1. The hypocholesterolaemic effects of pectins were studied in a series of five experiments in weanling Sprague-Dawley rats.

2. Expt A examined the effects of differing levels of dietary fat on plasma and liver lipids. Rats were given diets containing 100 g pectin, National Formulary (NF)/kg, and either 50,100, 150 or 200 g oil/kg. All diets contained 10 g cholesterol/kg. Plasma cholesterol levels were lower in all pectin-fed groups compared with rats given the control diet containing 100 g Solkafloc and 100 g oil/kg. Liver lipid and cholesterol levels increased with increasing fat content of the diet, reaching a plateau at 150 g fat/kg diet, but were still significantly lower in all pectin-fed groups compared with the control group.

3. Expt B. The effects of molecular weight and degree of methoxylation of pectins were studied in five groups of rats given either a control diet containing 100 g Solkafloc/kg or high molecular weight, high methoxyl pectin (HMW HMP); high molecular weight, low methoxyl pectin (HMW LMP); low molecular weight, high methoxyl pectin (LMW HMP); low molecular weight, low methoxyl pectin (LMW LMP). All diets in this and subsequent experiments contained 100 g fat and 10 g cholesterol/kg. Plasma cholesterol levels were significantly lower than control values only in the HMW HMP group. Compared with controls, animals given HMW pectins had lower levels of liver lipid and liver cholesterol; on the LMW HMP diet the liver cholesterol, but not the liver lipid, was lower.

4. Expt C. An attempt was made to clarify the possible effect of degree of methoxylation by feeding diets containing either 100 g Solkafloc/kg,100 g pectin NF/kg or 100 g very high methoxyl pectin/kg.Plasma cholesterol levels were significantly reduced by both pectins but there was no difference in effect between the two. Both had similar viscosities suggesting that this is a more important factor than methoxyl content.

5. Expts D and E. Effects of dose on hypocholesterolaemic effects of HMP and LMP were studied. Diets containing 50 or 100 g Solkafloc, HMP or LMP/kg were given in Expt D, and 25 g Solkafloc or HMP/kg, 50 g Solkafloc, HMP or LMP/kg and 100 g Solkafloc or LMP/kg in Expt E. Plasma cholesterol levels were significantly reduced in groups given 50 or 100 g HMP/kg and in groups given 100 g LMP/kg.

6.HMP were found to be more effective at lowering plasma cholesterol levels than LMP. LMW pectins were not effective. This suggests that the hypocholesterolaemic effects are at least partly due to viscosity.

7. Gut length and weight was increased in pectin-fed animals compared with controls despite their lower body-weight. The weight of small intestinal contents at death was also greater in pectin-fed rats (Expts A and B), particularly in the distal small intestine.

1. Zinc, copper, iron, protein and energy intakes of 232 lactating women (consuming self-selected diets during the first 3 months post-partum) were computed from food intake values obtained using a 3 d dietary-recall method. Non-pregnant, non-lactating women (100) served as controls. Blood samples of subjects were also analysed for packed cell volume and haemoglobin concentrations as well as for plasma Zn, Cu and Fe levels by atomic absorption spectrophotometry.

2. Except for Fe, intakes of all nutrients measured were significantly lower than recommended dietary allowances for lactation. Daily mean (and SD) Zn, Cu, Fe (mg), protein (g) and energy (MJ) intakes for lactating women were 8.2 (1.6), 1.6 (0.5),29.0 (5.8), 52.4 (9.2) and 10.21 respectively. There was a significant intercorrelation between the different nutrients in the diet.

3. Mean (and SD) plasma Zn, Cu and Fe concentrations (μg/l) during the first 3 months of lactation were 666.0 (76.0), 1290.0 (150.0) and 730.0 (185) respectively. These values were significantly (P < 0.05) lower in the case of Zn and Fe and higher in the case of Cu than those of non-pregnant, non-lactating women. Maternal plasma levels of the trace elements also vaned significantly with nutritional status as indexed by haemoglobin status.

4. Correlation analysis between dietary and plasma trace element concentrations was significant for Zn (r 0.26, P < 0.00Ol) and Fe (r 0.17, P <0.05). Dietary protein intake was significantly correlated with plasma Zn (r 0.18, P < 0.005) and Fe (r 0.12, P < 0.05).

5. While maternal weight, arm circumference and skinfold thickness measurements tended to decrease with increase in the period of lactation, growth performance of entirely breast-fed babies was satisfactory as at the 12th week post-partum.

1. Genetically obese mice (ob/ob) and their lean litter-mates were given diets iso-energetically supplemented with sucrose, hydrogenated coconut oil, safflower oil or evening primrose (Oenothera biennis) oil.

2. Weight gain over 15 weeks was significantly greater in the evening primrose oil-supplemented obese mice than in the other groups.

3. In all the groups of obese mice, liver total phospholipids contained proportionally less linoleic acid and more dihomo-γ-linolenic acid and arachidonic acid than did the lean controls.

4. As a percentage of total fatty acids, n-3 essential fatty acids (EFA) in liver and adipose tissue lipids were significantly lower in the obese mice than in the lean controls.

5. Supplementation with EFA-rich oils (safflower and evening primrose oil) increased the proportional composition of n-6 EFA and decreased the n-3 EFA more in the liver total phospholipids of the lean than the obese mice.

1. Genetically diabetic mice (db/db)and their non-diabetic litter-mates were maintained for 15 weeks on diets supplemented with safflower oil or evening primrose (Oenothera bienis) oil, both essential fatty acid (EFA)-rich sources, or hydrogenated coconut oil (devoid of EFA).

2. Plasma glucose was higher in the diabetic mice supplemented with the oils than in the unsupplemented diabetic mice. In the oil-supplemented non-diabetic mice, plasma glucose did not differ compared with the unsupplemented non-diabetic mice.

3. The proportional content of arachidonic acid in the phospholipids of the pancreas was significantly decreased in diabetic mice, an effect which was completely prevented by supplementation with safflower or evening primrose oil but not hydrogenated coconut oil.

4. In the liver phospholipids of the diabetic mice, dihomo-γ-linolenic acid was proportionally increased, an effect reduced by supplementation with safflower oil but not evening primrose or hydrogenated coconut oils.

5. In the liver triglycerides of the diabetic mice, γ-linolenic acid, dihomo-γ-linolenic acid and arachidonic acid were all proportionally decreased, effects which were also prevented by safflower or evening primrose oil but not hydrogenated coconut oil.

6. Alopecia and dry scaly skin were prominent in the diabetic mice but less extensive in the diabetic mice supplemented with EFA.

1. The milk production of one mother was determined post-partum for a period of 13 weeks, during which time breast milk was her infant's only source of food energy. The weight changes of both the mother and the male infant were recorded during this period.

2. The food intake and activity pattern of the mother were also recorded for 4-week periods: at 2, 6, 10 weeks after birth and 2 weeks after the cessation of lactation, which was maintained for a period of 27 weeks.

3. The infant regained his birth weight of 3310 g on the 14th day of life. His weight gain for the duration of the study, which averaged 233 g/week, was considered satisfactory.

4. The daily milk production increased gradually from an average of 241 g during the 1st week post-partum to 995 g during the 12th week. The infant's maximum milk intake and hence food energy intake per kg body-weight was (range) 198–204 g milk and 550–560kJ/kg respectively during the 3rd to the 7th week, followed by a gradual decrease from the 8th to the 13th week after birth.

5. The estimated efficiency of energy coversion for breast-milk production was consistent with other values reported in the literature.

1. The effect of incorporating guar gum into predominantly single-component meals of carbohydrate, fat or protein on liquid gastric emptying and on the secretion of gastric inhibitory polypeptide (GIP), gastrin and motilin, was studied in healthy human volunteers.

2. Volunteers were given either 80 ml Hycal (carbohydrate meal), 150 g cooked lean minced beef (protein meal) or 200 ml double cream (fat meal) either with or without 5 or 6 g guar gum. Liquid gastric emptying was monitored in the fat and protein meals by taking 1.5 g paracetamol, consumed in water, with the meals and monitoring its appearance in circulation.

3. Postprandial insulin and GIP levels were both significantly reduced by addition of guar gum to the carbohydrate meal. Postprandial GIP secretion was also reduced by addition of guar gum to the protein meal, but protein-stimulated gastrin secretion was enhanced by guar gum. There was a significant negative correlation between peak circulating gastrin levels and the corresponding GIP levels. Postprandial GIP secretion and plasma motilin levels were unaffected by addition of guar gum to the fat meal.

4. 5 and 10 g guar gum/l solutions in water possessed buffering capacities between pH 2.75 and 5.5.

5. Guar gum at 5 g/l caused no detectable change in liquid gastric-emptying time.

6. The observed augmentation of gastrin secretion by guar gum following a protein meal could be due either to the buffering capacity of guar gum or to the attenuation of GIP secretion. It is possible that the chronic use of guar gum could be associated with changes in gastric acid secretion.

1. Thiamin status has been measured using the erythrocyte transketolase (EC 2.2.1.1) assay in twenty-eight normal children and in twenty-five severely-malnourished children throughout the course of recovery.

2. Subclinical thiamin deficiency was found in 7% of the normal children and 36% of the malnourished children on admission.

3. There was no significant association between thiamin status and oedema, stunting or wasting, history of breast-feeding, pattern of weaning, age or sex.

4. Five malnourished children, who died, all had a normal thiamin status on admission; however, two developed biochemical evidence of thiamin deficiency preterminally.

1. Regression equations predicting body density from skinfold measurements were derived for a group of lactating women.

2. It was concluded that specific equations for lactation were not necessary, since the resultant equations were not significantly different from those published for non-lactating women.

3. The ability to predict an individual's body density from skinfold thickness measurements was unsatisfactory for either clinical or research applications.

1. The effect of corticosterone treatment on energy balance and heat production was investigated in growing rats. Animals were treated with daily subcutaneous injections of a vehicle containing 0, 50 or 100 mg corticosterone/kg for 5 d.

2. Measurements of digestible energy intake and urinary energy losses showed that corticosterone treatment resulted in a depression of metabolizable energy intake due to elevated urinary energy losses resulting from massive glucosuria.

3. Measurements of the metabolizable energy intake and the change in carcass energy indicated that at 50 mg/kg energy deposition and heat production were reduced, whilst at 100 mg/kg energy deposition was completely abolished with heat production increased. Postprandial oxygen consumption was unchanged at 50 mg/kg and increased at 100 mg/kg.

4. Factorial analysis of these results based on reported values for the energy cost of protein and fat deposition indicated that (a) the depression of total heat production at 50 mg/kg could be entirely accounted for by the concomitant suppression of growth, and (b) the elevation of total and postprandial heat production at 100 mg/kg reflected a specific influence of corticosterone on thermogenesis.

5. The significance of these findings is discussed in the light of reports that corticosterone in low doses suppresses heat production.

1. The nitrogen requirement of the weanling kitten was determined in a series of three experiments. In each experiment, diets were formulated to provide the growing kitten with the essential amino acids at or above the level of requirement. Expt 1 utilized a 4 x 4 balanced Latin square design with two groups of kittens (four male and four female). The crystalline L-amino acid diets were presented at four levels of dietary crude protein (N x 6.25) of 140, 160, 180 and 200 g/kg diet. The design for Expts 2 and 3 was a 6 x 6 balanced Latin square. For each of these experiments, groups of six male and six female kittens were assigned to diets. The six levels of dietary crude protein were 120, 140, 160, 180, 200 and 220 g/kg diet; dietary N was supplied by crystalline L-amino acids for Expt 2 and casein plus a supplementary amino acid mix for Expt 3. Food intake, weight gain and N retention were determined in each experiment.

2. A sigmoidal model y =P1+ P2/[1 +e(p2+p4. x)] was fitted to the response of weight gain and N retention to dietary N. The calculated requirement (95% of the upper asymptote, P1 + P2) for these experiments varied from 170 to 230 g protein/kg diet with the majority of these values falling between 180 and 200 g protein/kg.

3. On the basis of these three experiments, the kitten's requirement for dietary crude protein is between 180 and 200 g/kg diet (28.8–32.0 gN/kg) for purified diets which provide a calculated 21 MJ metabolizable energ//kg diet.

1. The effects of the amount and the type of dietary fibre on the apparent digestibility (AD) by growing pigs of neutral-detergent fibre (NDF) and NDF components, on nitrogen balance and on the rate of passage of digesta were studied using a semi-purified basal diet and fibre in the forms of soya-bean hulls, lupin (Lupinus sp.) hulls, pea (Pisum sativum) hulls, wheat bran, maize hulls, maize cobs, oat hulls and lucerne (Medicago sativa) stems.

2. Both the amount and the type of dietary fibre significantly influenced the AD of dietary dry matter, N and energy. The AD of NDF and of NDF components was markedly affected by the type and the amount of fibre in the diet. The proportion of NDF digested ranged from 0.016 to 0.905, of cellulose from 0.026 to 0.931 and of hemicellulose from 0.010 to 0.999.

3. N retention by the pigs ranged from 12.9 to 25.8 g/d and with some fibres there was a tendency towards increased N retention with increasing intakes of NDF.

4. Rate of passage of digesta, expressed as the 50 and 95% excretion times of stained feed particles, ranged from 22.2 to 85.1 h and 40.0 to 117.1 h respectively. Large individual variations in rate of passage occurred but, in general, the rate of passage tended to increase with increasing intakes of NDF. No strong associations between the rate of passage of digesta and apparent digestibility of NDF components were observed.

5. The results suggest that the extent of fibre digestibility depends predominantly on the origin of the fibre and to a lesser extent on the amount of fibre in the diet.

1. The effect of including lupin (Lupinus sp.) hulls, maize cobs, wheat bran and lucerne (Medicago sutiva) stems in a basal fibre-free diet on the concentrations and the relative proportions of volatile fatty acids (VFA) in the proximal colon of pigs, 17–18 h after feeding, was studied.

2. Concentrations of total VFA in the proximal colon increased with increasing levels of neutral-detergent fibre (NDF) intake, and this increase was highly dependent on the source of NDF in the diet.

3. Molar proportions of the VFA were significantly affected by the level of NDF intake only in the cases of acetic and butyric acids, whereas the source of dietary NDF had a marked influence on the molar proportions of all acids.

4. The results indicate that the extent of fermentative breakdown of fibre in the pig intestine can be influenced substantially by the type and the level of fibre in the diet.

1. The aim of the study was to determine the relative effects of feeding growing pigs with graded amounts of neutral-detergent fibre (NDF) from various sources on the empty wet weight of segments of the pig gastrointestinal tract, on the weight and moisture content of their digesta, and on the pattern of digesta movement in them.

2. Increased NDF intakes were associated with significantly higher wet weights of all gastrointestinal segments and increased lengths of the caecum. The lengths of both the small and the large intestines were unaffected by the ingestion by the pigs of different amounts of NDF from various sources. However, the caecum responded to these increased intakes of NDF by significant increases in length. The source of NDF in the diet was a factor that markedly influenced both the length and the weight of the distal colon. The nature of these increases in weight and length morphologically and their biological significance have not been determined.

3. Despite some significant differences, neither the type nor the level of dietary NDF had any appreciable effect on the dry weight and on the proportion of dry matter (DM) of the contents in the stomach. As the level of NDF intake was increased, more undigested dietary material was found in all segments of the digestive tract of the pigs. The proportion of DM in the residues decreased progressively from the caecal contents to the contents of the distal colon. In most cases the degree to which the level of NDF intake affected the weight of the contents and the proportion of DM in them was highly dependent on the source of NDF in the diet.

4. The distribution of the feed consumed in the morning and in the evening, as measured with stained feed particles and polyethylene beads, was extremely variable. It is concluded that prolonged intakes by pigs of diets containing high levels of fibre may lead to a hypertrophy and hence increased weight of segments of the gastrointestinal tract.

1. The myoelectric activity of the colon was examined in three dogs and three pigs when they were given a basal diet or a basal diet plus indigestible particles (IP), 2 mm in diameter, at 100 g/kg dry matter. The mean retention time was determined using coloured discs as a marker added to the daily meal.

2. Colonic electromyograms of dogs and pigs given IP revealed a 30% reduction in the number of long spike bursts (LSB) when compared with controls. The other components, propulsive migrating spike bursts (MSB) or non-propulsive short spike bursts (SSB), were unchanged. Mean retention time was decreased from 28.6 h to 17.6 h in dogs and from 129 h to 94.2 h in pigs.

3. These changes developed progressively during 3–4 d in both species, suggesting that the reduction in motor activity was an adaptation to the changes in bulk contents.

4. From the decreased motility of the colon linked to the reduction of LSB and paralleled by an increased transit time, it was concluded that one of the functions of the LSB is to impede the passage of digesta.

1. Sheep were given a diet of 400 g chopped grass hay/d and 500 g crushed barley/d in three equal meals. The mean retention time in the whole gut (MRT) and the rumen retention time (RRT) of chromium-labelled feed particles and of water were estimated from marker concentrations in faecal samples.

2. MRT of Cr-labelled hay (Cr-H), barley hulls (Cr-Bh), crushed peas (Pisum sativum) (Cr-CP) and rapeseed meal (Cr-RSM) were 53.5, 52.3, 44.3 and 37.0 h respectively when estimated from total faecal collections. The estimates obtained from spot samples of faeces were almost identical.

3. RRT of Cr-H, Cr-Bh, Cr-CP, Cr-RSM (Expts 1, 2 and 3) and Cr-labelled cottonseed meal (Cr-CSM) was 35.9, 36.7, 25.3, 18.8, 19.8, 22.8 and 25.3 h respectively.

4. The Cr-labelled feed particles showed marked variations in density in water (Dω). However, both MRT and RRT were closely related to Dω, (r—0.88 and —0.95 respectively).

5. Rumen outflow rates of Cr-RSM in individual animals were related to the rumen outflow rates of water (r 0.76).

1. The comparative and absolute growth response of Lactobacillus casei was measured nephelometrically for time periods of 17–23 h in the microbiological assay of folic acid and 5-methyl-tetrahydrofolic acid at concentrations of 0–8 ng/10 ml basal medium at pH 6.8.

2. At concentrations of 0–1 ng/10 ml the comparative growth response to 5-methyl-tetrahydrofolic acid was markedly depressed whereas growth was the same at 2 ng/10 ml and above. Comparative growth was unaffected by the length of assay incubation, depressed growth being due to differences in log-phase growth rates with the rate-plot for 5-methyl-tetrahydrofolic acid being sigmoidal and for folk acid being a rectangular hyperbola with linearity only in the 0–1 ng/10 ml range. The reciprocal rate-plot for folic acid was linear whereas that for 5-methyl-tetrahydrofolic acid was coincidental only in part, giving rise to the same estimate of maximum velocity and substrate concentration for half-maximum velocity, with the exhibition of a strong threshold at low concentration.

3. A previous observation (Phillips & Wright, 1982) that the L. casei growth response to 5-methyl-tetrahydrofolic acid may be significantly less than that to folic acid is confirmed as is the long-established view that the response to both folates may be equal. In the light of current knowledge regarding folate-binding, transport and metabolism by L. casei, it is argued that the intracellular oxidation of 5-methyl-tetrahydrofolic acid to 5, 10-methylene-tetrahydrofolic acid is a rate-limiting step at low substrate concentrations, subsequently giving rise to a threshold growth response peculiar to 5-methyl-tetrahydrofolic acid. Since the rate of L. cusei growth with folk acid is not linearabove 1 ng/10 ml, it is recommended that microbiological folate assays be conducted only in the 0–1 ng/10 ml range and at a pH that elicits the same growth response from L. casei to 5-methyl-tetrahydrofolic acid as to folic acid and other folate monoglutamates.

1. In vitro assay procedures were applied in the measurement of available amino acids in a selection of fish meals representing good- and poor-quality product. Results were assessed by comparing them with results from chick-growth assays.

2. Available methionine and tryptophan were assayed microbiologically with Streptococcus zymogenes, after predigestion of the test samples with papain or pronase. Results for methionine were correlated with chick-growth assays (r 0.86 for papain, 0.91 for pronase; P < 0.01). Compared with the chick assays, papain tended to give lower, and pronase higher, results. Finer milling of the test samples did not influence the pronase values.

3. Results for available tryptophan were also correlated with chick-growth assays (r 0.95 for papain, 0.96 for pronase; P < 0.001). Compared with the chick values, papain gave markedly lower results and pronasem marginally higher ones. Finer milling of the test samples increased the papain values by about 50% but had no effect with pronase.

4. Available lysine was assayed microbiologically with Tetrahymena pyriformis and with a dye-binding procedure (DBL). The results correlated with the chick-growth assays (r 0.99 for DBL, P < 0.001; 0.85 for Tetrahymena, P < 0.01) but both methods overrated the poorer-quality samples.

5. True nitrogen digestibilities and amino acid digestibilities were determined with chickens by the 'ileal analysis' procedure: the amino acid digestibilities were significantly higher and similar to the corresponding availabilities as measured in chick-growth assays.

6. Ball milling a poor-quality fish meal caused a marked fall in its N digestibility, whereas similar treatment of a good-quality meal caused a slight increase. An explanation for this finding is proposed.

7. Strep. zymogenes assays following pronase digestion of the test samples gave precise and acceptably accurate measures of the biologically available methionine and tryptophan in the test samples. For available lysine, Tetrahymena and DBL values for the poorer-quality samples were notably higher than the chick-growth assay; possible reasons for this are discussed. The ileal analysis procedure underestimated true N digestibility.

1. Eight newborn lambs were given milk-substitutes based on casein (n 4) or a soya-bean-protein isolate (n 4). On the morning before a 10 d collection period, the milk-substitutes were supplemented with 59Fe as ferric chloride and 5Zn as zinc chloride. Faeces and urine were collected daily and determinations of 59Fe and 65Zn were made on these separately. During a second 10 d period the dosing procedure and collection were repeated but the diet of each lamb was reversed.

2. Mean retention of 59Fe in lambs given the casein diet was 0.50 (SE 0.12) and in those given the soya-bean-protein diet 0.06 (SE 0.05). There were large variations among animals but the treatment effect was significant at P < 0.05. Retention of 65Zn was significantly greater than that of 59Fe for all lambs but the effect of dietary treatment was similar to that for Fe. 65Zn retention values for casein and soya-bean-protein diets were 0.84 (E 0.06) and 0.52 (SE 0.03) respectively, and the difference was significant at P < 0.01.

3. There were only very small amounts of 59Fe and 65Zn in urine, representing 0.002–0.003 of the dose.