1. The digestion of zinc present in human milk, cow's milk and a commercial babyfood was compared, using the piglet as a model for the human infant.

2. In piglets given human milk the pH of stomach contents was approximately 1 and 0.4 units lower than that of animals given respectively cow's milk and babyfood. The pH values of intestinal contents were approximately neutral and did not vary with the type of feed.

3. Hard casein curds were present throughout the stomachs and small intestines of animals fed on cow's milk or babyfood and between 55 and 70% Zn in these digesta samples were recovered in an insoluble form by centrifugation. In contrast, little solid material was observed in the digesta of animals fed on human milk, and 57 and 93% respectively of the Zn in digesta were recovered in a soluble form in the stomach and small intestine.

4. Soluble fractions prepared by centrifugation of digesta were analysed by filtration on Sephadex G-150. After any of the three feeds, soluble Zn in stomach contents was mainly in a low-molecular-weight form. In intestinal samples, however, Zn was present in low- and high-molecular-weight forms. Whilst there were similar amounts of Zn in the low-molecular-weight form in all samples, approximately three times as much of the total intestinal Zn was in a soluble high-molecular-weight form complexed to proteins in the animals fed on human milk compared with those fed on cow's milk or babyfood.

5. Analysis of protein-bound soluble Zn in intestinal samples on SDS-polyacrylamide gels resulted in a similar pattern of proteins for all feeds. Results indicated that at least some of these proteins were derived from intestinal secretions of the piglet.

6. Some implications of these results in respect of the mode of digestion of Zn and its biological availability to the human infant are discussed.

1. The present study was conducted to determine the biological availability to rats of the selenium in four high-Se seafoods: crab (CuZlinectes supidus), oyster (Crassostrea virginica), shrimp (Penueus duorarum) and Baltic herring (Clupea harengus).

2. Weanling male rats were fed on a Se-deficient Torula yeast diet for 4 weeks followed by either continued depletion or repletion for 4 weeks with 0.05, 0.1 or 0.2 μg Se as selenite/g, or 0.1 or 0.2 μg Se as freeze-dried cooked test food/g. Plasma and liver Se levels or glutathione peroxidase (EC 1.11.1.9; GSH-Px) activities were used as indicators of body Se status.

3. Except for oysters, the biological availability of Se in all these seafoods was close to that of selenite (selenite 100%) when the criterion used was either plasma Se level or plasma GSH-Px activity.

4. By the criterion of increased liver Se level of restored hepatic GSH-Px activity, only herringSe had a biological availability comparable to that of selenite-Se under all conditions tested, whereas crab-Se and oyster-Se were distinctly inferior in this regard.

5. Increasing the amount of crab-Se, oyster-Se or shrimp-Se supplied in the diet from 0.1 to 0.2 μg/g changed the apparent availability (%) of Se for hepatic GSH-Px restoration from 38 to 78, 22 to 53 and 57 to 90 respectively.

6. The present study demonstrates that the availability of Se in certain foods is a function of the criterion chosen, the level of Se supplied in the diet, and possibly other unknown interacting dietary factors.

1. Selenium status and blood levels of other nutrients related to lipid peroxidation were studied in patients with advanced alcoholic liver cirrhosis, in male alcoholics who had been abstinent for at least 1 month and in healthy control subjects.

2. Plasma Se was decreased in alcoholic cirrhosis but not among alcoholics in abstinence. Platelet glutathione peroxidase (EC 1. 11. 1.9; GSH-Px) activity was decreased in cirrhotic patients, whereas GSH-Px in blood and plasma was the same as in controls for both groups of patients.

3. Plasma retinol and plasma α-tocopherol were decreased in alcoholic cirrhosis, whereas plasma ascorbic acid was the same in all groups.

4. The decreases in platelet GSH-Px, plasma Se and α-tocopherol indicate a deranged antioxidant defence in patients with advanced alcoholic cirrhosis, but the levels of these and other nutrients were generally not correlated to common clinical chemical indicators of liver disease.

1. An in vitro method which used enzymic digestion of the food matrix to release biologically available vitamin B6 is described.

2. Vitamin B6-fortified liquid model foods were thermally processed. After these foods had been freeze-dried, one part was subjected to enzymic hydrolysis at pH 2.0 with pepsin (EC 3.4.23.1) followed by a hydrolysis at pH 8.0 with pancreatin. The vitamins that were found in the supernatant fraction, after an acidified methanol treatment of the hydrolysate, were estimated by high-performance liquid chromatography (HPLC). The other part was given to rats who were kept on a vitamin B6-depleted diet.

3. The biologically available vitamin B6 content of the processed model foods, as determined by rat bioassay, showed good correlation with the vitamin B6 determined by HPLC.

4. It has proved possible to use this in vitro, two-stage enzymic digestion system followed by HPLC determination to determine biologically available vitamin B6 in vitamin B6-fortified processed model foods.

1. The effect of extrusion cooking of a high-fibre cereal product on digestibility of starch, fibre components and phytate in the stomach and small intestine was studied by in vivo digestion in ileostomy subjects, as well as its effect on ileostomy losses of fat, nitrogen, sodium and potassium.

2. Seven ileostomy subjects were studied during two periods (each of 4 d) while on a constant low-fibre diet supplemented with 54 g/d of a bran-gluten-starch mixture (period A) or the corresponding extruded product (period B).

3. Extrusion cooking, using mild conditions, did not change the content of starch, dietary fibre components or phytate of the bran product, but the phytase (EC 3.1.3.26) activity was lost. During the period using the extruded bran product, there was a significant increase in recovery of phytate-phosphorus (period A, 44% of intake; period B, 73% of intake). The amount of fibre components, fat, fatty acids, N, Na, K, water and the ash weight of the ileostomy contents did not differ between the two periods. Only 0.6 and 0.7% respectively of ingested starch was recovered in ileostomy contents in periods A and B, while the fibre components were almost completely recovered.

4. Extrusion cooking, using even mild conditions, may lead to a considerable impairment in the digestion of phytate, probably due to a qualitative change in phytate and a loss of phytase activity. Starch, before and after extrusion cooking, is almost completely digested in the stomach and small intestine while fibre components are digested to a very small extent.

1. The effect of extrusion cooking, using mild conditions, of a high-fibre cereal product on apparent small bowel absorption of zinc, iron, calcium, magnesium and phosphorus was studied.

2. Seven ileostomy subjects were studied during two periods (each of 4d), on a constant low-fibre diet supplemented with either 54 g/d of a bran-gluten-starch mixture or the corresponding extruded product.

3. The apparent absorption of Zn, Mg and P was significantly decreased (P < 0.05) during the period with extruded product compared with the period with bran-gluten-starch. No difference was found for Fe and Ca.

4. The negative effect of extrusion cooking of a product containing phytic acid on availability of Zn, Mg and P was small but could be of nutritional relevance in foodstuffs that are consumed frequently and in infant formulas.

1. Gum arabic is a water-soluble polysaccharide resistant to human gut enzymes and thus can be described as dietary fibre.

2. Using a most-probable-number technique, estimates were made of total anaerobes and of gum-arabic fermenters in the faeces of a volunteer during a contro1 period and during addition of 10 g gum arabic/d to the diet. Using an enrichment technique, the principal bacteria able to utilize gum arabic as the only carbohydrate source were isolated and characterized.

3. Faecal samples were analysed for undegraded gum arabic and, following acid-hydrolysis, for total sugars.

4. The proportion of the faecal flora able to degrade the gum arabic polymer rose from an initial level of 6.5% to more than 50% during gum-arabic ingestion, and subsequently returned to the control level after ingestion ceased. The principal gum-arabic fermenters were species of Bucteroides and Bifdobucterium.

5. Undegraded gum arabic was not detected in any faecal sample nor were there significant differences in the level of total sugars in acid-hydrolysed faeces between gum arabic and control periods.

6. The results presented indicate a direct and rapid change in faecal flora in response to a specific change in the diet of a human volunteer.

1. During 1978 and 1979, the 343 members of seventy-nine families representative of households with two adults and two or three children living in Cambridge, England, completed 7-d records of food consumption using the semi-weighed technique. Nutrient intakes were calculated using food composition tables.

2. Amongst males, the average intakes of energy and most nutrients were highest in men and boys aged 11–17 years, and lowest in boys under 5 years. Amongst females, intakes were highest in girls aged 11–17 years, and lowest in those under 5 years. At each age, intakes in males were generally higher than those in females.

3. Nutrient distribution within families was described using the ratio, intake of each subject: intake of the male head of the household. The problems inherent in using this ratio are discussed.

4. The distribution of nutrient intakes within the families was not in accordance with the recommended daily amounts (RDA). Men and young boys received more than their fair share of the family diet, while women and girls aged 5–17 years received less.

5. Estimates of dietary adequacy based on the averages of family consumption and requirements (RDA) concealed up to twofold variations in the adequacy of diet of different age-sex-groups.

6. The interpretation of dietary adequacy in household food surveys should take into account the distribution of nutrient intakes within the household, as the distribution may be substantially different from that predicted by the RDA.

1. Iron absorption from 10 mg Fe (as ferrous sulphate), labelled with 1.3 mg 58Fe, was measured in fasting, non-anaemic adult subjects by the faecal-balance technique. The measurement was performed twice, each subject being given, in random order, either 50 mg Fe or a placebo 18 h before the 58Fe-labelled FeSO4.

2. The 50 mg Fe load significantly reduced Fe absorption the following day (P < 0.01), from a mean of 35.4 (SEM 4.6)% to 29.0 (SEM 5.1)%. This points to the importance of strict dietary control during Fe-absorption studies to eliminate bias in results.

3. In a separate study, the feasibility of using S6Fe-enrichment of erythrocytes, measured by neutron activation analysis (NAA), 10 d after a meal labelled with 0.69 mg 58Fe as an index of Fe absorption was examined. The levels of 58Fe in the blood were detectable by NAA. Regression analysis showed a significant relation between 58Fe-enrichment of blood and 58Fe absorption, calculated as the difference between intake and faecal excretion (R 0.59, P < 0.05).

1. The effects of a 100 g/kg dietary substitution of wheat bran on the body-weight gain, food consumption and faecal dry weight of mice given a high-sucrose diet and on the activities of some key enzymes of carbohydrate and lipid metabolism in liver and adipose tissue were studied.

2. Wheat bran had no effect on body-weight gain, food consumption or faecal dry weight.

3. Wheat bran had no effect on the activities of hepatic glucose-6-phosphate dehydrogenase (EC 1.1.1.49), 6-phosphogluconate dehydrogenase (EC 1. 1.1.44), malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+) (EC 1. 1. 1.40), ATP-citrate (pro-3S)-lyase (EC 4.1.3.8), pyruvate kinase (EC 2.7.1.40) and fructose-1, 6-bisphosphatase (EC 3.1.3.11). The activity of hepatic 6-phosphofructokinase (EC 2.7.1.11) increased but only when expressed on a body-weight basis.

4. Wheat bran had no effect on the activities of adipose tissue glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+), (ATP-citrate igro-3S)-lyase, hexokinase (EC 2. 7. 1. 1), 6-phosphofructokinase and pyruvate kinase.

5. These results suggest that unlike guar gum and bagasse, wheat bran does not change the flux through some pathways of lipogenesis in liver and adipose tissue when mice are given high-sucrose diets.

1. The effect of cholesterol feeding during and after a period of protein malnutrition lasting 4 weeks was examined in the rat. Indices measured were plasma total cholesterol, triglycerides and protein levels, and aorta total cholesterol, triglycerides, hexosamine and hydroxyproline concentrations.

2. In both plasma and aorta, total cholesterol and triglycerides levels were higher in the low-protein diet group than in the standard-protein diet group, when cholesterol was supplied in both diets.

3. During the malnutrition period, cholesterol feeding led to a greater decrease in plasma protein than that promoted by the low-protein diet without cholesterol, while aorta hexosamine levels decreased to a lesser extent.

4. Cholesterol feeding with a standard-protein diet promoted a slight and temporary increase in aorta hydroxyproline levels, while a decrease in aorta hexosamine concentration was observed. Cholesterol feeding with the low-protein diet, on the other hand, also promoted a decrease in aorta hexosamine levels but to a lesser extent.

5. During the recovery period, cholesterol feeding impaired the return of plasma protein, aorta hexosamine and lipid levels to that of the control values.

6. These findings demonstrate that cholesterol feeding promotes different changes in aorta and plasma, depending on whether or not protein is supplied by the diet in adequate amounts. This point could be important in relation to the development of atherosclerosis during recovery from a period of malnutrition.

1. Two duplicate groups of rainbow trout (Sulmo gairdneri; mean weight 27 g) were given diets of differing selenium content (deficient 0, 025 mg Se/kg; supplemented 1.022 mg Se/kg) for 30 weeks.

2. There were no significant differences between treatments in weight gain but packed cell volume, liver vitamin E and liver and plasma Se concentrations were all significantly lower in the Se-deficient trout.

3. Ataxia occurred in about 10% of the Se-deficient trout and histopathologies were evident in nerve cord (damage to axon sheath) and liver (loss of integrity in endoplasmic reticulum and mitochondria with appearance of increased vesiculation).

4. Glutathione peroxidase (EC 1.11.1.9) activity was significantly reduced in liver and plasma of Se-deficient fish but there was no indication, from differential assay, of any non-Se-dependent glutathione peroxidase activity. Glutathione transferase (EC 2.5. I.18) activity was significantly increased in Se-deficient trout.

1. Experiments involving 15N and 14C tracers were made in sheep consuming 800 g air-dry chopped lucerne (Merlicugo sativa) hay/d and providing 20.4 g N/d to study N and C flows within the caecal digesta and between the caecum, blood and rumen.

2. Continuous infusions of 15N tracers were made into the caecal ammonia, blood urea and rumen NH3 pools. The concentration and enrichment of caecal digesta NH3-N, caecal microbial N, caecal digesta non-urea. non-ammonia-N (NU-NAN), faecal NU-NAN, blood urea-N, rumen digesta NH3-N and rumen bacterial N were estimated at intervals during the infusions. A three-pool open-compartment model was solved to estimate N flows between the caecal digesta NH3-N, blood urea-N and rumen digesta NH3-N pools.

3. The rate of irreversible loss from the caecal digesta NH3-N pool was 2.17 (SE 0.623) g N/d. On average 0.9 (SE 0.56) g N/d of caecal digesta NH3-N was derived from blood urea and 0.1 (SE 0.08) g caecal digesta NH3-N/d was apparently derived from the fermentation of undigested rumen microbes in the caecum. The amount of NH3-N produced by proteolysis and deamination of dietary and endogenous N was 1.1 (SE 0.13) g/d.

4. There was net incorporation of 0.56 (SE 0.306) g caecal digesta NH3-N/d into caecal microbes. The microbial U synthesized de novo in the caecum was not determined, but 2.9 (SE 0.52) g microbial N/d of both rumen and caecal origin flowed out of the caecum and constituted 0.48 of the NU-NAN flow. The majority (mean 0.83 (SE 0.044)) of this microbial N was excreted in faeces.

5. On average 1.8 (SE 0.80) g caecal digesta NH3-N/d were absorbed. Of this NH3-N, 0.92 (SE 0.054) was converted to blood urea, contributing 0.10 (SE 0.031) of blood urea-N. Only 0.012 (SE 0.0041) of rumen digesta NH3-N and 0.005 (SE 0, 0009) of rumen bacterial N were derived from caecal digesta NH3-N.

6. Infusions of 14C tracers were made into the caecal digesta bicarbonate, blood bicarbonate, rumen digesta bicarbonate and blood urea pools, and samples were obtained at intervals to determine the specific radioactivity of each pool. A four-pool open-compartment model was solved to estimate C flows between these pools.

7. The rate of irreversible loss of blood urea estimated with [14C]urea (17.1 (SE 1.18) g N/d) was greater (P < 0.01) than that estimated with [15N]urea (14.0 (SE 0.87) g N/d).

8. Transfer of blood urea to the caecal digesta estimated with 14C tracers (1.4 (SE 0.61) g N/d) was greater (P < 0.01) than that estimated with I5N tracers (0.9 (SE 0.56) g N/d). The estimate of transfer of blood urea to the rumen digesta was also greater with 14C tracers (P < 0.05; 1.7 (SE 0.15) and 1.2 (SE 0.19) g N/d respectively). The urea hydrolysed in the gastrointestinal tract other than in the rumen digesta pool and the caecal digesta pool was 0.56 of total urea hydrolysis when estimated with 14C tracers, or 0.69 when estimated with 15N tracers. Results from previous acute experiments suggested that with three of the four observations made in three sheep in the present experiment the transfer of blood urea to the caecal digesta could have occurred entirely via ileal digesta. Similarly, urea transfer to the rumen digesta could have occurred entirely via saliva.

1. In Expt 1, the effects on laying hens of diets supplemented with zinc oxide providing up to 20 gadded zinc/kg were compared. In Expt 2 the diets contained up to 6 g added Zn/kg.

2. In both experiments, food intake, body-weight, egg number, and liver, oviduct and ovary weights/kg body-weight were significantly reduced by added ZnO; gizzard weight/kg body-weight was significantly increased. In Expt 2, pancreas weight was significantly reduced by added ZnO.

3. Liver, kidney and pancreatic Zn and iron concentrations were significantly elevated in both experiments.

4. In both experiments, liver, kidneys and pancreatic copper concentrations gave quadratic responses to added ZnO.

1. Ten Friesian male calves of about 100 kg and 3 months old were reared similarly and were worm-free. From 13 weeks of age five calves received a dose of 640 infective larvae (L3) of lungworms (Dictyocuulus viviparus) twice weekly for 8 weeks to simulate continuous infection. Animals not infected were fed to the same level as the infected animals (about 1.2–1.3 kg concentrates and 14–1.5 kg good-quality hay/d).

2. Heat production was measured twice weekly during 48 h (days 2 and 3, and days 5 and 6) in each group of experimental animals.

3. Infection caused considerable damage to the lungs, increased respiration frequency and clearly produced antibody titres against D. viviparus.

4. Animals infected with lungworms had on average a lower rate of weight gain, reduced by 70 g/d per animal. Digestibility was not affected. Nitrogen retention was much lower in infected animals (12.0 v. 14.6 g/d per animal in controls).

5. Metabolizability of energy was slightly reduced in infected animals. Heat production as found in infected animals may be associated with an increased maintenance energy requirement of 30 kJ/kg live weight0.75 per d or reduced partial efficiency of feed conversion above maintenance in animals infected with lungworms (58.5 v. 64.1 % in the control animals).

6. It was concluded that the depression in rate of gain was related to reduced intake of feed and to decreased N retention.

1. Rams, fauna-free from birth and initially of 48–65 kg live weight, were allocated to two groups of ten each and given a diet containing 14 μg copper/g dry matter; five additional rams were killed and their livers were analysed for Cu.

2. One group (faunated) was inoculated with a mixed population of ciliate protozoa, and contained between 60x105 and 195 x 105 protozoa/ml rumen fluid throughout the 184 d experiment. The other group remained fauna-free. Following blood sampling, three rams in each group were killed on day 63, two on day 125 and four on day 184. One sheep in each group died during the experiment.

3. Faunated rams showed higher weight gains and feed consumption than fauna-free rams.

4. Plasma Cu concentration (μg/ml) increased from an initial 0.82to a final 1.00 in faunated and 1.36 in fauna-free rams. Liver Cu concentration (μg/g dry matter) increased from an initial 745 to a final 962 and 1684 in faunated and in fauna-free sheep respectively, representing a 4.3-fold greater increase in the fauna-free than in the faunated group. The absorption and retention of Cu was 38–50% higher in the fauna-free than in the faunated rams.

5. It was suggested that rumen ciliate protozoa increased rumen production of sulphide (through increased breakdown of soluble proteins) which complexed part of the Cu, making it unavailable for absorption and utilization. Therefore, ciliate protozoa could determine susceptibility to chronic Cu toxicity in sheep.

1. Gel filtration on Sephadex G 75 was used to separate the medium-molecular-weight zinc-binding proteins from the soluble fractions from the duodenal and jejuno-ileal segments of the rat gut at 30 min after the intragastric administration of a tracer dose of 65Zn. These proteins were resolved by ion-exchange chromatography on DEAE cellulose.

2. In both the duodenum and jejuno-ileal segment an appreciable fraction of the total soluble Zn was bound in a protein fraction that resembled metallothionein [MT] in its behaviour on gel filtration. These fractions, however, were not homogeneous, but contained several medium-molecular-weight Zn-binding proteins. In the duodenum, but not in the jejuno-ileal segment, two ofthese proteins appeared to be the isometallothioneins, ZnMT-I and ZnMT-11.

3. These results suggest a possible role for MT in the binding of newly-absorbed Zn in the duodenal mucosal cells. They also show that gel filtration alone is insufficient for the identification of MT in the intestine.

1. The metabolism of dehydroretinyl ester has been studied in vitamin-A-deficient white leghorn chicks. Dehydroretinyl ester was metabolized to 3-hydroxyretinol diester, 3-hydroxyanhydroretinol and rehydrovitamin A2 which were isolated from the intestines and livers of chicks.

2. The metabolism of 3-hydroxyretinol diester and 3-hydroxyanhydroretinol, which were immediate metabolites of dehydroretinol, was studied in chicks.

3. Retinol was not detected in these experiments.

1. Six rumen and abomasal cannulated heifers were used to study the effects of intake on the fractional outflow rates (FOR) of chromium-mordanted cotton-seed meal (Cr-CSM) and meat meal (Cr-MM), CrEDTA, ytterbium and lignin from the rumen. Values of FOR of Cr-CSM and Cr-MM were combined with values of nitrogen disappearance from the protein supplements, placed in porous synthetic (nylon) bags and incubated within the rumen (P), to calculate effective degradation (D)of CSM and MM when fed to heifers eating sodium hydroxide-treated straw. Also, N degradation in vivo (V) was measured as the difference between abomasal N flow and the sum of flows of microbial and endogenous N.

2. FOR were positively related to intake and differences between supplements were significant (p <0.01). FOR pertaining to high and low intakes respectively were 0.073 and 0.052 for Cr-CSM, 0.082 and 0.071 for Cr-MM, 0.030 and 0.023 for lignin, 0.082 and 0.073 for CrEDTA and 0, 044 and 0.035 for Yb.

3. A rise of 28.8 and 13.4% in FOR of Cr-CSM and Cr-MM respectively, associated with an increase in intake from maintenance to 1.5 times maintenance, resulted in 10.7 and 2.2% reductions in D, 24 h after feeding, for CSM and MM respectively.

4. With the exception of CSM at the high intake, estimates of V were underestimated by D and were 8.6–25.0% greater than the D values when time of incubation (t)= ∞. The two techniques, however, ranked the degradation of the two supplements in the same order at both levels of intake.

5. Underestimation of V by D may be attributable to underestimation of P, overestimation of FOR (both resulting in underestimation of D) or overestimation of V due to biases associated with the estimation of this part of the comparison. The relative importance of these factors remains to be determined.

1. Four mature sheep were offered perennial ryegrass (Lolium perenne, cv. S23) silage (885 g dry matter/d) at hourly intervals. The silage was well fermented with a pH of 4.0, a lactic acid content of 139 g/kg dry matter and an organic matter digestibility of 0.766.

2. Continuous intraruminal infusions of 14C-labelled sodium salts of [U-14C]acetic acid, [2-14C]propionic acid, [2-14C]butyric acid and D- and L-[U-14C]lactic acid and an intravenous infusion of [U-14C]glucose were made on separate occasions to estimate the fluxes of rumen acetate, propionate, butyrate and lactate as well as plasma glucose. The data were resolved by the use of appropriate four-compartment (rumen) and three-compartment (rumen-plasma) models.

3. Irreversible loss rate (g C/h) of rumen acetate (5.32 g C/h) was considerably greater than values obtained for propionate (2.58), butyrate (2.80) and lactate (2.91).

4. Total flux of lactate (1.83 mol/d) exceeded the amount of lactate consumed in the diet (1.37 mol/d) indicating a net synthesis of 0.46 mol lactate/d. Approximately 0.90 of total lactate flux was metabolized in the rumen, with 1.00 mol/d converted to acetate, 0.57 to propionate and 0.08 to butyrate. The flux to acetate was significantly (P < 0.05) greater than that to propionate. Both the D- and L-isomers appeared to have similar metabolic fates.

5. Lactate appeared to make no direct contribution to glucose flux in the animal, but 0.10 of total lactate was converted to glucose through propionate.

6. The results are discussed in relation to overall lactate metabolism, and it is suggested that almost 0.30 of ruminally digested organic matter may be fermented via lactate.