The hypothesis that the energy cost of human pregnancy can be minimized by energy-sparing metabolic adaptations was tested using serial 24 h whole-body calorimetry. Eight healthy, well-nourished women were studied prepregnant and at 6, 12, 18, 24, 30 and 36 weeks gestation. Basal metabolic rate (BMR) showed highly characteristic changes within each subject and large inter-individual differences (F 3.5, P < 0.01). Some subjects showed a highly significant depression of metabolism up to 24 weeks gestation in support of the initial hypothesis. At 36 weeks BMR ranged from +8.6 to +35.4% relative to the prepregnant baseline. This wide variability was not explained by differences in the amount of lean tissue gained. Women displaying the energy-sparing suppression of BMR tended to be thin, suggesting that changes in metabolism may be responsive to initial energy status (ΔBMR ν. prepregnant body fat: r 0.84, P < 0.005). Changes in 24 h energy expenditure closely paralleled changes in BMR (r 0.98, P < 0.001), since the energy cost of minor voluntary activity and thermogenesis remained very constant within each individual. Pregnancy decreased the net cost of weight-dependent and weight-independent standard exercises when expressed per kg body-weight: stepping – 10 (sd 2)%, P < 0.001 at 18–36 weeks, cycling - 26 (sd 7)%, P < 0.01 at 12–36 weeks. The average integrated maintenance costs of pregnancy matched previous group estimates from well-nourished women, but individual estimates ranged from - 16 to + 276 MJ (coefficient of variation 93%). This high level of variability has important implications for the prescription of incremental energy intakes during pregnancy. It may also have had evolutionary significance.

The objective of the present study was to measure changes in splanchnic blood flow and oxygen consumption in sheep fed on a high-concentrate diet ad lib. (ADLIB) or an amount sufficient to maintain body-weight (MAINT) for 21 d. Eleven ram lambs were surgically implanted with chronic indwelling catheters in the portal, hepatic and mesenteric veins and mesenteric artery to measure blood flow and net O2 flux through the liver and portal-drained viscera (PDV). During the 21 d period, PDV (P < 0.05) and liver (P < 0.01) blood flow increased in ADLIB and decreased in MAINT lambs (treatment x day, linear). After 21 d, O2 consumptions in PDV and liver of MAINT lambs were 37 and 63% lower than in ADLIB lambs. In the control period, total splanchnic tissues represented an average of 52% of whole body O2 consumption. After 21 d, the relative contributions of PDV and liver to whole-body O2 consumption were 28 and 41% in ADLIB and 19 and 22% in MAINT lambs respectively. Allometric regression variables indicate that liver O2 consumption responds more rapidly to changes in metabolizable energy intake than portal O2 consumption. These results indicate that blood flow and O2 consumption in both PDV and liver are related to level of nutrition. Furthermore, splanchnic tissues represent a significant component of whole-body O2 consumption that is subject to manipulation by level of nutrition.

The aim of the present study was to determine how the long-term metabolic adaptations to winter shearing of the pregnant ewe result in significant changes in the rates of lipid mobilization and utilization of non-esterified fatty acids (NEFA) in comparison with unshorn controls. Continuous infusions of [1-14C]palmitic acid, [2-3H]glycerol and NaH14CO3 were used to measure whole-body lipid metabolism in fed (estimated metabolizable energy (ME) intake 9.54 MJ/d) and under-fed (estimated ME intake of 3 MJ/d), shorn and unshorn sheep over the final 4 weeks of pregnancy. Whole-body carbon dioxide, estimated heat production, total NEFA entry and oxidation rates were all significantly higher in fed shorn ewes compared with unshorn controls, even though there was no difference in the arterial plasma NEFA concentration. These differences may be mediated via an increase in the plasma concentrations of thyroid hormones in shorn animals. As a result of under-feeding any significant differences in lipid metabolism between shorn and unshorn groups were removed. In all sheep the mean total NEFA entry rate as measured using [1-14C]palmitic acid was 3.4 times the value obtained using [2-3H]glycerol. It is concluded that when sheep are fed on a diet from which no more than half the required ME for late pregnancy is obtained, then lipolysis of body fat depots occurs via the incomplete breakdown of adipose tissue triglycerides. This effect is significantly greater in the fed shorn pregnant ewe which exhibits higher entry and oxidation rates of NEFA.

During early lactation ruminants can mobilize considerable amounts of body fat to maintain milk production. The aim of the present study was to evaluate the efficacy of tritiated water (TOH) and non-esterified fatty acid (NEFA) kinetics as means of monitoring adipose tissue fat mobilization in lactating goats. Body fat, as estimated by a two-pool model of TOH kinetics, and NEFA entry rate were measured in four primiparous goats at days 11, 37 and 72 post partum. Estimated body fat decreased by an average of 64 g/d between days 11 and 37 of lactation, tending to increase between days 37 and 72. Plasma NEFA concentrations and NEFA entry rate decreased as lactation advanced, being significantly lower at day 72 than at day 11 of lactation. Both plasma concentrations of NEFA and NEFA entry rate were negatively correlated with calculated energy balance. Plasma NEFA concentrations and NEFA entry rate at days 11 and 37 of lactation were positively related to average body fat losses over the subsequent stage of lactation. These results demonstrate that NEFA kinetics reflect fat mobilization in primiparous lactating goats, particularly during negative energy balance.

Oxidation of dl-2-hydroxy 4-methylthiobutanoic acid (dl-HMB), dl-methionine (dl-MET) and l-methionine (l-MET) in chicken tissue homogenates was compared using 1-14C-labelled tracers. The pattern of oxidation of the substrates was similar at both low (0.7 mm) and high (20 mm) concentrations. The rate of conversion to 2-keto 4-methylthiobutanoic acid (KMB) was highest for dl-MET and lowest for l-MET in kidney, liver and intestinal mucosa. In breast muscle, rates for dl-MET and l-MET were similar at 0.7 mm, but dl-HMB showed the highest rate at 20 mm. Kidney contained the highest specific activity for oxidation of all three substrates. Raising the pH of liver and kidney homogenates from 7.5 to 8.6 increased the oxidation of dl-MET, exclusively. Experiments with inhibitors of D-2-hydroxy acid dehydrogenase (EC 1.1.99.6) and L-2-hydroxy acid oxidase (EC 1.1.3.15) suggested that d- and l-HMB were stereospecifically oxidized by the enzymes. KMB stimulated l-MET oxidation in kidney yet inhibited l-MET oxidation in liver homogenates. The effect of KMB on dl-MET and dl-HMB oxidation also varied between tissues. Amino-oxyacetate inhibited l-MET oxidation completely and dl-MET and dl-HMB oxidation almost completely in both kidney and liver. L-Cycloserine was less potent than amino-oxyacetate and decreased l-MET oxidation more in kidney than in liver. It can be calculated from the results that, at low substrate concentrations, the liver contributes principally to the whole body oxidation of both dl-HMB and dl-MET. At high (greater than physiological) concentrations, dl-HMB would be oxidized principally in skeletal muscle. At all concentrations, l-MET would be converted to KMB mainly in the muscle.

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.

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.

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.

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.

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.

The hypothesis that factors such as dietary fibre and phytate in wheat bran limit the availability of Zn was tested in growing rats fed on low-Zn diets with different wheat crispbreads as the major source of Zn. Six groups of six weanling male rats each were fed on 5 parts semi-synthetic Zn-deficient diet and 1 part wheat-endosperm crispbread for 1 week. At the beginning of the second week, the crispbread in the diet of five groups was exchanged for crispbread made using one of the following wheat flours: (1) whole grain, (2) bran-enriched whole grain, (3) endosperm with Zn added to the whole-grain level, (4) endosperm with Zn added to the bran-enriched level, (5) whole grain with Zn added to the bran-enriched level. These diets were given ad lib. together with deionized water for 2.5 weeks. The relative absorption of Zn was lowest from the three non-supplemented diets (75–82%). All the added Zn was absorbed. As appetite, body-weight increase, Zn absorption, Zn retention and the Zn concentrations in serum and bone differed only slightly among groups fed on diets with similar Zn concentrations, it is concluded that factors such as dietary fibre or phytate in wheat bran limit the availability of Zn in wheat crispbreads very little when all the Zn is needed for growth and development in rats.

Female C57BL mice heterozygous for the brindled gene were mated to normal males and fed on a purified diet low in copper throughout gestation and lactation with (+ Cu) or without (−Cu) Cu-supplemented drinking water. Male offspring of two genotypes (control, + /y and brindled, Mobr/y) were compared when 10–12 d old. Brindled mice from dams on the – Cu treatment were smaller and had lower packed cell volumes than brindled mice from dams on the + Cu treatment. The −Cu brindled mice were smaller than their littermate brothers (+/y) but had equivalent biochemical features consistent with severe Cu deficiency. Compared with control mice from dams on the +Cu treatment, caeruloplasmin (EC 1.16.3.1) activity was lower in offspring of all three other groups including Mobr/y mice who were not anaemic. Iron levels were similar in organs and bone marrow from all four groups of offspring. When dietary Cu is limiting in brindled mice a more severe Cu deficiency ensues. Thus, appropriate Cu nutriture is important to the management of Menkes' disease in humans, a genetic analogue of the brindled mouse.

The effect of dietary zinc deficiency on γ-glutamyl hydrolase (EC 3.4.22.12) activity and on pteroylpolyglutamate absorption was investigated in rats. Enzyme activity was determined in pancreas and gut lumen washings. Pteroylpolyglutamate absorption was studied by determining the rise in plasma folate levels following pteroylpolyglutamate ingestion. Two experiments were performed; in each purified diets were given to three groups of immature male Wistar rats for approximately 2 weeks. One group was given a Zn-deficient diet ad lib. (ZD), the second was pair-fed daily with this group on a Zn-adequate diet (PF) and the third was given the Zn-adequate diet ad lib. (AL). In Expt 1, significantly reduced pancreatic γ-glutamyl hydrolase activity was observed in ZD rats. In Expt 2, pteroylpolyglutamate was administered on day 14 and in the 3 h period following pteroylpolyglutamate ingestion, lumen γ-glutamyl hydrolase activity and plasma folate levels were significantly lower in ZD rats. Pancreas is reported as the source of lumen γ-glutamyl hydrolase in rats. The results presented indicate that the pancreatic enzyme is Zn-sensitive. It was concluded that, as a result, γ-glutamyl hydrolase activity was reduced in the lumen of ZD rats. Consequently the hydrolysis and subsequent absorption of pteroylpolyglutamate was impaired in ZD rats, as indicated by the smaller rise in plasma folate levels that occurred following pteroylpolyglutamate ingestion. Results of this study concur with previous observations in human beings and rats that Zn deficiency has an adverse effect on folate metabolism.

The aim of the present work was to determine the effect of giving increasing doses of supplements of β-carotene on serum retinoic acid levels in rabbits. Four groups of 7-week-old female rabbits were fed for 9 weeks on a pelleted diet containing 1.72 mg vitamin A as retinyl acetate/kg and including control gelatin beadlets devoid of β-carotene or 1, 2 or 4 mg β-carotene/kg body-weight per d. Serum was collected at 3, 6 and 9 weeks after the beginning of the experiment and the concentration of all-trans retinoic acid was determined by a gradient reverse-phase high-performance liquid chromatography system following a double-phase extraction. The average concentration of retinoic acid in serum of the combined control and 1 mg β-carotene/kg groups was 3.80, 3.06 and 2.40 nM at 3, 6 and 9 weeks respectively. The concentrations of retinoic acid in serum of the combined 2 and 4 mg β-carotene/kg groups were 4.80 nM (P < 0.05), 3.76 nM (not significant) and 4.90 nM (P < 0.005) at 3, 6 and 9 weeks respectively. A SAS (SAS Institute Inc., 1985) general linear model repeated-measures analysis of variance revealed that the effects of treatment (P <0.01), time (P < 0.05) and treatment x time interaction (P < 0.05) were statistically significant. It is concluded that giving β-carotene is associated with higher concentrations of all-trans retinoic acid in the serum of rabbits than in those receiving no β-carotene.

Responses of several folate-metabolizing pathways to dietary folic acid were studied in 2-week-old chicks. Oxidation of a histidine load to carbon dioxide was impaired in folate-deficient chicks. There was a curvilinear relation between oxidation and dietary folate, and maximum oxidation occurred with 2 mg supplemental folic acid/kg. Hepatic activities of glutamic acid formiminotransferase (EC 2.1.2.5) and glycine N-methyltransferase (EC 2.1.1.20) were not affected significantly (P > 0.05) by dietary folic acid. The activity of dihydrofolate reductase (EC 1.5.1.3) in erythrocytes was elevated in folate-deficient chicks. These studies show that the activities of two folate-dependent pathways can be used as biochemical criteria of folate status in chicks.

The calcium, magnesium and phosphorus status of a group of elderly inpatients was studied by use of duplicate meal analysis over a 5 d period and biochemical indices in twenty-one patients, and metabolic balance (5 d) in six of these. Mean daily Ca intake was lower than that of apparently healthy elderly subjects in metabolic equilibrium, although commensurate with present UK recommendations. Metabolic balance was negative for Ca. Mean daily Mg intake was approximately half the US recommendation, and half the intake at which metabolic balance has been observed in healthy elderly people. The five patients studied were in metabolic balance for Mg. Mean daily P intake was close to the UK recommendation, but negative metabolic balance was observed. The disparity between official recommendations for Ca intake, factors contributing to suboptimal Ca status, and measures that may improve Ca status in this group are discussed.