Male broiler chickens growing from 7 to 35d were fed on a diet containing 150g crude protein (N × 6·25)/kg diet supplemented with lysine to equal that in diets containing 166, 183 and 200g crude protein/kg diet (Expt 1). A second group of male broiler chickens growing over the same period were fed on a diet containing 120g crude protein/kg supplemented with lysine, arginine, tryptophan, threonine and isoleucine equal to that in diets containing 144, 172 and 200g crude protein/kg diet (Expt 2). Growth was improved by lysine supplementation but not to the level attained by feeding 200g crude protein/kg (Expt 1). Lysine, arginine, tryptophan, threonine and isoleucine supplementation of a low-protein diet also improved growth, but growth again fell short of that attained by feeding a diet containing 200g crude protein/kg. Plasma insulin-like growth factor-1 and thyroxine concentrations increased and triiodothyronine decreased as the crude protein level increased from 150 to 200g/kg diet. Supplemental lysine did not affect plasma levels of these hormones. Although dietary crude protein levels noticeably changed rates of in vitro lipogenesis, changing either the level of a single limiting amino acid or the levels of several limiting amino acids did not change lipogenesis.

Nutrient intakes estimated using a short self-administered semi-quantitative food frequency questionnaire (FFQ) were compared with results obtained from five 2 d diet records using household measures in a group of fifty-three elderly people (mean age 70 years) in Dunedin, New Zealand in 1989. Mean intakes for most nutrients were less than 5% different between the two methods. Correlations between the nutrient intake values (excluding supplements) from the diet records and those from the FFQ ranged from 0·34 for Zn in women to more than 0·75 for protein, Zn and Ca in men. For most nutrients, at least 70% of the subjects when classified by the food records fell into the same quintile or into the within-one- quintile category when classified by the FFQ. These data indicate that in elderly subjects a simple self- administered semi-quantitative FFQ can provide very similar information (for both group and individual intakes for many nutrients) to that obtained from 10 d of careful diet recording.

Four steers were maintained wholly by intragastric infusion of volatile fatty acids (VFA) and protein, together with a mineral–vitamin supplement. The infusion was given at three levels of energy, namely 450, 675 and 900 kJ/g live weight0·75, calculated to supply energy at 1·0,1·5 or 2·0 times that required for maintenance. The VFA provided 0·837 and the protein 0·163 of the energy infused. The molar proportions of individual VFA were varied so that the infusate contained 0·36–0·91 of acetic acid, 0·56–0·01 of propionic acid and a constant 0·08 of butyric acid. Heat production was measured in respiration chambers. Urine was analysed for N, urea, β-hydroxybutyrate and VFA. Blood plasma was analysed for β-hydroxybutyrate, free fatty acids, insulin and glucose. As the proportion of acetic acid was increased, and propionic acid reduced, there was no change in blood or urine metabolites or in heat production until acetic acid exceeded a proportion of about 0·75. At higher proportions β-hydroxybutyrate increased in plasma and urine, blood glucose and insulin tended to fall and urinary N excretion rose. At a proportion of acetic acid of > 0·80, acetate appeared in the urine and at > 0·86 heat production declined. The effect of level of infusion on the molar proportion at which plasma and urine metabolites changed was less clear. There was a tendency for the increase in β-hydroxybutyrate to occur at a slightly lower proportion of acetic acid at the highest level of infusion. It is concluded that differences in heat production that are observed between diets are probably not caused by differences in rumen VFA proportions. The reaction to a highly elevated proportion of acetic acid is to excrete β-hydroxybutyrate and acetate in the urine and so decrease rather than increase heat production. Regardless of level of infusion a metabolic crisis occurred when the proportion of acetic acid was above the levels found in the rumen content of normally-fed animals.

Eight Friesian calves were reared from birth to the start of the experiment at a predetermined growth rate of 1.0 kg/d. Four calves (group 1) commenced the experiment at 22 weeks of age and the remainder (group 2) at 34 weeks, and feed intake was calculated to provide sufficient metabolizable energy to sustain zero energy balance (Em). Between experimental days 30 and 56 at maintenance levels of feeding, respiratory exchange measurements were made using open-circuit calorimetry to provide indirect estimates of heat production (H) simultaneous with measurements of faecal and urinary excretion of energy and N. A datum point for Em and H was established for each animal giving mean values for Em of 491 and 537 and for H of 476 and 511 kJ/kg live weight (LW)0.75 per d for groups 1 and 2 respectively. Treatment levels calculated as 0·25, 0·5, 0·75 and 1·25 of dry matter intake required to sustain the measured Em, were imposed on individual animals after day 56 and further measurements of H and faecal/ urinary balance were made between days 72 and 84 followed by measurements of fasting heat production (FHP) during days 86–90 from the two animals in each group which had received the 0.75 and 1.25 levels of intake. Regression analysis of the treatment levels indicated separate linear models which predicted Em at 419 and 473 kJ/kg LW0·75 per d for groups 1 and 2 respectively. The incorporation of FHP with partitioning of faecal and urinary energy losses measured during fasting altered the relationship but not the predicted Em. Overall predicted Em (days 72–84) from all models were 406 and 478 kJ/kg LW0.75 per d for groups 1 and 2 respectively which were significantly lower (P < 0·05) than Em measured during days 30–56.

As part of the 16–17 year follow-up of the 1970 longitudinal birth cohort study, The International Centre for Child Studies collected dietary data from a National sample of 4760 teenagers. Dietary intake data were collected in 4 d unweighed dietary diaries, distributed by schools and returned by post. Dietary intake data were quantitatively coded, and the intakes of energy, macronutrients and non-starch polysaccharides (NSP) are reported. Intakes of fat and extrinsic sugars, expressed as a percentage of energy intake, exceeded recent recommendations (Department of Health, 1991), and the intakes of intrinsic sugars, milk sugars and starch, and NSP were considerably lower than recommended. Only 25 % of males and 10 % of females achieved intakes of 18 g NSP/d. The main food groups contributing fat (%) to the diets of teenagers (for males and females respectively) were meat and meat products (24·2, 22·1). Spreading fats (18·6, 18·1) and cereals and cereal products (18, 17·8), whilst the major sources of sugars (%) were (for males and females respectively) sugar and confectionary (28·2, 26·4), cereals and cereal products (24·5, 23) and beverages (21·9, 21·5). Less than half the cohort drank alcohol during the recording period, and about 6% of females drank more than 2 units alcohol/d, and about 6% of males drank more than 3 units alcohol/d.

A large variation in seasonal weight loss between individuals exists in rural communities in developing countries. Therefore, it was investigated whether some individuals show a metabolic adaptation and, through that, prevent large body-weight losses during the preharvest season. Basal metabolic rate (BMR), energy intake and physical activity level (PAL) of rural Beninese women were measured in three seasons. Groups of subjects were: women with a body mass index (BMI) < 18 (n 18), and a BMI > 23 (n 16), and women who had shown small (n 18) and large (n 15) preharvest weight loss. All groups of subjects decreased energy intake during the preharvest season by 0·66–1·09 MJ/d. PAL did not show significant seasonal changes in any of the four groups. Only subjects with a BMI < 18 decreased BMR during the preharvest season with 2·9 (SD 6·7) J/kg per min (P < 0·05), with a decrease of 0·8 (SD 1·4) kg (P < 0·05) in body weight. In very thin women with a BMI < 17 (n 5) BMR expressed per unit body weight decreased even more during the preharvest season (by 12 %).

Rates of energy expenditure (J/kg fat-free mass (FFM) per min) in normal weight, ‘small-eating’ men were compared with those obtained for normal weight (n 8) and underweight (n 5) ‘large-eating’ men. For the matched groups of ‘large-’ and ‘small-eaters’ there were no differences in resting metabolic rate (RMR) measurements but during controlled daily activities there was a small but significant increase (P < 0.05) in energy expenditure in the ‘large-eaters’. These results contrast with those obtained for the unmatched groups where energy requirements were about 10 % (P < 0.01) higher in the underweight ‘large-eaters’ at rest but were not different during the more energetic (walking) activities. However, after adjustment for differences in FFM between these two groups, the resting energy expenditures of the ‘large-eaters’ (82·54 (SE 1·51) J/kg FFM per min) were similar to those of the ‘small-eaters’ (81·87 (SE 1·51) J/kg FFM per min). Oral temperatures were significantly higher in the matched (0·35–0·65°) and unmatched (0·7–0·9°) ‘large-eaters’ both at rest and during the different activities, but the thermic effect of food (50 kJ/kg FFM) was one fifth lower (not significant) in both groups of ‘large-eaters’. These results provide little evidence for any major metabolic differences between groups of ‘large-eating’ and ‘small-eating’ men.

The effects of body size and feed intake on N digestibility, pancreas and liver weight, and digestive enzyme activities in male broiler chicks were compared with those induced by dietary tannins. Four groups (SSM, ad lib., pair-fed and young) of sixteen birds each (2 weeks old) were used as experimental animals. They were fed on experimental diets for 4 weeks, except the young group which were fed from age 15 d to 24 d only. Two isonitrogenous and isoenergetic diets with (SSM) or without salseed (Shorea robusta) meal (CONTROL) were used. SSM diet was fed ad lib. to SSM group and control diet was fed ad lib. to ad lib. and young birds and to pair-fed birds at same intake level as SSM birds. Birds fed ad lib. utilized their diet more efficiently than the SSM and pair-fed birds. Digestibility of N, both apparent and ileal, was substantially lower with SSM diet than with the control diet. Each of the treatments induced enlargement of the pancreas (g pancreas/kg live weight) when compared with ad lib. birds. There was no difference between the relative liver weights of SSM and ad lib. birds; however, pair-fed and young birds had comparatively bigger livers. In pair-fed birds the trypsinogen activity of pancreatic tissue (U/g pancreatic tissue) was significantly depressed but there was a significant elevation in trypsinogen (U/kg live weight) activity in SSM birds; again pair-fed birds exhibited the lowest value for this variable. Compared with control birds all the other treatments resulted in significant depression of α-amylase (EC 3.2.1.1) activity in pancreatic tissue (U/g) and jejunal digesta (U/g), but because of pancreatic enlargement α-amylase activity per kg live weight was significantly lower only in SSM birds. The activity of trypsin (EC 3.4.21.4) in jejunal digesta was very low in SSM birds, but it was slightly higher in the young birds. Dipeptidase (EC 3.4.13.11) and disaccharidases in duodenal and jejunal mucosa were markedly depressed by the diet containing salseed meal, with the exception of maltase (EC 3.2.1.20) which was unaffected in jejunal mucosa. Enterokinase (EC 3.4.21.9) activity was not inhibited by the presence of tannins in the diet, rather it increased in the duodenal mucosa of SSM birds.

Digestible energy (DE), metabolizable energy (ME) and net energy for maintenance (NEm) values of a set of fourteen diets were measured in six adult sows fed at and below their maintenance energy level. The efficiency of ME for NEm was estimated from heat production (HP) measurements (indirect calorimetry) at these different feeding levels. HP was partitioned between HP due to physical activity, thermic effect of food (TEF) and fasting heat production (FHP). The amounts of DE digested in the small intestine or in the hindgut were measured. Equations for prediction of NEm from dietary characteristics were calculated. HP at maintenance level averaged 400 kJ/kg body-weight0.75, 16 and 19% of the total being due to physical activity and TEF respectively. The efficiency of ME for NEm averaged 77·4% with higher values for digestible diethyl ether extract (100%) and starch + sugar (82 %). The efficiencies of digestible crude protein (N × 6·25) and digestible residue averaged 69 and 56 % respectively. The energy absorbed from the small intestine was used more efficiently than the energy fermented in the hindgut (82 v. 59%). These values are comparable with those obtained in growing pigs. The NEm content of diets can be predicted accurately from equations including DE (or ME) values and some dietary chemical characteristics.

Human diet planning is generally carried out by selecting the food items or groups of food items to be used in the diet and then calculating the composition. If nutrient quantities do not reach the desired nutritional requirements, foods are exchanged or quantities altered and the composition recalculated. Iterations are repeated until a suitable diet is obtained. This procedure is cumbersome and slow and often leads to compromises in composition of the final diets. A computerized model, planning diets for humans at minimum cost while supplying all nutritional requirements, maintaining nutrient relationships and preserving eating practices is presented. This is based on a mixed-integer linear-programming algorithm. Linear equations were prepared for each nutritional requirement. To produce linear equations for relationships between nutrients, linear transformations were performed. Logical definitions for interactions such as the frequency of use of foods, relationships between exchange groups and the energy content of different meals were defined, and linear equations for these associations were written. Food items generally eaten in whole units were defined as integers. The use of this program is demonstrated for planning diets using a large selection of basic foods and for clinical situations where nutritional intervention is desirable. The system presented begins from a definition of the nutritional requirements and then plans the foods accordingly, and at minimum cost. This provides an accurate, efficient and versatile method of diet formulation.

Using a new-generation open-circuit calorimeter capable of monitoring the cost of activity, and thereby both the real thermic effect of feeding (TEF) and basal metabolism in free-moving freely-feeding rats, we have reassessed the proposal that when food intake is restricted an adaptative reduction in energy expenditure participates in the achievement of energy balance. Total energy expenditure, energy expenditure due to spontaneous activity, TEF, basal energy expenditure and respiratory quotient (RQ) were computed by indirect calorimetry in rats given either a mildly restricted (MR) feed intake for 20–30 d (17 g feed/d) or a severely restricted (SR) feed intake for 1–10 d (4 g feed/d). In MR rats no significant changes in any of the measured variables were observed. In contrast, SR rats exhibited an adaptative reduction in energy expenditure due to a reduced spontaneous activity and probably also due to a reduced basal energy expenditure. On the other hand none of the animals fed on a restricted feed intake showed an adaptative TEF decrease, suggesting that TEF under ad lib. feeding is rather an obligatory process that does not include an adaptative component. Taken together, these results point out that under restricted feeding most of the decrease in energy expenditure is associated with simple passive mechanisms, such as body weight loss, and with the reduced feed intake per se. Only under severe feed restriction can some additional energetic economy be obtained from a possible reduction of basal metabolism, and to some extent from reduced activity.

An experiment was conducted to determine the utilization of ileal digestible methionine by growing pigs. Three methionine-deficient diets (0·09 g ileal digestible methionine/MJ digestible energy (DE)) were formulated using cottonseed meal, meat-and-bone meal and soya-bean meal respectively as the only source of methionine in the diet. An additional three diets were formulated with supplements of methionine to confirm that methionine was limiting in the first three diets. The growth performance and retention of methionine by pigs given the six diets over the 20–45 kg growth phase was then determined. Growth rates (g/d) of pigs given the three diets formulated to 0·09 g ileal digestible methionine/MJ DE were significantly different (P < 0·01): cottonseed meal 411, meat-and-bone meal 442, soya-bean meal 496 (SED 24·6). The response of pigs to the addition of methionine confirmed that methionine was limiting in these diets. Crude protein (N × 6·25) deposited by the pigs (g/d) was significantly higher (P < 0·05) for those given soya-bean meat (61) and meat-and-bone meal (57) relative io cottonseed meal (47; SED 3·3). The proportion of ileal digestible methionine retained by pigs given the three protein concentrates was: cottonseed meal 0·39, meat-and-bone meal 0·45, soya-bean meal 0·47 (SED 0·019). These results indicate that values for the ileal digestibility of methionine in protein concentrates do not reflect the proportion of methionine that can be utilized by the pig. It appears that, with heat-processed meals, a considerable proportion of the methionine is absorbed in a form(s) that is (are) inefficiently utilized.

Sheep fed ad lib. on a good-quality pelleted diet (g/kg; hay 500, barley 300, molasses, fish meal and minerals) were infused via the hepatic portal vein with mixtures of the sodium salts of volatile fatty acids, acetate and propionate, and a variety of equivalent osmotic loads. Propionate infused at rates between 0·6 and 2·5 mmol/min consistently reduced food intake in a linear, dose-related manner. Propionate infusions resulted in consistent dose-related increases in peripheral venous plasma glucose concentration but variable changes in insulin concentration. Infusion of osmotically balanced mixtures of propionate, acetate, mannitol or saline (9 g NaCI/I) indicated that at constant osmotic loading propionate caused a greater reduction in intake than other infusions. Acetate infusions only depressed food intake when administered as a 1 M solution. Lower concentrations had little effect, similar to that of equivalent osmotic loads of mannitol or saline. It is concluded that portal propionate flow has a potential role in the control of food intake in ruminants which is independent of osmotic effects or changes in plasma insulin concentration.

The question addressed is whether an increased intake of cholesterol affects esterase-1 (EC 3.1.1.1; ES-1) and butyrylcholinesterase (EC 3.1.1.8) activity in plasma. Rats were fed on a purified diet either without or with cholesterol (10 g/kg) added at the expense of the carbohydrate source. Dietary cholesterol significantly decreased plasma butyrylcholinesterase activity, but raised plasma ES-1 activity. Evidence is discussed, suggesting that plasma butyrylcholinesterase is involved in plasma cholesterol metabolism, whereas esterase-1 is involved in intestinal cholesterol absorption.

The aim of the present study was to investigate the usefulness of abdominal diameters to indicate visceral fat, their relationship with serum lipids and their capability of detecting changes in visceral fat. Before and after weight loss, visceral and subcutaneous fat, and the sagittal and transverse diameters were assessed by magnetic resonance imaging (MRI) in forty-seven obese men and forty-seven premenopausal obese women with an initial body mass index of 31·0 (SD 2·4) kg/m2. In a subsample (n 21), diameters, were also measured by anthropometry in the standing and supine positions. They were strongly correlated with the diameters derived from the MRI scans. Serum levels of total and HDL-cholesterol and triacylglycerol were measured before weight loss. In women the sagittal diameter correlated less strongly with visceral fat than anthropometrically-assessed waist circumference and waist:hip ratio (WHR). In men these associations were comparable. Changes in visceral fat with weight loss were more strongly correlated with changes in the sagittal diameter and sagittal:transverse diameter ratio (STR) than with changes in waist circumference or WHR in men. In women, changes in the anthropometric variables and the separate diameters (except STR) were not associated with visceral fat loss. In men, but not in women, both the sagittal diameter and the visceral fat area were related to serum lipids. It is concluded that the sagittal diameter and STR may have advantages over waist circumference and WHR in men, particularly in assessing changes in visceral fat, but this could not be demonstrated in women. The ability to predict visceral fat from circumferences and diameters or their ratios is, however, limited in obese men and women.