-protein diet, although the same diurnal pattern was maintained for non-essential amino acids, that occurring among the essential amino acids had virtually disappeared.

4. In plasma, the mean 24 h concentration of essential amino acids decreased from 24· mmol/l in control animals to only 1·29 mmol/l in the low-protein-fed animals. Concentrations in muscle and liver were reduced by a similar proportion (from 8·6 to 5·56 μmol/g and from 8·67 to 5·05 μmol/g respectively). Conversely the concentrations of non-essential amino acids in animals given the low-protein diet were increased in plasma (from 1·53 to 2·00 mmol/l), muscle (from 12·5 to 14·3 μmol/g), and liver (from 16·8 to 20·5 μmol/g), muscle showing the lowest increase.

5. With the exceptions of lysine, threonine, cystine and tyrosine, the concentrations of all other essential amino acids were reduced more in liver than in muscle. The relationship between this and the failure to maintain plasma albumin concentrations is discussed.

1. Preruminant calves, fistulated in the abomasum and distal ileum, were given by infusion into the abomasum, at intervals of 2–3 d, single experimental feeds of cow's milk or a synthetic milk diet in which the protein source was casein or a soya-bean product. Polyethylene glycol (PEG) and phenol red were included as markers.

2. After infusion of the experimental feed, measurements were made of transit time from proximal duodenum to distal ileum and mean ileal flow-rates for the first 3 and 21 h after food residues reached the distal ileum. PEG recoveries for these two periods and net nitrogen absorption up to the distal ileum were also determined. In some experiments sodium, potassium and magnesium concentrations and numbers of viable bacteria in ileal digesta were determined.

3. Measurements of passage of digesta, recovery of marker and net N absorption did not differ greatly between calves given cow's milk and the synthetic milk diet containing casein. Compared to the casein-based diet, a diet based on heated soya-bean flour given to a calf for the first or second time produced a somewhat higher ileal flow-rate and a significantly lower net N absorption. Net N absorption was even lower when a calf received a diet containing unheated soya-bean flour.

4. Calves given the diet containing heated soya-bean flour on several occasions appeared to develop a sensitivity to the flour, and after further feeds containing it they had significantly higher rates of ileal flow (accompanied by correspondingly high rates of Na and K flow), lower small intestine transit times and lower net N absorption values than similarly fed unsensitized calves. They also had significantly lower rates of passage of marker in the first few hours after food residues reached the ileum, indicating inhibition of abomasal emptying. Over all, the changes indicated a severe disturbance in digestive function which was not caused by abnormal bacterial growth and may have been due to a gastrointestinal allergy.

5. Diets prepared from water-extracted flour and from soya-bean-protein isolate also led to digestive disturbances in sensitized calves, but those containing concentrates prepared by extracting soya-bean meal with hot aqueous ethanol did not.

1. A study has been made by gel-filtration techniques of the soluble copper- and zinc-binding proteins in rat liver after both intraperitoneal injection of Cu and dietary Cu supplementation.

2. Liver Cu and Zn concentrations increased after injection of Cu, both metals accumulating in the cytosol, mainly in a fraction with an apparent molecular weight of (about 12 000)

3. When Zn-deficient rats were injected with Cu, there was little change in liver Zn concentration and the occurrence of Cu in the low-molecular-weight form (about 12 000) was more transient. At most periods after injection, Cu accumulated mainly in a fraction with a molecular weight greater than 65 000.

4. When the rats were Cu-loaded by dietary supplementation, virtually no Cu or Zn was found in the low-molecular-weight form in Zn-deficient rats, although they were found in the Zn-supplemented animals.

5. The results suggest that Zn is essential for the accumulation of Cu in this form, but not for Cu to stimulate production of the metal-binding protein by a process requiring active protein synthesis.

1. Six closely shorn sheep were given brome grass (Bromus inermis) pellets at 1 h intervals and maintained at ambient temperatures of −1 to 1° and 18–21° for 28 d. Measurements of digestion were made during the last 10 d of temperature exposure.

2. Cold exposure resulted in a reduction in apparent dry matter (DM) digestibility from 0·482 to 0·450, and of apparent digestibility of organic matter (OM) from 0·511 to 0·477. Neither apparent digestibility nor retention of nitrogen was affected.

3. Apparent digestibility of OM in the rumen decreased from 0·300 to 0·242 with cold exposure, and was highly correlated with turnover time in the rumen of 108Ru, which was used as a particulate marker.

4. The efficiency of microbial synthesis (g N incorporated into microbial cells/kg OM apparently digested) was correlated with the dilution rate of the solute marker (51Cr) and with the turnover time of the particulate marker (103Ru) in the rumen.

5. Digestion in the intestine of DM and OM accounted for significantly more of apparent digestion in the whole gastrointestinal tract for sheep kept in the cold than for sheep kept in the warm. The apparent digestibilities of DM and OM entering the intestines were similar in sheep on both treatments, but significantly more non-ammonia-N was digested in the intestines of cold-exposed sheep.

6. The influence of dilution rate of rumen fluid on the efficiency of synthesis of microbial cells in the rumen is discussed.

1. Lipolytic and proteolytic activities and pH values were determined in secretions collected from innervated abomasal pouches and in abomasal contents from preruminant calves given liquid diets.

2. No lipolytic activity was detected in pouch secretions collected during 1 h after feeding, though lipolytic activity was present in abomasal contents; pepsin (EC 3.4.23.1) and rennin (EC 3.4.23.4) were present in both pouch secretions and abomasal contents. The pH values of pouch secretions ranged from 1.2 to 1.8 and those of abomasal contents from 4.2 to 5.9.

3. When diet was placed directly into the abomasal pouch soon after feeding, the pH values of pouch and abomasal contents decreased similarly (i.e. from 6.3 to approximately 5). Protease activity (U/ml) of pouch contents ranged from 0.1 to 0.8 and that of abomasal contents from 0.1 to 0.2. No lipolytic activity was detected in pouch contents, though abomasal contents contained 0.6 to 1.2 U/ml and when the diet contained milk-fat as the dietary fat source considerable lipolysis of triglycerides containing shorter-chain fatty acids was found.

4. It is concluded that there is no significant secretion of lipolytic enzymes by the fundal mucosa and that the lipolysis of triglycerides in the abomasum of the preruminant calf is due predominantly to a lipolytic enzyme in saliva.

1. The effects of copper and zinc on organ cultures of chick embryo cartilage and bone maintained in low-trace-metal, chemically defined media for up to 8 d were studied macro-scopically, histologically and histochemically. Length and wet-weight measurement of explants were assessed statistically.

2. No effects were found with Cu concentrations of 0·5–1·5 μg/ml medium. Between concentrations of 5 and 40μg Cu/ml medium, lengths and wet-weights of cartilage cultures decreased significantly (P < 0·001) compared with controls. The decrease was directly proportional to increasing Cu concentration, and that of the length was greater with increasing period of culture (P < 0·001).

3. With 5–20 μg Cu/ml medium cartilage and bone became yellow in colour, and chondrocytes were swollen, rounded and basophilic. They were detached from their lacunae and the quantity of matrix was reduced. Loss of alkaline phosphatase (EC 3.1.3.1) activity and disappearance of glycogen accompanied the degeneration. Osteogenesis ceased, cells failed to divide and mature, lost their enzymes and died. Cu did not accumulate in the bone matrix.

4. The direct toxic effects of Cu for cartilage and bone may underlie some of the skeletal changes in hepatolenticular degeneration (Wilson’s disease).

5. As Zn concentrations were increased from 2·5 to 7·5 μg/ml medium, lengths and wet-weights of cartilaginous cultures were significantly increased (P < 0·001). As Zn concentrations were further increased (from 10 to 40 μg/ml medium), lengths and wet-weights were significantly decreased (P < 0·001).

6. Zn stimulated chondrocyte division and vacuolation of cytoplasm. With higher Zn concentrations toxic changes of granular basophilia, lacunar detachment and necrosis were seen. Differentiation and functioning of osteoblasts, osteoclasts and chondroclasts were stimulated by Zn.

7. Zn was found in bone matrix, osteoblasts, osteocytes and hypertrophied chondrocytes.

1. Nutritional evaluation of dried tomato pomace (DTP-20) as a source of protein was carried out using weanling rats. Comparisons were made with casein (CS), soya-bean meal (SOM-45) and the hydrocarbon-grown yeast Toprina (BP-T). The growth-promoting effects of the diets were evaluated over a period of 28 d of ad lib. feeding.

2. The unsupplemented DPT-20 had a protein efficiency ratio (per) of 2.18±0.13 and a net protein utilization (npu) of 0.55. The addition of dlmethionine (5 g/kg) resulted in a per of 1.74±0.15 (t 2.99, P < 0.01) and a npu of 0.40, while the addition of an amino acid mixture resulted in a per of 2.33±0.08 (t 1.84, P < 0.1) and a npu of 0.70.

3. The reason for the decrease in growth and the reduced per and npu values recorded for the methionine-supplemented group of rats is not clear and it is discussed in connexion with an imbalance or a slight toxicity caused by the added amino acid.

1. Livers from rats fed on a standard diet were perfused with whole blood, and infused continuously with glucose and fructose at equimolar rates.

2. Infusion of fructose increased both the secretion of very-low-density-lipoprotein (VLDL)-triglycerides and the incorporation of free fatty acids (FFA) from the perfusate into VLDL-lipids, but neither of these two processes was affected by infusion of glucose.

3. Infusion of fructose decreased the oxidation and increased the esterification of FFA, but glucose infusion had no effect on these processes. When fructose and glucose were infused together there was a further decrease in oxidation.

4. When fructose was infused alone or together with glucose, blood concentrations rapidly became stabilized at those found in the hepatic portal vein in vivo, with similar rates of hepatic uptake to those found in the intact animal. Infusion of glucose alone resulted in continuously increasing perfusate glucose concentrations, and rates of uptake which were only 20 % of those for fructose. Blood glucose concentrations were reduced, and lactate concentrations were increased by fructose infusion, and when glucose and fructose were infused together there was a greatly increased rate of glucose uptake.

5. Liver glycogen was not affected by the infusion of fructose or glucose alone; however, their combined addition significantly increased its concentration.

6. Uptake of perfusate FFA was not affected by either fructose or glucose infusions.

7. The results are discussed in terms of the differences in nutrition and metabolism between glucose and fructose, with particular reference to the development of hyper- triglyceridaemia.

1. Food intake, and the rates of protein, lipid and energy deposition during growth were measured for lean and congenitally obese (fatty) female Zucker rats given diets of different protein content ad lib. Six semi-synthetic diets were used, which contained 40, 100, 150, 300, 500 and 700 g casein/kg (diets 40C, 100C, 150C, 300C, 500C and 700C).

2. Dietary treatments began when the rats were 34 or 35 d old. Collections of urine and faeces were analysed for energy content. The total carcasses of all the rats were analysed individually for protein, lipid and energy.

3. In the first experiment, twelve rats of each phenotype were given diets 150C or 300C. Four fatty and four lean rats were killed at 50, 66 and 98 d of age. In the second experiment groups of four fatty and four lean rats were given diets 40C, 100C, 500C and 700C ad lib. until they were killed at 66 d of age. Other groups of fatty rats were pair-fed from 35 to 67 d of age on diets 100C and 500C. Rats were also killed at 24 and 34 d of age to provide initial samples for the comparative slaughter procedure.

4. When given food ad lib., fatty and lean rats had identical rates of protein deposition at all ages and for all diets, but lipid and energy deposition were always much greater in the fatty rats. Food intake was also much greater for the fatty rats (except on diet 40C). Differences in food intake and growth rate attributable to diet were most pronounced for the range of diets 40C-150C.

5. Fatty rats pair-fed to lean rats deposited less protein but about twice as much energy and lipid as lean rats on the same diets.

6. The results are discussed in relation to existing theories of appetite control. It appears that food intake is precisely regulated in the congenitally obese Zucker rat. This regulation is intimately linked with the impetus for protein deposition and the rates of retention of lipid and energy appear to be of no importance in relation to appetite control.

1. Deficits in weight- and length-for-age, and serum albumin and transferrin concentrations were determined for children who were either marginally undernourished (twenty-five children) or suffering from either marasmus (thirty-two children) or kwashiorkor (twenty-six children) defined according to the Wellcome Classification (Waterlow, 1972). The measurements were also made in eight children with kwashiorkor after the loss of oedema, and in sixteen children who were recovering from either marasmus or kwashiorkor.

2. The mean concentration of serum albumin was similar for children from the ‘under-nourished’ group and from the group with marasmus, but was significantly reduced in those with kwashiorkor.

3. The concentration of serum transferrin was significantly reduced in both the group of children with marasmus and those with kwashiorkor. The serum transferrin concentration was significantly lower in children with kwashiorkor when compared with the level in those with marasmus.

4. Seventeen children (seven with kwashiorkor and ten with marasmus) died. These children were neither lighter nor shorter than the severely malnourished children who survived. The concentration of serum albumin was not lower in the children who died than in those who survived.

5. In contrast to the results for serum albumin concentrations, the children who died had significantly lower levels of serum transferrin than those who survived.

6. There was a significant linear relationship between serum transferrin concentrations and the deficits in length-for-age (P < 0·05) and weight-for-length (P < 0·001) in the marginally undernourished children. The deficit in weight-for-length was also linearly related to the serum transferrin concentrations (P < 0·001) in children recovering from severe malnutrition.

7. It is suggested that the measurement of serum transferrin concentrations provides an index of severity in severely malnourished children, and should prove useful in field assessments of nutritional status.

1. The forms of vitamin B12 were determined in foods, most of which had been prepared for consumption.

2. Five forms were detected: adenosylcobalamin, hydroxocobalamin, methylcobalamin, cyanocobalamin and sulphitocobalamin. Adenosylcobalamin and hydroxocobalamin were the predominant forms.

3. The intestinal absorption of [57Co] sulphitocobalamin was estimated and found to be lower than that of [58Co]cyanocobalamin.

1. In a preliminary experiment, growth of conventional chicks given a basal diet containing adequate amounts of all the essential but none of the non-essential amino acids was improved by supplements of 10·3 g urea or 50·4 g glutamic acid/kg diet or both.

2. In the main study the effects of supplementing the basal diet with 2·6 g urea/kg were compared in groups of sixteen germ-free and conventional chicks.

3. The germ-free chicks did not benefit from the urea supplement whereas the conventional birds showed improved food conversion efficiency and significantly better growth.

4. In both environments nitrogen retention ((mg N intake – mg N excreted) ÷g food intake) was higher in the birds given urea, but N utilization ((mg N intake – mg N excreted) ÷ mg N intake) was reduced. This reduction was greater in the germ-free birds.

5. There was a small increase in plasma ammonia concentration in the germ-free birds given urea but a significantly greater increase in the corresponding conventional group.

6. Plasma uric acid concentrations were variable in both groups, and much lower than the normal range. They followed a similar pattern to the plasma ammonia values.

7. More insoluble N was excreted by the conventional chicks given urea than by the corresponding germ-free group, or by either group given the basal diet.

8. It was concluded that the gut micro-organisms are responsible for the growth-promoting effect of urea, presumably through release of ammonia by bacterial urease (EC 3.5.1.5) and its consequent incorporation into amino acids.

1. Seasonal variations in plasma retinol-binding holoprotein concentration have been found in two groups of entire ewes and in a control group of wethers (castrated rams).

2. In each group retinol-binding holoprotein level was minimal in summer and increased to peak values in September just before the autumn breeding season.

1. The digestibility of the cell wall polysaccharides of an alkane-grown yeast in different parts of the digestive tract of two veal calves fitted with re-entrant cannulas at the end of the ileum was studied by replacing part of the skim-milk powder of their ‘normal’, milk-substitute (all-milk-protein) diet by yeast (yeast diet).

2. The lactose and glucose of both the all-milk-protein diet and the yeast diet were almost completely digested before the end of the ileum. During this digestion a small amount of oligosaccharides composed of galactose and glucose was synthesized. These oligosaccharides were digested again in the large intestine.

3. The constituent sugars of the water-soluble fraction of the yeast cell wall carbohydrates were glucose and mannose. The 0.5 m-sulphuric acid-hydrolysate of the water-insoluble fraction contained glucose and mannose and the 12 m-H2SO4-hydrolysate only glucose.

4. Digestibilities of these fractions over the whole gastrointestinal tract ranged from 0.77 to 0.90. Digestibilities measured at the end of the ileum varied considerably between the two animals and averaged only about 0.40.

5. These findings suggest that the cell wall polysaccharides of yeast are digested very little by the normal digestive enzymes of the calf's small intestine, but are used as a substrate by the bacterial flora which are mainly concentrated in the large intestine.

1. Rats were maintained for 10 d on a semi-synthetic diet containing 700 g glucose or 700 g fructose/kg. Individual enzymie reactions in bile acid synthesis and metabolism were studied by measuring the 7α-hydroxylation of [4-14C]cholesterol, the 12α-hydroxylation of 7α-[6β-3H]hydroxy-4-cholesten-3-one, the 26-hydroxylation of 5β-[7β-3H]cholestane-3α,7α-diol and the 6β-hydroxylation of [3H]lithocholic acid in liver homogenates.

2. The serum cholesterol level was approximately the same in both groups of animals, but the serum triglyceride level was almost twice as high in the fructose-fed rats compared to the glucose-fed rats.

3. The 6β-hydroxylation of [3H]lithocholic acid was increased by about 20% in the fructose-fed rats compared to the glucose-fed animals. The activities of the other enzymic reactions studied did not differ significantly between the two groups of animals. The findings are discussed in relation to previous knowledge concerning mechanisms regulating triglyceride, pre-β-lipoprotein and bile acid synthesis.