The effect of acetic or propionic acid rumen fermentation patterns on whole-body protein turnover, tissue protein synthetic rates and body composition was investigated in growing lambs. Protein turnover was assessed using a continuous intravenous infusion of [2,3-3H]tyrosine and tissue protein fractional synthetic rates (FSR) from the specific activities of plasma free, intracellular free and tissue bound tyrosine. Only the FSR of muscle tissue approached significance. The high FSR in the propionic group was attributed to the high plasma insulin concentration. Values for whole-body protein synthesis, corrected for tyrosine oxidation, were similar to those obtained by summating protein synthesis in individual tissues, confirming that tyrosine oxidation should be measured accurately if reliable whole-body protein synthesis values are required. Tyrosine oxidation and flux were high in the acetic acid group, suggesting that amino acids are used for gluconeogenesis. The high protein turnover rate probably ensures an adequate supply of gluconeogenic amino acids and that the penalty of mobilizing body proteins for gluconeogenic amino acids is minimal. In the propionic acid group, high plasma glucose and insulin concentrations were associated with a low protein turnover rate, high ratio of deposited: synthesized protein and a high body fat content. It is concluded that changing the proportion of ruminal volatile fatty acids influences protein turnover, protein synthesis and the efficiency of protein retention. Such factors probably contribute, indirectly, to the observed differences in body composition.

Sequential measurements of body density or total body water yield inaccurate estimates of body composition change unless the proportions of protein, water and mineral in lean tissue remain constant. Since rates of change of bone mass in adults are likely to be small compared with those of fat or protein mass, volume and total body water measurements can be combined in a three-compartment model to estimate fat and protein changes assuming constant mineral mass. This new model minimizes the bias inherent in estimates of fat or protein changes made from separate density or total body water measurements.

A series of four nitrogen-balance experiments was carried out with growing pigs to determine the optimum balance amongst the amino acids in the diet. The reduction in N retention when 20 % of a single amino acid was removed from the diet was used to calculate a dietary amino acid pattern in which each amino acid would he equally limiting. A mixture of amino acids simulating the amino acid pattern of casein was used with the same efficiency as casein. From two successive deletion experiments an optimum balance amongst the essential amino acids was derived. Expressed relative to lysine = 100 this had threonine 72, valine 75, methionine + cystine 63, isoleucine 60, leucine 110, phenylalanine + tryosine 120, tryptophan 18. No estimate was made for histidine. Essential amino acids in this pattern were mixed with non-essential amino acids in ratios of 36:64 up to 57:43. The highest efficiency of N retention was achieved with diets having a ratio of at least 45:55. This included (g/16 g N) lysine 6 5, threonine 4.7, valine 4 9, methionine + cystine 4.1, isoleucine 3 9, leucine 7.2, phenylalanine + tyrosine 7.8, tryptophan 12. The N of diets with this amino acid pattern was utilized significantly better than when the pattern proposed by the Agricultural Research Council (1981) was used. The flow of amino acids past the terminal ileum of pigs given the semi-synthetic diet with this amino acid pattern was no greater than that observed with protein-free diets. The proposed pattern thus describes the intrinsic requirements of the growing pig for absorbed amino acids.

An experiment was conducted using steers cannulated at the rumen, duodenum and ileum to study the effects of increasing the levels of barley and fishmeal in straw-based diets. Diets A, B, C and D contained ammonia-treated straw, barley and fishmeal in the ratios, 67:33:0, 66:23:11, 53:47:0 and 52:36:12 (by weight) and were offered in daily amounts of 3·9, 3·9, 4·8 and 4·8 kg dry matter. The effects of barley were attributable to increased intakes of digestible organic matter and consequently to increased flows of microbial matter to the duodenum. There were no modifications in the balance of energy to nitrogen-yielding nutrients available for absorption. Introducing fishmeal into diets improved digestibility of cellulose and xylose by up to 6.7 and 4.7 % respectively, and shifted digestion towards the large intestine. Second, it increased amino acid N supply to the small intestine which averaged 52·2, 63·2, 68·8 and 84·0 g/d with diets A, B, C and D. Some changes were also noted in the balance of amino acids absorbed. Consequently, the contribution of amino acids to metabolizable energy intake increased with the proportion of fishmeal in diets (0·17, 0·20, 0·18 and 0·21 for diets A, B, C and D).

Growth rates measured in heifers amounted to 259, 431, 522 and 615 g/d for diets A, B, C and D. They appeared to be related to intestinal amino acid supply.

The doubly-labelled water (2H218O) method was used to measure total energy expenditure (TEE) in ten non-pregnant, non-lactating (NPNL), six pregnant (P) and fourteen lactating (L) women in a rural Gambian community. Measurements were made on free-living subjects at a period of peak energetic stress when high agricultural work loads coincided with a hungry season to induce moderately severe negative energy balance. TEE averaged 10.42 (SD 2.08) MJ/d, equivalent to 1.95 (SD 0.38) times resting metabolic rate (RMR). The energy cost of physical activity plus thermogenesis, derived as TEE – RMR, averaged 4.94 (SD 1.96) MJ/d. Expressed per kg body-weight (103 kJ/kg per d) this component of expenditure was 2.5 times greater than comparative values from inactive, affluent women studied previously (39 kJ/kg per d). Estimated energy intake (EI) in a subset of the women (n 13) was only 4.80 (SD 1.58) MJ/d, yielding an apparent deficit of 6.08 MJ/d between EI and TEE. Weight changes suggested that endogenous fat oxidation accounted for only about 0.85 MJ/d, leaving an unexplained difference of over 5 MJ/d. Critical analysis of possible errors suggests that the new doubly-labelled water method has provided the most reliable estimates and that the estimates of EI were substantially in error. This finding has important consequences for other food intake studies.

The measurement of energy expenditure has wide applications in clinical and scientific studies. Ethical and practical problems, however, have limited the acquisition of information on total energy expenditure in infancy. The doubly-labelled-water technique, recently validated for use in infants, has now been used to measure, non-invasively, total energy expenditure in a cohort of forty-one normal, full-term infants at or close to 1·5, 3 and 6 months of age. Mean total energy expenditure was 270, 280 and 330 kJ/kg per d at these ages. Centiles for total energy expenditure in early infancy are presented; it is suggested such data are most appropriately expressed as kJ/√ (kg body-weight per d). These findings will be of importance in the re-evaluation of energy requirements in infancy and in the study of lesions in energy metabolism in disease states at this age.

Recent reports indicate that oats have a relatively low glycaemic effect in comparison with other carbohydrate food, and that their consumption leads to a reduction in plasma-cholesterol levels in man. These properties may be due to a soluble non-starch polysaccharide in oats. The present study was undertaken to explore the physiological properties of this material. Three groups of male Wistar rats were meal-fed on a control diet free of soluble dietary fibre for 10 d before being given a 10 g meal of either the control diet, a diet containing oat gum (β-glucan), or finely ground rolled oats. The contents of the stomach, small intestine and caecum were later recovered and the weight, water content and viscosity were measured. The small intestinal contents from oat-gum-fed or oat-fed rats had a higher wet: dry weight ratio than that of the controls, and a higher viscosity. In in vitro studies the rate of uptake of d-galactose by jejunal rings was reduced in the presence of oat gum. The estimated Michaelis-Menten constant for the carrier-mediated component in the presence of oat gum was higher than that for controls, but the maximum transport rates were similar. Cholesterol uptake by everted jejunal sacs was progressively inhibited by increasing concentrations of oat gum in the mucosal medium. It is concluded that increased viscosity of the contents of the small intestine may contribute to the low glycaemic index and hypocholesterolaemic effects of oats in man. Oats appear to be amongst the few palatable sources of viscous dietary fibre in the conventional Western diet.

Adult male rabbits were fed on semi-purified diets containing soya-bean protein isolate, casein or formaldehyde-treated casein as the protein source and 1 g cholesterol and 5 g of the non-absorbable marker chromic oxide/kg diet. The concentration of cholesterol in serum and in liver was increased on both the casein and formaldehyde-treated-casein diets. Excretion of bile acids and their concentration in faeces were lower in rabbits fed on casein or formaldehyde-treated casein when compared with rabbits fed on soya-bean protein. Apparent digestibility of nitrogen was lowest when formaldehyde-treated casein was fed, and highest on the casein diet. In rabbits fed on casein treated with formaldehyde, higher proportions of N were found in the water-soluble and trichloroacetic acid-insoluble protein fractions of the gastrointestinal tract contents compared with rabbits on the other two diets. Absorption of phosphate from the gastrointestinal tract was higher in rabbits fed on casein than in rabbits fed on soya-bean protein or formaldehyde-treated casein. The results indicate that, in rabbits, protein digestibility may not be an important determinant of serum cholesterol.

The purpose of the present study was to compare basal metabolic rates (BMR) of pregnant Nigerian women from rural and urban areas with values from similar studies in other Third World countries. We also investigated possible changes in BMR during the course of pregnancy. An open-circuit indirect calorimeter was used to measure BMR and energy expenditure (EE) during sedentary activity in forty-one pregnant Nigerian women. The results showed marked variability in BMR among individuals. A correlation analysis between BMR and other biological and physical characteristics revealed body-weight and gestation as the only variables related to BMR and oxygen consumption.

The study revealed no significant difference between BMR and EE of sedentary activity in the subjects. The wide variability may have been due to the nutritional status of the subjects studied, who were drawn largely from the lower socioeconomic groups of Nigerian society. The present study shows that socioeconomic status and nutritional interventions should be taken into account when framing recommendations for maternal nutrition during pregnancy.

The effects of ingestion of poorly digestible carbohydrates on bacterial transformations of cholic acid and β-muricholic acid were studied in rats fed on increasing levels of lactose, lactulose, amylomaize or potato starches. Each level was given for 3 weeks and, at the end of each dietary treatment, bile acid faecal composition was analysed and a group of six rats was killed every 4 h during 24 h to determine the amounts of fermented carbohydrate and fermentation characteristics (caecal pH, volatile fatty acids (VFA) and lactic acid concentrations). Fermentation of carbohydrates decreased caecal pH and enhanced caecal VFA and lactic acid concentrations. Irrespective of the poorly digestible carbohydrate, the variation of bacterial transformation always occurred in the same way: the bacterial transformation of β-muricholic acid into hyodeoxycholic acid was the first to disappear, while ω-muricholic acid formation increased; second, cholic acid transformation decreased and finally all bile acid transformations were strongly affected. There was a significant correlation between bile acid transfer and the minimal caecal pH in vivo. This effect of pH was similar in vitro. To determine whether the levels of bacteria which transformed bile acids were modified, rats fed on the highest amounts of poorly digestible carbohydrates were introduced into isolators and carbohydrate feeding was stopped. Caecal pH recovered its initial value but bile acid transformations remained changed, suggesting that the intestinal microflora were modified by ingestion of fermentable carbohydrates.

In six normal subjects administered 5 μCi of an oral dose of a commercially available 14C-labelled cellulose, significant amounts of 14CO2 were detected in expired air within 30 min, suggesting that other 14C-labelled non-cellulosic material was present. Chemical and microscopical examination confirmed that starch was the principal contaminant. The commercial preparation was purified using amyloglucosidase (EC 3.2.1.3) digestion following gelatinization of the starch by autoclaving. Subsequent administration of the purified cellulose to a further six normal subjects decreased the expired air 14CO2 during the subsequent 10 h from 13.0 (sd 4.0) to 4.1 (sd 1.9)%. Administration of the purified product to a further group of four normal subjects, before and after a regimen of increased dietary fibre, showed a cumulative increase in expired 14CO2 over 24 h from 7.9 (sd 1.1) to 12.1 (sd 2.6) % on fibre. In six ileostomy subjects the cumulative excretion of 14CO2 was greatly decreased compared with normal controls (3.0 (sd 1.14) and 10.5 (sd 3.9) % respectively). In constipated subjects expired 14CO2 continued beyond 48 h, in contrast to normal subjects where expired 14CO2 at this time was negligible.

Adult male rats were fed on a control diet containing (g/kg) carbohydrate 600, lipid 35 and protein 190, or on a high-fat diet containing carbohydrate 360, lipid 420 and protein 120. After 30 d, the high-fat diet provoked a decrease in serum cholinesterase (EC 3.1.1.8) activity which was reversed by feeding rats on the control diet. The observed decrease after 90 d on the high-fat diet was not seen if a simultaneous daily intraperitoneal injection of a lipotrophic agent containing (mg/kg) S-adenosyl-l-methionine 3, coenzyme A 0.1, UDP-glucose 30 and CDP-choline 1.5 was given to rats on the high-fat diet. The findings are discussed in relation to the apparent susceptibility of serum cholinesterase to dietary components and its possible role in lipid metabolism.

Cellular sodium transport via the Na+, K+-ATPase contributes significantly to daily energy expenditure. The effect of a meal on leucocyte Na+ transport and intracellular electrolytes was therefore investigated in lean normal subjects at room temperatures of 23° and 33°, to determine if the Na pump responds to the need for thermogenesis. In the fasting state, the ouabain-sensitive efflux rate which reflects active Na+ transport, and the intracellular electrolytes were similar. At 2 h after eating a 4·2 MJ (1000 kcal) meal, the ouabain-sensitive efflux rate constant rose when the room temperature was 23° but not at 33°. The ouabain-sensitive Na+ efflux rate, an index of active Na+ transport, 0rose post-prandially at 23° only. The post-prandial activation of leucocyte active Na efflux in normal subjects was blunted at higher environmental temperatures, when the need for thermogenesis was reduced.

Under conditions of food deprivation the lipid fraction of red seabream (Pagrus major) larvae shows patterns of conservation or loss in the profile of fatty acids and lipids. These changes were used for qualitative formulation of the dietary requirements of this species. Red seabream larvae were deprived of food for 5 d after hatching. Their lipid was extracted, weighed and analysed by gas–liquid chromatography and iatroscan for the presence of twenty-four fatty acids including n−3 polyunsaturated fatty acids (PUFA), four polar lipids (PL) and four neutral lipids (NL). The results show an exponential decline in lipids with food deprivation, from a mean of 27.7 down to 11.8 mg/g wet larvae weight (LW). This loss could mainly be attributed to a decline in NL from 22.4 to 7.7 mg/g LW, in triacylglycerols, from 21 to 1 mg/g LW, and a change in cholesterol, from 1.3 to 4.2 mg/g LW after 5 d of food deprivation. PL declined from 5.3 to 4.1 mg/g LW in this period. The chief components of this fraction were phosphatidyl choline, and phosphatidyl ethanolamine. Among the fatty acids, the chief decline was observed in saturates and monoenes. Carbon chain lengths of 14 to 18 made up 18.2 mg/g LW in hatched larvae, but only 4.8 mg/g LW in larvae which were deprived of food for 5 d after hatching. n−3 PUFA were lost at a slower rate, from 5.4 to 3.5 mg/g LW for the same period, suggesting that they were conserved. Finally, early larvae of red seabream showed a reduced rate of loss of n−6 relative to n−9 fatty acids, suggesting that the latter were used preferentially as an energy source.

The effect of frequency of feeding (once daily or six equal portions at intervals of 3 h) of diets containing lysine (6.4 g/kg) supplied as either protein-bound or free lysine on the metabolism of essential amino acids was investigated in pigs over the 23–34 kg weight range. The amounts of radioactivity from 14CO2 produced by the pigs given oral doses of [14C]lysine or [14C]phenylalanine were determined. [14C]Lysine was confirmed to be unsuitable presumably because the oral dose was diluted by the dietary free lysine or was absorbed ahead of the protein-bound lysine, or both. With [14C]phenylalanine addition, there was a significantly (P < 0.01) greater production of 14CO2 by pigs fed once daily on the diet containing free lysine. However, with frequent feeding, there was no significant difference (P > 0.05) in the amount of 14CO2 produced by pigs from [14C]phenylalanine for either diet. Growth responses of the pigs were lower when the diet containing free lysine was given once daily (P < 0.01) but were similar when the diets were given frequently. It is concluded that the more rapid absorption of free lysine by growing pigs fed once daily results in an imbalance of amino acids at the sites of metabolism. This leads to greater oxidation of essential amino acids than occurs when all the amino acids are supplied in the protein-bound form. With frequent feeding, a better balanced supply of amino acids is absorbed, leading to similar rates of oxidation of excess essential amino acids from diets containing either free or protein-bound lysine.

The present study was designed to examine the effect of cellulose (CL) on postprandial glycaemia and insulinaemia when ingested with glucose (G), casein (CS) and maize oil (CO) in various combinations. The study was conducted on five healthy male volunteers, on each of whom five meal tolerance tests were performed. The meals were isoenergetic and consisted of G; G and CL; G, CS and CL; G, CO and CL; G, CS, CO and CL. The meals were administered after an overnight fast. In addition to a fasting venous blood sample, blood was collected 0.5, 1.0, 1.5 and 2.0 h after ingestion for measurement of serum glucose and insulin levels. The glycaemic response to G+CS+CL and G+CS+CO+CL was significantly lower, while the insulinaemic response to G+CL was significantly higher than that to G. Addition of CL to G did not alter the glycaemic response, but accentuated the insulinaemic response. Further addition of CS in isoenergetic meals attenuated the glycaemic response, which may be because of a reduction in the amount of G in the meals. Like CS, CL also seemed to have an insulinotropic effect. The mechanism of the insulinotropic effect of CL cannot be deduced from the present study, but it is possible that like G, CL also stimulates gastric inhibitory peptide (GIP) secretion from the duodenum, which in turn stimulates insulin secretion.

Dietary records were obtained twice in pregnancy and once post-partum, from 265 women in all social classes in London and Edinburgh. Some Edinburgh women, and lactating women, showed the higher levels of calcium intake. For iron, retinol, ascorbic acid and folic acid, there was a consistent and significant regional and social class gradient in intakes. This favoured English women in ‘non-manual’ social groups, leaving the Scottish ‘manual’ class, after pregnancy, with the lowest intakes. Mean intakes of Ca and Fe were consistently below the current UK recommended daily amount (RDA). Intakes of retinol were all above it, and ascorbic acid intakes ranged above and below the RDA.

The effect of injection with bovine somatotropin (bST) on the fractional rate of protein synthesis (FSR) in tissues of beef steers was studied using a continuous infusion of [1-14C]leucine. Minimum and maximum FSR were calculated from free leucine specific radioactivity (SRA) in plasma or tissue homogenate respectively. Tissue nucleic acid concentrations were also quantified. Tissue samples were obtained from several muscles, sections of the small intestine and liver. In response to bST, both minimum and maximum FSR increased in muscle but not liver or intestinal tissues. Absolute synthesis rate increased in several muscles and small intestine tissues. Treatment with bST increased the relative SRA of protein-bound leucine in muscles compared with liver; increased the amount of protein synthesis per unit empty body-weight (EBW) in most muscles; and increased weight of small intestine relative to EBW, suggesting a differential response between liver and the other tissues measured. Compositional changes in response to bST occurred only in muscles. DNA concentration increased while protein:DNA decreased in the gastrocnemius muscle and RNA:DNA increased in the longissimus dorsi. The maximum percentage contribution of tissue protein synthesis to whole-body protein synthesis was 12·6, 25·7 and 20·5, and 13·0, 29·4 and 25·8 for liver, muscle, and small intestine in placebo-treated and bST-injected steers respectively.

A total of 360 I-d-old broiler chickens were fed on a diet based on rye and wheat in equal proportions without or with supplementation of increasing levels (0.11, 0.22, 0.44 and 0.88 g/kg) of a technical enzyme preparation containing pentosanase and β-glucanase activities. In vitro investigations revealed that the enzyme preparation solubilized pentosans, increasing the relative viscosity of buffer extracts from enzyme-supplemented diets. Enzyme supplementation generally improved body-weight by approximately 27% at day 15 and 15% at day 27, increased feed intake by 15 and 8% respectively, and improved feed conversion efficiency by 10 and 5% respectively. There was also a decreased occurrence of sticky droppings. Enzyme supplementation increased the digestibility of organic matter, crude protein (nitrogen x 6.25) and starch measured in the last third of the small intestine, and of organic matter and crude fat measured in excreta. Solubilization of insoluble pentosans by the enzyme included led to negative digestibility values for soluble pentosans in the small intestine at the higher levels of supplementation. Most of the dietary fibre degradation observed occurred before the middle section of the small intestine, with some degradation of soluble fibre in the caeca and colon. The solubilization and disruption of feed endosperm cell walls by enzyme supplementation probably was primarily responsible for the observed improvements in digestibility and production results.

Two experiments were carried out in which rats were offered diets containing different amounts and types of dietary fibre, i.e. commercial stock diet and three semi-purified diets containing no fibre, 200 g wheat bran or 200 g pectin/kg. Dietary inclusion of fibre, and especially pectin, stimulated large bowel fermentation, as indicated by caecal hypertrophy and reduced caecal pH. After 3 weeks, mucosal:serosal zinc transfer and Zn accumulation by tissue were measured using the everted-gut-sac technique. In Expt 2, incubations were carried out in the presence and absence of 0.25 mm-ouabain to assess the importance of transfer by Na+, K+-ATPase-dependent mechanisms, and some observations on glucose transport were also made. Ouabain reduced rates of transfer of both Zn and glucose and also tissue Zn accumulation. There were no significant differences in rates of Zn transfer by everted sacs from duodenal, ileal and colonic sites, but accumulation of Zn by tissue was a more important fate than transfer across the serosal surface, and accumulation by duodenal tissue was approximately twice as great as by other tissues. Mucosal:serosal transfer of glucose by ileal tissue was much more sensitive to ouabain than was Zn transfer. Previous diet appeared to alter the capacity of the intestinal tissue to transfer Zn, with the highest rates of transfer being by colonic tissue from pectin-fed rats.