1. Sixty marasmic children and fifteen normal age-matched controls were investigated for the absorption of fats and proteins. Their duodenal juice samples were also analysed for bile salts and microflora.

2. A significant amount of malabsorption, with respect to both the dietary ingredients, was observed in the majority of the marasmic children.

3. The levels of conjugated bile acids in the duodenal juice samples of marasmic children were significantly lower as compared with those of normal controls, while the reverse was true for free bile acids and bacterial counts.

4. Significant correlations were observed between bile acid levels and fat absorption and also between microflora and free bile acids.

5. The pathophysiology of malabsorption in marasmus is discussed in the light of these findings.

1. Nicotine has been implicated as a causative factor in the intrauterine growth retardation associated with smoking in pregnancy. A study was set up to ascertain the effect of nicotine on fetal growth and whether this could be related to the actions of this drug on maternal adipose tissue metabolism.

2. Sprague-Dawley rats were mated and assigned to control and nicotine groups, the latter receiving nicotine in the drinking-water throughout pregnancy. Animals were weighed at regular intervals and killed on day 20 of pregnancy. Rates of maternal adipose tissue lipolysis and lipogenesis were measured. Fetal and placental weights were recorded and analysis of fetal body water, fat, protein and DNA carried out.

3. Weight gains of mothers in the nicotine group were less in the 1st and 2nd weeks of pregnancy, but similar to controls in the 3rd week. Fetal body-weights, DNA, protein and percentage water contents were similar in both groups. Mean fetal body fat (g/kg) was significantly higher in the nicotine group (96.2 (se 5.1)) compared with controls (72.0 (se 2.9)). Rates of maternal lipolysis were also higher in the nicotine group.

4. The cause of these differences and their effects on maternal and fetal well-being is discussed.

1. Heats of combustion and energy equivalents of cytoplasmic ATP have been estimated for glucose, 101 food proteins and 116 food fats based on amino acid and fatty acid composition data from food composition tables and the heats of combustion and energy equivalents of cytoplasmic ATP of each individual amino acid, fatty acid, glycerol and glucose. The isodynamic equivalents of carbohydrate, fat and protein at the biochemical level have been investigated.

2. Heats of combustion of food proteins and fats derived from compositional data were within 1 % of published values obtained by calorimetry.

3. Cytoplasmic ATP equivalents for glucose, fat and protein range from 9·0 to 14·7, 8·6 to 14·6 and 6·4 to 13·2 mol cytoplasmic ATP/MJ of metabolizable energy respectively, depending on the choice of mitochondrial proton stoichiometries for these estimations. The range is extended further when considering the level and type of mitochondrial ‘uncoupling’.

4. Isobioenergetic relationships between the efficiencies of glucose (G) and fat (F) (F = 1·05 G-0·9) and glucose and protein (P) (P = G(1·02–0·19f)-(1.8+0·5f)) energy conversions (wheref is the fraction of protein oxidized via gluconeogenesis) were obtained and were essentially independent of the choice of mitochondrial proton stoichiometry and the level and type of uncoupling of oxidative phosphorylation.

5. Potential errors in previous estimates of ATP yield from protein are shown to be as much as -17·6 to < 118%; accounting for the efficiency of mitochondrial oxidative phosphorylation narrows this to between -7·9 and 17·4% and accounting for the fraction of protein oxidized via gluconeogenesis limits this further to between - 7·9 and 11·1%. Remaining uncertainty is attributed mostly to lack of knowledge about the energy cost of substrate absorption from the gut and transport across cell membranes.

6. Coefficients of variation (cv) in the cytoplasmic ATP yield/g protein and /g protein nitrogen for the 101 food proteins were large (0·033 and 0·058 respectively). This is attributed mostly to variation in the metabolizable heats of combustion (cv 0·033 and 0·053 respectively) and to a much smaller extent in the efficiency with which cytoplasmic ATP equivalents are generated/MJ of metabolizable energy (cv 0·01).

7. It is concluded that the current understanding of biochemical energy transduction is sufficient to permit only a crude estimate of the energy equivalents of cytoplasmic ATP but that these equivalents vary by less than 5% between both different food proteins and different food fats. Isobioenergetic equivalents for carbohydrates, fats and protein which could be applied to modify the Atwater conversion factors are possible but require first an accurate quantification of the energy equivalent of cytoplasmic ATP for glucose in vivo, and an indication that oxidative phosphorylation is similarly efficient in different individuals.

1. Residual antigenic protein in heat-denatured cow's milk whey and in two commercial infant milk formulas was determined using enzyme-linked immunosorbent assays specific for β-lactoglobulin, α-lactalbumin, bovine serum albumin, bovine IgG1 and α-casein. This immunochemical assessment of antigenicity was related to the capacity of the preparations to sensitize immunologically when fed to guinea-pigs for 2 weeks. Antibody production was measured and the susceptibility of the animals to systemic anaphylaxis was assessed by injecting them intravenously with heated or unheated milk proteins.

2. Whey protein that had been heated at 100° or 115° for 30 min was extensively denatured and, in contrast to pasteurized whey, failed to sensitize guinea-pigs for anaphylaxis. Antibody production was undetected or very low. The proteins in SMA powder and SMA Gold Cap liquid concentrate were less denatured and animals given these formulas prepared according to the maker's instructions produced relatively high levels of antibodies to β-lactoglobulin and α-casein and a majority developed anaphylaxis when injected intravenously with these products.

3. As well as failing to sensitize, whey that had received severe heat treatment did not, in most cases, elicit anaphylaxis when injected into animals that had been sensitized with unheated milk.

4. Discrimination between antibodies of the IgG1 and IgG2 subclasses specific for β-lactoglobulin showed that IgG1, the principal anaphylactic antibody in guinea-pigs, was preferentially depressed in animals drinking heat-denatured milk preparations.

5. The results suggest that heat denaturation of whey protein may be a logical and simple strategy for producing a hypoallergenic baby milk. Nevertheless, the value of experiments in guinea-pigs for predicting results in man is uncertain and the proposal awaits assessment in clinical trials.

1. Non-haem-iron absorption from a variety of cereal and fibre meals was measured in parous Indian women, using the erythrocyte utilization of radioactive Fe method.

2. The present study was undertaken to establish whether alteration of the phytate and polyphenol contents of sorghum (Sorghum vulgare) affected Fe absorption from sorghum meals, and to assess the influence of fibre on Fe absorption.

3. Removing the outer layers of sorghum grain by pearling reduced the polyphenol and phytate contents by 96 and 92% respectively. This treatment significantly increased the geometric mean Fe absorption from 0.017 to 0.035 (t 3.9, p < 0.005).

4. The geometric mean Fe absorption from a sorghum cultivar that lacked polyphenols (albino sorghum) was 0.043, which was significantly greater than the 0.019 absorbed from bird-proof sorghum, a cultivar with a high polyphenol content (t 2.83, p < 0.05).

5. Fe was less well absorbed from the phytate-rich pearlings of the albino sorghum than from the pearled albino sorghum (0.015 v. 0.035 (t 8.4, P < 0.0005)). Addition of sodium phytate to a highly Fe-bioavailable broccoli (Brassica oleracea) meal reduced Fe absorption from 0.185 to 0.037.

6. The geometric mean Fe absorption from malted sorghum porridge was 0.024 when 9.5 mg ascorbic acid were added and 0.094 when the ascorbic acid was increased to 50 mg (t 3.33, P < 0.005). This enhancing effect of 50 mg ascorbic acid was significantly depressed to 0.04 by tea (t 38.1, P < 0.0005).

7. Wheat bran significantly decreased the geometric mean Fe absorption from white flour from 0.116 to 0.043 (t 7.2, P < 0.0005).

8. Some of the constituents of the dietary fibre complex, such as apple pectin, guar gum, gum tragacanth and microcrystalline cellulose did not inhibit Fe absorption. On the other hand, hemicellulose and lignin decreased absorption. The geometric mean absorption of Fe given with hemicellulose was 0.079 v. 0.269 with microcrystalline cellulose (t 2.95, P < 0.05). Addition of cocoa, which contains approximately 280 g lignin/kg, reduced the geometric mean Fe absorption from milk from 0.075 to 0.035 (t 2.7, P < 0.05).

1. Gum arabic (GA) is a water-soluble polysaccharide (molecular weight approximately 850000) containing rhamnose, arabinose, glucuronic acid and galactose.

2. The metabolism of GA has been studied in the rat. Adult male Wistar rats were given GA incorporated into either an Oxoid breeders (OB) diet or an elemental (Elem) diet.

3. Intestinal contents were examined for precipitable GA using acidified ethanol. GA was found from stomach to small intestine but not in the caecum, colon or rectum.

4. Caecal excision and restoration of intestinal continuity resulted in GA recovery from stomach to rectum.

5. Excreted methane, hydrogen and volatile fatty acids (VFA) were measured as indicators of bacterial activity in the caecum and colon. Methane excretion increased on the OB+GA diet and H2 concentrations remained unaltered. The Elem diet abolished gas production. When the animals were given the Elem+GA diet, H2 and methane were only produced after 28 d. Faecal VFA increased with increasing GA intake, acetate concentration increased and butyrate concentration decreased with increasing GA dosage. Significant decreases in concentrations of VFA were found from caecum to left colon and from left colon to faeces.

6. It can be concluded that GA degradation occurs in the caecum and is associated with increased methane excretion, increased VFA concentrations and changes in the proportions of various VFA in the faeces.

1. Female rats were given throughout pregnancy and lactation a semi-synthetic diet, in which the fat was provided entirely by a soft margarine rich in linoleic acid (18:2ω6) or by mixture of butter and lard, and the influence on the fatty acid composition of fetal and pup brain and retinal phosphoglycerides was studied.

2. The percentage of docosahexaenoic acid (22:6ω3) was much lower but that of docosapentaenoic acid (22:5ω6) was correspondingly higher in the brains of the day-22 fetuses and the 21-d-old pups from the margarine group compared with those from the group given the animal fats. Similar changes were noted in the synaptosomal and retinal phosphoglycerides, being most marked in the ethanolamine phosphoglycerides.

3. The remaining pups from two groups were weaned on day 21 post partum on to the same stock diet that contained preformed 22:6ω3. After 9 weeks of this diet, the differences between the two groups in the fatty acid composition of the brain phosphoglycerides were barely discernible. The percentage of 22:5ω6 had decreased and had been replaced by 22:6ω3.

4. It is concluded that the consequences of consuming a diet rich in linoleic acid and almost devoid of 22:6ω3 on brain fatty acid composition deserve consideration in man.

1. Children (405), initially of average age 11.5 years, recorded all food and drinks consumed for three consecutive days (with an interview on the fourth day) on five separate occasions over a 2-year period. Food tables (Paul & Southgate, 1978) enabled nutrient intakes to be calculated. The data collected were found to be of high reliability (Hackett et al. 1983).

2. The mean energy intakes showed broad agreement with other recent British dietary surveys but were well below those recorded in the prewar study by Widdowson (1947) and the FAO/WHO (1973) recommended levels. They were slightly below the current Department of Health and Social Security (DHSS; 1979) recommended intakes.

3. Over the 2-year period, the energy intake of the boys increased by 13% compared with an increase of only 7% in the girls.

4. The iron and vitamin A intakes of all groups of children were low compared with current recommendations (DHSS, 1979). This seems to be a result of falling energy intake. Mean calcium intakes were also only marginally in excess of the recommended intake, and those of most of the girls would fall below the recommendation if the proposal to end the fortification of flour (DHSS, 1981) is implemented.

1. Protozoa-free steers with simple rumen and abomasal cannulas were given basal diets consisting of a concentrate mixture of flaked maize and tapioca with barley straw (BS) or alkali-treated barley straw (BSA). Other diets were supplemented with urea (BSU and BSAU respectively) or with fish meal replacing the tapioca (BSF and BSAF respectively). The diets were isoenergetic and calculated to provide sufficient metabolizable energy (ME) to support a growth rate of 0.5 kg/d. Rumen-degradable nitrogen (RDN): ME values (g/MJ) were estimated to be 0.50, 1.20 and 0.80 for the basal diet, urea- and fish-meal-supplemented diets respectively. RNA and α, ε-diaminopimelic acid (DAP) were used as microbial markers. 103Ruthenium and polyethylene glycol (PEG) were given as flow markers and flows (g/24 h) at the abomasum of organic matter (OM) and nitrogenous constituents were calculated.

2. Samples of mixed bacteria separated from rumen digesta from animals receiving N-supplemented diets contained significantly more N than those from animals receiving basal diets (approximately 74 and 62 mg/g dry matter (DM) respectively) but there were no other significant differences in total-N contents between treatments. RNA-N: total-N values were similar for all diets (approximately 0.13). DAP-N: total-N values were significantly lower in bacteria from animals receiving alkali-treated (AT) rather than untreated (UT) straw (approximately 0.008 and 0.011 respectively).

3. The proportion of OM intake digested in the rumen (ADOM) was significantly higher for animals receiving AT straw rather than UT straw (approximately 0.54 and 0.43 respectively). N supplementation had no effect on OM digestibility.

4. When basal rather than N-supplemented diets or AT-straw- rather than UT-straw-containing diets were given, there were significantly lower flows of ammonia-N, non-ammonia-N (NAN) and microbial-N (based on RNA flow, MN(RNA)) at the abomasum. Mean daily MN(RNA) flows (g) were 21, 30, 31, 16, 27 and 28 for diets BS, BSU, BSF, BSA, BSAU and BSAF respectively. These correspond to estimated efficiencies of microbial protein synthesis, expressed as g MN(RNA) /kg truly-digested OM, at 14, 22, 22, 12, 18 and 19 respectively. Values were significantly lower for basal as compared with corresponding N-supplemented diets and for AT-straw diets as compared with corresponding UT-straw diets.

5. Estimated mean proportions of total feed-N intake degraded in the rumen, based on MN(RNA) as microbial marker, of diets BS, BSU and BSF were 0.60, 0.74 and 0.47 respectively; corresponding values for diets BSA, BSAU and BSAF were 0.72, 0.73 and 0.36 respectively. Making certain assumptions, the mean proportions of fish-meal-N digested in the rumen were calculated to be 0.23 and 0.14 respectively for UT- and AT-straw diets. The values were not significantly different. Values for microbial flows based on DAP as marker were significantly lower, by about 25%, than those based on RNA.

1. The availability of lysine in nine vegetable-protein concentrates was assessed using the slope-ratio assay for growing pigs and rats. Diets were equalized for crude fibre using solka floc to minimize any possible effects of variation in fibre content on availability estimates.

2. The availability of lysine in the nine proteins for pigs, using food conversion efficiency (FCE) on a carcass basis as the criterion of response were (proportion of total): cottonseed meal 0.39, lupin (Lupinus angustifolius) seed meal no. 10.37, no. 20.65, no. 30.54, no. 40.54, field peas (Pisum sativum) 0.93, peanut (groundnut) meal 0.57, soya-bean meal no. 10.98, no. 2 0.89.

3. Estimates of available lysine for rats as assessed by the slope-ratio assay using FCE on a carcass basis were in close agreement with the pig estimates for cottonseed meal (0.35) and soya-bean meal no. 1(0.91) and no. 2(0.89), higher for lupin-seed meals (range 0.70–0.94 with a mean of 0.81) and peanut meal (0.76) and lower for field peas (0.76).

4. The differences in available lysine were not detected by the chemical Silcock available-lysine test (Roach et al. 1967) or by the direct 1-fluoro-2,4-dinitrobenzene procedure (Carpenter, 1960).

1. The effects of feeding meals, in amounts equivalent to ad lib. intake or to 75% and 50% restriction by intubation, were studied in chicks.

2. Growth estimated by body-weight gain and shank length was improved by tube feeding in the 50%-restricted chicks.

3. Tube feeding increased energy retention at all feeding levels and nitrogen retention in the restricted chicks only.

4. Body fat was increased in the full-fed chicks by intubation and decreased in the 50%-restricted chicks only.

5. Crop and gizzard weights were increased by food restriction and by intubation. Tube-feeding increased the weight of the small intestine at all feeding levels.

6. The activities of the digestive enzymes were lower in the pancreas and higher in the small intestine of the tube-fed chicks than in the voluntarily-fed ones at all feeding levels.

7. It is suggested that synthesis, secretion and stablity of the different pancreatic enzymes could be affected diversely by feeding regimens.

1. Four steers were given straw and tapioca diets, twice daily, in a 4 x 4 Latin-square design. These diets, containing 4.2 g nitrogen/kg dry matter (DM), were further supplemented with either urea, decorticated groundnut meal (DCGM), untreated (UT) casein or formaldehyde-treated (FT) casein to give a total of 19.7 g N/kg DM and 10.5 MJ/kg DM daily.

2. Concurrent samples of rumen bacteria and protozoa and abomasal digesta were collected for each period of the experiment and the concentrations of 2-aminoethyl phosphonic acid (AEPA), diaminopimelic acid (DAPA), total nitrogen (TN), total phosphorus (TP), amino acids and hexosamines were determined in the dried preparations. The nature of the dietary supplements had little effect on the concentrations of most of these constituents or on the total protozoal numbers.

3. Abomasal digesta samples marked with polyethylene glycol (PEG) and chromic oxide for flow estimation were collected over 24 h, and the proportions of protozoal-N, bacterial-N and microbial-N estimated simultaneously using the markers AEPA, DAPA and RNA respectively. These digesta-N components were also estimated using an amino acid profiling (AAP) method which gave, in addition, estimates of the dietary and endogenous components. For the diets containing casein, the proportion of dietary casein was estimated directly using casein-P as a marker.

4. Estimates of the respective mean proportions of microbial-N in abomasal digesta non-ammonia-N (NAN) for the diets containing urea, DCGM, UT casein or FT casein were: AEPA 0.56, 0.32, 0.27 and 0.16; DAPA 0.88, 0.70, 0.81 and 0.57; RNA 0.98, 0.85, 0.92 and 0.53.

5. Giving FT casein significantly (P < 0.001) increased the flow of casein-N at the abomasum and a significantly (P < 0.001) greater proportion of casein-N was found in abomasal NAN (0.51 v. 0.09) where FT rather than UT casein was given.

6. The AAP method gave results for the proportions of microbial- and dietary-N (where casein was given) which were, in general, slightly lower than those obtained using RNA and casein-P as markers. Agreement with estimates of bacterial protein (from DAPA) and of protozoal protein (from AEPA) was less satisfactory.

7. Comparisons of the various estimates of the proportions of microbial-N in abomasal digesta suggested that the results obtained for protozoal-N by AEPA were overestimates. AEPA was found in mixed rumen bacteria which may have accounted in part for these overestimates. However, AEPA was not detected in any of the dietary ingredients.

1. Forty-eight Friesian entire male cattle, with an initial live weight (LW) of 135 kg, were used in two experiments to measure the response to increasing levels of dietary protein (9–11 and 7.5–10.5 g nitrogen x 6.25/kg LW0.75) at differing energy levels (800–900 kJ metabolizable energy (ME) kg LW0.75) over 120-d periods. Digestibility and N balance measurements were also made during the experiments. The diets, which were based on barley and soya-bean meal, were individually fed twice daily.

2. In a third experiment, similar diets were given to four similar animals fitted with intestinal cannulas, at constant energy intake but with variations in dietary protein of 7.5–13.5 g N x 6.25/kg LW0.75. Chromic oxide paper was used as a digesta marker.

3. Positive responses in LW gain and N balance to additional protein were found in both experiments but these were significant (P < 0.05) only in the second experiment and were associated with significant (P < 0.01) increases in the digestibility of modified acid-detergent fibre and ME intake.

4. Mean values, which were not significantly different between treatments, for the degradability of dietary protein in the rumen and the efficiency of microbial protein synthesis were 0.57 and 31.3 g/kg organic matter apparently digested in the rumen respectively. Corresponding values obtained by regression analysis were 0.56 and 28.2.

5. The results in general support the Agricultural Research Council (1980) proposals and suggest that undegraded dietary protein was not limiting in these experiments but that rumen-degradable protein levels were limiting on some treatments.

6. Regression analysis indicated that the mean response to additional protein (g LW gain/g N x 6.25) per kg LW was 0.52 in Expt 1 and 0.51 in Expt 2. These responses could be largely explained by increases in ME intakes.

7. Measurements of duodenal amino acid flow showed marked increases in essential amino acids (EAA) across the rumen. However, EAA flows, were not significantly increased at higher N intakes suggesting that protein per se was not limiting in these experiments.

1. Intestinal radiocalcium absorption was measured in goats by a double-isotope technique involving injection of 45CaCl2 intravenously and 47CaCl2 into the abomasum. Cumulative absorption of radiocalcium was calculated by deconvolution analysis form curves of plasma radioactivity.

2. Repeated measurements at 2 d intervals gave highly reproducible results (r 0.94, P < 0.001). No systematic difference between two consecutive measurements was observed. A good agreement between absorption of radiocalcium from simultaneously administered 47CaCl2 and 45Ca-labelled hay (r 0.93, P < 0.001) seems to justify the use of inorganic 47Ca as a tracer for Ca in ruminant diets.

3. Two- to three-fold increases in radiocalcium absorption 48 h after oral treatment with 1,25- dihydroxycholecalciferol or leaves of Solanum malacoxylon showed the usefulness of the method in situations of rapidly changing Ca absorption.

4. Endogenous adaptations in intestinal radiocalcium absorption from 20 to 43% were observed in lactating goats when Ca intakes decreased from 12 to 4 g/d.

5. It is concluded that the double-isotope technique is a suitable method for studies of Ca absorption in ruminants when tracer is introduced into the abomasum. The test is completed in 3–4 h and may therefore be used in situations where the absorption of Ca undergoes rapid changes.

1. Intestinal absorption of 47Ca was measured by a double-isotope technique in goats treated with 1, 5 or 25 μg of 1,25-dihydroxycholecalciferol (1,25(OH)2D3). The effects of giving 1,25(OH)2D3 by intravenous (iv) infusion for 30–36 h were compared at each dose level with the effects obtained by oral administration of 1,25(OH)2D3 either in ethanol or protected against rumen degradation in fatty acid pellets.

2. Dose-dependent increments in absorption followed the treatments, with a doubling of absorption at the 1 μg dose and three- to fivefold increases with the 5 and 25 μg doses. 47Ca absorption was equally stimulated 2 and 6 d after treatment but had returned to pretreatment levels 12–14 d after treatment.

3. Intravenous and protected oral administration of 1,25(OH)2D3 stimulated 47Ca absorption to the same extent, in spite of two- to fivefold higher plasma concentrations of 1,25(OH)2D3 after iv treatment. Somewhat lower increments in 47Ca absorption were seen using ethanol as the vehicle for oral administration.

4. The naturally occurring metabolites 1,24(R),25-trihydroxycholecalciferol and 1,25(S),26-trihydroxy-cholecalciferol had only one-tenth to one-fifteenth the potency of 1,25(OH)2D3 in stimulating 47Ca absorption, while synthetic lα-hydroxycholecalciferol appeared to be twice as effective as 1,25(OH)2D3 when tested at a high (10μg) dose.