Eight Friesian calves were reared from birth to the start of the experiment at a predetermined growth rate of 1.0 kg/d. Four calves (group 1) commenced the experiment at 22 weeks of age and the remainder (group 2) at 34 weeks, and feed intake was calculated to provide sufficient metabolizable energy to sustain zero energy balance (Em). Between experimental days 30 and 56 at maintenance levels of feeding, respiratory exchange measurements were made using open-circuit calorimetry to provide indirect estimates of heat production (H) simultaneous with measurements of faecal and urinary excretion of energy and N. A datum point for Em and H was established for each animal giving mean values for Em of 491 and 537 and for H of 476 and 511 kJ/kg live weight (LW)0.75 per d for groups 1 and 2 respectively. Treatment levels calculated as 0·25, 0·5, 0·75 and 1·25 of dry matter intake required to sustain the measured Em, were imposed on individual animals after day 56 and further measurements of H and faecal/ urinary balance were made between days 72 and 84 followed by measurements of fasting heat production (FHP) during days 86–90 from the two animals in each group which had received the 0.75 and 1.25 levels of intake. Regression analysis of the treatment levels indicated separate linear models which predicted Em at 419 and 473 kJ/kg LW0·75 per d for groups 1 and 2 respectively. The incorporation of FHP with partitioning of faecal and urinary energy losses measured during fasting altered the relationship but not the predicted Em. Overall predicted Em (days 72–84) from all models were 406 and 478 kJ/kg LW0.75 per d for groups 1 and 2 respectively which were significantly lower (P < 0·05) than Em measured during days 30–56.

Rates of energy expenditure (J/kg fat-free mass (FFM) per min) in normal weight, ‘small-eating’ men were compared with those obtained for normal weight (n 8) and underweight (n 5) ‘large-eating’ men. For the matched groups of ‘large-’ and ‘small-eaters’ there were no differences in resting metabolic rate (RMR) measurements but during controlled daily activities there was a small but significant increase (P < 0.05) in energy expenditure in the ‘large-eaters’. These results contrast with those obtained for the unmatched groups where energy requirements were about 10 % (P < 0.01) higher in the underweight ‘large-eaters’ at rest but were not different during the more energetic (walking) activities. However, after adjustment for differences in FFM between these two groups, the resting energy expenditures of the ‘large-eaters’ (82·54 (SE 1·51) J/kg FFM per min) were similar to those of the ‘small-eaters’ (81·87 (SE 1·51) J/kg FFM per min). Oral temperatures were significantly higher in the matched (0·35–0·65°) and unmatched (0·7–0·9°) ‘large-eaters’ both at rest and during the different activities, but the thermic effect of food (50 kJ/kg FFM) was one fifth lower (not significant) in both groups of ‘large-eaters’. These results provide little evidence for any major metabolic differences between groups of ‘large-eating’ and ‘small-eating’ men.

Digestible energy (DE), metabolizable energy (ME) and net energy for maintenance (NEm) values of a set of fourteen diets were measured in six adult sows fed at and below their maintenance energy level. The efficiency of ME for NEm was estimated from heat production (HP) measurements (indirect calorimetry) at these different feeding levels. HP was partitioned between HP due to physical activity, thermic effect of food (TEF) and fasting heat production (FHP). The amounts of DE digested in the small intestine or in the hindgut were measured. Equations for prediction of NEm from dietary characteristics were calculated. HP at maintenance level averaged 400 kJ/kg body-weight0.75, 16 and 19% of the total being due to physical activity and TEF respectively. The efficiency of ME for NEm averaged 77·4% with higher values for digestible diethyl ether extract (100%) and starch + sugar (82 %). The efficiencies of digestible crude protein (N × 6·25) and digestible residue averaged 69 and 56 % respectively. The energy absorbed from the small intestine was used more efficiently than the energy fermented in the hindgut (82 v. 59%). These values are comparable with those obtained in growing pigs. The NEm content of diets can be predicted accurately from equations including DE (or ME) values and some dietary chemical characteristics.

Using a new-generation open-circuit calorimeter capable of monitoring the cost of activity, and thereby both the real thermic effect of feeding (TEF) and basal metabolism in free-moving freely-feeding rats, we have reassessed the proposal that when food intake is restricted an adaptative reduction in energy expenditure participates in the achievement of energy balance. Total energy expenditure, energy expenditure due to spontaneous activity, TEF, basal energy expenditure and respiratory quotient (RQ) were computed by indirect calorimetry in rats given either a mildly restricted (MR) feed intake for 20–30 d (17 g feed/d) or a severely restricted (SR) feed intake for 1–10 d (4 g feed/d). In MR rats no significant changes in any of the measured variables were observed. In contrast, SR rats exhibited an adaptative reduction in energy expenditure due to a reduced spontaneous activity and probably also due to a reduced basal energy expenditure. On the other hand none of the animals fed on a restricted feed intake showed an adaptative TEF decrease, suggesting that TEF under ad lib. feeding is rather an obligatory process that does not include an adaptative component. Taken together, these results point out that under restricted feeding most of the decrease in energy expenditure is associated with simple passive mechanisms, such as body weight loss, and with the reduced feed intake per se. Only under severe feed restriction can some additional energetic economy be obtained from a possible reduction of basal metabolism, and to some extent from reduced activity.

Total body electrical conductivity (TOBEC) is a simple and non-invasive method for the assessment of body composition in vivo. Information regarding the applicability of TOBEC in the condition of abnormal fluid balance is scarce. In the present paper we give the results of the comparison between TOBEC and total body water (TBW; assessed by the tritium dilution technique) in three groups of animals: (1) healthy (n 17), (2) expanded fluid volume by secondary biliary cirrhosis (SBC; n 9) and (3) Fiirosemide®-treated rats (n 9). The TOBEC score and TBW by tritium dilution were found to be highly correlated in the pooled sample (r 0·90) and in normal (r 0.·87), SBC (r 0·73) and Furosemide-treated (r 0·89) rats. However, the relationship between TOBEC and TBW, described by least-squares regression analysis, was found to be similar for SBC and normal rats but was significantly different for Furosemide-treated and normal rats. These findings suggest that TOBEC is unable to track TBW accurately when the ratio between intracellular and extracellular water is chronically or acutely altered.

A short-term N balance study was conducted in twelve healthy female adults aged 21–32 years to determine their protein requirement. Four dietary protein levels (0·3, 0·4, 0·5 and 0·6 g protein/kg per d) were used. Energy intake of the subjects was kept constant at 0·18 MJ/kg per d. All subjects maintained their normal activity throughout the study period. N excretion was determined from the measurements of N in a total collection of urine, faeces, sweat and menstrual fluid for each dietary period. N balance during the four protein levels were −15·15 (SD 5·95), −5·53 (SD 6·71), + 6·15 (SD 4·76) and +12·05 (SD 8·63) mg N/kg per d for 0·3, 0·4, 0·5 and 0·6 g protein/kg per d respectively. The calculated average N requirements from regression analysis was 76·0 (sd 3·37) mg N/kg per d (0·48 g protein/kg per d). The estimate of allowance for individual variation to cover the 97·5 % population was 95 mg N/kg per d (0·6 g protein/kg per d). The net protein utilization (NPU) of the diet was 0·55. When compared with a similar study with men, there was a significant difference in the protein requirement between sexes. Thus, the unjustifiable sex difference in the protein allowance recommended by the Food and Agriculture Organization/World Health Organization/United Nations University (1985) Expert Consultation group must be reviewed.

A long-term N balance study was carried out to determine the adequacy of an estimated protein requirement level recommended for young healthy Nigerian women and the effect of the menstrual cycle on the requirement. Eleven healthy young women, 25 (SD 2·6) years, were fed on a diet providing 0·6 g protein (N × 6.25)/kg per d and an average energy intake of 0·17 (SD 0·012) MJ/kg per d. Urine, faeces, sweat and menstrual fluids were collected for estimation of N balance. Menstrual N loss varied among individuals ranging from 46 to 124 mg N/d with an average of 89 (SD 21.8) mg N/d. Individual N balance was found to vary according to the day of the menstrual cycle. Positive N balances were recorded at about ovulation while negative balances were observed just before the onset of menstruation. The average N balance ranged from + 8·49 (SD 5·64) to − 430 (SD 7·84) mg N/kg per d. Nevertheless, an overall cumulative positive N balance of + 5·7 (SD 6·98) mg N/kg per d which did not change significantly with time was observed for the last 5 d of two consecutive 20 d diet periods, although three subjects were in negative N balance. Blood biochemical measurements were stable except for one subject who had elevated serum aspartate aminotransferase (EC 2.6.1.1) levels. These findings suggest that our estimate of protein requirements was sufficient to achieve N balance equilibrium in a majority (70 %) of young women. However, to satisfy 97·5 % of the population, slight adjustments might be necessary in the energy intake since subjects who were in cumulative negative N balance also lost weight.

The ADP:O values in both cardiac and hepatic mitochondria have significantly decreased with an increase in protein level after 7, 14 and 21 d of feeding (Toyomizu et al. 1992). The present studies were undertaken to clarify tissue-specific effects of dietary protein levels on oxidative phosphorylation in the liver, kidney, skeletal muscles and small intestine and to characterize oxidative metabolism with diverse substrates in the liver. Chicks were fed on semi-purified diets of different protein levels (7, 25, 43 and 61% of metabolizable energy content) for 21 d. The responses of protein levels to oxidative phosphorylation showed tissue-dependency; although liver mitochondria of chickens fed on higher- protein diets exhibited reduced ADP:O values and state 3, neither changes in ADP:O value nor state 3 and state 4 rates were observed in the isolated mitochondria from kidney and skeletal muscles. Small intestinal mucosal mitochondria from chickens fed on a high (61%)-protein-energy diet showed significantly reduced ADP:O value and respiratory control ratio when compared with medium-protein- energy diets (25 and 43%). In liver mitochondria showing the most sensitive dependency to the levels of dietary protein, the ADP:O value decreased with increasing protein levels when pyruvate + malate- or glutamate-requiring complexes I, III and IV of the electron transport chain were used as substrates, but it did not change when succinate-requiring complexes II, III and IV or ascorbate + tetramethyl-p- phenylenediamine requiring complex IV was used. These results imply that impaired oxidative phosphorylation capacities with increasing dietary protein levels may be associated with functional damage to the respiratory chain for electron flow from NAD-linked substrates to the ubiquinone pool.

Hydration of feeds and bacterial attachment to feed particles are thought to play major roles in rumen digestion of fibrous feedstuffs. The objective of the present study was to integrate these phenomena in a mechanistic model that could be used for data analysis. The proposed model was based on the conversion of biomass, where digestion end-products can be used for the synthesis of bacterial mass. Digestion of the potentially digestible fraction and subsequent accumulation of bacterial mass was based on a sequential, three-compartment model. These compartments represented substrate undergoing hydration, digestion, and bacterial mass accumulation. A fraction of the substrate was used for synthesis of bacterial mass. It was assumed that these bacteria associate either temporarily or permanently with the remaining substrate. Dacron bags containing either dry or fully-hydrated lucerne (Medicago sativa), maize (Zea mays) cobs, orchard grass (Dactylis glomeratd), and wheat straw were incubated in the rumen of a steer that was infused continuously with (15NH4)2SO4. The 15N-enrichments of isolated particle-associated bacteria and residue remaining in the bags were used to estimate bacterial attachment. Substrate remaining and microbial mass accumulation were analysed simultaneously. Hydration did not appear to limit digestion. Fractional rate of digestion and appearance of attached bacterial mass was fastest for lucerne. For lucerne, 5 % of the digestion end-products were used for synthesis of bacteria that associated with the substrate, whereas for maize cobs, orchard grass, and wheat straw this was 16, 14, and 19% respectively. Less than 2% of digestion end-products were used for synthesis of bacteria that permanently remained associated with the substrate. Permanent association can occur only with the indigestible fraction, and probably represents bacterial debris. Lysis and/or detachment of bacterial cells was highest for lucerne, and was indicative of the rapid dynamics of lucerne digestion.

Information on diet composition, daily energy expenditure, energy storage and the utilization of energy in the prey are important factors when evaluating the food consumption of minke whales (Balaenoptera acutorostrata) during their summer stay in northern waters. The purpose of the present study was in this context to obtain information on the digestible energy (DE) of different prey selected by minke whales. An in vitro three-stage digestion technique, simulating the different compartments of the digestive system, has been developed. The initial step simulated the anaerobic microbial fermentation of substrate in the fortestomach. The next stage included the addition of pepsin (EC 3.4.23.1)–HCI, simulating ventricle enzymic decomposition, and finally, in the third step, fresh extract from duodenal contents was used to simulate enzymic intestinal degradation of the remaining components of the food. The inoculum was normally obtained from animals which had recently eaten the prey to be tested. In such tests we obtained a dry matter disappearance (DMD) and a DE for herring (Clupea harengus) of 80·4 (SD 5·0)% (n 18) and 92·1 (SD 3·7) % (n 16) respectively, and a DMD of krill (Thysanoessa sp.) of 83·4 (SD 4·9)% (n 6). The DMD of krill was reduced to 73·8 (SD 7·3)% (n 8) while the DE was 70·6 (SD 10·4) % (n 7) when inoculum from whales which had recently eaten cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) was used. These results indicate a high digestibility of the most common species of prey in these animals, and also that the whales have little difficulty in changing from one prey species to another.

The effects of guar gum, sugar-beet fibre (SBF) and wheat bran supplementation of a high-fat test meal were compared with an NSP-free control meal and a meal containing an equivalent amount of the ion- exchange resin cholestyramine in healthy non-obese human volunteers. Their effects on gastric emptying, postprandial circulating bile acids, triacylglycerols and gastrointestinal hormone levels were studied. The in vitro binding of NSP and cholestyramine to [l-14C]glycocholic acid was measured and compared with their in vivo effect. Guar gum and cholestyramine supplementation significantly lowered circulating postprandial bile acid, triacylglycerol and gastric inhibitory polypeptide concentrations, but sugar-beet fibre and wheat bran were without effect. Liquid gastric emptying, as assessed by circulating paracetamol levels, was slightly accelerated in the guar gum-supplemented meal. Glycocholic acid bound strongly to the insoluble fraction of cholestyramine and the soluble fraction of guar gum. The insoluble fractions of SBF and wheat bran bound only small quantities of glycocholate; no bile acid binding was detected in the soluble fractions of these NSP. The study demonstrates that measurement of postprandial bile acids enables an indirect measurement to be made of bile acid binding to NSP in vivo. The results support the hypothesis that the hypocholesterolaemic action of guar gum is largely mediated via interruption of the enterohepatic bile acid circulation, but indicate that the hypocholesterolaemic action of SBF is mediated by another mechanism.

Adult male pigs were fed on a diet containing (% of energy) fat 25 starch 55 from white rice and providing 20 g fibre/pig per d (diet WR). In two other groups rice bran was added to the diet to provide 43 g fibre/d. One group received the diet unmodified (diet RB), but in another (diet RO) heat-stabilized unrefined rice oil replaced the palm oil. In a further group brown rice replaced white rice and provided 37 g fibre/pig per d (diet BR). Plasma cholesterol concentrations were similar with diets WR, RB and BR. With diet RO the concentration was significantly lower than with diets WR and BR but was not different from diet RB. Plasma high-density-lipoprotein-cholesterol and plasma triacylglycerols were unaffected by diet. In all groups, digesta mass rose from the caecum to the proximal colon but fell in the distal colon. Diet WR gave the lowest digesta mass while diet BR gave a significantly higher mass along the large bowel length. RB- and RO-fed pigs had equal masses of digesta which were intermediate between BR- and WR-fed pigs at all sampling sites. Pools of individual and total volatile fatty acids (VFA) in the proximal large bowel were unaffected by diet. Pools of total and individual VFA in the median and distal colon were lowest with diets WR and RB and significantly higher with diet BR. In these regions of the colon pools of acetate in RO-fed pigs did not differ from those in the BR-fed group but were higher than in other groups. However, pools of propionate and butyrate with the RO diet were significantly lower than with diet BR and the same as with diets WR and RB. Portal venous VFA concentrations were unaffected by diet. The higher large bowel digesta masses and VFA with diet BR may reflect the escape of starch from the smallintestine.

The aim of the present study was to measure the effect of graded inclusion of baked beans (Phaseolus vulgaris) on plasma and liver lipids in hypercholesterolaemic pigs fed on a Western-type diet. Twenty- four Large White × Landrace pigs of about 30 kg body weight were made hypercholesterolaemic by feeding a semi-purified diet, high in saturated fat and supplemented with 10 g cholesterol/kg, for 14 d. After that, six pigs were randomly assigned to one of the four experimental groups. They received their respective diets, containing 0, 100, 200 or 300 g baked beans/kg, on a dry-matter basis, for a further 28 d. Fasting blood samples were taken and analysed for total plasma cholesterol, lipoproteins and triacylglycerols. After the pigs were slaughtered at the end of the study, livers were analysed for their cholesterol content. Consumption of baked beans at 100, 200 and 300 g/kg reduced plasma total cholesterol by 5·3, 20·2 and 35·6 % respectively. However, only the diet with 300 g baked beans/kg showed a significant reduction (P < 0·05) compared with the control (without baked beans)- The level of low-density-Hpoprotein-cholesterol was also significantly (P < 0·05) reduced by 48% at 300 g baked beans/kg. Plasma very-low-density-lipoprotein-cholesterol, high-density-lipoprotein-cholesterol and triacylgiycerol contents were not affected by bean consumption. The supplements of 200 and 300 g baked beans/kg promoted a significant (P < 0·05) reduction of about 50% in cholesterol deposition in the liver, compared with the control.

The effects of bran and starchy endosperm fractions of oat and rye on faecal weight and on biliary and faecal bile acids were studied in Syrian golden hamsters (Mesocricetus auratus). The animals fed on diets supplemented with steam-flaked oat bran, oat bran or rye bran had higher wet and dry weights of faeces compared with the animals fed on the fibre-free or low-fibre endosperm diets. A higher mean percentage of biliary cholic acid and a lower mean percentage of chenodeoxycholie and lithocholic (LCA) acids was observed in the bran-supplemented dietary groups. Animals fed on the bran-supplemented diets had increased daily faecal excretion of both total saponifiable and total free bile acids compared with the animals fed on fibre-free or endosperm-supplemented diets. The mean percentage of total saponifiable bile acids in the faeces was higher, and that of free bile acids lower in the animals fed on bran-supplemented diets. A significantly lower concentration of faecal free LCA was observed in the animals fed on the rye-bran diet. Both bran and endosperm diets reduced the faecal LCA: deoxycholic acid compared with the fibre-free diet, but the bran diets had a more pronounced effect than endosperm diets.

The digestibility of polysaccharides and other major components and the metabolic response of the microflora in the small and large intestines to oat diets varying in mixed linked (β(l →3; 1 →4)-D-glucan β-glucan) were studied in experiments with ileum-cannulated pigs. The oat fractions for diets were prepared in a dry milling process in which oat groats were milled into two endosperm fractions (oat flour 1 and oat flour 2) and oat bran. The digestibility of polysaccharides and the metabolic response of the microflora were followed for the two contrasting diets, oat flour 1 and oat bran, from ingestion to excretion while the digestibility of oat groats and oat flour 2 were estimated only at the ileum and in faeces. There was no degradation of β-glucan from either oat flour 1 or bran in the stomach and the first, middle and distal thirds of the small intestine (average digestibility approximately 0), while in the terminal ileum digestibility increased to 0·30 to 0·17 respectively. The digestion of starch in the first third of the small intestine was lower for the high-β-glucan oat-bran diet (0·49) than for the low-β-glucan flour diet (0·64). However, digestibility differences between the two diets levelled out as the digesta moved aborally in the small intestine and the digestibility at the terminal ileum was almost complete (0·970–0·995) for all diets. Oat non-starch polysaccharides (NSP) were an easily digestible energy source for the microflora in the large intestine less than 13% of dietary NSP being recovered in faeces. The bulk of β-glucan which survived the small intestine was degraded in the caecum and proximal colon while arabinoxylan was more slowly degraded. The amount of residues passing the ileo-caecal junction has little impact on the density of micro-organisms in the large intestine, which on the flour and bran diets were in the range of 1010–1011 viable counts/g digesta, but a high impact on the activity of the flora in colon. Oat bran resulted in a higher proportion of butyric acid in large intestinal content compared with the flour diet. The faecal bulking effect of oat bran was mainly caused by an increased excretion of protein and fat, presumably of bacterial origin. Of all the diets tested the oat-bran diets had the lowest digestibilities of protein and fat at the terminal ileum and in the faeces.

Pigs (25–45 kg) were fed on either cereal or semi-purified basal diets supplemented with either high or low levels of sugar-beet pulp or wood cellulose (Solka-floc). The apparent digestibility and retention of N and apparent digestibility and metabolizability of energy (GE) and the apparent digestibility of non-starch polysaccharides (NSP) and their constituent monomers were measured during weeks 2, 4 and 6 of the trial. N and GE were less well-digested, retained or metabolized from cereal basal diets than from the corresponding semi-purified diets during all three periods. NSP from sugar-beet pulp was highly digestible, unlike that from Soka-floc which was relatively poorly digested. These differences of NSP digestibility were seen more clearly when incorporated in semi-purified diets. There was no significant increase in the digestibility or retention of N, or digestibility or metabolizability of GE, or in the digestibility of sugar-beet pulp NSP with increasing time-period on the diets. In contrast, the digestibility of Solka-floc NSP tended to increase with the time-period. The digestibility of NSP from the semi-purified diet with the high level of Solka-floc inclusion was much lower than that for the low level of inclusion, indicating that microbial activity had been reduced. In conclusion, adaptation to the diets in terms of N and GE balance may be complete after 1 week, but 3–5 weeks may be necessary before stability of measurements of the digestibility of resistant NSP monomers can be obtained.

The present experiment was designed to test the hypothesis that ageing modifies the gastrointestinal responses to a change in diet composition. Rats of the Wag/Rij strain, either young adult (4 months of age) or elderly (27 months of age), were given a basal semi-purified diet or a diet of similar major nutrient composition containing 500 g oatmeal/kg for 17–18 d. Elderly rats digested the dry matter (DM) and organic matter (OM) of both diets less well than did their young adult counterparts, with more of this digestion occurring in the distal intestine. The greater flow of OM to the caecum of oats-fed animals was accompanied by significant reductions in caecal pH and increases in caecal total short-chain fatty acids (SCFA) concentration which appeared to be independent of age. However, young adults responded to feeding on oats by showing a much larger increase in the molar proportion of butyrate (332%) than did elderly animals (79%). Elderly rats had longer duodenal villi than did young adults but effects of age or diet were not detectable at other sites. With both age-groups oats consumption was associated with significant stimulation of crypt cell proliferation rate (CCPR) in the small intestine and caecum, but for the colon there was a significant reduction in CCPR with oats feeding. A reduced ability of the aged large bowel (LB) to produce butyrate may contribute to the prevelance of LB disorders in the elderly.

The hypothesis tested was that Zn deficiency aggravates impaired thyroid function as induced by I deficiency. In two separate experiments male rats were fed on diets either deficient in Zn or in I, or deficient in both. An identical, restricted amount of food was given to each rat so that body-weight gain of the experimental groups was comparable. Zn deficiency was evidenced by reduced tibial Zn concentrations. I deficiency was evidenced by goitre, reduced urinary I excretion, reduced plasma thyroxine concentrations and reduced absolute amounts and concentrations of thyroxine in the thyroid. Zn deficiency had no effect on the raised thyroid weight as induced by I deficiency. Zn restriction from 184 μmol Zn/kg diet to 31 μmol Zn/kg diet, hut not to 92 μmol Zn/kg diet, significantly lowered plasma thyroxine concentration. There were no interrelated effects of Zn and I deficiencies on thyroid hormone levels. These results indicate that marginal Zn deficiency does not influence thyroid hormone metabolism in I deficiency.