1. A computer programme is described which simulates energy metabolism in the whole animal. Simulation was based on representation of the animal as a quasi-steady-state system.

2. Input for the programme consisted of the chemical composition of the diet and an estimate of either the maintenance energy requirement or an estimate of energy retention.

3. Simulation was performed by estimating the yield of adenosine triphosphate in the major metabolic pathways operative in simple-stomached animals, and on the utilization of adenosine triphosphate in major anabolic processes.

x4. Results obtained from simulation were in close agreement with experimental observations reported by McCracken (1975).

1. Responses of the protozoa population to the composition and the components of the diet were studied in permeable continuous cultures of rumen contents.

2. In Expt I a study was made of responses to diets containing different combinations of rice straw, lucerne meal and mixed concentrates given to the cow supplying inocula for cultures. It was found that (1) when a diet devoid of concentrates was fed, entodiniomorphs decreased in numbers; (2) their numbers increased with the increase in the amount of concentrates; (3) holotrich numbers were hardly affected by the type of diet; (4) rice straw and lucerne meal were not essential for protozoa to survive in culture medium.

3. In Expt 2 responses were determined to diets containing different combinations of maize, maize starch, sugars (glucose-sucrose (1:1, w/w)), soya-bean meal and isolated soya-bean protein. The results suggested the following relationship between dietary component and protozoa population. (1) The diet rich in both starch and sugars sustains the increased numbers of protozoa on the whole. (2) The diet rich in starch and deficient in sugars decreases selectively Dasytricha and small species of Entodinium such as Entodinium minimum and E. nanellum. The other species of protozoa, especially large entodiniomorphs such as Ophryo-scolex and Polyplastron, are maintained at relatively high levels. (3) The diet deficient in starch and abundant in sugars decreases general entodiniomorphs except small species, while the numbers of Holotrichs are kept at relatively high levels.

1. Six experiments, involving a total of 320 pigs, were conducted to examine the reponse of growing pigs to diets supplemented with free lysine when fed either once daily or in six equal portions at intervals of 3 h. The effect of dry or wet feeding on the response to free lysine was examined in Expt nos. 4 and 5. The assumption of linear lysine response over the range of lysine supplementation was examined in Expt no. 6.

2. A significant (P < 0.01) interaction between lysine supplementation and frequency of feeding occurred for growth rate and food conversion ratio. Growth responses to the supplements of free lysine with once daily feeding were only 67 % of that achieved with frequent feeding.

3. Wet feeding had no effect on the growth responses to free lysine supplements.

4. The lysine response was linear over the range of lysine supplementation examined.

5. The implications of these results to the interpretation of experiments examining the lysine requirements of pigs are discussed.

1. The net protein utilization (npu, the percentage of dietary nitrogen retained in the body, allowance being made for endogenous urinary and faecal N) of diets composed of Nigerian foodstuffs, based on rice, sorghum (Sorghum sativa) or cassava (Manihot utilissima), was compared to that of a minimal protein diet used to determine endogenous N excretion, supplemented with whole egg. The addition of dl-methionine and l-tryptophan to the rice diet produced a small but non-significant increase in npu, whereas the addition of dl-methionine to the cassava diet produced a very significant increase in npu. The npu of a diet based on home-pounded, winnowed, sorghum flour was higher than that of a diet based on milled whole-meal sorghum due to the low digestibility of the latter diet.

2. The digestibility of the rice and cassava diets were the same, although the total crude fibre content of the rice diets was lower than that of the cassava diets.

3. Nigerian men used the proteins of the egg diet and of mixed diets based on rice, sorghum and cassava more efficiently than predicted by applying methods recommended by the FAO/WHO ad hoc Expert Committee on Energy and Protein Requirements (FAO/WHO, 1973).

4. The recommendations of that Committee (FAO/WHO, 1973) to reduce the amounts of sulphur amino acids and tryptophan, contained in the ‘provisional pattern of amino acids’ proposed by the FAO Committee on Protein Requirements (FAO, 1957), are supported, but the increases in lysine and threonine are not supported, by the present results.

1. Adult male Japanese quail (Coturnix Coturnix Japonica) were overfed at different intensities during varying periods: (1) by gradually increasing the daily amount of food up to twice the control level in a period of 11 d and keeping this level constant during the subsequent 12 d period (prolonged overfeeding); (2) by gradually increasing the daily amount of food up to approximately twice the control level in a period of 6 d (short, low-intensity overfeeding; SL); (3) by gradually increasing the daily amount of food up to approximately 2.5-fold the control level in a period of 7 d (short, high-intensity overfeeding; SH).

2. The activities of acetyl-CoA carboxylase (EC 6.4.1.2; CBX), fatty acid synthetase (FAS), ATP citrate lyase (EC 4.1.3.8; CCE) and malate dehydrogenase (decarboxylating) (NADP) (EC 1.1.1.40; ME) were determined in adipose tissue (AT) and liver of the overfed and ad lib.- fed chicks. Size and fat content of carcass, AT and liver were also determined in order to evaluate the extent of obesity.

3. The weight of carcass, lean body mass, liver and AT and the extent of fat deposition increased with the total amount of food consumed. Obesity was particularly pronounced in quail after prolonged overfeeding.

4. Lipogenic enzymes in liver were much more active than those of AT. The specific activities of CBX, FAS and CCE in liver and AT in overfed Japanese quail increased consistently in the SL and SH groups only and the increase was related to the level of food intake in these groups. ME was the only enzyme whose specific activity increased in all overfed groups. Total AT enzyme activities were increased most strongly after prolonged overfeeding because of the pronounced tissue enlargement in that treatment. But in liver, where tissue enlargement was less and differences in size due to the three overfeeding treatments were less marked, total activities depended mainly on the enhancement of specific activities.

5. The results lead to the conclusion that the increase in hepatic lipogenic enzymes roughly reflects the current food intake and may thus be considered to represent the primary adaptation in the overfed Japanese quail. Secondary adaptation, involving tissue enlargement, occurs principally in AT of Japanese quail after prolonged overfeeding, in which situation AT contributes significantly to total lipogenic activity.

1. 65Zn uptake by blood cells in vitro has been compared with plasma Zn concentration and plasma alkaline phosphatase (EC 3.1.3.1) activity as indicators of an animal's Zn status.

2. Dietary Zn deficiency, low food intake, reduced dietary protein content and endotoxin administration all reduced plasma Zn concentration in the rat. In each case there was a parallel reduction in plasma alkaline phosphatase activity and an increase in 65Zn uptake in vitro by cells of whole blood.

3. A similar relationship between the three measurements existed in sheep with lowered plasma Zn concentrations whether these were caused by dietary deficiency or by post-surgical stress.

4. 65Zn uptake by cells of whole blood did not differentiate dietary Zn deficiency from the other factors which reduce plasma Zn under ‘field’ conditions.

5. 65Zn uptake by the cells in whole blood in vitro was three to five times less rapid in blood of ruminant origin than in that from non-ruminants. This difference related to the erythrocytes rather than to the leukocytes or the plasma.

1. The activities of alkaline phosphatase (EC 3.1.3.1) and phytase (EC3.1.3.8) were similarly distributed in the small intestine of rats. Regional differences in activity were reflected by similar differences in the capacity of ligated intestinal segments to hydrolyse phytate in vivo. Activities were greatest in the duodenum and lowest in the terminal ileum.

2. Specific activities of both enzymes were tenfold greater in the brush border fraction of duodenal mucosa compared with entire mucosal homogenates.

3. Brush-border alkaline phosphatase and phytase activities required both magnesium and zinc ions for maximal activity.

4. Zn deficiency induced by feeding a diet low in Zn (0.5 mg Zn/kg) caused similar reductions in activity of both enzymes.

5. Zn deficiency induced by feeding diets marginally adequate in Zn (12 mg/kg) and phytate (10g/kg) caused reductions in alkaline phosphatase, phytase activities and phytate hydrolysis in vivo.

6. It is suggested that phytase activity is a manifestation of alkaline phosphatase and the significance of this in relation to phytate-induced Zn deficiency is discussed.

1. The effects of chronic ethanol administration on the metabolism of ethanol and acetaldehyde were studied in rats fed on a commercial diet containing an aldehyde dehydrogenase inhibitor, calcium cyanamide (calcium carbimide), as a contaminant in the calcinated bone-meal fraction of the diet.

2. Rats given an ethanol solution (150 ml/l) for 3 months and fed on a diet containing calcinated bone meal showed two times higher activity of the low-Km acetaldehyde dehydrogenase in the liver, 26 % higher rate of ethanol elimination, and two to three times lower acetaldehyde levels in blood during ethanol elimination compared with control rats pair-fed on the same diet.

3. The results obtained from the ethanol-treated rats were similar to those obtained in experiments on control rats fed on diets not containing calcinated bone meal.

4. Experiments performed in vitro and in vivo on the inhibition of the acetaldehyde metabolism by cyanamide suggested that the apparent effects of chronic ethanol intake were really caused by calcium cyanamide in the diet.

1. A 30-week study has been made in growing ewe lambs of the effects of dietary supplementation with molybdenum, or Mo plus inorganic sulphate on the distribution of copper in their blood plasma and kidneys.

2. The addition of 25 mg Mo and 5 g SO42-/kg diet increased Cu concentrations in plasma and kidney and decreased those in liver. Plasma caeruloplasmin activities (ferroxidase; EC 1.16.3.1) were unaffected.

3. Subcellular fractionation of the kidney cortex and gel filtration of the plasma and kidney cortex cytosol showed that the increased Cu content of these tissues was associated with abnormalities in the distribution of Cu. It appeared that both Cu and Mo were associated with the same proteins.

4. Dietary supplementation with Mo alone (25 mg/kg) had no effect on plasma or kidney Cu concentrations, suggesting that S metabolism is involved in the formation of the abnormal Cu-binding proteins in plasma and kidney.

5. The results are discussed in relation to the induction of Mo-induced Cu-deficiency states and the possible involvement of thiomolybdates.

1. Methane production rates were estimated simultaneously in the rumen and caecum of sheep given 200, 400, 600, 800 and 1000 g lucerne (Medicago sativa) chaff/d using isotope dilution techniques. Estimates were also made of volatile fatty acid (VFA) production in the rumen at each level of feeding. In all studies three to four animals were used at each level of intake.

2. Production of VFA and of methane were both related to digestible energy (de) intake. Regression lines for both VFA production and methane production v.de intake had significant intercepts indicating an input of endogenous, fermentable organic matter into the rumen in excess of 50 g/d.

3. The values obtained for rates of methane production were compared with those calculated from stoicheiometric equations relating rates of methane and VFA production. Comparisons of methane production with that predicted from de intake were also made.

4. Balances for digestion of food determined for the rumen indicated that the energies in the end-products were more than 100% of the de intakes at low intakes of lucerne chaff. Correction for fermentation of apparent endogenous materials resulted in more realistic values. Endogenous materials appeared to make a significant contribution to VFA and methane production, particularly at low levels of intake.

1. Placental blood flow rate and calcium transfer rate were measured at 61 d of pregnancy in guinea-pigs carrying between one and eight foetuses.

2. Placental blood flow rate was significantly correlated with foetal weight. Ca transfer rate was related to placental size. Irrespective of litter size the mean amount of Ca transferred across a placenta was between 0.22 and 0.34 mg/h per g placental tissue.

3. It was concluded that there was a limit to the rate of transfer which was produced by a combination of limitations in placental blood flow rate, maternal plasma Ca concentration and placental tissue transfer capacity.

1. A prospective randomized study of two dietary regimens has been started in newly-diagnosed diabetics to determine their effect on circulating metabolites and on diabetic complications.

2. During the first year of treatment the fasting plasma glucose concentrations on both the low-carbohydrate diet and the high-carbohydrate, modified-fat (MF) diet showed a similar decrease.

3. Plasma cholesterol showed a sustained decrease only in patients recommended a MF diet. Transient changes in plasma triglyceride concentrations occurred in patients on both dietary regimens.

4. Increased plasma cholesterol levels are associated with atheromatous disease which is common in diabetics in Europe and North America. A MF diet may therefore have an advantage in that it lowers the plasma cholesterol as well as being effective in lowering the plasma glucose.

1. The effect of caffeine (2.5 g/kg diet) on lipid metabolism was examined in rats fed on a stock (low-cholesterol) diet or on a cholesterol plus cholic acid-supplemented (high-cholesterol) semi-synthetic diet.

2. When caffeine was included in the stock diet fed to rats for 7 d, there was a moderate but significant increase in the concentration of serum cholesterol compared to the levels observed in the control rats. This change can be accounted for by the increase that was observed in the rate of cholesterogenesis in the liver.

3. After 25 d of caffeine in the stock diet, hepatic cholesterogenesis was still increased but the concentration of serum cholesterol was now the same as in the control rats. During the experimental period there was a progressive increase in the faecal excretion of neutral sterols in the rats receiving caffeine.

4. When caffeine was added to a cholesterol plus cholic acid-supplemented diet, there was a marked increase in the concentration of serum cholesterol but hepatic cholesterogenesis was now reduced.

5. Caffeine in the high-cholesterol diet appeared to delay, but probably did not reduce, the absorption of an oral dose of radio-labelled cholesterol. This conclusion was confirmed using rats which had not previously received either caffeine or cholesterol in the diet.

6. When the effect of caffeine in the high-cholesterol diet was investigated during a 24 h period, an exacerbation of the hypercholesterolaemia was seen only at certain times.

7. After a 4-month period of feeding rats on the caffeine-supplemented high-cholesterol diet, histological examination did not detect any damage to the heart and aorta.

8. The metabolic regulations involved in the effects of caffeine in the two diets are discussed and the relevance of the present results to observations made with human subjects is considered.

1. Deficiency of zinc inhibits growth and also increases the activity of alkaline ribonuclease in certain tissues of the rat (Prasad & Oberleas, 1973). Zn could influence ribonuclease activity by direct effects on the enzyme or its natural inhibitor, or non-specifically as occurs when growth rate is affected by various other factors. These possibilities were studied.

2. Alkaline ribonuclease was shown to be inhibited by Zn in vitro, but the concentrations of Zn required were so high that the enzyme was probably not directly affected by changes in tissue Zn concentration caused by dietary deficiency.

3. At lower concentrations, Zn added in vitro increased the activity of alkaline ribonuclease in tissue homogenates probably by inactivating the inhibitor of the enzyme.

4. Age, weight and particularly food restriction caused tissue-specific alterations of ribonuclease and ribonuclease inhibitor concentrations in liver, kidney, oesophagus, testis and thymus.

5. The ribonuclease activities in liver, kidney and testis of Zn-deficient rats were unaltered in comparison with those of pair-fed rats. In thymus, which decreased in weight in the Zn-deficient animals, there was a concomitant increase in ribonuclease activity, but in oesophagus, the deficiency reduced the activity of ribonuclease.

6. The effects of Zn deficiency upon alkaline ribonuclease and its inhibitor are probably secondary consequences of reductions in food intake or growth.

1. Serum ferritin concentrations were measured in 378 Zulu children aged 1–4 years living in Nqutu, KwaZulu and in 342 children of mixed race (Cape coloureds) aged between 1 and 16 years living near Johannesburg.

2. The pattern of serum ferritin concentrations encountered in the children at different ages tended to parallel the changes in iron stores which are known to occur during development.

3. Serum ferritin concentrations showed a significant direct correlation with age, haemoglobin, serum Fe and percentage saturation of transferrin values.

4. Anaemia was most prevalent in the younger children. Of the rural and urban children aged 13–24 months 60 and 53% respectively were anaemic while only 11% of those over 24 months had haemoglobin concentrations that were below normal.

5. The prevalence of anaemia among children who had serum ferritin values below 12 μg/l was only slightly higher than that for the groups as a whole (38.8 % v. 24.3%), while the prevalence in those with values of 12 μg/l or more was only slightly less (18.2%). However, when a ferritin concentration of less than 12μg/l was associated with a percentage saturation of transferrin of less than 16%, the prevalence of anaemia was 70.0%, and only 10.2% of children in whom both values were within the normal range were anaemic.

6. Since 67% of children had either a normal serum ferritin and a normal percentage saturation of transferrin or both values below the normal range, the two measurements taken together provided a useful means of separating the children who had significant Fe deficiency from those whose Fe stores were sufficient to make the appearance of anaemia unlikely.

1. The amount of selenium in nationally representative samples of prepared and cooked groups of foods, and in a variety of raw individual foods, was determined fluorimetrically.

2. The average British diet was calculated to provide approximately 60 μg Se/d, of which half was derived from cereals and cereal products and another 40% from meat and fish. Milk, table fats, fruit and vegetables provided little or no Se.

3. Individual foods which were particularly rich in Se (>0.2 mg/kg) included ‘bread-making’ and wholemeal flours, kidney, fatty fish, brazil nuts (Bertholletia excelsa) and several other varieties of nut. In contrast, breast milk and other foods for babies (except some cereal products) contained little Se.

4. The total intake, and the amounts of Se in major foods, were lower than in most other studies. This is probably the result of the comparatively low levels of this element in British soil.

1. The body compositions of obob and lean (ob+ and + +) mice at 10, 12, 17 and 28 d of age were investigated using a ‘cold stress’ test to identify the two groups.

2. At each of these ages the obob mice were found to contain significantly more fat than the lean. At 10 d 20 % more fat was present and by 17 d the increase was 72 %. The obob mice at 28 d contained nearly three times as much fat as the lean.

3. Carcass energy was significantly higher in obob mice at all ages investigated.

4. Other changes in body composition found in the 28 d obob mice, i.e. a reduction in total carcass nitrogen and water content, were already established in the 17-d-old mice but differences at 10 and 12 d were not apparent.

5. The livers of obob mice were significantly heavier than those from lean control mice at 28 d but no differences were detected at the earlier ages.

6. The results are discussed with reference to the early origin of obesity in obob mice.

Fat-free body mass is an important component of body composition which is of particular interest to nutritionists and related workers. Fat-free mass has been determined from the simple measurement of skinfold thickness and it has been demonstrated that there is a close correlation with total body nitrogen even though the test subjects had a wide range of nutritional status.