The nutritional effects of giving raw (RSF) or heated (HSF) soya-bean flour to young guinea-pigs were investigated in trials 1 and 2, in which the levels of dietary protein were 120 and 190 g/kg diet respectively. The growth rate of animals fed on RSF was lower than that of those fed on HSF. Growth retardation of guinea-pigs fed on RSF was accompanied by a lower apparent digestibility of the protein (0.49–0.53) compared with HSF (0.67–0.76) and lower food conversion efficiency. In RSF-fed animals, increasing dietary protein affected growth and food conversion efficiency negatively. The pancreas of animals fed on RSF and HSF was similar in weight but secreted less trypsin, chymotrypsin and amylase, in RFS-fed animals. It was concluded that the mechanism by which raw soya-bean negatively affects the growth rate of guinea-pigs by reducing the activity of intestinal enzymes, differs from that suggested for rats and chicks, but is similar to that of pigs and calves.

A relationship between bile acid conjugation and hepatic taurine concentration was investigated in rats fed on citrus pectin. When rats were fed on the diets containing varying amounts of pectin (10, 30, 60 and 100 g/kg dietary levels), biliary excretion of bile acids increased as the dietary levels of pectin increased. The increase was entirely due to the glycine-conjugated bile acids. The biliary excretion of taurine-conjugated bile acid was somewhat decreased as the dietary level of the fibre increased. Consequently, most of the bile acids were conjugated with glycine in rats fed on the diet containing 100 g pectin/kg. On the other hand, dietary cellulose (60 and 100 g/kg) did not affect the biliary bile acid excretions. The major proportion of bile acids in rats receiving a fibre-free diet and the diets containing cellulose were conjugated with taurine. Hepatic taurine concentrations decreased as the dietary levels of pectin, but not of cellulose, increased. Although dietary pectin (100 g/kg) also slightly decreased the taurine concentration in the kidney, those concentrations in other non-hepatic tissues examined (heart, brain and serum) were unaffected by the dietary fibre. Supplementation of the diet containing 100 g pectin/kg with methionine (10 g/kg) and taurine (10 and 50 g/kg) strikingly increased hepatic taurine concentrations. In this situation, the conjugation of bile acid with glycine was almost abolished and taurine conjugates became abundant in the bile of these animals. It is suggested that dietary pectin mediated an increase in the biliary bile acid excretion which may have depleted the hepatic pool of taurine available for bile acid conjugation and, thus, increased glycine conjugation of bile acids.

The quantity of re-ingested faeces was calculated by comparing faecal dry matter of unrestricted rats and coprophagy-restricted rats after correcting for differences in food intake. Due to high day-to-day variations of produced and re-ingested faeces it was not possible to calculate precisely the extent of coprophagy of an individual rat at a particular day with this difference method. Reliable quantitative estimates require at least two rats and a collection period of 7 d. When fed on a nutritionally complete diet, rats re-ingested 0-11 % of their faeces. When fed on low-protein diets (66 g egg albumin/kg) or diets diluted with 200 g cellulose/kg, coprophagy was not significantly increased. A high re-ingestion rate (6–25 %) was observed with thiamin and pantothenic acid deficiencies. After re-ingestion of faeces had been prevented for 1 week, the amount of faeces re-ingested during the subsequent week without tail-cups was increased twofold. It is concluded that rats are able to regulate the amount of faeces eaten precisely according to their requirements.

Characterization of the carbohydrates of pea (Pisum sativum) hulls, carrot and cabbage using both colorimetric and gas–liquid chromatographic techniques permitted a detailed investigation into the extent of digestion of differing types of fibre. These digestion studies were greatly aided by the development of a rapid bioassay employing starved adult cockerels. Total collection of undigested residues, uncontaminated by food spillage, could be made from trays placed under the cockerels. Chemical analysis showed that pea hulls consisted mainly of fibre with very little available carbohydrate present, whereas more than half of freeze-dried carrot and cabbage consisted of available carbohydrate (sucrose, glucose, fructose, starch) and consequently considerably less fibre was present. The fibre of carrot and cabbage was similarly composed of nearly equal amounts of neutral and acidic polysaccharides, whereas pea-hull fibre had four times as much neutral as acidic polysaccharides. The digestibility of total neutral polysaccharides from all three foodstuffs was extremely low. However, there appeared to be preferential digestion of polysaccharides composed of rhamnose, arabinose and galactose residues, all associated with pectic material, in contrast to the indigestibility of polysaccharides composed of fucose, xylose and glucose. Acidic polysaccharides were digested to a greater extent than neutral ones, and those of carrot and cabbage more so than pea hulls. The polysaccharides which were the most soluble were also the most digestible, but due to the arbitrariness of polysaccharide solubility, quantification of their total digestibility per se was considered not possible.

The concentrations of holotrichs, reducing sugars and fermentation end-products, and the fluid dilution rates, in the cranial (CR), ventral (V) and caudal (CA) regions of the reticulo-rumen of cows were compared. Additionally, holotrich numbers in fluid and solid digesta samples taken from the dorsal (D) region were determined at different time-intervals. Holotrich numbers expressed per ml fluid at site D were almost twofold those expressed per g solid digesta, and the fluctuation of their numbers in fluid preceded that in solid digesta. Holotrich concentrations at site CR were higher before feeding than after feeding, while those at sites V and CA were lower before feeding than for a few hours after feeding. At sites V and CA, holotrich concentrations fluctuated in good agreement with reducing sugar concentrations, but the increase in the former always preceded that in the latter. The concentration of volatile fatty acids (VFA) tended to decrease from site CA to site CR, while the dilution rate was highest in site CR. The results suggest that migration of holotrichs from the reticulum to the rumen and vice versa are the cause of fluctuation in their numbers, and also the mechanism by which they are retained in the rumen of cattle.

The effect of post-rumen supply of nutrients on the rumen digesta load and voluntary consumption of roughage by Border Leicester × Merino ram lambs was investigated. A chopped wheaten hay was offered to the ram lambs (n 24), whose nutrient intake was altered by infusing into the abomasum a liquid supplement, containing reconstituted cow's milk, sodium caseinate, minerals and vitamins, for a period of at least 30 d. Either two or three lambs were allocated by live weight to each of ten rates of nutrient supplementation. The lambs were slaughtered at a target live weight of 31 kg. Voluntary intake of hay was estimated over the last 7 d of feeding. The amounts of digesta and organic matter (OM) in the rumen were measured by emptying after slaughter. The particle size distribution of the digesta was measured by wet sieving and the fractional outflow rate of particulate matter by reference to the marker lignin. Growth rate of the lambs increased linearly as total energy infused increased. The linear increase in growth rate indicated that roughage was not substituted for infused nutrients on a direct energy basis. OM intake from hay declined linearly as the amount of nutrients infused increased. The decline in intake was associated with a decline in both total digesta and the amount of rumen OM. Both the fractional digestion rate of OM and the fractional outflow rate of particulate matter from the rumen were unaffected by the amount of nutrients infused. The results indicated that the rumen digesta load of young sheep fed on a single roughage is directly related to their energy deficit, that is the difference between the capacity of the animals to use energy and the energy available to them for metabolism.

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 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.

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.

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.

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 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.

The object of the present study was to determine the effect of thyroxine (T4) treatment of sheep on protein synthesis and associated energy costs in skeletal muscle and hepatocytes. Protein synthesis, and ouabain-sensitive and cycloheximide-sensitive respiration in isolated intercostal muscle and hepatocytes were determined in sheep after 5 weeks of daily injections of either saline or T4. Plasma T4 and total triiodothyronine (T3) concentrations were doubled and free T3 concentrations were quadrupled by T4 injections. The fractional rates of protein synthesis increased in isolated external intercostal muscle and hepatocytes from hyperthyroid sheep. Fractional rates of protein synthesis in isolated external intercostal muscle and hepatocytes were linearly correlated with plasma free T3 concentrations. Total oxygen consumption of muscle and hepatocytes was unaffected by T4 injections. Ouabain-sensitive respiration increased in hepatocytes and muscle of T4-treated animals. Cycloheximide-sensitive respiration was elevated in hepatocytes from hyperthyroid sheep. Cycloheximide-sensitive respiration in muscle was unaffected by T4 treatment. The present experiment demonstrates that T4 increases protein synthesis in ruminants. The energy expenditure in support of Na+, K+-ATPase and protein synthesis in skeletal muscle and hepatocytes may account for 34–60% of total cellular energy expenditure.

Administration of oral glutathione (GSH) increases hepatic GSH levels in fasted rats, in mice treated with GSH depletors such as diethyl maleate and in mice treated with high doses of paracetamol. An increase in hepatic GSH levels after administration of oral GSH does not occur in animals treated with buthionine sulphoximine, an inhibitor of GSH synthesis. Administration of oral GSH leads to an increase in the concentration of l-cysteine, a precursor of GSH, in portal blood plasma. Oral administration of l-methionine produced a significant decrease of hepatic ATP in fasted rats, but not in fed rats. Administration of N−acetylcysteine or GSH did not affect the hepatic ATP levels. The results show that the oral intake of GSH is a safe and efficient form of administration of its constituent amino acids in cases when GSH synthesis is required to replete hepatic GSH levels.

The total lipid fatty acid composition of mature breast milk has been analysed in a group of twenty-five mothers of children with atopic eczema, and compared with breast milk from twenty-two controls. Total lipids were extracted into chloroform–methanol (2:1, v/v) and the methyl esters prepared by alkali-catalysed trans-esterification were separated by gas–liquid chromatography and identified by comparison with standard fatty acid methyl esters. Results show that mothers of children with atopic eczema have a significantly greater proportion of linoleic acid, and a smaller proportion of dihomo-γ-linolenic acid in their total breast milk lipid than the controls. Proportions of total derived fatty acids were similar between groups and there were no differences in the principal saturated and monounsaturated fats. It was concluded that mothers of children with atopic eczema have an abnormal breast-milk fatty acid composition. This supports previous evidence of a defect of conversion of linoleic acid into its long-chain polyunsaturated metabolites in the condition.

Adipose tissue levels of linoleic acid were determined from biopsies of subcutaneous abdominal fat of normal healthy controls (n 40) and from two patient groups with endoscopically evaluated non-ulcer dyspepsia (n 40) or peptic ulcer disease (n 38). The level (g/100 g) of adipose tissue linoleic acid in the normal healthy controls (15·0 (sd 4·1)) was significantly (P < 0·05) greater than that in patients with non-ulcer dyspepsia (12·8 (sd 3·5)) and in patients with peptic ulcer disease (11·7 (sd 2·7)). A dietary history revealed a lower intake of linoleic acid and a significantly (P < 0·05) lower intake of dietary fibre (g/d) for both the non-ulcer dyspepsia (15·9 (sd 6·2)) and peptic ulcer disease (15·2 (sd 7·8)) patients compared with normal healthy controls (20·2 (sd 11·2)). Adipose tissue linoleic acid tended to increase with indices of increasing socioeconomic status, although the differences between patient and controls were not confounded by socioeconomic status. Patients with dyspepsia reported more foods causing symptoms (onion, fried foods, alcohol, citrus fruits and spices) and more foods giving relief (milk, bread) compared with control orthopaedic patients.

The effect of iron intake on 59Fe absorption throughout pregnancy, and on maternal and fetal Fe status towards the end of pregnancy, was investigated in rats. The influence of pregnancy and dietary Fe on duodenal morphology was also studied. Female rats were fed on a diet containing 17 or 100 mg Fe/kg for 2 weeks before and throughout pregnancy. 59Fe absorption was measured on days 1 or 2, 8 or 9 and 17 or 18 of pregnancy, and maternal and fetal Fe status was determined on days 18 or 19. Pregnancy resulted in a fall in haemoglobin (Hb) concentration. Compared with non-pregnant counterparts, total liver Fe was reduced in the low-Fe group, but not in the high-Fe group, indicating that the fall in Hb in the high-Fe rats was not associated with an Fe-deficient state. 59Fe absorption in rats fed on both diets increased throughout pregnancy, demonstrating that Fe supplementation of the diet, to a level that prevented the development of Fe-deficiency, failed to suppress an increase in absorption. Fetal weight appeared to be an important determinant of the efficiency of Fe absorption in late pregnancy. Poor maternal Fe status was accompanied by a reduction in fetal Fe concentration but results also suggested that fetuses were partly protected from maternal Fe-deficiency. Pregnancy resulted in increased duodenal circumference and villus dimensions, whilst high dietary Fe reduced duodenal growth in both pregnant and non-pregnant animals. The relevance of this finding is discussed. It was concluded that, in rats, pregnancy per se causes an enhancement in Fe absorption and that the degree of enhancement is in part related to fetal mass.

Male Wistar rats (188 g) were fed on a semi-synthetic (SS) diet (38 mg iron/kg) ad lib. for 7 d and then meal-fed for 1 d. After a 21 h fast each rat was given one meal (10 g) of high-Fe SS (500 mg Fe/kg; high-Fe group) or control (38 mg Fe/kg; control group) diet. After 16 h 2 ml of an 59Fe-labelled ferrous sulphate solution (18 kBq 59Fe; 120 μg Fe) was administrated by gavage and equal numbers of rats from each group were killed 6 or 24 h after dosing. Mucosal uptake of 59Fe from the gut lumen and transfer of 59Fe from mucosa into the carcass were measured. Total Fe content of the duodenum was also determined. Mucosal 59Fe uptake and transfer were markedly lower in the high-Fe group compared with the control group. The Fe content of the duodenum, the major region of Fe absorption, was significantly greater in the high-Fe group than in the controls. A larger amount of Fe may thus have been released into the lumen of the high-Fe rats, via mucosal cell turnover, resulting in a greater lumen dilution of the 59Fe dose in this group compared with the controls. Calculations are presented which demonstrate that such an effect could not possibly account for the observed difference in mucosal 59Fe uptake between groups. Differences in rates of ‘cold’ Fe and 59Fe loss from the duodenal mucosa during the 6–24 h interval suggested that, at the time of dosing, Fe retained in the mucosa from the previous meal had been incorporated into a non-exchangeable pool and as such would not dilute radioactive Fe entering the mucosa. It was concluded that whole-body 59Fe retention from a labelled source, given orally after an overnight fast, provided an accurate estimate of Fe absorption.

Eight lambs were fed on a cobalt-deficient whole-barley diet supplemented with urea, vitamins and minerals. Four control lambs were fed on the same diet which had been further supplemented with Co. Plasma vitamin B12 levels in the Co-depleted group declined rapidly, falling below the normal range within 5 weeks. Differences between the live weights of the animals in the two groups approached statistical significance by week 14. However, methylmalonic acid (MMA) rose above normal levels in the Co-depleted group within 7 weeks. This suggested that an elevated plasma concentration of MMA is a comparatively early indicator of functional vitamin B12 deficiency. It is recommended that 10 μmol/l be the upper level of normality for plasma MMA concentration in barley-fed animals, in contrast with the level of 5 μmol/l for grass-fed animals. Changes in the plasma concentrations of MMA and ethylmalonic acid associated with feeding the barley-based diet per se did not significantly affect the validity of the gas-liquid chromatographic assay for MMA.