1. Albumin, α1-, α2-, β- and γ-globulin fractions were demonstrated in serum from control and copper-depleted rats, but no quantitative difference was found in the distribution of the proteins between the two groups of animals. Both the total number of leucocytes and the number of polymorphonuclear leucocytes increased during copper depletion.

2. Plasma copper content was found to be superior to whole blood copper content as an index of the copper status of rats at intermediate stages of depletion. The copper content of erythrocytes was found to be unaffected even in the severely depleted animals; this explains, in part, the poor response of whole blood copper content to intermediate stages of depletion.

3. A single dose of orally administered copper was reflected in the plasma copper content of depleted rats about 12 h after dosing. No similar rise was observed in control animals, and the extent of the response was not increased by increasing the dose of copper.

4. It is suggested that plasma copper response to a single oral dose of copper sulphate may provide a useful method for the detection of subnormal copper status in individual farm animals without the necessity of determining breed norms.

1. Variation in endogenous nitrogen metabolism was determined by giving eleven healthy men, aged 17–22, a diet supplying daily only 6 mg N/kg body-weight. Eight subjects were given the diet for 7–10 days and three other subjects were given it for 16 days.

2. Body cell mass (BCM) was calculated from whole-body 40K in ten subjects and basal metabolism was determined in seven subjects during the ‘protein-free’ period. Urine was analysed daily for N and creatinine, and faecal N was measured in pooled samples. Plasma free amino acids, serum albumin and protein were measured in preprandial morning blood samples at the beginning and end of the study.

3. BCM did not change during the ‘protein-free’ period and accounted for 48% of the total body-weight. Basal calorie expenditure amounted to 48 ± 5 kcal/kg BCM per day.

4. Mean daily endogenous urinary N excretion in the eight subjects given the ‘protein-free’ diet for 7–10 days was 36·6 ± 3·0 mg N/kg body-weight, 79·4 ± 4·4 mg N/kg BCM and 1·6 ± 0·2 mg N/basal kcal. Endogenous faecal N excretion was 9·9 ± 1·1 mg N/kg body-weight and accounted for 20% of the total endogenous loss. Results obtained with three other subjects given the diet for 16 days were similar.

5. Plasma essential amino acids were reduced, glutamic acid, alanine and glycine increased, and the ratio of essential to non-essential amino acids decreased after 7 or 10 days of ‘protein-free’ diet.

6. The loss of endogenous N per basal kcal and of faecal N per kg body-weight was lower than the values assumed in the factorial approach to protein requirements by the FAO/WHO (1965) Expert Group on Protein Requirements.

1. An attempt has been made to compare the nutritive value of beef from intensively reared animals with that from more extensively reared stock.

2. The difficulties of such a comparison are described and the consequent limitations of this experiment specified.

3. It was found that samples of longissimus dorsi and superficial digital flexor muscles showed no significant differences between intensively reared and extensively reared animals in their content of moisture, intramuscular fat, protein, non-protein nitrogen, iron, thiamine, riboflavine, or nicotinic acid.

4. The longissimus dorsi muscles had more non-protein nitrogen and more nicotinic acid, but less iron and less riboflavine, than the superficial digital flexor muscles.

5. There was less vitamin A and less carotene in samples of liver from intensively reared animals than in comparable samples from extensively reared animals.

1. Two experiments were carried out with non-pregnant ewes in which individual drymatter intake (DMI) and total water intake (TWI) were measured. TWI was closely correlated with DMI; TWI/unit DMI was higher for silage than for cubed dried grass and with both foods water intakes were higher than with long hay.

2. Twelve ewes were fed on silage and twelve on hay from the 9th to the 19th week of pregnancy. TWI/unit DMI of each feed doubled during this period. Another twenty-four ewes were fed on silage from the 14th to the 20th week of pregnancy. TWI/unit DMI was positively related to litter size.

3. Fifteen ewes were fed on hay from the 4th week of pregnancy until the 7th week of lactation. Milk yield was estimated weekly. Six non-pregnant ewes were controls. TWI/unit DMI for the seven twin-bearing and the nine single-bearing ewes in the last 4 and 3 weeks of pregnancy respectively was significantly higher than that of the six non-pregnant ewes. In the control group TWI/unit DMI was closely related to environmental temperature. In the first 4 weeks of lactation TWI/unit DMI was greater than the sum of TWI/unit DMI of the non-pregnant ewes plus the water in the milk.

4. The results supplement those used by the Agricultural Research Council (1965) to assess the water requirements of sheep.

1.Eight groups of weanling rats were maintained for 60 days on diets containing calcium and phosphorus in the ratio 0·1 at four different levels of mineral, namely 0·08, 0·12, 0·23 and 0·32% Ca, and in the presence and absence of added ergocalciferol.

2. Provision of vitamin D increased final body-weight, whereas at the highest mineral intake body-weight was reduced.

3. At each level of dietary mineral the serum Ca concentration was raised by vitamin D, whilst the serum P concentration was lowered except when the mineral intake was lowest.

4. With increasing mineral intake the serum Ca increased until at the highest intake it declined. Serum P was increased only at the highest mineral intake.

5. Measurements were made of bone weights, ash content and volume. Provision of vitamin D increased the fresh weight of bone at all levels of dietary mineral, and the dry weight and ash content were increased except at the lowest level of mineral intake. In general, the higher the dietary mineral the greater was the bone weight and its ash content.

6. The presence of vitamin D resulted in an increase in tooth mass and ash content at each level of mineral intake. Tooth mass and ash increased with increasing dietary mineral except at the highest level when there was a decline.

7. At the lower levels of mineral intake the ratio of tooth mass to bone mass was greater than at the higher levels of intake.

8. Histological examination of the bones revealed no increase in the width of the epiphyseal cartilage in any group. In the group with the lowest levels of Ca and P without vitamin D (0·08% Ca, 0·8% P) the shafts of the femurs appeared thinner and porotic, and the trabeculae were thin; in the group fed the same diets supplemented with vitamin D the shafts were even thinner but less porotic; in all other groups the histological appearance of the bone was within normal limits.

9. Changes in the appearance of the dentine were demonstrated in all groups.

1. The rates of production, or entry rates, of acetic, propionic and butyric acids in the rumen of grazing sheep have been measured by a radioisotope technique previously used on penned animals.

2. Regression equations were derived relating entry rates to ruminal concentrations. The equations from penned and grazing sheep did not differ significantly.

3. The standard errors of entry rates predicted for a single sheep from equations based on all results were calculated to be ± 0·06, 0·18 and 0·15 m-mole/min for acetic, propionic and butyric acids respectively.

4. Interconversions between acetic and butyric acids in the rumen were similar in extent to those found in penned sheep. These values were used to calculate from entry rates the net amounts of the acids becoming available to the animals.

5. An equation was derived that permits the amount of energy supplied to an animal by the acids to be predicted from concentrations with a standard error of ± 0·17 kcal/min.

6. The applicability of the prediction equations is discussed.

1. Glucose entry rates into the blood and propionate production rates in the rumen have been measured in sheep given rations containing varying proportions of starch and roughage (lucerne).

2. Glucose entry rates and propionate production rates were similar for all rations studied.

3. The proportion of the glucose entry rate arising from propionate produced in the rumen was highest on the ration containing the greatest quantity of lucerne and decreased as the proportion of starch in the ration increased. Rate of conversion of propionate into glucose was estimated and was found to decrease as the amount of starch in the ration increased.

4. Concentrations of total volatile fatty acids (VFA) in the ruminal fluid were lowest in the ration with the greatest proportion of starch, implying lower VFA production rates with the starch rations although intakes of digestible energy were approximately the same. The mean concentrations and rates of production of propionate in ruminal fluid were similar for all rations.

5. The low VFA concentrations and the reduced conversion of propionate into glucose on the high rations, despite similar propionate production rates and glucose entry rates, may have been due to starch escaping ruminal fermentation. It is suggested that this glucose absorption may have reduced gluconeogenesis from propionate.

1. The skeletal response of vitamin D-deficient chicks to dietary ascorbic acid was tested.

2. The epiphyseal cartilaginous plate width, which was increased by the vitamin D deficiency, was further increased when ascorbic acid was added and the effect appeared sooner.

3. Absence of vitamin D was associated with a reduction in the relative amount of cancellous to compact bone ash in the tibia. Dietary ascorbic acid intensified this effect to a significant degree.

4. Plasma ascorbic acid levels in rachitic chicks were approximately 25% less than in controls. This observation may explain the skeletal response to added vitamin C and suggests that avian bone tissue has a particularly high requirement for this vitamin.

1. The total body calcium (Expt 1) of litter-mate male rats given a diet adequate in phosphorus and high (0·74%) or low (0·13%) in Ca from the age of 3 weeks was determined after 21, 48 and 60 weeks on the diet. In Expt 2, the ash content of ten groups of bones from 10-week-old rats given these same diets for 7 weeks was studied to ascertain whether all groups were equally affected by the difference in dietary Ca level. Four groups of bones, i.e. skull and mandibles, vertebras, the shafts and the ends of long bones, were consequently chosen for examination in Expt 3 where their growth and composition were studied in rats given the Ca diets for 24, 48 or 60 weeks from the age of 3 weeks.

2. Total body Ca (Expt 1), expressed as g Ca or as a percentage of the net body-weight or of net dry, fat-free carcass weight, was always significantly higher in rats given the higher level of Ca. The dietary effect was greatest after 21 weeks.

3. The higher level of dietary Ca led to a highly significant increase in the weight of the dry, fat-free bone and in the percentage ash content of all ten bone groups after 7 weeks (Expt 2). The greater treatment differences in ash content occurred with the less well mineralized bones.

4. In Expt 3, irrespective of diet, the four groups of bones developed at different rates. In rats given the diets for 24 weeks or longer, the vertebras and the shafts of long bones showed the greatest proportional increase in weight of dry, fat-free bone and ash relative to the corresponding values for 3-week-old rats; the greatest change in percentage ash content occurred in the ends of the long bones.

5. Increasing the level of Ca in the diet increased the weight of the dry, fat-free bone and its ash content. The effect of diet decreased with increasing time on the diets, in general persisting most strongly in the skull and mandibles and declining most rapidly in the ends of the long bones. The percentage Ca and P content of the bone ash was only slightly affected by diet and, except for the Ca in the ash of vertebras, significant differences were only found in the composition of the ash of bones from 27-week-old rats.

1. The micro-iodimetric method has been used to study some factors affecting the concentration of lipid peroxides in the adipose tissue of vitamin E-deficient rats.

2. Cod-liver oil methyl esters (CLOME) or maize oil methyl esters (MOME) with peroxide values ranging from 3 to 330 μ-equiv./g were given by mouth to vitamin E-deficient rats deprived of food before and after the dose. Lipid peroxides did not accumulate in the adipose tissue of these rats.

3. Experiments with dietary CLOME and MOME of varying peroxide values (2–230 μ-equiv./g) showed that exogenous lipid peroxide accumulates in the adipose tissue when the rats received these lipids at 10% in the diet for 4 weeks, but not if the dietary concentration was only 4% or if the diet with 10% lipid was given for 5 days only.

4. Rats were given dietary CLOME for 4 weeks. Their adipose tissue was then found to contain about 50 μ-equiv. lipid peroxide/g. They were divided into three groups. One group was given a fat-free diet and, after 10 days, the adipose tissue concentration of lipid peroxide had decreased to about 10 μ-equiv./g. The other groups were given the fat-free basal diet supplemented with vitamin E or DPPD (N,N′-diphenyl-p-phenylenediamine). Neither supplement significantly affected the rate of disappearance of the peroxides from the adipose tissue.

5. It was shown that neither α-tocopherol nor DPPD reacted with the lipid peroxides of CLOME or MOME in vitro, at room temperature or even after 65 h at 37°.

6. It was concluded that unsaturated lipids do not become peroxidized after incorporation into the adipose tissue of vitamin E-deficient rats. Lipid peroxides taken up from the diet into the adipose tissue are not of fleeting existence, having a half-life of about 6 days. Dietary vitamin E probably prevents the accumulation of exogenous lipid peroxides in the adipose tissue by reinforcing the barrier to their absorption in the gut.

7. These studies provide further evidence that current concepts of lipid peroxidation in vitamin E-deficient animals are incorrect. In fact, vitamin E-deficient animals have low concentrations of peroxide in their adipose tissue, unless they have received large amounts of unsaturated lipid for long periods, and the role of vitamin E in controlling this concentration is not due to any effect on peroxidation in vivo.

1. The extent of liberation of radioactive cobalamin in rabbit tissues incubated with acid and pepsin was evaluated by bag dialysis.

2. Between a half and two-thirds of the cobalamin—probably hydroxocobalamin—was dialysable after acid pepsin treatment and this process may be a factor in the absorption of cobalamins from foods.

3. Studies of pure cobalamin solutions at different concentrations gave apparently anomalous results, which may have been due to the adherence of cobalamin to the dialysis membrane. Measurement of the amount adherent to the membrane is an important factor in dialysis studies with cobalamins.

1. Lipid extracted from breast and leg muscle of 10-week-old turkeys was fractionated by preparative thin-layer chromatography and five individual ‘neutral’ and eight individual phospholipid fractions, representing 95% by weight of the extractable lipid, were recovered from the plates for analysis.

The ‘neutral’ lipids from breast and leg muscle consisted mainly of triglyceride (202–497 and 1644–2333 mg/100 g), together with cholesterol (74 and 103 mg/100 g), free fatty acid (27 and 123 mg/100 g), diglyceride (17 and 66 mg/100 g) and cholesterol ester (9 and 12 mg/100 g).

The phospholipids contained phosphatidylcholine (367 and 500 mg/100 g), phosphatidylethanolamine (157 and 279 mg/100 g), phosphatidylinositol (60 and 109 mg/100 g), sphingomyelin (43 and 62 mg/100 g), phosphatidylserine (31 and 61 mg/100 g), ‘cardiolipin’ (23 and 35 mg/100 g), lysophosphatidylcholine (9 and 11 mg/100 g) and ‘origin fraction’ (6 and 7 mg/100 g), accounting together (700 mg and 1070 mg/100 g for breast and leg muscle respectively) for 98% of the lipid phosphorus extracted.

Partial replacement of carbohydrate in the cereal-based diet by beef fat (2·5%) or anchovy oil (2·5 or 5·0%) had no effect on the amount of any of the lipid fractions, except for triglyceride, which varied considerably and was lowest in tissue from groups receiving 2·5% anchovy oil.

1. Seven samples of meat meal have been assayed with rats by the protein efficiency ratio (PER) test and with Streptococcus zymogenes by Ford's (1960) ‘relative nutritive value’ (RNV) test.

2. A correlation coefficient of r = + 0·895 was obtained for the results from the two series of tests.

1. The effect of vitamin E on the metabolism, utilization and storage of vitamin A has been studied in the rat.

2. Male weanling rats were given a vitamin A-deficient, vitamin E-deficient diet until growth had ceased for 3 days, and each rat was then given 50 i.u. vitamin A palmitate. The rats were divided into four groups and given the diet with the addition of 10% methyl oleate or 10% cod-liver oil methyl esters, or either of these diets supplemented with 100 ppm D-α-tocopheryl acetate. There was no increase in maximum weight-gain response in the two groups given vitamin E. There was a significantly lower weight-gain response in the groups given cod-liver oil methyl esters. This effect was not influenced by the presence of vitamin E in the diet.

3. Weanling rats of both sexes were made deficient in vitamins A and E and then divided into two groups. One group received, every other day, 1·75 i.u. vitamin A palmitate and 0·6 mg D-α-tocopherol given together; the second group received the two vitamins, in the same amounts, on alternate days. After 28 days there was no difference in the growth of the two groups of rats, irrespective of sex.

4. Vitamin A-depleted, vitamin E-deficient rats were given 17·51 μg ‘14C-carbinol’retinyl acetate and then a vitamin A-deficient, vitamin E-deficient diet or that diet supplemented with 100 ppm D-α-tocopheryl acetate. After 6 days, the total remaining ‘14C’retinol and its lipidsoluble metabolites were measured in the carcasses of the rats. Vitamin E administration did not affect the metabolism of the vitamin A dose or its effect on growth.

5. Vitamin E-deficient rats were given vitamin A until their liver reserves exceeded 30000 i.u. and were then divided into two groups. One group received a diet deficient in vitamins A and E and the other received, in addition to this diet, a weekly oral supplement of 1 mg D-α-tocopheryl acetate. The vitamin E supplement significantly decreased the rate of vitamin A depletion from the liver during the next 6 weeks. This effect, which was not found to occur when the initial liver reserves were only 3000 i.u., suggests a role for vitamin E in connexion with the capacity of the liver to bind vitamin A.

6. The relationship between vitamin A and vitamin E in vivo cannot, in the light of these results, be regarded as that between an antioxidant and a peroxidizable substrate.