1. Long-term variations in breast-milk fat concentration of mothers feeding on demand were studied in 120 rural West African women over a 12-month period.

2. The over-all mean 12 h breast-milk fat concentration was 39.3 g/l.

3. Mean breast-milk fat concentrations were affected by season in a manner which was correlated with seasonal changes in maternal subcutaneous fat stores (P > 0.05) but which was unrelated to seasonal variations in maternal energy intake and breast-milk output.

4. Breast-milk fat concentrations were highest in early lactation, decreasing to a constant level during the first year.

5. There was significantly greater between-mother than within-mother variation in breast-milk fat concentrations measured in successive months, after correcting for season and stage of lactation (P > 0.001).

6. Breast-milk fat concentrations were highest for primiparous mothers, decreasing to a constant level at parity 4 and higher.

7. A mother's relative breast-milk fat concentration was not correlated with her levels of dietary energy intake and breast-milk output but was positively correlated with her relative subcutaneous fat deposits (P > 0.01).

1. A partial purification of kynureninase (L-kynurenine hydrolase, EC 3.7.1.3) from rat liver and a total resolution of the apoenzyme have been achieved. The hypothesis that conjugates of oestrogenic steroids compete with pyridoxal phosphate for the cofactor binding site of the enzyme, and so disturb tryptophan metabolism, leading to apparent vitamin B6 deficiency, has been tested.

2. Kynureninase from rat liver was partially purified, and the cofactor-free apoenzyme was prepared. Oestrone sulphate inhibited the enzyme uncompetitively with respect to pyridoxal phosphate, and competitively with respect to kynurenine, with a mean (±SE) inhibitor constant (Ki) of 82 ± 6 μM.

3. The addition of a saturating concentration of pyridoxal phosphate to unfractionated liver homogenates led to an approximately fivefold increase in kynureninase activity, indicating the presence of a relatively large amount of apo-kynureninase in the tissue.

4. It is suggested that the abnormal results of tryptophan load tests in women receiving oestrogens are the result of inhibition of kynureninase by oestrogen conjugates, and that there is no evidence for oestrogen-induced vitamin B6 deficiency in such cases.

1. The energy balance of eleven male and fourteen female adult farmers was measured for 6 d after the harvest, in December-January. Their energy intake was recorded by weighing their food consumption and their energy expenditure was determined using indirect calorimetry.

2. Body-weight, expressed as percentage of expected weight-for-height was 91 and 86% of the Inter-departmental Committee on Nutrition for National Development (1963) standard for women and men respectively.

3. The staple foods were sorghum (Sorghum vulgare) and millet (Pennisetum typhoïdes); carbohydrates, fat and protein supplied approximately 80, 13 and 12% of the total energy of the diet respectively.

4. In the male group, the mean energy intake (9.0 MJ (2148 kcal)) was in good agreement with the average energy output (8.91 MJ (2130 kcal)). By contrast, in the female group, the mean energy expenditure (8.11 MJ (1941 kcal)) exceeded the mean energy intake (6.3 MJ (1515 kcal)) and the deficit was statistically significant.

5. This study allows an evaluation of the adequacy of food intake for subjects living in a particular hostile environment, by using their actual energy output instead of current standard values. The energy deficit found for female farmers whose energy intake was similar to that reported in other developing countries emphasizes the need for a better understanding of the regulation of energy balance in such conditions.

1. Thirty Mossi male farmers from Upper-Volta were investigated, twenty-three in the dry season (March-April) and sixteen in the rainy season (July-August), eight of them being studied twice. A 48 htime-and-motion study was carried out and the daily energy expenditure was computed.

2. The mean height was 1.70 m and the mean weight 58.5 kg. The average percentage of body fat calculated from skinfold thickness was 10.

3. During the dry season the subjects could be classified as very moderately active with an energy output of 10.1 MJ (2410 kcal)/d. By contrast, with an energy expenditure of 14.4 MJ (3460 kcal)/d, they were considered as exceptionally active in July-August when performing the agricultural work.

4. In this study we measured the intensity of physical work in a society where human labour is still the main tool of production. The determination of seasonal variations in energy expenditure may be useful to assess the nutritional requirements in arid zones of West Africa.

1. The hypothesis that soya-bean saponins, by binding bile salts in the gastrointestinal lumen, are responsible for some of the plasma-cholesterol-lowering effect of soya-bean preparations, was tested. In a double-blind crossover study 50 g soya-bean flour/d, containing either 22 or 4 g saponins/kg (adjusted by ethanol extraction) was incorporated in biscuits as a substitute for biscuits or bread into the diet of ten outpatient hypercholesterolaemic men over two consecutive 4-week study periods. The diet was monitored to ensure constancy, saponin-rich foods excluded, faeces collected for bile acid and neutral sterol analysis, and blood taken for plasma lipoprotein lipid analysis.

2. Neither diet had any effect on cholesterol in any plasma lipoprotein fraction, on fasting plasma triglyceride, or on faecal bile acids and neutral sterols.

3. These results suggested that soya-bean saponins are not responsible for the hypocholesterolaemic effect of soya-bean products.

1. A rumen bacterial culture containing specifically labelled nucleic acids was prepared using [8-14C]adenine.

2. The labelled preparation was given in a liquid diet to two preruminant lambs and via a rumen tube to two ruminant lambs. The radioactivity excreted in exhaled gases, faeces and urine and that incorporated into tissues was determined.

3 The preruminant lambs absorbed 58.3% of the total radioactivity measured after 24 h and the ruminant lambs 66.6% of the total activity measured after 48 h.

4. Of the total radioactivity absorbed the preruminant lambs exhaled 38%, excreted 34% in urine and retained 29% in tissues. The corresponding values for the ruminant lambs were 12,41 and 47% respectively.

5. There was a close relationship between total nucleic acid content and radioactivity per g of tissues of both preruminant and ruminant lambs.

6. Of the radioactivity in the urine, the ruminant and one preruminant lamb excreted most in the fraction containing allantoin, while the other lamb excreted most activity in the uric acid fraction.

7. The salvaging of the breakdown products of bacterial nucleic acids to make tissue nucleic acids appears to be an important synthesis in preruminant and ruminant lambs and of the likely precursors the purine base may be more important than the nucleoside.

1. Bowel transit time has been investigated in vegetarians and non-vegetarians and related to dietary fibre intake and the presence of diverticular disease.

2. Vegetarians who have less diverticular disease than non-vegetarians have more rapid transit times.

3. Subjects with total dietary fibre intake of more than 30 g/d all had transit times of less than 75 h whereas 38% of those eating less had transit times exceeding 75 h and varying up to 124 h.

4. Individuals with diverticular disease were found to have faster transit times than those without the disease.

5. The colon may respond to a fibre-depleted diet either by becoming hyperactive and prone to diverticular disease or by becoming hypoactive leading to constipation.

1. The effect of varying dietary levels of casein (40–140 g/kg) on hepatic lipogenesis and the levels of hepatic fatty acid synthetase (FAS), glucose-6-phosphate dehydrogenase (EC 1.1.1.49; G6PD), malic enzyme (EC 1.1.1.40; ME), citrate cleavage enzyme (EC 4.1.3.8;CCE), acetyl CoA carboxylase (EC 6.4.1.2; AcCx), glucokinase (EC 2.7.1.2; GK), and pyruvate dehydrogenase (PDH) was examined in young, growing rats.

2. The activities of AcCx, FAS, G6PD and in vivo fatty acid synthesis were generally found to increase with increased dietary protein.

3. The levels of GK and PDH were not related to dietary protein.

4. ME decreased with increasing dietary protein.

5. The results demonstrate a dissociation between hepatic fatty acid synthesis and ME and suggest that when rats consume low-protein diets the NADPH needed for fatty acid synthesis is generated primarily by ME but that as the level of dietary protein is increased the contribution of ME is reduced while that of the phosphogluconate pathway becomes more important.

1. An experimental model for the determination of dietary fibre according to the definition of Trowell et al. (1976) is described. Food was subjected to in vivo digestion in ileostomy patients, and the ileostomy contents were collected quantitatively, the polysaccharide components of which were analysed by gas–liquid chromatography and the Klason lignin by gravimetric determination. The model was used for the determination of dietary fibre in AACC (American Association of Cereal Chemists), wheat bran and for studies on the extent of hydrolysis of wheat-bran fibre in the stomach and small intestine. The effect of wheat bran on ileostomy losses of nitrogen, starch and electrolytes was also investigated.

2. Nine patients with established ileostomies were studied during two periods while on a constant low-fibre diet. In the second period 16 g AACC wheat bran/d was added to the diet. The ileostomy contents and duplicate portions of the diet were subjected to determinations of wet weight, dry weight, water content, fibre components, starch, N, sodium and potassium.

3. The wet weight of ileostomy contents increased by 94 g/24 h and dry weight by 10 g/24 h after consumption of bran. The dietary fibre of AACC bran, determined as the increase in polysaccharides and lignin of ileostomy contents after consumption of bran, was 280 g/kg fresh weight (310 g/kg dry matter). Direct analysis of polysaccharides and lignin in bran gave a value of 306 g/kg fresh weight. Of the added bran hemicellulose and cellulose 80–100% and 75–100% respectively were recovered in ileostomy contents. There was no significant difference between the two periods in amount of N, starch and K found in the ileostomy contents. The Na excretion increased during the ‘bran’ period and correlated well with the wet weight of ileostomy contents.

4. In conclusion, it seems probable that determination of dietary fibre by in vivo digestion in ileostomy patients comes very close to the theoretical definition of dietary fibre, as the influence of bacteria in the ileum seems small. Bacterial growth should be avoided by using a technique involving the change of ileostomy bags every 2 h and immediate deep-freezing of the ileostomy contents. True dietary fibre can be determined by direct analysis of polysaccharides and lignin in the food, at least in bran. Very little digestion of hemicellulose and cellulose from bran occurs in the stomach and small bowel. The 10–20% loss in some patients may be due to digestion by the gastric juice or to bacterial fermentation in the ileum, or both. The extra amount of faecal N after consumption of bran, reported by others, is probably produced in the large bowel.

1. Dietary fibre has a water holding capacity (WHC) and this is a function of the fibre source and method of measurement. Water can be associated with fibre either as trapped water or bound water. This makes it difficult to predict the ability of fibre to influence stool weight in humans.

2. Examination of various fibre concentrates for chemical composition, as neutral detergent fibre (NDF), acid detergent fibre (ADF) and lignin; structure, by scanning electron microscopy; WHC, by centrifugation, suggests that WHC is more a function of fibre structure than chemical composition. Cereal fibre and vegetable fibre have a different chemical composition and are structurally very distinct. Structure is also dependent on the method of fibre preparation.

3. Measurement of WHC by centrifugation gives an estimate of the water which can be bound and also trapped by the fibre. The amount of trapped water will depend on the structure of the fibre whereas bound water will depend on the chemical composition.

1. The relationships between the intakes of protein and of non-protein energy (NPE), nitrogcn retention and body protein synthesis have been studied in female pigs weighing 30 and 35 kg.

2. Four animals were assigned to three regimens and given a conventional (basal) diet supplemented with fat, carbohydrate or protein. After 1 week, measurements of N excretion in urine and faeces (7 d collection) and gaseous exchange (3–4 d) were made. At the end of the balance period a solution of [l-14C]leucine was infused at a constant rate. Body protein synthesis was then calculated as the difference between the apparent irreversible loss of blood leucine and the loss of 14C in expired air.

The animals were then offered the basal diet without supplement for 10 d and the measurements of N retention, energy retention and protein synthesis were repeated.

3. The intakes of metabolizable energy (ME; MJ/kg body-weight (W)0.75per d) were 1.75 for fat, 1.58 for carbohydrate, 1–25for protein and 1.18 for the basal diet; corresponding intakes of apparently digestible N (ADN; g N/kgW0.75 per d) were 2.30,2.31,4.35 and 2–17. Daily N retention, which during the period of basal feeding was 13.6 g was increased by between 3.4 and 7.2 g by the supplements. Daily fat deposition was also increased in the animals that received the diets supplemented with carbohydrate and fat.

4. The rate of leucine catabolism was significantly reduced in the animals receiving the diets that were supplemented with W Eand increased by the addition of protein to the diet.

5. When based on the specfic radioactivity of blood leucine both the synthesis and breakdown of body protein (per unit metabolic body-weight) were increased by 30% in the animals receiving the high-protein diet but the increases in protein synthesis associated with the addition of carbohydrate (+14%) and fat (+12%) were much less marked. Consideration of these results together with previous observations (Reeds et al. 1980) suggested that body protein synthesis(g N/d) increased by 0.88 for each g increase in daily ADN and by 0.93 for each MJ increase in daily ME intake.

6. Comparison of the results obtained with the animals given high-carbohydrate diets and those given high-protein diets suggested an increase in heat production of 14 KJ/g of additional fat deposition. A similar comparison of animals receiving the high-protein and basal diets suggested a heat increment of 23.5KJ/g additional protein deposition. The changes in heat production and protein synthesis in the animals given the protein supplement were compatible with a heat increment of 5.3 KJ/g additional protein synthesized. Because of the large proportion of heat production associated with the deposition of fat this could not be confirmed with either of the other supplements, but it is possible that the energy cost of protein accretion varies with the relative proportions of protein and NPE in the diet.

1. Two groups of weanling male rats were fed on a powdered proprietary diet for up to 6 weeks. The diet of one group was supplemented with 2 g Cu/kg and the other group received the unsupplemented diet.

2. The livers in the supplemented group accumulated more Cu within the right vascular compartment than the left. This difference was observed in the unsupplemented group after 6 weeks but not at 4 weeks.

3. The distribution of Cu between the different lobes of the livers of the supplemented groups displayed a characteristic pattern, the median lobe containing the most Cu and the omental lobe the least.

4. The distribution of Cu within the liver is thought to reflect the site of its absorption from the gastointestinal tract and a consequence of portal streaming.

1. Previous measurements of energy intake on sledging journeys in Antarctica have given a mean intake of 14.2 MJ (Acheson, 1974; Campbell, 1975), markedly lower than values reported earlier (see Edholm & Goldsmith, 1966). The technique used (individual weighed-diet survey) was more detailed and could be assumed to be more accurate than most of the earlier work where intakes had been largely inferred from the known energy content of food boxes. In the present study an individual weighed-diet survey was carried out on male subjects during a summer manhauling journey on the east coast of Greenland.

2. Mean daily energy intake of six subjects over 33 d travelling was 16.5 MJ. Mean weight loss was 2.3 kg, probably accounted for entirely by fat loss. Weight loss occurred despite the presence of excess food. Mean daily energy intake rose gradually but persistently over the 5 weeks of the journey despite a constant level of activity and to 20.1 MJ during the 4 d rest at the end of the journey.

3. Intakes were thus higher than those found in the earlier Antarctic studies (Acheson, 1974; Campbell, 1975) but not as high as intakes reported previously (see Edholm & Goldsmith, 1966). The fact that weight loss occurred despite the presence of excess food was ascribed to the monotonous nature of the diet. The fact that energy intake rose persistently over the 5-week study period may imply that a new state of balance of intake and expenditure was reached.

1. One hundred and fourteen pigs between 7 and 35 d of age were given diets containing milk or soya-bean proteins in four separate experiments.

2. The substitution of milk protein by soya-bean meal (SBM) to 75% of the total dietary protein reduced the weight gains and food conversion efficiencies of the pigs by 85% between 7 and 14 d of age and 31% between 21 and 28 d of age.

3. The treatment of soya-bean protein with alkali did not improve the performance of the pigs.

4. The substitution of milk protein by two different isolated soya-bean proteins (ISP) resulted in weight gains of 34 and 60% of the gains of pigs given milk protein diets.

5. Supplementation of the soya-bean-protein diets with methionine to 13.7 g/kg (5 g/16 g nitrogen) resulted in reduced food intakes and weight gains of the pigs and a 20-fold increase in the concentration of methionine in the blood plasma.

6. Supplementation of soya-bean-protein diets with lysine to 22 g/kg (8g/16 g N) in addition to methionine doubled the concentration of lysine in the blood plasma.

7. The apparent digestibility (AD) of dry matter (DM) and N of the diets containing soya-bean protein increased with increasing age of the pigs, but the AD of the milk-protein diet was not affected by the age of the pigs. The retention of N as a percentage of the N intake increased from 57–67% for soya-bean protein over the duration of the experiments while the average value for the milk-fed pigs was 85% at all ages.

8. At 35 d of age, the fat content of the carcasses of the pigs given the ISP diet was 249 g/kg DM compared to 164 g/kg DM for the pigs given the milk diets.

1. Eighteen male sledge dogs were weighed immediately on removal from their sheltered winter quarters at Halley Bay, Antarctica (75° 31′s, 26° 42′W) and weekly thereafter for 14 weeks. The first 2 weeks they were tethered and inactive and the following 12 weeks travelled an average of 10.9 km/d fully laden. Daily energy intake during winter and while tethered averaged 18–25 MJ/d and while travelling 13.9 MJ/0d.

2. Mean weight loss during the 2 weeks of inactivity was 2.3 kg despite an energy intake almost twice the recommended requirement. During the 12 weeks travelling energy intake decreased to 13.9 MJ/d but the weight loss stopped. Weather conditions at this time were becoming progressively milder.

3. The evidence suggests that sledge dogs are capable of high levels of cold-induced and possibly diet-induced thermogenesis and that these factors, particularly the former should be taken into account when designing dog rations and feeding schedules.

1. In two experiments measurements were made of food intake, live-weight change, milk yield and milk composition in early lactation when dairy cows were given diets containing varying proportions of protein as fish meal (low rumen degradability) or as groundnut meal (high rumen degradability). In a preliminary trial measurements were also made with cows given supplements of either fish meal or barley and fed at a restricted level of feeding.

2. When metabolizable energy (ME) intake exceeded 160 MJ/d there was no evidence of responses to changes in protein degradability, but at ME intakes below 135 MJ/d increases in the supply of undegradable protein led to increases in fat-corrected milk yield, protein content and live-weight loss.

3. The interaction between energy intake and protein degradability is unexpected because net protein:net energy requirement increases as milk yield increases, but may be explained in terms of differential effects of changing rumen outflow rates on degradabilities.

1. In two separate experiments, forty-four pigs weaned at 4–5 d of age were given diets containing milk or soya-bean proteins until slaughtered at 14, 28 or 35 d of age.

2. The retention times of digesta in the stomach and the entire gastro-intestinal tract did not differ between pigs given pelleted diets containing milk or soya-bean protein.

3. Digesta retention times in the stomach were shorter (61 v. 146 min) in pigs given a milk-protein diet in a liquid form than in pigs given the same diet in a pelleted form. The retention times in the whole gastro-intestinal tract were 42.8 v. 29.6 h on the respective diets.

4. The total retention time of digesta in the gastro-intestinal tract increased with age of pigs between 14–35 d of age when given pelleted diets but not when given a liquid diet.

5. The daily amount of digesta flowing through the anterior small intestine was unaffected by the source of protein. Greater endogenous secretions into the anterior small intestine were observed when pigs were fed ad lib. than when fed at 2 g nitrogen (45 g dry matter (DM))/kg live weight0.75 per d.

6. The apparent digestion of DM to the ileum of pigs given milk, isolated soya-bean protein (ISP) (Promine D) or soya-bean meal (SBM) protein at 28 d of age was 0.826, 0.825 and 0.644 respectively.

7. The apparent digestion of DM to the ileum of pigs given ISP (Supro 610) significantly increased with age of pigs from 0.851 at 14 d of age to 0.883 at 35 d of age. No increase was observed for pigs given milk protein.

8. Differences in the digestibility of DM between protein sources were greater to the ileum than over the entire gastro-intestinal tract. The greatest increase in DM digestion from the ileum to the faeces occurred in pigs given SBM (0.644–0.874).

9. Neither the protein source nor age of pigs influenced gastric pH values, the mean value being 4.05. pH increased along the small intestine and was not affected by the protein source or age of pig.

1. An experiment was designed to provide information on the alterations in body metabolism which would account for the loss of body-weight in cattle due to the specific effect (factors other than reduced food intake) of the tick Boophilus microplus.

2. Two groups of British (Shorthorn × Hereford) and Africander × British calves, each approximately 6 months old, were used: one group (treated) of each breed was tick-infested and the other (control) was tick-free. Within breeds, calves in the control group were pair-fed to calves in the treated group.

3. In both breeds, the effect of ticks: (a) depressed packed cell volume, serum alkaline phosphatase (EC 3.1.3.1) and amylase (EC 3.2.1.1) activities, plasma cholesterol and phospholipid levels, serum iron and albumin levels. (b) increased the plasma levels of urea-nitrogen and γ-globulin (c) increased rectal temperature, water intake, urine volume, urinary and faecal total N, urinary urea-N and α-amino acids, the excretion of water, sodium and potassium in the faeces and (d) reduced N balance, N and dry-matter digestibilities.

4. In the British breed, ticks increased the excretion of K with a corresponding decrease in the excretion of Na in the urine and inreased the plasma clearance of bromsulphthalein.

5. A second experiment showed that the specific effect of tick infestation increased the flow of organic matter (OM) from the abomasum and the fractional turnover of rumen fluid of Hereford steers. It was also shown that the decrease in OM digestibility in the gastrointestinal tract was largely due to a decrease in OM digestibility in the rumen and that the increased urinary urea excretion and plasma urea concentration was caused by higher production rates of urea despite a tendency for lowered urea degradation in the gastroinestinal tract.

1. An experiment is reported in which copper, as cupric oxide, was fed to two breeds of laying hen for 336 d at levels equivalent to 150, 300, 450, 600 and 750 mg added Cu/kg diet. The results obtained were compared with those found using similar diets to which the Cu was added as CuSO4. 5H2O.

2. Addition of the CuO had no effect on food intake, food conversion efficiency, body-weight or egg production. The CuSO4 addition caused the quadratic response of food intake and the adverse effects on food intake, egg production and body-weight noted in previous experiments.

3. The CuO had no effect on liver, kidney, ovary, oviduct or gizzard weight per unit body-weight while the CuSO4 decreased these with the exception of gizzard weight which was significantly increased.

4. CuO addition did not affect liver Cu concentration but CuSO4 caused a subtantial increase of liver Cu especially at the 750 mg Cu/kg level of addition.

5. CuO addition had no effect on liver lipid concentration but this was depressed at the highest level of CuSO4 addition. Effects on individual fatty acids are presented but no specific conclusions have been reached.

1. In two separate experiments, forty-four pigs weaned at 4–5 d of age were fed on diets containing milk or soya-bean protein until slaughtered at 14, 28 or 35 d of age.

2. Daily amounts of nitrogen flowing through the stomach and proximal small intestine of pigs were similar with both sources of protein fed.

3. Endogenous N flows in the duodenum, jejunum and ileum of pigs given an N-free diet were 22.9, 7.4 and 4.6 g N/kg dry matter (DM) intake. Endogenous N in faeces was 0.970 g N/kg DM intake.

4. The apparent and true digestibility of N to the ileum of 28-d-old pigs was 0.86 and 0.92 for the pigs given the milk-protein diets, 0.80 and 0.86 for the pigs given the isolated soya-bean protein (ISP; Promine D) diets and 0.51 and 0.62 for pigs given the soya-bean meal (SBM)-protein diet. These values over the entire gastro-intestinal tract were 0.98 and 1.00 for milk, 0.92 and 0.95 for ISP and 0.82 and 0.85 for SBM.

5. The apparent and true digestibility of N to the ileum of 14-d-old pigs given a liquid milk diet was 0.92 and 0.94, while the values for the pigs given a pelleted milk diet were 0.86 and 0.87. At 35 d of age there were no differences in the apparent digestibility of the N in the liquid and pelleted milk diets.

6. The apparent digestibility of N to the ileum and over the entire gastro-intestinal tract of pigs given ISP (Supro 610) increased with increasing age of pigs from 0.83 at 14 d of age to 0.88 at 35 d of age.

7. Of the N in the stomach 14–32% could not be precipitated by trichloroacetic acid (TCA; 30 g/l).

8. In the jejunal and ileal contents an average of 46 and 24% of the N was precipitated by TCA in pigs given soya-bean proteins and milk proteins respectively.