1. Spray-dried diets were prepared containing (g/kg): dried skim-milk 665, dried whey 65, soya-bean oil 270 (diet U); or single-cell protein (Pruteen; SCP) 308, dried whey 440, soya-bean oil 252 (diet X). The diets had a crude protein (nitrogen × 6·25) content (g/kg) of 250 (diet U) and 240 (diet X), excluding nucleic acids (36 g/kg) in diet X.

2. The diets were reconstituted (200 g dry matter/l) and mixtures of diets U and X prepared to give diets supplying 0 (diet U), and approximately 400 (diet V), 600 (diet W) and 800 (diet X) g crude protein from SCP/kg total protein. All diets were supplemented with vitamins, and minerals to equalize the calcium, phosphorous, sodium and potassium concentrations.

3. Pigs weaned at 2 d of age were given the diets at hourly intervals on a scale based on live weight. At 28 d age the experiment was terminated and pigs killed 1 h after a feed for a study of protein digestion. Polyethylene glycol (PEG) was fed in the diets (0.5 g/l) for 24 h before slaughter.

4. Performance of pigs fed on diet V was as good as on the all-milk diet U. Greater levels of replacement by SCP (diets W and X) reduced performance. Mortality was greater on the all-milk diet, but protein source had no effect on the incidence of scouring. N retention (g/d per kg live weight) was similar for all diets but declined with age.

5. SCP appeared to stimulate secretion of pepsin and chymotrypsin, and reduced the pH value in digesta in the stomach. Enzyme adaptation may have been insufficient to digest high levels of SCP in the diet, and together with the decreased transit time observed using PEG as a marker, may account for the poorer performance when 600 or 800 g/kg milk protein was replaced.

6. Nucleic acids from SCP were metabolized and not retained for tissue synthesis. Allantoin excretion accounted for 75% of the theoretical maximum for complete excretion of nucleic acids, and uric acid excretion was also increased.

1. Pigs were fed on semi-purified food. The magnesium content of the experimental diet was 1·0 and that of the control diet 1·9 g/kg.

2. In the low-Mg group serum triglycerides and blood lactate values were increased and base excess and standard bicarbonate values were decreased, indicating metabolic acidosis.

3. A significant positive dependence was found between blood pH and serum Mg:Ca value as well as between blood pH and serum Mg, and also between body temperature and blood lactate values in the low-Mg group. None of these dependences was significant in the control group with magnesium acetate supplementation in the food.

4. No specific histopathological changes were found in heart, liver or kidney of the experimental animals.

5. The results indicate that an increase in serum triglycerides does not need to depend on the amount or quality of food fat.

6. The present study shows that, in pigs, a low-Mg diet may cause metabolic disturbances in instances when the food Mg content is distinctly higher than the normal values recommended by the (UK) Agricultural Research Council (1966) and (US) National Research Council (1968).

1. Pigs (twenty-one/diet) were weaned at 2 d of age and given liquid diets (200 g dry matter/l) at hourly intervals during a 26 d experiment. The pigs were fed on a scale based on live weight. The diets contained (g/kg DM): dried skim-milk 730 (diet A), dried whey 508·5, isolated soya-bean protein 218, DL-methionine 3·5 (diet S), and soya-bean oil 270 (diets A and S). Diet T contained equal proportions of diets A and S. Soya-bean supplied 0, 370 and 740 g crude protein (nitrogen × 6·25)/kg total crude protein in diets A, T and S respectively.

2. Performance was similar for both diets A and T (P > 0·05). Pigs given diet S scoured severely, and fourteen died. The survivors grew very poorly. Nitrogen retention (g/d per kg live weight) was greater for diet A compared with diet T (P < 0·0r), and decreased with age (P < 0·01).

3. Protein digestion was examined in the pigs killed at 28 d of age. The amount of soya-bean protein in the diet did not affect the amount of digesta in the stomach, but soya-bean protein decreased the pH, DM and total N content of the digesta (P < 0.01), and increased, though not significantly (P < 0·05), pepsin activity in the digesta and stomach tissue. Acid secretion into the stomach appeared to be enhanced in pigs given a diet containing soya-bean protein.

4. Amounts of trypsin, chymotrypsin, total N and proportion of non-protein-N in the digesta from the small intestine were similar for both diets A and T. The amounts for both diets were greater in the distal compared with the proximal region of the small intestine (P < 0·05). Chymotrypsin activity in the pancreas was reduced (P < 0·05) in pigs given diet T, although this reduction did not seem to impair digestion in 28-d-old pigs. Trypsin activity in the pancreas was similar for both diets A and T.

5. It seems likely that the neonatal pig does not have the digestive capacity to tolerate the large daily intakes of soya-bean protein when dried skim-milk was totally replaced in the diet (diet S). When half the dried skim-milk was replaced, protein digestion was not impaired in 28-d-old pigs.

1. The chromium in the diets of lactating Finnish mothers and of their breast milk was determined by graphite furnace atomic absorption.

2. The average maternal diet was estimated to provide approximately 30 μg Cr/d. Breast milk samples had a mean Cr content of 0.4 ng/ml, with a range of 0.1g-06g ng/ml.

3. Cr intake of the lactating mothers did not correlate with the corresponding breast milk Cr concentration.

4. The diets and the breast milk of these Finnish mothers were lower in Cr than those of any other population studied in the world.

1. Female rats were undernourished from birth through replacement for 12 h/d of the lactating mother by a nipple-ligated mother. This resulted in slow growth so that at 22 d of age the body-weights equalled those of well-nourished animals at 14 d.

2. At 14, 17, 20 and 22 d groups of eight to ten animals each of undernourished and well-nourished rats were autopsied, serum follicle-stimulating hormone (FSH) concentration was determined by radioimmunoassay, utersuses were weighed and ovaries examined by light microscopy.

3. Undernutrition caused a 3–4 d delay in the third-week drop in serum FSH and in ovarian development as indicated by the number of antral follicles and by the maximal diameter of the ovaries and of the largest follicles.

4. It is postulated that the effect of undernutrition on serum FSH may be due to delayed increase in ovarian feedback effectiveness, which may be the result of either the retardation in ovarian development or a continued high level of serum oestrogen-binding protein. It remains uncertain through which mechanism(s) undernutrition brings about delayed onset of puberty.

1. The early effects of a moderate polyunsaturated fat diet on the composition of circulating lipoproteins and adipose tissue fatty acids were measured in five healthy adults.

2. The fatty acid content and gross composition of the three major plasma lipoprotein fractions altered within 7 d of treatment. The response of depot fat was slower but did show a significant and progressive change after 14 d on the diet.

3. The efficiency of the moderate diet in changing the composition of the lipoproteins suggests that it should be equally dfective in altering their metabolic handling.

1. Growing rats were fed either ad lib. or with six (equal) meals offered every 4 h (form 10.00 hours). Rats of each group were killed at intervals of 4 h begining at 11.00 hours. Activities of cathepsin A (carboxy-peptidase A; EC 3.4. 12. 2), C (dipeptidyl peptidase; EC 3.4.14.1) and D (endopeptidase D EC 3.4.23.5) were measured in liver and muscle homogenates and free amino acids in blood were determined.

2. In the rats fed ad lib. activities of carboxypeptidase A and endopeptidase D in liber and muscle showed significant variation, with maximum activity in the light period. In general, meal-feeding only caused minor differences in cathepsin activities; although significant differences occurred for carboxypeptidase A. For the latter enzyme a peak in activity occurred in the dark as well as in the light period.

3. Irrespective of the feeding schedule, the lower concentration of free essential amino acids of blood occurred generally during the night period. With the controlled-feeding schedule there is an increase of essential amino acids and a slight decrease of non-essential amino acids of blood.

1. Romney wethers were infused intravenously with [2-14C]acetate for 5 d during which time they were given, three/group, different amounts of lucerne(Medicago sativa L.) chaff. The groups and the amounts fed were: MS, 700 g but starved during the infusion period; M, 700 g throughout; 1.3 M, 950 g throughout; AL, ad lib. throughout.

2. On day 4 of the infusion, the oxygen consumption, and production rate of expired 14CO2 were measured. At the end of the infusion, the sheep were killed and the amounts of radioactivity in the lipids of various tissues wre determined.

3. Significant differences were present between the specific activities of the tissues. The internal adipose tissues generally had higher specific activities than subcutaneous or intermuscular adipose depots. Although the intramuscular lipid also was highly labelled, the liver had the greatest specific activity.

4. Food intake did not significantly affect this pattern of specific activity of labelling of the tissues.

5. While most of the total lipid radioactivity was present in adipose tissues, the proportion in the liver increased to 40% during starvation.

1. A combination of a mineral balance and a radioisotope technique has been used to study the relationship between dose rate of 1-α-hydroxycholecalciferol (1α-OH-D3) and the magnitude and duration of its effect on the various processes of calcium and phosphorous metabolism in adult wether sheep.

2. The rate of absorption of Ca was markedly increased by treatment and maximum response occurred at the lowest dose rate.

3. Although sheep were already Ca-replete, the extra Ca absorbed was all retained and increased retention was brought about by a combination of an increase in bone accretion and a decrease in bone resorption. This finding conflicts with the generally-held belief that bone resorption is increased by cholecalciferol treatment.

4. The rates of absorption and retention of P were increased by 1α-OH-D3 treatment and maximum response occurred at the lowest dose rate.

5. That P absorption could be increased by treatment suggests that not all the available dietary P was absorbed in the control period.

6. Although the loss of endogenous P in the faeces was unaltered by treatment, the secretion of P into the gut was increased, and the increase was directly related to increased serum inorganic P concentration.

7. Nearly all the extra P absorbed was retained and increased retention was achieved by a combination of an increased incorporation into and a decreased loss from the non-exchangeable pools of bone and soft tissues.

8. The time interval taken for absorption rates of Ca and P to return to normal after the end of each treatment was related to the dose rate of 1α-OH-D3. Although higher dose rates had little effect on the magnitude of response, they did prolong slightly the duration of response.

1. A case is described of an Englishman who suffered severe ‘wet beriberi’ whilst a prisoner of war (POW) of the Japanese in World War II.

2. Following release he developed a congestive cardiomyopathy which increased in severity until his death 31 years after repatriation.

3. Autopsy findings were consistent with chronic cardiac damage due to beriberi.

1. The effects of restricted feeding, and ad lib. feeding following food restriction, on hepatic carbohydrate and lipid metabolism in the laying hen were studied.

2. The birds were allocated to four groups and given either 92, 84 or 75 g/d or allowed ad lib. access to food.

3. Food restriction significantly reduced liver total lipid content compared with ad lib.-fed control birds and this was reflected in reduced hepatic lipogenic enzyme activities.

4. When birds from the restricted regimens were allowed free access to food they intially consumed more food than the control group but after 2 weeks of ad lib. feeding the food consumptions of the birds in all the groups were similar.

5. Concomitant with the increase in food intake there were also increases in liver lipid content and hepatic lipogenic enzyme activities. After 18 d of ad lib.feeding these measurements were similar in the previously restricted birds and the ad lib.-fed control group.

6. Despite these effects on lipid metabolism, food restriction, and the subsequent release from food restriction, had no significant effects on the specific activities of the glycolytic enzymes examined.

7. Although there were large increases in liver lipid content following release from feed restriction no birds died from, or showed any of the symptoms of, fatty liver-haemorrhagic syndrome. This suggests that, in the absence of any other factor which may be involved in the syndrome, these high liver lipid contents were not, alone, sufficient to cause FLHS. The results also indicate that free access to food following food restriction is unlikely to be a major factor in initiating the syndrome.

1.Weight loss, resting metabolic rate and nitrogen loss were measured in forty obese inpatients on reducing diets.

2. Five subjects ate 3·55 MJ/d for 6 weeks (Expt I). Twenty-one subjects ate 4.2 MJ/d for the first week, 2·0 MJ/d for the second week and 4 2 MJ/d for the third week (Expt 2). Fourteen subjects ate 3·4 MJ/d for the first week and then 0.87 MJ protein or carbohydrate for the second or third weeks, using a cross-over design for alternate patients (Expt 3).

3. Patients in Expt I had highest weight loss and N loss in the first 2 weeks, but adapted to the energy restriction over the remaining weeks. On average subjects were in N balance at the end of the study.

4. In Expt 2 patients eating 2·0 MJ/d in week 2 showed increased weight loss compared with week I.N loss was not raised but it failed to decrease as it had in Expt I. Weight loss and N loss were reduced on return to 4.2 MJ/d for a third week.

5. In Expt 3 patients eating 0·87 MJ protein showed significantly more weight loss and less N loss than patients eating 0·87 MJ carbohydrate.

6. Resting metabolic rate decreased with time on the low-energy diet, but the manipulations of energy or protein content did not significantly affect the pattern of decrease.

7. Both weight loss and N loss were greater the lower the energy intake, and both decreased with time. Diets with a high protein:energy value give a favourable value for N:weight loss at each level of energy intake.

1. Neonatal hypoglycaemia is a relatively common clinical problem in children but ethical constraints limit the investigations that may be made in the newborn.

2. As a preliminary step to assess the suitability of the piglet as a model for glucose metabolism in man, whole-body glucose turnover and glucose pool size were measured using [2-3H]glucose in forty piglets from ten litters.

3. Glucose pool size was linearly related to brain weight. However, multiple regression showed that the most useful predictors of pool size were body-weight and resting plasma glucose concentration.

4. Glucose turnover was related to both brain weight and body-weight alone, but multiple regression showed that better predictors of turnover were liver weight, spleen weight and pancreas weight.

5. Similarities between our own results in piglets and those obtained in human neonates by Bier et al. (1977) extend not only to glucose turnover, but also to its relationship with body-and brain weight. These findings suggest that the piglet may be a useful model for the study of glucose metabolism in babies.

1. Male and female Japanese quail (Coturnix coturnix japonica) were reared under short daily photoperiods (8 h light–16 h dark) to inhibit sexual development with free access to food and water. Blood was sampled at frequent intervals for 13 weeks from hatching in order to monitor the developmental changes in plasma concentrations of the two proteins which are important in the transport of retinol, retinol-binding protein (RBP) and thyroxine-binding prealbumin (TBPA).

2. Measurements of body-weight, blood packed cell volume and plasma total protein concentration showed that the birds had a normal pattern of growth and haematological development. Plasma concentrations of TBPA, total immunoreactive RBP (IRBP) and holoRBP were 220, 60 and 45 μg/ml respectively in 1-d-old quail and rose to 430, 165 and 140 μg/ml at 14 d of age, which was 10 d after the corresponding change in total protein. Neither RBP nor TBPA concentrations were significantly different between the sexes during the 13 weeks, but there were minor fluctuations in concentration within relatively narrow limits.

The metabolism of [1-C14]linolenic acid (18:3ω3) by the foetal rat was studied in vivo and in vitro. It is suggested that foetal brain has the capacity to convert linolenic to docosahexaenoic (22:6ω3) acid to meet its requirements for docosahexaenoic acid.

1. Five groups of rats were investigated: (a) unmated rats allowed free access to a commercial stock rodent diet (NP group); (b) rats in the second week of lactation allowed free access to the stock diet; (c) rats in the second week of lactation allowed only that amount of the stock diet eaten by the NP group; (d) rats in the second week of lactation allowed that amount of the stock diet eaten by the NP group and in addition free access to a high-energy, protein-free supplement; (e) rats in the second week of lactation allowed that amount of the stock diet eaten by the NP group and in addition free access to a protein supplement.

2. The weight and length of the small intestine, the mucosal content of protein and of DNA and the mucosal activities of alkaline phosphatase (EC 3.1.3.1), acid phosphatase (EC 3.1.3.2), isocitric de- hydrogenase (NADP+)(EC 1.1.1.42)and glucose-6-phosphatase (EC 3.1.3.9) were measured in individual animals.

3. For the factors investigated it was, with few exceptions, found that: there were markedly higher values in lactating animals allowed unrestricted access to food than in unmated animals; in restricted lactating animals the values were considerably lower than in unrestricted lactating rats and often similar to those in unmated animals; supplements of dietary energy restored none or only a proportion of the in- creases usually found in lactation but a protein supplement restored most or all these increases. Reasons for departure from this general picture on the part of some factors are discussed.

4. The results presented here support the view that changes found in lactation are hormonally induced but governed by nutrient availability, that protein is the important nutrient raw material but that dietary energy can support some changes probably by a ‘protein-sparing’ effect. Some changes appear to be less susceptible to the effects of dietary restriction, whether of protein or total energy. It is suggested that the additional nutrients eaten by unrestricted lactating rats permit the development of more, but less mature, enterocy tes.

1. An experiment was carried out with goats fed on a low-protein ration to clarify the importance of the rumen and significance of saliva in the appearance of re-cycled urea in the digestive tract during the final third of a once daily feeding regimen. The isotope-dilution method with [15N]urea and 15NH4Cl was used.

2. When the serum urea level was 58 mg N/l, the amount of urea transferred from the blood urea pool to the rumen ammonia pool was 48.6 mg N/l, which was estimated to be approximately 43% of the total amount of urea having appeared in the NH3 pool of the digestive tract. When the serum urea level was 106 mg N/l, the corresponding amount of NH3 was 77.7 mg N/h, which was estimated to be approximately 46% of this total amount.

3. The amount of saliva secreted was measured directly by the oesophageal fistula method. Salivary secretion serves as a mode of transfer of blood urea to the rumen NH3 pool. Then the ratio, salivary secretion:diffusion through the rumen wall during the final third of the cycle was calculated to be 1:4–1:6.

4. In goats fed on a low-protein diet, the rumen is an important site of appearance of blood urea in the digestive tract. It was verified that the principal mode of transfer of blood urea to the rumen was the direct diffusion through the wall of the rumen.

1. Nucleic acids and breakdown products were estimated in digesta taken from different sites in the small intestines of slaughtered steers given different diets. Amounts passing different sites were compared using cellulose as a non-digestible marker. The validity of this marker was checked with chromic oxide in some experiments. In other experiments, nucleic acids or derivatives were infused into the proximal duodenum of steers receiving diets of approximately equal proportions of flaked maize and hay. The amounts disappearing during passage through the small intestine were estimated using polyethylene glycol (PEG) as a non- absorbable marker.

2. In the slaughter experiments the amounts of nucleic acids entering the small intestine varied with the type of diet. RNA and DNA disappeared on average, to extents of 89% and 80% respectively between the abomasum and the terminal ileum, irrespective of the diet. RNA disappearance occurred almost entirely in the proximal quarter of the small intestine, whereas that of DNA extended further along the tract.

3. Nucleic acid degradation in the upper small intestine was accompanied by the transient appearance of adenosine, guanosine and pyrimidine nucleosides. These products were in greatest concentration in digesta from the first quarter of the small intestine and had generally completely disappeared by the terminal ileum.

4. Of the different substances infused into the small intestine, free nucleic acids were removed to extents greater than 97%, adenine, guanine and uracil had completely disappeared, thymine and xanthine to approximately 80% and 95% and hypoxanthine and cytosine to only 51% and 48% respectively. The nucleosides adenosine and cytidine were also completely removed in the small intestine but were replaced, in part, by the catabolic products inosine plus hypoxanthine or cytosine respectively. Other nucleosides were removed to approximately half the extent of the corresponding bases.

5. Serum and urine allantoin and uric acid levels were related to the amounts of purines entering the small intestines in free or bound form.