1. Serum folate level, packed cell volume and haemoglobin concentration of apparently healthy rural Sri Lankan women, between 20 and 45 years and earning up to Rs. 500 (Sri Lankan Rs. 35 ⋍ £1 Sterling) per month, were estimated during pregnancy and when on oral contraceptive (OC) treatment with Ovulen 50 (ethinyl oestradiol 0·05 mg,ethinodiol diacetate 1 mg).

2. Ovulen 50 administration led to a fall in serum folate levels which occurred very rapidly during the first 6 months and more slowly thereafter, stabilizing at 2·2 ng/ml in women of very low economic status and at 2·9 ng/ml in the more privileged.

3. There was a steady fall in serum folate concentrations during pregnancy, the levels at the end of pregnancy being higher than those in women under OC treatment for 9 months.

4. The need for folate supplementation during OC treatment is stressed.

1. The capacity of wheat bran to impair mineral absorption independent of its phytate content was studied by metabolic balance studies in man.

2. Three breads were prepared, equivalent to white, brown and wholemeal, by adding bran in different quantities to white flour. Calcium, iron, zinc and sodium phytate were added to the loaves to make the amounts equal in all breads.

3. Six healthy volunteers were studied for three consecutive 24-d-periods during which they ate a controlled diet, typical of that normally consumed in the UK but with 200 g bread/d. Only the type of bread changed between each dietary period.

4. The phytate contents (mmol) of 200 g of each of the breads after baking were: white 2·3, brown 2·1 and wholemeal 2·2; non-starch polysaccharide contents (9) were: white 3·3, brown 10·9 and wholemeal 18·7

5 . The increased amount of bran in the breads increased stool output in the expected way but no change was seen in Ca, Zn and Fe balance. Blood levels of these minerals remained unchanged.

6. It is concluded that wheat bran and, in particular, the cell-wall polysaccharides of bran, are unlikely to exert a significant effect on mineral absorption in man, in amounts customarily eaten, independently of the effect of phytate present in the bran.

1. The concentration and distribution of iron in 59Fe-labelled chicken leg and breast meat and liver were determined by gel filtration. In all samples approximately 50% of the Fe was insoluble (haemosiderin) and the haemoproteins (haemoglobin and myoglobin) constituted from 15% (liver) to 25% (leg meat) of the total Fe. Ferritin accounted for from 12% (leg meat) to 27% (liver) of the total Fe.

2. A technique was developed which enabled the time-course of the passage of 59Fe-labelled whole and fractionated meat and liver through the gastrointestinal tract of Fe-replete and Fe-deficient rats to be followed and it was found that the rate of stomach emptying appeared to be a function of the viscosity of the meal. In Fe-replete rats approximately 71% of a meal of raw chicken meat had left the stomach within 1 h of administration and by 2 h the stomach was almost empty and much of the unabsorbed 59Fe was in the ileum. By 4 h the ileum and colon contained almost equal amounts of 59Fe. Between different test meals there were only slight differences in gastrointestinal distribution and these reflected the different rates of stomach emptying.

3. Stomach emptying was slower in Fe-deficient compared with Fe-replete rats.

4. In Fe-replete, but not Fe-deficient, rats it was found that the amount of 59Fe lost (absorbed) from the gastrointestinal tract 2 h after administration of a test meal was not significantly different from the value found using a 7 d faecal collection technique.

5. Comparison of the 2 h absorption values for several test meals indicated that 59Fe absorption from raw whole meat was significantly higher than from the soluble extract and the residue after extraction (haemosiderin).

6. Heat treatment caused a significant decrease in the absorption of Fe in whole meat and the soluble meat extract but a significant increase in the liver absorption values. It is suggested that denatured haemoproteins are less available for absorption than their native forms but that heating increases the availability of the Fe of haemosiderin or ferritin or both.

7. Isolated muscle ferritin was poorly absorbed but on the addition of excess bovine serum albumin the absorption of the Fe was markedly increased.

8. It is concluded that, to estimate the Fe availability of a food such as chicken meat or liver one must not only take account of the concentration and type of each Fe-containing compound present but also such factors as their possible synergistic effects, the presence of chelating agents, the extent of cooking and the concentration and type of proteinaceous digestion products.

1. A randomized double-blind crossover trial was carried out to compare the influence on plasma lipid concentrations, platelet thromboxane B2 production and platelet aggregation induced by ADP, collagen and U46619 (a prostaglandin endoperoxide analogue), of a daily 10 g supplement of a fish-oil concentrate (MaxEPA), which provided (g): 1·7 20:5ω3, 0·3 22:5ω3 and 1·2 22:6ω3, taken for 2 weeks by ten healthy subjects, with one of vegetable oil providing 3·4 18:2ω6.

2. A lower response to platelet aggregation induced by 0·5 μg collagen/ml but not by other aggregating agents was observed following both types of supplement. Platelet thromboxane B2 production induced by collagen also tended to be lower following the supplements.

3. Plasma total cholesterol concentrations were unaffected by the supplements. The MaxEPA but not the vegetable-oil supplement lowered the concentration of plasma triglycerides and increased that of high-density-lipoprotein-cholesterol.

1. Lipid-lowering diets enriched in polyunsaturated fat decrease the serum cholesterol in hyperlipoproteinaemia, usually by reducing both the low-density-lipoprotein (LDL) and high-density-lipoprotein (HDL) cholesterol concentrations. The aim of the present study was to investigate whether the effects on LDL could be maintained but those on HDL cholesterol be diminished by reducing the ratio, polyunsaturated: saturated fat (P:S) of the diet.

2. Twenty hyperlipoproteinaemic patients (six with type IIa, eight with type IIb and six with type IV) in a metabolic ward were given two fat-modified diets during two consecutive 3–week periods in a randomized order. The diets were identical with regard to nutrient composition but differed with regard to the P:S values, which were 2.0 and 1.3 respectively.

3. The lipoprotein-lipid composition and serum apolipoprotein concentrations were similar at the end of the two dietary periods in type IIa and type IV patients but in type IIb patients a more pronounced reduction of the LDL-cholesterol concentration by 9% (P < 0·05) was achieved on the diet with the higher P:S value. The HDL-cholesterol did not differ significantly.

4. The results indicate that increasing the P:S value of lipid-lowering diets from 1.3 to 2·0 does not offer a great advantage with regard to the lipoprotein-lipid reductions achieved in moderate hyperlipoproteinaemia.

1. Experiments to measure the effect of a fibre source in the diet on stool bulk are difficult and lack precision. In vitro methods which would identify fibre sources that are effective for clinical and epidemiologic use would be valuable. One important property of fibre which influences the ability of fibre to increase stool weight is its water-holding capacity (WHC).

2. WHC was measured using centrifugation, filtration, suction pressure and water flow-rate techniques using fibre concentrates of potato, cereal bran and gum arabic.

3. Dietary supplementation of three preparations of potato fibre (20 g/d) had no significant effect on stool weight but 16 g bran/d increased stool weight from 107 (SE 44) g/d to 174 (SE 51) g/d.

4. The effects of these fibres on stool weight can be related to the nature of the water-holding properties of fibre rather than absolute WHC.

1. Rates of lipogenesis de novo have been studied in liver and epididymal fat pads of male rats chronically treated with ethanol. A solution of ethanol (150 ml/l) was administered as the only drinking fluid for 3 months with a standard solid diet; both food and drink were available ad lib.

2. Lipogenesis in vivo was measured by the incorporation of tritiated water into lipid fractions: non-saponifiable lipid and fatty acids. Non-saponifiable lipid, both in liver and in adipose tissue, was unaffected by ethanol treatment. However, fatty acid synthesis de novo was significantly enhanced in both liver and adipose tissue, by 150 and 300% respectively.

3. Plasma triacylglycerol and non-esterified fatty acid levels were unchanged and plasma glucose concentration slightly increased by ethanol administration.

4. The rate of lipogenesis increased when insulin: glucagon increased twofold due to the effect of ethanol.

1. Twelve grain mixtures, one lucerne (Medicago sativa) hay and one maize silage which had been used in mixed diets for which dietary nitrogen undegraded in the rumen (UDN) had been estimated with duodenally-cannulated cows, were studied. Total N in the feeds was fractionated into pool A (N soluble in borate–phosphate buffer), pool B (total N–(pool A + pool C)) and pool C (acid-detergent-insoluble N or residual N after 24 h incubation in protease solution).

2. N solubilization in protease solution containing 6·6 units/ml (substrate-saturating enzyme concentration) indicated the presence of subfractions in pool B, with different rates of solubilization. Such subfractions were not detectable from in situ, Dacron bag, estimates of N solubilization.

3. UDN was estimated using a dynamic mathematical model and rate-constants obtained from N solubilization in protease solution or in situ.For three grain mixtures tested using the protease technique the model predicted UDN values of 7, 10 and 12% compared with values of 47, 66 and 59% estimated in vivo. The full range of experimental feeds was tested using the in situtechnique and UDN values predicted by the model were used to derive UDN values for twelve mixed diets. The latter values were significantly but not closely correlated with those determined in vivo (r2 0·41, P < 0·05).

4. An attempt was made to simulate rumen proteolysis in vitro by choosing a protease enzyme concentration (0·066 units/ml) providing a proteolytic activity similar to that of whole rumen fluid. The experimental samples of feed were subjected to simulated rumen proteolysis for 18 or 48 h to resemble the mean retention times in the rumen for grain mixtures and roughages respectively. The residual N at the end of incubation was considered as an estimate of UDN. The UDN values estimated from simulated rumen proteolysis and those determined in vivo for twelve mixed diets were in close agreement (r2 0·61, P < 0·01).

5. Simulated rumen proteolysis can serve as a simple, rapid and sensitive method to estimate UDN in a variety of feedstuffs.

1. A method is described for the determination of protein degradation based on measurements of ammonia concentration and gas production (Menke et al. 1979) when a feedingstuff was incubated with rumen fluid in vitro.

2. NH3 liberated during incubation is in part used for microbial protein synthesis. Production of carbon dioxide and methane can be regarded as a measure of energy available for protein synthesis. The ratio, gas production: incorporation of NH3-nitrogen was estimated by addition of starch to the substrate. The response in gas production was linear in the range 0–200 mg starch, when starch was added to 0–200mg feedingstuff dry matter and 30 ml rumen fluid-medium mixture.

3. Linear regression between NH3-N concentration (y, mg) and gas production (x, ml) yielded an intercept (b0) representing that amountof NH3-N which would be released when no fermentable carbohydrates were available and consequently no bacterial protein synthesis took place.

4. The difference between this intercept b0 and NH3-N content in the blank (rumen fluid without substrate added) indicated the amount of NH3 liberated from protein and other N-containing compounds of the feedingstuff incubated. In vitro-degradable N (IVDN) was calculated as a proportion of total N by the equation:

1. The absorption of methionine and methionine sulphoxide was compared in inverted rings from three sections of rat intestine.

2. In all sections, absorption of unoxidized methionine was 20–40% higher than that of methionine at low physiological substrate concentrations. At higher substrate levels, the difference was not so pronounced.

3. Inhibition studies indicated that absorption of methionine and of methionine sulphoxide took place by different absorption systems.

4. Glutathione increased the absorption of methionine and, to a greater extent, the absorption of methionine sulphoxide.

1. Groups of kids were reared from birth to 5 d on goat's milk. On the 6th day five of the kids received by bottle a morning feed of goat's milk with [3H]folic acid added to saturate the folate-binding proteins (FBP) (Expt 1); three kids received raw goat's milk containing only the endogenous folate and hence a large surplus folate-binding capacity (FBC) (Expt 2). The contents of the stomach, duodenum, jejunum and ileum were recovered by washing out 1·5 h after feeding (Expt 1) or at 0·5, 1 and 3·5 h after feeding (Expt 2).

2. Recovery of [3H]folic acid 1·5 h after feeding (Expt 1) in all segments was 58·4%, mainly in a soluble form, most of this being in the stomach (37·0%) and ileum (14·3%). No surplus FBC was found in any gut segment. Sephadex G-75 chromatography of the soluble fractions of the contents of the various gut segments showed that [3H]folic acid remained bound to FBP throughout the stomach and small intestine. The bound [3H]folic acid exhibited a molecular weight of 81000 in stomach contents, similar to that in the milk feed, presumably representing an aggregated form of the FBP, whereas in the intestinal contents its molecular weight was 39000 indicating dissociation to monomer due to dilution in the recovery process.

3. In Expt 2, the total recovery of free FBP in all four gut segments was 67, 54 and 23% respectively at 0·5, 1 and 3·5 h after the milk feed, and the distribution of FBP along the gut at 1 h was similar to that of [3H]folic acid-labelled FBP at 1·5 h in Expt 1. In mature goat's milk the endogenous 5-methyltetrahydrofolate was shown to be associated with species of molecular weight 80000 and 38000.

4. The results indicate that goat's-milk FBP is relatively resistant to digestionby gastric and intestinal enzymes in vivo in the kid and survives along the length of thesmall intestine.

5. The implications of the findings are discussed in relation to the possible influence of FBP on uptake of folate by mucosal cells and their relevance to neonatal folate nutrition.

1. Male weanling rats were maintained on diets either deficient or adequate in zinc for a period of 4 weeks. The rats on the deficient diet showed a reduction in food intakesand growth.

2. After 4 weeks both soleus muscles and the lateral portion of the diaphragm were studied histochemically to examine the relative frequencies of the fibre types.

3. The soleus muscles of the deficient animals showed a significant change in the proportion of slow and fast fibres. The diaphragm muscles of the deficient animals had a significant increase in the proportion of fast-twitch oxidative glycolytic fibres and a significant decrease in fast-twitch glycolytic fibres compared with the controls.

4. Stainable lipid increased in the diaphragm muscle of the deficient animals with respect to their pair-fed controls.

1. The effects of feeding either a high-protein (HP) diet or a low-protein (LP) diet between 1·8 and 15 kg live weight (LW) and a low-energy (LE) or a high-energy (HE) intake but at the same protein intake subsequent to 15 kg LW on the performance and body composition of pigs growing to 75 kg LW were investigated.

2. During the LW period 1·8–15 kg, pigs given the LP diet exhibited poorer growth performance (P < 0·01) and at 15 kg contained more fat (P < 0·01) in their empty bodies than pigs given the HP diet.

3. On the LE treatment subsequent to 15 kg LW, pigs previously given the LP diet deposited protein at a faster rate and exhibited more rapid and efficient growth to 60 kg LW than those given the HP diet before 15 kg. However, on the HE treatment, pigs previously given the LP diet deposited protein at a slower rate and exhibited poorer growth performance (P < 0·05) between 15 and 45 kg LW but grew at a faster rate between 45 and 60 kg LW than pigs previously given the HP diet.

4. On the LE treatment subsequent to 15 kg LW the differences in body composition between the two protein groups were no longer significant at 45 kg. However, on the HE treatment, pigs previously given the LP diet remained fatter (P < 0·05) to 60 kg LW than those previously given the HP diet.

5. The results suggested that restricting protein intake between 1.8 and 15 kg LW reduced, temporarily, the upper limit of protein retention and growth performance during subsequent development. This finding is discussed in relation to the effects of protein nutrition in early life on the hyperplasic development of muscle tissue.

1. The effects of feeding either high-protein (HP) or low-protein (LP) diets between 1·8 and 15 kg live weight (LW) and a low-energy (LE) or high-energy (HE) intake subsequently on the cellularity of muscle and adipose tissue in pigs growing to 75 kg LW were investigated.

2. The effects of the nutritional treatments on muscle tissue were assessed from the weight and DNA content of the m. adductor. For adipose tissue the total DNA content and fat cell size of the subcutaneous adipose tissue contained in the left shoulder joint were determined.

3. Feeding the LP diets in early life reduced the weight and DNA content of the m. adductor (P < 0·01) and increased fat cell size (P < 0·01) at 15 kg LW.

4. Subsequent to 15 kg there was an almost linear increase in muscle DNA with increasing LW, and the difference between pigs from the initial protein treatments progressively diminished and was no longer apparent at 60 kg LW.

5. At 30 kg LW, pigs given the LP diets before 15 kg LW contained less DNA in the subcutaneous adipose tissue from the shoulder joint (P < 0·01) and had larger fat cells (P < 0·05) than pigs given the HP diets initially. However, adipose DNA and fat cell size increased with increasing LW and the differences resulting from the initial protein treatments progressively diminished. On the LE and HE treatments subsequent to 15 kg these differences were no longer evident at 45 and 60 kg respectively.

6. Pigs given the HE intake subsequent to 15 kg, contained less DNA in muscle tissue (P < 0·05) at 60 and 75 kg LW and had larger fat cells (P < 0·05) at 45, 60 and 75 kg LW, than pigs on the LE treatment.

1. The addition of lysine hydrochloride (50 g/kg) to a diet supplemented with methionine (3 g/kg) had no effect on liver lipids when rats (Wistar and Sprague-Dawley) were fed ad lib. for 14 d. However, refeeding a diet supplemented with methionine and excess lysine hydrochloride to previously-starved rats (Wistar) for 6, 7 or 9 d, but not 3 or 4 d, resulted in liver lipid accumulation, mainly triglycerides, which was prevented by the addition of arginine, citrulline, ornithine, adenine, allopurinol or maize oil, but not by guanine, cytosine, thymine or uracil.

2. The addition of lysine hydrochloride to a methionine-supplemented diet resulted in reduced serum triglyceride levels after refeeding for 3 or 4 d and reduced serum cholesterol levels after refeeding for 3, 4 or 6 d. Serum lipids were unaffected by refeeding the diets for 7 or 9 d.

3. Since hepatic lipid accumulation was preceded by the decline in the level of serum triglycerides, one of the factors responsible for lipid accumulation in the liver might be reduced transport of triglycerides from the liver into the blood.

4. When adenine and allopurinol were added to the diet supplemented with methionine and lysine hydrochloride refed for 4 d, there was an increase in serum triglycerides. However, when this diet was refed for 7 d, with the addition of arginine, citrulline, guanine, pyrimidine bases, allopurinol or maize oil, no effects on serum cholesterol and triglyceride levels were observed.

1. Immature and mature lucerne (Medicago sativa) and tall fescue (Festuca arundinacea) hays were analysed for their lignin and phenolic monomer (hydroxybenzoic and hydroxycinnamic acid derivatives) contents. These hays were given to four sheep with rumen, duodenal and ileal cannulas, and to a steer with rumen and abomasal cannulas, to investigate the extent and sites of digestion of lignin and phenolic monomers.

2. The hays and digesta samples were analysed for alkali and nitrobenzene-extractablephenolic monomers. Lanthanum oxide was used as an external marker in the digestion studies. Urine was also collected for estimates of total phenolic balance.

3. Grass hays contained greater concentrations of alkali-labile phenolic monomers than did legume hays, whereas legume hays had higher levels of nitrobenzene oxidation products. Mature tall fescue hay had greater concentrations of phenolic monomers than did immature tall fescue hay, but corresponding differences with maturity were not observed with lucerne hays.

4. There were quantitative differences between diets in the digestibilities and in the sites of digestion of phenolic monomers. Digestibilities ranged from 0·191 to 1·004 for alkali-labile compounds and from −1·137 to 0·868 for nitrobenzene oxidation products. Composition of lignin was altered during its passage through the digestive tract. The proportion of phenolic monomers not recovered in urine and faeces varied from −1·014 to 0·871 for individual compounds and differed between diets. Soluble phenolic monomers decreased in concentration as digesta passed from the rumen to the abomasum and duodenum, but increased again in the ileum; levels varied with diet. Phenolics were rapidly solubilized in the rumen after feeding.

5. Results indicate that forages differ in their phenolic monomer content and in the digestibility of these compounds. Therefore, lignin is not an inert compound in the digestive tract of ruminants as has been previously reported.

1. Studies of anaemia and tissue iron distribution were carried out in copper-deficient rats and pair-fed control animals given Fe orally or parenterally in varying doses.

2. The anaemia of Cu deficiency was partially but incompletely corrected by oral Fe supplementation of one-to five-fold normal dietary levels or by intramuscular Fe supplementation.

3. Serum Fe increased in Cu-deficient animals as the dose of supplemental Fe was increased.

4. Hepatic Fe accumulation occurred in Cu-deficient rats which were administered with either oral Fe in two-to five-fold excess or low doses of intramuscular Fe. This difference was not seen in animals receiving high doses of intramuscular Fe, but similar relativedifferences were seen in Cu-deficient and Cu-replete rats which had been given no Fe supplementation.

5. Duodenal Fe was not increased in Cu deficiency. Bone marrow Fe was present in Cu-deficient animals receiving either parenteral or oral Fe supplementation.

6. Present studies suggest that a decrease in caeruloplasmin (EC 1. 16. 3. 1) activity does not wholly explain the anaemia of Cu deficiency.Fe accumulation may be restricted to the liver, suggesting that Cu may be required for normal intracellular Fe metabolism.

1. The voluntary food intake, during 30 min periods after morning and afternoon feeds and during 24 h, by growing pigs given diets containing rapeseed meal (Rsm) or soya-bean meal (Sbm) as the only protein supplement was determined. One diet was offered at a time and a daily changeover sequence of feeding was followed.

2. Four rapeseed meals were compared, one from seeds of British-grown winter Brassica napus varieties (Brsm) and the others from seeds of the var7ieties Tower (Trsm), Erglu (Ersm) and Span (Srsm). The effects on feed intake of adding flavouring substances to the Brsm diet were also determined. The flavouring substances were molassine meal, sucrose and four commercially-available substances: P, pig nectar; H, hog nectar; S, sow nectar and A, apple.

3. Intake of the Brsm diet was significantly less than those of the Sbm, Trsm and Ersm diets.

4. Addition to the Brsm diet of molassine meal or sucrose at 50 or 100 g/kg did not improve voluntary feed intake. None of the commercial flavouring substances raised the intake of the Brsm diet to the level of the Sbm diet but they improved intake of the Brsmdiet to varying extents. Flavourings H, S and A gave similar improvements which were substantial.

5. The Sbm, Brsm and Trsm diets were each fed ad. lib. to groups of growing pigs continuously for 4 weeks. Weekly feed intakes and weight gains were determined. Feed intakes and weight gains followed closely the intake values obtained in the changeover experiments. The highest values were for the Sbm diet; those for the Trsm diet were slightly lower and those for the Brsm diet were substantially and significantly lower.

6. The glucosinolate, sinapine and tannin contents of the rapeseed meals were determined and the results suggested that voluntary feed intake of diets containing these meals was related to their glucosinolate content, but not to their sinapine or tannin contents.

1. Phytase (EC 3.1.3.8) concentration has been measured in the small intestineof rat, rabbit, guinea-pig and hamster. Levels varied from 0·12 units (μg phosphorus released/min)/mg protein in the rat to 0·03 units/mg protein in the rabbit.

2. The enzyme is localized in the brush border of the small intestine of the rat.

3. It is suggested that the levels and location of phytase are an important factor inthe uptake of metals from metal–phytate complexes. Metal ions released in the immediate vicinity of the absorptive surface of the intestine could be absorbed before being rendered insoluble by competing reactions such as hydrolysis.

1. The influence of three diets ((1) high-fibre–low-fat, (2) low-fibre–high-fat, (3) commercial breeding diet) on the concentration of short chain fatty acids (SCFA) has been investigated in male and female rats up to 14 weeks of age.

2. Hydrogen was detected in respired gas in all rats with no significant differences between diets or sex. Methane was detected only in control-fed rats at 12 weeks of age and thereafter. Caecal contents contained higher concentrations of SCFA than were found in faeces. There were no significant differences in the total faecal SCFA excreted by rats on the three diets. The proportions of SCFA in the caecum and faeces were influenced by diet.

3. The production and excretion of hydrogen, methane and SCFA in the rat appeared to reflect different aspects of bacterial metabolism. Comparison of caecal and faecal SCFA may indicate differential absorption from the colon or differential metabolism by bacteria or colonic mucosa which may be influenced by diet.