A diet questionnaire was developed in association with a computer program to provide rapid nutritional feedback to the general public. The questionnaire was validated against 16 d of weighed diet records and biochemical variables in blood and urine. The highest Pearson correlation coefficients obtained between the questionnaire and the weighed records were for alcohol, fibre, iron, riboflavin (r 0.74, 0.67, 0.66, 0.66 respectively). Striking sex differences were shown in the results; the trend for higher correlations persisted in females. At least 65% of subjects were classified by questionnaire to within one quintile of the classification by weighed record for the majority of nutrients.

Treatment of lactating rats with the anti-progestin Mifepristone or Onapristone adversely affects growth of their litters. The present studies aimed to elucidate the underlying mechanism. The treatment did not interfere with the behavioural interactions between mothers and pups, which are required for normal litter growth. Treatment with the antagonists had a stimulatory action on ovarian oestrogen production. However, ovarian hormones did not play a role in litter growth impairment, as this also occurred with lactating ovariectomized rats. Treatment with anti-progestins did not affect the concentrations of the macronutrients in milk (protein, lactose and lipid), nor did it change the fatty acid composition of lipid. Reduced litter growth was not related to a possible direct effect of exposure of the suckling young to the drugs via the milk. Direct injections into them unequivocally affected adrenal gland and testicular development, but did not affect their body-weight development. Milk secretion, as measured by the milk weight accumulating during 6 or 24 h following sudden removal of litters in advanced lactation, was not impaired by the treatments. However, the ingestion of food and water by dams treated with Mifepristone was significantly below that of control animals. It is concluded that litter growth impairment during treatment of lactating rats with anti-progestin results from the reduction of the intake of food and water by the mother.

Digestibility coefficients (DC) of protein, dry matter, energy, starch, and dietary fibre in individual feedstuffs were used to predict the DC in feed mixtures. Digestibility studies with growing rats involved six feed sources: soya-bean meal, barley, rapeseed meal, peas, wheat bran and wheat, given individually and in various combinations, i.e. fourteen diets in total. True digestibility of protein (TD) and apparent digestibility of starch could be predicted in feed mixtures from their respective DC values for the individual ingredients, except in the diet composed of peas+barley. Dry matter (DM) and insoluble dietary fibre digestibilities in the mixtures could also be calculated from their individual DC values. Energy digestibility could be predicted in all mixtures except for barley+wheat and peas + wheat. Although the discrepancies were significant, the differences were not great. The digestibility of soluble dietary fibre in the mixtures could be predicted as for the individual ingredients in all but three diets: rapeseed meal + barley, peas + barley and peas + wheat. The results confirm that DC values for TD, DM, energy, starch and dietary fibre in mixtures can be calculated with high precision from DC determined from individual ingredients. Caution should be taken though when mixtures contain a high amount of dietary fibre, especially of the soluble type.

Digestible energy (DE) values were measured in a selection of feedstuffs for the tilapia (Oreochromis niloticus Linn.) and used to develop equations for predicting DE values of a wider range of feedstuffs from chemical analyses. Preliminary work examined the influences of substitution level in a reference diet and adaptation over time on DE values for soya-bean meal. Length of adaptation period significantly affected DE values (P < 0.01), but substitution level, over the range 200–600 g soya-bean meal/kg reference diet, did not. The DE values of sixteen feedstuffs, thirteen derived from plant sources and three animal by-products, were subsequently determined. DE values for plant-derived feedstuffs were found to be higher than those quoted in the literature for trout (Oncorhynchus mykiss) and catfish (Ictalurus punctatus), whereas DE values for animal-derived feedstuffs were lower than those for trout and pigs. It was concluded that energy values quoted in tables of feed composition for other species are inaccurate when used as proxy values for tilapia. Regression equations were therefore computed using data from the present study to provide a rapid means of predicting DE values of feedstuffs for tilapia. Equations using neutral-detergent fibre as an independent variable were found to predict DE values of plant-derived feedstuffs reliably. Where fibre values were not used as independent variables, available carbohydrate and crude protein (nitrogen × 6.25) were found to be useful predictors of DE values. These equations offer the possibility of reducing the need for time-consuming digestibility trials with tilapia when formulating least-cost production diets for this species.

The effects of different types of Se supplementation on the selenium concentration of beef, bovine internal organs and some other tissues were studied. The animals (thirty-two bulls) were kept in four dietary groups from birth until to the age of 13–14 months, and fed on rations containing either 0.03 mg Se/kg (basic level in local feeds), 0.25 mg inorganic Se supplemented as sodium selenite, or 0.25 or 0.4 mg/kg plant Se in dry matter from feed produced by spraying with sodium selenite. Samples of four muscles and ten other tissues and organs were taken at slaughter. Se was determined by an electrothermal atomic absorption method. Se supplementation significantly increased the Se concentration of all tissue samples. The maximum response was caused by the diet containing 0.40 mg/kg plant Se. In muscles, this diet raised the Se concentration by a factor of 10–12. In other samples, the increment was 1.5–7.5 fold, depending on the type of tissue. In general, plant Se raised the Se level more effectively than inorganic Se. Se supplementation did not affect the vitamin E status of muscle tissue.

Intrinsically-labelled foods are required to validate extrinsic-labelling techniques used to study the bioavailability of trace elements. Wheat (Triticum aestivum), peas (Pisum sativum), goat's milk, human milk, eggs and chicken meat were selected for intrinsic-labelling studies with 67Zn. Peas were grown hydroponically in enriched nutrient solution and wheat was grown in sand and watered with enriched nutrient solution. Some of the wheat plants were also given stem injections of 67Zn solution. Eggs and chicken meat were prepared by administering 67Zn intravenously to chickens, and human milk was collected after an oral dose of 67Zn in a cola drink. All the foods investigated were sufficiently enriched with 67Zn for Zn absorption studies except wheat prepared by the sand and water-culture method.

A variety of foods (peas (Pisum sativum), chicken meat, eggs, goat's milk, human milk) enriched with the stable isotope 67Zn were prepared by means of intrinsic- and extrinsic-labelling procedures. They were fed to rats and apparent absorption of 67Zn determined from faecal excretion measurements using thermal ionization mass spectrometry. There were significant differences in the absorption of the extrinsic and intrinsic label which differed in magnitude between the foods tested. The extrinsic 67Zn was less well absorbed in peas, chicken meat, eggs, and human milk than intrinsic 67Zn, but in goat's milk the extrinsic 67Zn was better absorbed than the intrinsic label. These results demonstrate that extrinsically-added stable Zn isotopes do not fully exchange with endogenous Zn in many foods, and illustrate the need for caution when using extrinsic labels for Zn bioavailability studies.

The effects of salt (sodium chloride) supplementation of rat diets (80 g/kg diet), with or without lactose (150 g/kg), were studied in weanling rats over 14 d. Dietary salt increased water intake and reduced weight gain and food conversion efficiency, but these variables were unaffected by lactose. Salt-supplemented rats exhibited a three- to fivefold increase in urinary calcium excretion and a small increase in urinary magnesium and phosphorus excretion, irrespective of dietary lactose content. In addition, salt supplementation reduced plasma alkaline phosphatase (EC 3.1.3.1) activity. Lactose increased urinary Ca and Mg excretion and plasma Ca and P concentrations. Salt reduced tibia mass but not tibia mass expressed relative to body-weight, but neither variable was affected by lactose. Both tibia Mg content and concentration were reduced by salt but unaffected by lactose, and neither tibia P content nor concentration was affected by salt or lactose. Tibia Ca content was reduced by salt but this was prevented by lactose. Tibia Ca concentration was unaffected by salt or lactose, although there was a reduction (not significant) in tibia Ca concentration in animals fed on the lactose-free diet. These results show that lactose had no independent effect on bone and that reduced accretion of bone mass and mineral content in rats fed on the high-salt diets was due, at least in part, to reduced growth. Failure to offset sodium-induced hypercalciuria by a compensatory increase in net Ca absorption may have contributed to reduced bone Ca accretion. The protective effect of lactose against reduced bone Ca accretion may be due to increased Ca absorption.

Hemicellulose consists primarily of pentose sugars, joined together in a polysaccharide chain with d-xylose as the most abundant component. Ileal digestibility and urinary excretion of d-xylose and associated effects of this pentose sugar on ileal and faecal digestibility of dry matter (DM), organic matter (OM), gross energy (GE) and nitrogen were studied in pigs. Castrated pigs were prepared with a post-valvular T-caecum cannula to measure ileal digestibility. Faecal digestibility was measured in non-cannulated pigs. d-xylose was given at dietary inclusion levels of 100 and 200 g/kg, and the control sugar, d-glucose, at a rate of 200 g/kg diet. Ileal digestibility of d-xylose as well as that of d-glucose was found to be close to 100%. The presence of d-xylose in the diet decreased ileal digesta pH and increased ileal flow of volatile fatty acids, suggesting the occurrence of microbial degradation of d-xylose in the pig small intestine. In pigs fed on the 100 g d-xylose/kg diet, 44.5% of the d-xylose intake appeared in the urine. This percentage increased significantly to 52.6 when pigs were fed on the 200 g d-xylose/kg diet. Ileal and faecal digestibility of DM, OM, GE and N, as well as N retention, decreased significantly in pigs fed on the 200 g d-xylose/kg diet.

Glycogen synthase (GS) activity was characterized in rat brown adipose tissue (BAT) and the activity was found to be much higher than that in white adipose tissue. Prolonged starvation had no effect on the active form of GS, as found in the liver and muscle. The GS activity was similar in BAT of rats housed in an animal room (21+± 1°) whether they were fed on high-carbohydrate, high-fat, or stock diets. Acclimatizatioin of rats to cold (4+± 1°) for 2 weeks significantly increased GS activity. This increase in the cold was fivefold greater when rats were fed on high-carbohydrate diets than in control rats at room temperature fed on an identical diet. The increase was accompanied by a large accumulation of glycogen in BAT. It was concluded that GS may play an important role in BAT and may contribute to the control of blood glucose in a cold environment. Its relevance to thermogenesis requires further elucidation.

The effect of protein deprivation on plasma concentration of insulin-like growth factor-binding proteins (IGFBP) was studied in rats. A significant decrease in the concentration of IGFBP of molecular weight (mass) approximately 40 kDa was observed in protein-deprived rats. There was no prominent effect of protein deprivation on the concentration of IGFBP with molecular weights of about 30 kDa or 22–24 kDa. The binding capacity to plasma IGFBP of exogenously-added 125I-labelled insulin-like growth factor-1 (125I-IGF-1) was also studied. IGFBP of molecular weight about 30 and 22–24 kDa (the native form of this protein is presumed to be 29 kDa) in protein-deprived rat plasma bound more 125I-IGF-1 than those in protein-fed rat plasma. This suggested that these IGFBP in protein-deprived rat plasma are relatively unsaturated by endogenous IGF-1. The response of IGFBP to protein deprivation which was elucidated in the present investigations add further evidence to our previous assumption that IGFBP play an important role in protein nutrition.

Plasma corticosterone clearance in anaesthetized rats was measured from the disappearance of radioactivity after a bolus injection of [3H]corticosterone. Mean fractional clearance rates were significantly (P < 0.05) reduced after a 48 h fast, by 32 and 22% for males and females respectively. Plasma corticosterone concentrations were increased by fasting in both sexes. Corticosterone secretion rates, calculated as the product of fractional clearance and plasma corticosterone concentration, did not differ between fed and fasted groups in either sex. The mean activity (U/liver) of the rate-limiting enzyme for corticosterone degradation, hepatic 4,5-dihydrocorticosterone:NADP+ Δ4-oxidoreductase, was significantly reduced by 51 and 78% after fasting in males and females respectively. This was due to changes in both the soluble and microsomal forms of the enzyme. The binding capacity of corticosterone-binding globulin in plasma was significantly reduced by fasting in females (P < 0.001), but was not altered in males. The results suggest that reduced hormone clearance is the dominant cause of fasting hypercorticosteronaemia in the rat.

The short-term effects of whole milk and milk fermented by Pseudomonas fluorescens, of the amino acid composition of the diet and of feeding frequency on the level of plasma lipids, were investigated in six 1-year-old adult boars. The experimental diets contained equal amounts of protein, carbohydrates, fat and cholesterol. After an adaptation period of 5 d for each experimental treatment, blood was collected at regular intervals during 48 h and plasma levels of cholesterol, triacylglycerol, high-density-lipoprotein (HDL)-cholesterol and low-density-lipoprotein (LDL-cholesterol were examined). All variables except HDL-cholesterol showed distinct diurnal fluctuations, which were substantially influenced by feeding frequency. Variations in the amino acid composition of the experimental diets, which were within a physiological range, had no effect on the level of plasma lipids. Plasma lipid levels were significantly lower when the animals received the diets containing milk instead of the diet without milk: cholesterol, triacylglycerol, and LDL-cholesterol were reduced by 5.6, 5.8 and 10% respectively (pondered means) while HDL-cholesterol remained unaffected. Fermentation of whole milk by P. fluorescens reduced the lipid-lowering effect. Our findings suggest that the intake of diets containing milk results in a lower plasma cholesterol and LDL-cholesterol level than the intake of diets with a similar nutrient content which do not contain milk.

The effect of different concentrations of tannin-rich field-bean (Vicia faba L.) hulls at 0, 20, 50, 150 and 300 g/kg dietary inclusion on the activities of lipase (EC 3.1.1.3) and α-amylase (EC 3.2.1.1) in digesta and pancreas and on the digestion of lipid and starch was studied in 2–3-week-old male broiler chicks. Low dietary concentrations of tannins (20 and 50 g hulls/kg) enhanced the activity of lipase in digesta from both the jejunum and ileum, the 20 g hulls/kg effecting the greatest enhancement, but no stimulatory effect on the activity of digesta α-amylase was observed. High dietary concentrations of tannins (150 and 300 g hulls/kg) inhibited both lipase and α-amylase activities in digesta from both the jejunum and ileum, the 30 g hulls/kg causing the most inhibition. Tannins did not increase the activities of lipase or α-amylase in pancreatic homogenates, but at high concentrations (150 and 300 g hulls/kg) they lowered slightly the pancreatic activity of α-amylase. Nutrient digestion was less influenced by the concentration of tannins than digesta enzyme activities.