1. Monozygous twin cattle with permanent rumen fistulas were used to measure the rate of degradation of casein and ovalbumin. One twin was used as a control and the other had protein administered by fistula about 4.75 h after eating a standard ration.

2. Casein was rapidly degraded with a half-life in the range 5.6–21.5 min, with the formation of peptides, free amino acids and finally ammonia. Up to 43% of the casein nitrogen was found as ammonia in the rumen fluid. Most of the amino acids present in casein were found in the free state in the rumen fluid to an extent of less than 7%, but valine, leucine, isoleucine and lysine were present as 25, 27, 21 and 38% respectively of the amounts present in the casein administered.

3. When acid-hydrolysed casein was given, ammonia was rapidly formed, the maximum amount found in the rumen being equivalent to 39% of the casein N. The individual amino acids were rapidly broken down except for valine, leucine, isoleucine and lysine of which synthesis in addition to degradation may occur.

4. Ovalbumin was degraded slowly with a half-life of 175 min, which was reduced to 132 min by feeding the cattle with ovalbumin for 5 d. Ammonia was produced slowly.

5. When added together the two proteins were degraded in the rumen independently at their own rates.

6. δ-Amino-n-valeric acid was produced in large quantity when casein or casein hydrolysate was degraded in the rumen.

1. Radioactive calcium has been used to study the placental transfer of Ca in ewes at three stages of gestation.

2. At each stage virtually all the radioactive Ca injected into a foetus was still present 5–6 h later and little or none was found in the mother or in a twin foetus if present.

3. It was concluded that there is neither exchange of Ca between foetal and maternal pools nor transfer from foetus to mother. Passage of Ca across the placenta of the ewe is therefore a one-way process.

4. The rapidly exchangeable Ca pool of the foetus tended to increase in size with the stage of gestation and was found to contain only about half of the total Ca of the foetal soft tissues.

5. Two methods for calculating the rate of accretion of Ca into the foetal skeleton have been applied. The results obtained from these calculations suggested that rates of foetal bone accretion also increased with the stage of gestation. Accretion per unit foetal weight, however, remained fairly constant irrespective of age or number of foetuses present.

6. Bone accretion rates calculated from the results of the present work were very similar to the rates obtained previously for transfer of Ca across the sheep placenta, indicating that resorption of Ca from bone is negligible in the foetus.

1. Two pairs of Friesian steers were changed from ad lib. to restricted intake of a pelleted barley diet and were maintained on this latter intake for periods of 18 or 25 weeks. The restricted level of intake was 70 g/kg0.73 and was adjusted weekly according to individual live weights. The daily allowance was given in three equal feeds during day-time.

2. After an initial period of 9 weeks on the restricted diet, during which all four animals were kept free of rumen ciliate protozoa, one member of each pair was given an inoculum of rumen ciliates. Eight weeks later, the ciliate-free member of the younger pair of steers was similarly inoculated. Observations were made on the rumen bacterial and protozoal populations and on changes in rumen pH and volatile fatty acids (VFA) throughout each treatment period. The concentrations of urea and haemoglobin in blood and of glucose and amino acids in plasma were examined on one occasion in each animal.

3. In the absence of ciliates, restriction of intake resulted in rumen pH values and molar proportions of VFA similar to those normally encountered on an ad lib. intake of a barley diet. A decrease in bacterial numbers and certain minor changes in bacterial types were observed on changing from ad lib. to restricted intake but the resultant population under ciliate-free conditions was basically the same as that found later in the faunated animals. In culture, organisms of the genus Bacteroides were predominant.

4. Large populations of rumen ciliates were established in each animal inoculated. Relative to the ciliate-free periods, the presence of ciliates resulted in an increase in rumen pH, a reduction in total VFA concentration and a decrease in the ratio of propionic to butyric acid in rumen fluid. It is concluded that these changes are a direct effect of ciliate activity.

5. Conditions within the rumen remained more stable from day to day when large ciliate populations were present than when ciliates were absent. In one animal, spontaneous fluctuations in ciliate number were accompanied by corresponding changes in rumen pH and VFA proportions.

6. Significant differences were observed between faunated and ciliate-free animals in the concentration urea in blood and of glucose in plasma; only minor differences were noted in blood haemoglobin and plasma amino acid concentrations.

1. The influence of diets, particularly dietary carbohydrate, on the development of the intestinal disaccharidases of the chick was studied.

2. The maltase activity in the small intestine was similar in groups of 25-d-old chicks that had been fed, from hatching, on diets containing either starch, glucose, maltose, sucrose, or a mixture of 50% glucose + 50% lactose, as the source of carbohydrate. The sucrase activity in the small intestine was also similar in the different groups, as was the palatinase (the enzyme that hydrolyses palatinose, i.e. 6-o-α-D-glucopyranosyl-D-fructose) activity. The maltase activity in the large intestine of the group receiving the starch-containing diet was significantly increased. The lactase activity in the large intestine was significantly higher in the group receiving the 50% glucose + 50% lactose and in the group receiving glucose than in the other groups. Body- weights were similar with all the diets.

3. The fasting of chicks for a period of 3 d caused a marked decrease in the activity of the disaccharidases and in the protein content of the homogenates of the small intestine.

4. The maltase activity was similar in the small intestine of chicks that had been fasted for 3 d and subsequently given diets containing either starch, glucose, maltose, sucrose or fructose for 5 d. The sucrase activity, the isomaltase activity and the palatinase activity were also similar in the small intestine of the chicks given the different diets. Feeding with a fat-free or protein-free diet did not affect the development of disaccharidases in the small intestine, but feeding with a carbohydrate-free diet resulted in reduced disaccharidase activity.

5. The results suggest that, in the chick, dietary carbohydrate is necessary for the development of the disaccharidases but the form of the carbohydrate is not important. None of the sugars tested had a specific effect on a particular disaccharidase.

1. Serum β-lipoprotein and cholesterol have been measured in children ‘at risk’ to severe protein-calorie malnutrition and in others with kwashiorkor or marasmus. β-Lipoprotein was estimated by an immunological technique. In children recovering from kwashiorkor, serum triglyceride estimations and lipoprotein electrophoretic separations were also carried out.

2. β-Lipoprotein concentrations did not fall significantly until serum albumin concentration was less than 2.5 g/100 ml; cholesterol concentration fell before β-lipoprotein.

3. In frank kwashiorkor, serum β-lipoprotein concentration was reduced by about 30%, whereas cholesterol and triglyceride concentrations were reduced by about 50% in comparison with apparently normal children. Electrophoretic evidence showed that serum α-lipoprotein concentration was also reduced or absent altogether. Marasmic children had normal serum concentrations of β-lipoprotein and the other lipid components measured.

4. The metabolic significance of this degree of reduction in serum β-lipoprotein concentration in the pathogenesis of the fatty liver of kwashiorkor has been discussed. It was concluded that, in Ugandan children with serum albumin concentrations below 2.50 g/100 ml, the β-lipoprotein concentration was probably insufficient for normal mobilization of fat from the liver and the children could therefore be considered susceptible to the development of a fatty liver.

5. The recovery from kwashiorkor was marked by a rapid rise in serum β-lipoprotein concentration and hypertriglyceridaemia but a slower rise in cholesterol concentration. This confirmed the results of previous investigations.

1. Metabolic balance studies of manganese were made on four young women, using brilliant blue and chromic oxide as faecal markers.

2. Mn concentrations in food, faeces and urine were measured by atomic absorption spectrophotometry.

3. No difference in Mn concentrations was obtained between dry-ashing and wet-digestion for removal of organic matter from food or from faeces.

4. Retentions of 0.05–0.46 mg Mn/d were obtained. Dermal and menstrual losses were not measured or allowed for.

5. Unlike most other Mn balance studies reported, the retentions obtained were consistent with the accepted size and stability of the body pool of Mn in healthy adult subjects.

1. A combination of balance and isotope techniques has been used to study the effects of dietary supplements of NH4Cl, given for 1 and 10 weeks, on calcium metabolism in 1- and 2-year-old wethers.

2. The main effects of the NH4C1 supplements were to decrease urinary pH, increase urinary Ca excretion and to increase Ca absorption and the percentage of dietary Ca absorbed.

3. The results were different from those obtained by other workers in man and rat, and possible explanations of this difference are discussed.

4. A difference was also found between 1- and 2-year-old animals in their long-term response to the NH4Cl supplement. This difference may have been due to a lack of available Ca in the diet of the younger animals, and prolonged ingestion of NH4C1 may increase the amounts of Ca absorbed and retained.

1. The oxygen utilization of ten women was measured after consuming meals supplying 230–1200 kcal (0.96–5.02 MJ) in three experiments.

2. In the first experiment four subjects consumed one-ninth, one-third or one-half of the daily allowance and the oxygen consumption was measured for 3 h after the meal. The response was unrelated to the size of the meal.

3. Resting conditions were rigidly controlled in the second experiment. Each woman reclined on a bed for 5–7 h while the effect of a meal providing 600 or 900 kcal (2.51 or 3.77 MJ) for the two lighter subjects and 800 or 1200 kcal (3.35 or 5.02 MJ) for two heavier subjects was measured. A greater increment in energy expenditure was obtained after the larger meal for each subject. The effect of two 30 min walks before and after the large meal was negligible.

4. In a third experiment the effect of exercise was measured with five women consuming 900 kcal (3.77 MJ) (a) followed by 5 h rest and (b) preceded and followed by exercise (two 30 min walks on a treadmill). The energy increment during 90 min after the meal was equivalent in (a) to 15 kcal (63 kJ) per h and in (b) to 16 kcal (67 kJ) per h, whereas the response following exercise but without food was insignificant.

1. A comparative study on the digestibility of beef, buffalo, camel and mutton fats was made with chicks during the 4th week of age. Each fat was added to a low-fat diet at levels of 3, 6 and 9%.

2. The mean digestibilities of beef, buffalo, camel and mutton fats were 85.4, 72.6, 83.9 and 94.1% respectively. Thus mutton fat appeared to be significantly superior to other fats, whereas buffalo fat was significantly inferior.

3. The melting points of the fats seemed to have no influence on their digestibilities.

4. With the exception of beef fat, the digestibility of the fats improved as the iodine value increased.

1. The effect of zinc deficiency on the activities of rat duodenal alkaline phosphatase and inorganic pyrophosphatase has been investigated.

2. Zn deficiency adversely affected the activity of these enzymes before growth rate and food intake were reduced.

3. The level of food intake was without effect on the activity of alkaline phosphatase but markedly influenced that of inorganic pyrophosphatase.

4. The relevance of changes in the activities of Zn-dependent intestinal enzymes to the food intake of Zn-deficient rats is discussed.

1. The production and metabolism of volatile fatty acids were studied in sheep offered a cobalt-deficient diet.

2. The molar proportions of acetic (60%), propionic (26%) and butyric (14%) acids in the rumen fluids of sheep given the Co-deficient diet, but whose stores of vitamin B12 were adequate, were similar before and after administration of an oral supplement of Co.

3. In pair-fed sheep, one member of which was vitamin B12-deficient and the other (control) treated with vitamin B12 parenterally, the concentrations after feeding of both total and individual volatile fatty acids in the blood tended to be higher in deficient than in control sheep.

4. Following injection of the respective salts of individual volatile fatty acids into the blood-stream, formate clearance was apparently not affected, whereas that of acetate was slightly, and that of propionate very significantly, delayed in vitamin B12-deficient sheep compared with pair-fed control animals.

5. Acetate metabolism was retarded in the presence of propionate; the effect was greater in deficient than in pair-fed control sheep.

6. The hypothesis is advanced that it is the failure to metabolize propionate at the normal rate that leads to the progressive loss of appetite in vitamin B12-deficient sheep.

1. The reproducibility of an assay for methionine based on live-weight gains in young chicks has been tested in a collaborative study in six laboratories.

2. Results were analysed by the slope-ratio procedure and, in general, the assays were statistically valid. The variability between laboratories was similar to that found in previous studies of variablity within a single assay in one laboratory.

3. With the combined estimates from five or six laboratories the standard error of the estimates was apporoximately 10% of the mean. Expressing response as‘g gain/g food eaten’ gave no more precision than using ‘weight gain’ alone, but is nevertheless thought to be less open to error due to apetite effects.

4. The experiments have shown that materials can be ranked consistently, but that the absolute estimates of potency varied between assays and further improvements are desirable if potency estimates are to be used for the calibration of in vitro procedures of protein evaluation.

1. The increase in metabolic rate which occurs after ingestion of protein (the so-called ‘specific dynamic action’) has been attributed to the energy requirements for urea synthesis and amino acid degradation.

2. We have tested, in normal adult subjects, the effect of meals which increase or decrease the rate of urea production, and our results do not substantiate this hypothesis.

3. The difficulties of accurate measurement of resting metabolic rate are discussed.

4. The term ‘specific dynamic action’ is inappropriate since the effect is not specific. We believe that it may prove to be a reflection of protein synthesis rather than of protein catabolism.

1. Sheep prepared with a rumen cannula and with re-entrant cannulas at the proximal duodenum and terminal ileum were given diets of dried grass, and dried grass supplemented with formalin-treated or untreated casein. They were fed either continuously or once daily. Paper impregnated with chromic oxide was given once daily via the rumen fistula.

2. The observed daily flows of magnesium at the duodenum and ileum were highly correlated with the corresponding flows of Cr.

3. There was a net absorption of Mg from the stomach as well as the intestinal region of all sheep.

4. Protein supplementation had no effect on the extent or sites of Mg absorption, but altering the feeding regimen changed the proportions of the net absorption of Mg occurring in the stomach and intestinal regions.

1. Groups of twelve female rats were fed from 4 weeks of age on four different experimental dietary regimens, and on a stock diet containing 18% protein given ad lib. as a control (group 1). The rats in two of the experimental groups were malnourished either by being given a low-protein (9%) diet ad lib. (group 2), or the stock diet containing 18% protein in limited amounts to maintain weight as in group 2. These animals were designated calorie-deficient (group 3). Two other groups of twelve rats were more severely malnourished from 4 to 13 weeks of age by being given a low-protein (6%) diet ad lib. (group 4) or the stock diet in limited amounts to maintain weight as in group 4 (group 5). From 13 weeks all the rats in groups 4 and 5 were rehabilitated on stock diet ad lib.

2. Well-nourished males were introduced into the cages 1 week after the vaginas opened, and again immediately after the females had suckled successive litters. This was repeated until the females were 60 weeks old and had reared up to six litters.

3. Chronic deprivation of protein or of calories delayed puberty, reduced fertility and gave rise to smaller numbers in the litters. It also interfered with lactation.

4. More severe malnutrition for 9 weeks further delayed puberty, but when these animals were rehabilitated they produced as many young as those that had been well-nourished throughout. They lactated well and there was no carry-over of the effects of the early deficiencies.

1. A study was made of the changes in electrolyte concentrations and ruminal function which resulted from the provision of 1.3% sodium chloride solutions instead of fresh water to sheep consuming roughage rations in chaffed and in ground pelleted forms.

2. Significantly higher osmotic pressures were observed in the rumen fluid of the sheep drinking saline water, the change being especially marked when the ration was ground and pelleted.

3. Of the individual electrolytes measured, chloride showed a larger rise in concentration than did sodium plus potassium and it appeared that the sodium and chloride ions in the ingested saline water were differentially removed from the rumen.

4. Provision of 1.3% NaCl solution in place of fresh water resulted in greater voluntary intakes of fluid and consequently in greater flows of fluid through the rumen.

5. Based upon measurements of deoxyribonucleic acid and polysaccharide, there appeared to be a tendency for the total microbial populations in the rumens of sheep drinking 1.3% NaCl solution to be smaller than for the sheep drinking fresh water.

6. The total metabolic activity of the rumen flora, measured calorimetrically, was not appreciably changed when saline water was drunk and the chaffed ration eaten, but was significantly reduced when the ration was ground and pelleted.

7. Adaptation of the rumen microflora to high concentrations of NaCl was demonstrated in animals accustomed to drinking 1.3% NaCl solution.