1. An alternative statistical technique, based on analysis of the 25th percentile, was used to examine teenagers' diets. The technique was developed to identify personal characteristics that affected the prevalence of low energy and nutrient intakes. It provided useful information not obtainable from methods based on average intakes.

2. The study sample was a representative sample of 1055 high-school students in Tasmania, Australia, aged 11–16 years.

3. Among girls, different characteristics had the greatest influence on the prevalence of low intakes (‘low’ being defined as below the 25th percentile for girls). Fatness had the greatest influence for several dietary components. Fatter girls were more likely to have low intakes of energy, carbohydrate, iron, calcium and niacin-equivalent, and also of ‘empty-energy’ foods. School type had the greatest influence for fat, riboflavin and vitamin A. Exercise had the greatest influence for protein, low intakes being more usual among the least active girls.

4. Among boys, height and age generally had the greatest influence on the prevalence of low intakes (‘low’ being defined as below the 25th percentile for boys). Taller and older boys were less likely to have low intakes. This was attributed partly to increased physiological needs, but peer-group influences appeared more important in relation to food choices. Thiamin was unusual, in that recent use of analgesics had the greatest influence on the prevalence of low intakes.

1. The effect of leavening of bread containing bran on the phytic acid content and on zinc absorption in man was studied.

2. Twenty breads with leavening times varying from 0 to 120 h were prepared. The breads contained 250 g wheat bran/kg flour. The phytic acid content was determined after baking.

3. The phytic acid content of bread containing bran was reduced to about 40% after 2 h of leavening and to 15 % after 2 d. No further decrease was observed.

4. Zn absorption from single meals was determined using a radioisotope technique. Forty-two students volunteered for these studies. They were served a breakfast of milk, butter, bread and 10, 16 or 30 g bran served either raw or baked into the bread with fermentation times of 15 min, 45 min, 3 h or 16 h. One meal contained no bran, but phytate and Zn were added in amounts equivalent to the content of 10 g bran.

5. The amount and percentage of Zn absorbed increased at each bran level as fermentation was prolonged. The percentage of Zn absorbed was reduced by increased bran content in the meal.

6. It is concluded that the fermentation of bread containing bran reduces the phytic acid content and increases Zn absorption from such bread. This may be of importance to people subjected to diets with a high cereal content, especially in combination with a low animal-protein intake.

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. Twenty-six gilts were used in an experiment to study the effects of level of feed intake on the growth and chemical composition of the gravid uterus and mammary tissue at several stages of gestation. The animals were given either 1.8 or 2.5 kg feed/d (20 or 30 MJ metabolizable energy (ME) respectively) and were slaughtered at intervals between days 40 and 110 of gestation. The gravid uterus was dissected into fetal, placental, fluid and empty uterus components. From day 70 of gestation the mammary tissue was also dissected. The fresh weight and dry matter (DM), energy and nitrogen contents of the various tissues were determined.

2. (a) With the exception of the fluid component, there was a significant increase (P < 0.01) in the fresh weight of each tissue with both stage of gestation and level of feeding. At comparable litter sizes the total weight of the fetuses in late gestation was 16% higher with the higher feed intake. (b) The DM content of the individual uterine tissues increased significantly (P < 0.01) with increase in stage of gestation so that the mean DM content of the gravid uterus increased from 74.6g/kg at day 50 to 103.1 and 159, 0g/kg at days 90 and 110 of gestation respectively. (c) Neither stage of gestation nor feeding level influenced the respective energy contents of the individual uterine tissues, when expressed per g DM. The mean energy content of the total gravid uterus was 19.5 kJ/g DM. (d) The N content (g/g fresh weight) of the tissues increased with stage of gestation and was generally higher at the higher feeding level. The mean N contents (g/g DM) of the fetal, placental, fluid and empty uterine tissues were 0.090, 0, 101, 0.098 and 0.128 respectively.

3. The mammary tissue was the most variable of all the tissues investigated. Whereas the fresh weight and N content increased with stage of gestation, both the DM and energy content decreased.

4. Gompertz equations were fitted to describe the effects of stage of gestation, level of feed intake and litter size on the fresh weight and chemical content of the individual uterine tissues, total gravid uterus and mammary tissue. The use of these equations for calculating the nutrient requirements of pregnancy is demonstrated.

5. It was calculated that between days 50 and 110 of gestation the ME requirement for reproduction increased from 3 to 12% of maternal energy intake. The calculated requirement for protein was from 7 to 41 % of maternal dietary protein intake respectively.

1. The heat losses and energy and nitrogen balances of pregnant gilts, and of their non-pregnant litter sisters (controls), were measured for periods of 7 d at feed intakes of 1.8 or 2 3 kg/d (20 or 30 MJ metabolizable energy (ME) respectively) at an environmental temperature of 20°. The measurements were made within three separate periods of gestation; 40–60 d (early), 60–80 d (mid) and 90–110 d (late). Values for ME intake, heat loss, energy retention (ER), protein deposition and fat deposition were determined for both the pregnant and control animals on each treatment.

2. When expressed per kg body-Weight 0.75 per d, there was little difference in heat loss between pregnant and non-pregnant animals and between pregnant animals at the different stages of gestation at any given ME intake. However, heat loss was higher at the higher ME intake.

3. ER vaned inversely with heat loss. The decrease in ME intake (kJ/kg body-Weight 0.75 per d) during pregnancy resulted in a decrease in ER so that the pregnant animals were in negative energy balance at the low feed intake during late gestation. From the relation between ER and ME intake, estimates of the maintenance energy requirement (MEm) of 411 and 401 kJ/kg body-weight0.75 per d were calculated, with corresponding partial efficiencies of energy utilization (k) of 0.74 and 0.68 for the pregnant and non-pregnant animals respectively.

4. For the pregnant animals, protein deposition was highest during mid-pregnancy and was relatively independent of level of feeding during mid- and late pregnancy. There was little difference in protein deposition between pregnant and non-pregnant animals at the high feed intake. At the low feed intake, the pregnant animals generally had a higher protein deposition than their non-pregnant litter sisters and this was entirely associated with the accretion in reproductive tissue.

5. Fat deposition depended on the level of feeding, and at any given ME intake was similar for pregnant and control animals. In late gestation the low level of feeding was insufficient to prevent the pregnant animals losing fat. It was calculated that at term these animals lost 140 g fat/d from maternal stores.

6. From the relation between ME intake and protein and fat deposition, estimates of ME, and the energetic efficiencies of protein (k,) and fat (k,) deposition were determined. There was little difference in ME, (422 and 420 kJ/kg body-weight 0.5 per d) and k, (0.88 and 0.90) between pregnant and non-pregnant animals respectively. However, the pregnant animals had a higher k, (0.69 compared with 0.49 for controls) and this reflected the higher rates of protein deposition associated with pregnancy.

7. The efficiency of energy deposition in the reproductive tissue was calculated to be 0.72.

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. The production of propionate in the caecum of the horse has been measured in two Shetland-type ponies fitted with caecal and colonic cannulas and fed on hay or on hay and wheat bran. A continuous intracaecal infusion of 14C-labelled sodium propionate was used and samples were obtained from a cannula at the origin of the right ventral colon. A simultaneous intravenous infusion of [2-3H]glucose was used to measure total glucose entry.

2. On a hay diet which provided 177 kJ/kg body-weight per d, mean caecal propionate production was 19.6 (range 17.2–21.2) mg/h per kg body-weight and on a hay and wheat bran diet, which provided 187 KJ/kg body-weight per d, mean caecal propionate production was 34.0 (range 28.9–38.3) mg/h per kg body-weight.

3. Mean total glucose production (mg/h per kg body-weight) in one pony was 104 (range 100–110) and in the other 135 (range 123–153). Rates were not influenced by diet.

4. About 7% of total glucose production was derived from propionate produced in the caecum and this percentage was unaffected by diet or by individual animals.

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 reactions between protein-bound amino acids and oxidizing lipid were investigated in a whey protein-methyl linolenate (C18.3)–water model system. The extent of fat oxidation was followed by measuring oxygen uptake, hydroperoxide formation and hydrocarbon (ethane and pentane) formation.

2. Significant losses occurred with lysine (up to 71 %), tryptophan (up to 31 %) and histidine (up to 57%). Methionine was extensively oxidized to its sulphoxide but less than 2% was further oxidized to the sulphone. No other amino acids were affected.

3. Increasing storage temperature (20°, 37°, 55°) resulted in an enhancement of fat oxidation reactions and amino acid degradation.

4. Increasing water activity (0.28, 0.65, 0.90) increased losses of lysine and tryptophan but had no influence on the oxidation of methionine, the level of remaining hydroperoxides or 02 uptake. Hydrocarbons were decreased.

5. Limitation of 02 uptake to 1 mol/mol lipid instead of excess 02 (02 uptake about 2.5 mol/mol lipid in 4 weeks) significantly reduced the degradation of lysine and tryptophan but had less influence on the oxidation of methionine. The level of remaining hydroperoxides was increased but hydrocarbons were unaffected.

1. The stability of tryptophan was evaluated in several different food model systems using a chemical method (high pressure liquid chromatography after alkaline-hydrolysis) and rat assays. Losses of tryptophan were compared with the losses of lysine and methionine.

2. Whey proteins stored in the presence of oxidizing lipids showed large losses of lysine and extensive methionine oxidation but only minor losses of tryptophan as measured chemically. The observed decrease in bioavailable tryptophan was explained by a lower protein digestibility.

3. Casein treated with hydrogen peroxide to oxidize all methionine to methionine sulphoxide showed a 9% loss in bioavailable tryptophan.

4. When casein was reacted with caffeic acid at pH 7 in the presence of monophenol monooxygenase (tyrosinase; EC 1.14.18.l), no chemical loss of tryptophan occurred, although fluorodinitrobenzene-reactive lysine fell by 23%. Tryptophan bioavailability fell IS%, partly due to an 8% reduction in protein digestibility.

5. Alkali-treated casein (0.15 M-sodium hydroxide, 80°,4 h) did not support rat growth. Chemically-determined tryptophan, available tryptophan and true nitrogen digestibility fell 10, 46 and 23% respectively. Racemization of tryptophan was found to be 10% (D/(D+L)).

6. In whole-milk powder, which had undergone ‘early’ or ‘advanced’ Maillard reactions, tryptophan, determined chemically or in rat assays, was virtually unchanged. Extensive lysine losses occurred.

7. It was concluded that losses of tryptophan during food processing and storage are small and of only minor nutritional importance, especially when compared with much larger losses of lysine and the more extensive oxidation of methionine.

1. Tryptophan losses in stored milk powders and in different model systems representing the major reactions of food proteins during processing and storage were determined using four different chemical methods and in a rat assay.

2. Similar tryptophan values were obtained by the three chemical methods which included high pressure liquid chromatography (HPLC) after sodium hydroxide hydrolysis. colorimetric reaction with p-dimethylamino- benzaldehyde (p-DAB) after barium hydroxide hydrolysis, and fluorescence of the Norharman derivative after NaOH hydrolysis.

3. Tryptophan losses in the treated proteins as measured by the alkaline-hydrolysis methods were generally smaller than those determined by the rat assay. Good agreement however was obtained when the chemical value was multiplied by the true nitrogen digestibility.

4. Determination of tryptophan by reaction with p-DAB after papain (EC 3.4.22.2) digestion gave lower values in the processed proteins than the other chemical methods or the rat assay.

5. A method using alkaline-hydrolysis is recommended, preferably combined with HPLC-measurement of the liberated tryptophan.

1. The consequences of reactions between protein and oxidizing lipids on the nutritional quality of food proteins have been investigated using a whey protein–methyl linolenate-water model system.

2. In rat assays, significant reductions were observed in protein efficiency ratio, net protein ratio, net protein utilization, biological value and true nitrogen digestibility, especially when the reaction had taken place at high moisture content, high temperature and in the presence of excess oxygen.

3. The losses of bioavailable lysine and tryptophan as measured by rat assays followed a similar pattern. The chemical value of each amino acid multiplied by the true N digestibility closely resembled the rat assay value. In general, the reaction products of lysine and tryptophan formed during lipid oxidation were biologically unavailable.

4. The bioavailabilities of methionine and of ‘methionine plus cyst(e)ine’ were determined in separate assays. Cyst(e)ine was calculated as ‘methionine plus cyst(e)ine’ minus methionine. In whey protein which had reacted with oxidizing methyl linolenate, the bioavailable methionine content was not significantly reduced even though 82% of the methionine residues were present as methionine sulphoxide. In hydrogen peroxide-treated casein in which all methionine residues were oxidized to the sulphoxide, methionine sulphoxide was found to be 96% as utilizable as a methionine source to the rat. Free methionine sulphoxide was 87% utilizable.

5. Cyst(e)ine appeared to be as sensitive as lysine to reactions with lipid oxidation products. In whey protein which had reacted with oxidizing methyl linolenate, the bioavailabilities of cyst(e)ine, lysine, tryptophan and methionine were reduced by 28, 24, 11 and 8% respectively and true N digestibility by 9%. These results are discussed in relation to food products.

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. Male Wistar rats (100 g) were given a commercial pellet feed or a semi-synthetic diet ad lib. Although the pellet-fed group grew slightly faster than the other group during the early part of the feeding period, there was no significant difference between the final weights of the groups.

2. The fractional rates of protein synthesis in jejunum, proximal ileum and liver were measured by a technique based on the determination of L-[4−3H]phenylalanine incorporation over a short time period. Protein synthesis was higher in both jejunum and ileum of the pellet-fed rats compared with those eating the semi-synthetic diet, but there was no difference between the rates of protein synthesis measured in the livers of the groups.

3. The rate of mucosal cell division was significantly faster in the ileal mucosa of the pellet-fed group compared with the other group, and there were significant differences in some aspects of mucosal morphology.

4. The maintenance of higher rates of cell turnover and protein synthesis in animals given commercial pellet feed is unexplained, but it may be related to the presence of non-absorbable polysaccharides or other complex plant materials in the pellet feed.

1. Resting heat production, 18 h post-feeding, was studied in Hariana cattle (Bos indicus; Zebu) and in their F1 crosses with Jersey, Brown Swiss and Holstein Friesian, at 18.5° ambient temperature in a psychrometric chamber at different ages.

2. There was no significant change in the resting heat production on a per kg body-weight (W)0.75 per 24 h basis from 16–19 to 37–40 months of age in any of the genetic groups. The daily resting heat production, however, increased with increases in body-weight and age.

3. The resting heat production in all three F1 crosses was higher than that in Hariana cattle. Among the crosses, the resting heat production was highest in the Holstein Friesian x Hariana and lowest in the Jersey x Hariana.

4. Metabolizable energy (ME) intake per 24 h was significantly different between genetic groups and in different age groups. However, ME intake per kg W0.75 was not significantly different between genetic groups.

1. Twenty germ-free and twenty conventional male Fischer 344 rats, 3 months old, were fed ad lib. diets based either on normal or on amylomaize starch for 1 month. The absorption rate of sodium taurocholate. 25 mmol/l, was determined in vivo in jejunal or ileal segments. Each determination included five rats.

2. Jejunal absorption rate was not modified either by the amylomaize-based diet or by the digestive microflora.

3. Ileal absorption rate was slightly higher in germ-free than in conventional rats.

4. Ileal absorption rate was largely increased by the amylomaize-based diet. This increase was slightly larger in germ-free rats than in conventional rats.

5. It is suggested that dietary amylomaize starch has an action on the active absorption process of bile acid.

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. Young female rats were made riboflavin-deficient by feeding a purified diet containing casein (210 g/kg). This basal diet provided 0.40 mg riboflavin/kg diet, to which was added additional riboflavin at 0, 0.12 or 0.25 mg/kg diet. Control animals received the same diet with 15 mg added riboflavin/kg. The diets were given for 4 weeks before mating, then throughout pregnancy and for 15 d of lactation.

2. With no added riboflavin in the diet, reproduction was severely impaired and fetal resorption was usually observed. With 0.12 mg added riboflavin/kg diet, however, reproduction was usually successful, and the growth of dams and pups was only marginally depressed in comparison with pair-fed controls optimally supplied with riboflavin.

3. The activation coefficient (stimulated: basal activity) of erythrocyte glutathione reductase (NAD(P)H) (EC 1.6.4.2)was high, and the concentration of riboflavin in the liver was correspondingly low in the dams receiving diets containing 0.12 or 0.25 mg added riboflavin/kg and in their sucking pups at 15 d post partum. Riboflavin levels in the milk from both groups of dams were about eightfold lower than in controls. There was little evidence that the sucking pups could maintain their riboflavin level at the expense of that in the maternal tissues.

1. The vascular anatomy of the bovine omasal lamina permitted perfusion of a discrete area of the tissue. As occurs in vivo, oxygen was provided through the vascular system, while the luminal sides of the tissue could be kept in an anaerobic environment, thus allowing study of foregut tissue metabolism under physiologically realistic conditions.

2. O2 consumption of perfused leaves in the presence of anaerobic buffer was 64.9 and 73.5 nmol O2/mg dry weight per h in Expts 1 and 2 respectively, and was elevated (P < 0.05) when the lumen side of the tissue was exposed to an atmosphere of nitrogen gas.

3. In Expt 1, the rate of O2 consumption was increased (P < 0.01) by 35% as a result of suspension of a boiled preparation of rumen micro-organisms and particles (< 1 mm) in the anaerobic lumen buffer. Replacement of the boiled preparation with an unboiled suspension increased O2 consumption further by 11 %, but this was not statistically significant (P > 0.05).

4. In Expt 2, sequential addition of the following substrates or preparations to the lumen chambers all resulted in stepwise increases (P < 0.05) in O2 consumption; 8 mM-butyrate, boiled rumen micro-organisms and particles and, finally, unboiled rumen micro-organisms and particles.

5. Identities of the heat-labile and heat-stable components of the microbial and particle suspensions that caused enhancement of O2 removal across the perfused tissue are discussed.