1. The body temperatures and resting oxygen consumptions of calorie-deficient and protein-deficient pigs have been measured at 12, 21, 26, 30, 36 and 40°.

2. A fall in the environmental temperature was followed by a rise of the same order in the oxygen consumptions of the two groups of animals, and past and present evidence indicates that the rise in normal animals of the same size is similar.

3. The rectal temperatures and oxygen consumptions of the protein-deficient pigs were higher at all the above temperatures than those of the calorie-deficient animals but not as high as those of normal animals.

4. The differences in rectal temperatures and oxygen consumptions were highly significant at 30°, which is probably within or near the zone of thermal neutrality of all the animals.

1. In an attempt to explain the antagonism between polyunsaturated fatty acids (PUFA) and vitamin E in the promotion of post-mortem autolysis and increased lysosomal fragility in the kidney of rats, studies were made by gas chromatography of the incorporation of PUFA into the lysosomes.

2. Kidneys were taken from rats that had received various diets, which differed in their fat components and which were with or without vitamin E. Since the inclusion of cod-liver oil in the diet reduces the period of dietary preparation necessary for rapid kidney autolysis, the effect of this oil on the PUFA distribution in the lysosomes was specially studied.

3. In purified preparations of kidney lysosomes from rats that had received substantial amounts of cod-liver oil for several weeks, C 20:5 acid was incorporated mainly at the expense of C 18:2 (linoleic) and C 20:4 (arachidonic) acids. In less purified lysosomal fractions the incorporation of C 20:5 and C 22:6 acids and the corresponding reductions in linoleic and arachidonic were well advanced after 10 days, but were not maximal until about 30 days. The same changes took place in the reverse direction, with about the same rapidity, when rats that had previously been given cod-liver oil were changed to a diet containing lard.

4. The percentage of PUFA in the kidney lysosomes of rats not dosed with vitamin E was not significantly different from that of rats given adequate doses.

5. Thus the increased tendency to kidney autolysis, and the reduced stability of the lysosomes, caused by the feeding of cod-liver oil were associated with the partial replacement of linoleic acid and of the endogenous arachidonic acid by an acid, usually foreign to the rat, which is even more unsaturated. Since vitamin E did not prevent the entry of this acid into the lysosomes its potency in retarding autolysis and stabilizing the lysosomes must be exerted at some point subsequent to the incorporation of PUFA.

6. Since change in the percentage of lysosomal PUFA in response to dietary changes is slow, this suggests that the lysosornal lipidsescape usage in general metabolism as an immediate source of calories and that they have a half-life of at least 15 days. Individual fatty acids, however, may differ in their half-lives.

1. Four Ayrshire bull calves between 8 and 34 days of age and fitted with duodenal and ileal re-entrant cannulas were used to study the effect of heat treatment of the milk they received on the pH and nitrogen composition of the pyloric outflow and ileal contents.

2. Milk A contained a spray-dried skim-milk powder pre-heated during the drying process at 74° for 30 min and milk B a similar powder pre-heated at 77° for 15 sec. In milk A about 50% of the non-casein protein N had been denatured.

3. Milk B resulted in a lower pH than milk A in the pyloric outflow throughout the sampling period of 6.5 h after feeding. It resulted also in an increased volume of outflow during the 1st h after feeding, a reduced output of undigested protein, an increased output of non-protein nitrogen (NPN) and a different pattern of flow of NPN during the first 4 h after feeding.

4. These differences between milk A and milk B were associated largely with different clotting characteristics, which were demonstrated in vitro at two levels of addition of rennet with or without the addition of calcium. The buffering capacity of the two milks was similar.

5. Variation between calves in their response to these two milks was attributed to the age of the calves and to differences in inherent clotting or proteolytic activity.

6. In the ileal outflow, bacterial activity, as measured by dehydrogenase activity, was positively related to N concentration, but the N concentration when milk A was given did not appear to differ from that when milk B was given.

7. One calf had diarrhoea when given milk A at a young age. This was associated with an increased pyloric outflow, an increased outflow of undigested protein but little difference in the rate of proteolysis, and a high pH. In the ileal outflow the volume and amount of N was much increased although the N concentration was reduced.

8. It is concluded that the detrimental effect of milk A, found in earlier experiments, was largely associated with high pH and poor digestibility of protein in the abomasum, conditions which allow multiplication of coliform organisms in the intestine.

1. A new method has been devised for the nutritional evaluation of food protein quality. The method is analogous to the classical determination of net protein utilization (NPU). The suggested new criterion, the protein utilization by the liver (LPU), expresses the amount of food nitrogen ‘retained’ in the liver as a percentage of the food nitrogen intake.

2. Five different foods, casein, soya-bean protein isolate, maize gluten, wheat gluten, cottonseed meal alone or with supplements of amino acids, a total of thirteen samples, were tested for LPU and NPU in groups of six rats. The correlation coefficient between values for LPU and NPU for all seventy-eight rats was +0.85 and was highly significant.

1. Chemical analysis was carried out on samples of brain, liver, skeletal muscle, heart and kidney obtained from children who died of malnutrition. Total body potassium was measured before autopsy by the ‘whole body counting’ technique.

2. There was a marked increase in liver fat, and the brain contributed a higher percentage of the body-weight in the more severely malnourished children.

3. All the organs had approximately the same concentrations of non-collagen nitrogen. The proportion of collagen was highest in muscle.

4. All organs were depleted of potassium, but the muscle was most severely affected. Brain potassium as a percentage of total body potassium was higher than normal in the most severely potassium depleted children.

5. Measurements of tissue magnesium showed that there was no difference in magnesium content of tissues when expressed in terms of non-collagen nitrogen. When compared with normal values, muscle was magnesium depleted. The potassium to magnesium ratio was lowest in muscle.

1. Adult rats were maintained on a protein-deficient diet for 6 weeks following which laparotomy was performed and peritoneal wounds of standard size were constructed,

2. The diet resulted in a progressive weight loss and a fall in plasma protein. Tissue protein, expressed as percentage protein in dried voluntary muscle, did not fall significantly.

3. Following laparotomy the rats were killed in groups on successive days and the peritoneal wounds were removed for measurement of area and for histological examination.

4. There was no apparent difference between control and protein-deficient animals in the rate or extent of peritoneal wound contraction although there was histological evidence of delay of collagen formation in the protein-deficient animals. This supports the theory that collagen formation is not a function of wound contraction.

1. Eighty-seven rats were fed a diet of milk treated with hydrogen sulphide together with copper-free mineral and vitamin supplements. Forty-three of the eighty-seven rats were used controls and given Cu supplements varying from 50 to 500 μg/week. In addition to the eighty-seven rats, twenty-eight rats were fed a commercial diet.

2. Rats which did not receive Cu supplements developed signs of Cu deficiency and their liver Cu levels were significantly lower than those of control and stock animals. Oestrous cycles were normal and the majority of the rats were successfully mated.

3. Litters developed to full term in stock rats and in those given Cu supplements but the Cu- deficient rats did not produce litters.

1. After 14 days on a diet containing 5 or 25% casein male rats received a fracture of the left femur. Four hours before they were killed the injured and control rats were injected with [1-14C]leucine; the incorporation of radioactivity into an isolated fraction of skeletal muscle ribosomes was studied 6, 12, 24, 48, 72, 96 and 228 h after injury.

2. The incorporation of [14C]leucine into the ribosome fraction in right thigh muscles dropped to 40% of control values 72 h after fracture in well-nourished rats and after 96 h with diets containing 5 or 25%, casein.

3. The specific activity of the trichloroacetic acid-soluble fraction of muscle from injured rats was equal to or higher than that of the controls during the first 72 h but lower at 96 h.

4. These results suggest that a reduced incorporation of amino acids by ribosomes from the right thigh muscle occurred on day 3 after fracture in the group receiving 25% casein but not in the group receiving 5% casein.

5. Muscle RNA and DNA concentrations were not affected by the injury.

6. The relationship between these findings and the loss of muscle N after injury is discussed.

1. Weanling pigs were fed under three dietary regimens, control, low protein and total calorie restricted.

2. In the protein-deficient group the amino acid ratio did not start to become elevated until growth was impaired and total serum protein and albumin concentration began to fall.

3. In the protein-deficient group, but not in the control or undernourished animals, the magnitude of the ratio was statistically correlated with the rate of growth, appetite, serum protein and albumin concentration and hydroxyproline excretion.

4. The results provide information on the relationship between the serum amino acid ratio and nutritional status.

1. The effect of saccharin and cyclamate on growth of young rats fed on a poor rice diet or a balanced diet was investigated.

2. Saccharin and cyclamate retarded the growth of rats on the multi-deficient diet but not of those on the well-balanced diet during an 8-week feeding period.

3. The sweeteners did not produce any macroscopic or microscopic changes in the liver, kidneys, intestines, spleen or lungs of the animals receiving the poor rice diet other than the changes resulting from the nutritional deficiency of the diet.

4. The sweeteners did not inhibit the liver xanthine oxidase activity of rats receiving the poor rice diet to an extent greater than the inhibition brought about by the deficiency of protein in the diet.

5. When given by intubation to healthy rats, the sweeteners inhibited the induction of liver tryptophan oxygenase; given in vitro, they inhibited the succinate dehydrogenase activity of rat liver mitochondria.

1. Control groups of pigs were given a basal diet alone and treated groups received the same diet supplemented with 250 ppm of copper. The animals were about 10 weeks of age at the start of the experiments and were killed when they weighed 90 kg live weight.

2. The ratio of oleic acid to stearic acid in the whole back fat (inner plus outer layers) was somewhat higher in the pigs given the copper supplement than in the control animals. The melting point of the back fat was about 10° lower in the pigs given the copper supplement than in the control groups.

3. Separate analyses of the inner and outer layers of the back fat showed that the ratio of oleic acid to stearic acid in the outer fat layer of the control pigs, and in both the inner and the outer fat layers of the pigs given the copper supplement, was somewhat higher than that in the inner fat layer of the control animals. The melting point of the outer fat layer of the control pigs and of both back fat layers in the pigs given the copper supplement was 10–15° lower than that of the inner fat layer of the control groups.

4. Evidence is presented that changes in the positional distribution of the fatty acids within the triglycerides of the back fats rather than differences in gross fatty acid composition are mainly responsible for the observed differences in physical properties.

1. Twenty-six rats were fed a diet of milk treated with hydrogen sulphide together with copper-free mineral and vitamin supplements; fourteen of these rats were used as controls and were given 500 μg Cu per rat per week. Seven other rats were fed a commercial diet.

2. Mating to stock males commenced when the rats had been fed the diets for 6 weeks, and they were killed from the 10th to the 16th days of pregnancy.

3. The average number of placental sites was 17.9 in stock, 10.4 in control and 11.8 in deficient rats. Spontaneously resorbing sites were seen in three stock, seven control and six deficient animals.

4. The foetuses of the stock and control animals grew normally but in the Cu-deficient rats normal development ceased on the 13th day of pregnancy when the foetal tissues were seen to be disintegrating. Necrosis of the placenta was seen on the 15th day of pregnancy and until then blood islands were present.

5. Lesions were not seen in the maternal mammary glands, ovaries or pituitary glands.

1. An artificial rumen is described together with associated analytical and sampling procedures.

2. The equipment was used to study the effects of linseed oil fatty acids on the fermentation of sugar-beet pulp and of sucrose by rumen micro-organisms.

3. With sugar-beet pulp the addition of small amounts of linseed oil fatty acids had little effect on total gas production, utilization of sugar and the molar proportions of steam-volatile acids formed, but they strongly inhibited methane production, whereas large amounts of the fatty acids temporarily inhibited the production of gas and utilization of sugar.

4. With sucrose even the smaller amounts of fatty acids had a marked inhibitory effect on the production of gas and utilization of sugar.

5. The technique is assessed critically and the results are discussed in the light of previous experiments in vivo.

1. Changing cows from a diet with low hay and high flaked maize content, which depressed milk fat secretion, to a high-roughage diet resulted in increased milk fat secretion and in changes in the pattern of rumen fermentation and in the composition of the blood plasma.

2. During the 1st week following the change in diet the proportions of propionic and valeric acids in the rumen decreased and the proportion of acetic acid increased. These changes in rumen volatile fatty acids were associated with decreases in the concentration of lactic acid, increases in pH and increases in the rate of breakdown of cotton threads in the ventral sac of the rumen. After 1 week, only minor fluctuations in the proportions of volatile fatty acids occurred from day to day.

3. The percentage of fat in the milk increased over a period of 3 weeks following the change in diet and, with the exception of linoleic acid which decreased, the yields of all fatty acids in milk progressively increased over this period. The increase in yield of oleic acid was relatively much smaller than the increases in yield of saturated acids.

4. The concentrations in blood plasma of acetic acid and β-hydroxybutyric acid increased in two cows and, in all cows, saturated triglyceride fatty acids increased, whereas the concentrations of the unsaturated triglyceride fatty acids decreased, during the 1st week after change to the high-roughage diet. The recovery in milk fat secretion is discussed in relation to the observed changes in rumen fermentation and blood composition.

1. A vitamin E-low diet containing 7% stripped lard was given to hooded rats for periods up to 14 months. Control rats were given the same diet with a vitamin E supplement (I i.u./rat per day).

2. No consistent pattern of changes was found in the total fatty acids of testis, lung, spleen, pancreas, heart, kidney, liver, brain, skeletal muscle and small intestine from rats given the deficient diet for 5, 6 or 7 months when compared with control rats.

3. The fatty acids of the total phospholipid from the same tissues were examined after 4, 5, 8 or 14 months. In the rats deficient in vitamin E the polyunsaturated fatty acids of the linoleic series (ω6) decreased, except for 20:4ω6, which in some tissues tended to increase. After 14 months there were considerable decreases in the percentages of all the ω6 series including 20:4ω6 with increases in the percentages of 18:1ω9 and 20:3ω9 the pattern was similar to that found in essential fatty acid deficiency.

1. Three wethers fitted with permanent rumen cannulas were given a pelleted roughage–concentrate ration containing 45% ground barley straw as roughage. The animals were given 1 kg of the diet at 08.00 h and 500 g at 17.00 h.

2. The measurements made to determine the buffering components of the rumen fluid were: rumen pH, buffering capacity value (β), total volatile fatty acids (VFA), CO2 and inorganic phosphorus concentrations. β was expressed as the quantity of titrant (m-equiv./l.) required to bring about 2 unit changes in rumen fluid pH. The pH ranges in which the β values were measured were 4–6, 5–7 and 6–8. All measurements were made at hourly intervals over a 9 h period commencing 1 h before feeding.

3. Rumen pH values were high before feeding, decreased to a minimum 2 h after feeding and then increased to approximately the original values. The concentrations of total VFA followed an inverse pattern. There was diurnal variation in the concentrations of CO2 but inorganic P levels varied very little throughout the day.

4. Significant correlations were obtained between VFA, inorganic P and CO2 levels and the β values. It would appear that the bicarbonate and phosphate buffers were not effective in regulating the rumen pH when sheep were given a roughage–concentrate ration.

1. Eight groups of ten weanling rats were maintained for 60 days on diets containing calcium and phosphorus in the ratio 10:1 at four different levels of mineral, namely 0.8, 1.19, 2.29 and 3.33% Ca.

2. At the two lower levels of mineral intake the provision of vitamin D reduced final body-weight. Increasing the mineral intake increased final body-weight except at the highest level.

3. Increasing the dietary mineral content had no effect on serum Ca, but serum P was higher in the groups receiving the two higher levels of dietary mineral. Vitamin D raised the serum Ca level in the rats receiving the two lower levels of mineral, and serum P was raised by the vitamin at all levels of mineral intake.

4. Provision of vitamin D at the two lower levels of mineral intake decreased the fresh weight, dry weight and volume of the humerus but had no significant effect on the absolute amount of mineral ash in the bone. Consequentially there was an increase in percentage of ash, overall density and the ratio of weight of ash to organic matter in dry fat-free bone (A:R value). With increasing mineral intake there was an increase in all the bone measurements except volume.

5. The presence of vitamin D had no effect on tooth mass or ash content. Increasing the mineral intake caused an increase in tooth mass and ash except at the highest level of intake.

6. The ratio of tooth ash to bone ash was very much greater at the lower levels of mineral intake than at the higher levels.

7. In the animals on the two lower levels of mineral intake the bones were frankly rachitic, and the presence of vitamin D ameliorated the condition. With increase in mineral intake histological signs of rickets were reduced, but even at the highest level of dietary mineral the epiphyseal discs appeared slightly wider than normal.

8. The incisor teeth of animals on the two lower levels of dietary mineral had wide predentine, and the presence of vitamin D reduced the amount of predentine. At the two higher levels of mineral intake the dentine appeared normal when vitamin D was present in the diet.

9. Quantitatively, the bones were much more affected than the teeth by a low intake of mineral at a Ca to P ratio of 10:1.

1. The effect of oxygen on the fermentation of sucrose by mixed rumen micro-organisms in vitro was studied by adding oxygen to the gas phase in three ways: at the beginning of incubation, at two hourly intervals during incubation and continuously.

2. The additions of oxygen had no measurable effect on the utilization of sucrose or on the production of carbon dioxide, steam-volatile acids and particulate organic matter by the micro-organisms. The addition of oxygen at the beginning of incubation inhibited methane production and increased the accumulation of hydrogen. Similar but much less pronounced changes occurred when the oxygen was infused continuously.

3. In all the experiments there was a net uptake of oxygen by micro-organisms. When large amounts of oxygen were present in the gas phase the rates of uptake were proportional to these amounts. When small amounts of oxygen were added, the rates of uptake were independent of the amount added and had a value of approximately 5 ml/h when 100 ml of strained rumen contents were incubated.

1. It has been suggested that carbon tetrachloride damages rat liver by accelerating processes of lipid peroxidation at subcellular sites and that the protective action of vitamin E is due to its functioning as an antioxidant in vivo. Direct evidence for these mechanisms in vivo has been sought and is critically examined.

2. The increased production of malondialdehyde by rat liver microsomal fractions during incubation with CCl4 was shown to be a function of the vitamin E status of the rat and of an in vitro reaction, which could not be correlated with the hepatotoxic action of CCI4.

3. Evidence for the production of lipid peroxides by CCl4 in the livers of vitamin E-deficient and vitamin E-supplemented rats was sought (I) by measurement of ultraviolet spectral changes ('diene' formation) and (2) by direct micro-iodimetric determination of the peroxide. No differences in peroxide content were found between CC14-treated and control rats, nor were the spectrophotometric changes in the ultraviolet region related to the presence of vitamin E.

4. The effect of CCI4 (2.0 ml/kg orally) on ATP levels in rat liver was studied at intervals from 3 to 68 h. The primary lesion leading to necrosis and fat accumulation after CCl4 treatment occurred many hours before the eventual slight decline in ATP. Although the levels of ATP were somewhat higher in vitamin E-deficient rats, vitamin E did not prevent the slight decline in ATP that took place. Since ATP is known to be highly sensitive to peroxidation, the results suggest that lipid peroxidation is not the primary event in CCl4 poisoning.

5. The effect of CC14on the metabolism of [14C]D-α-tocopherol in the rat was studied. A single intraperitoneal dose of CCl4 (2.0 m/kg) did not increase the destruction of α-tocopherol in the liver or carcass after 24 h. Three smaller daily doses of CC14 (0.25 ml/kg) also did not increase α-tocopherol catabolism; on the contrary, significantly more α-tocopherol was found in the livers of rats treated with CCI4. These results suggest that CCl4 does not increase lipid peroxidation in vivo.

1. The daily methane production of sheep given sugar-beet pulp was greater than that of sheep given hay. The rates of methane production on both diets increased during feeding and then decreased to an apparently steady value. When no food was given the rates of methane production continued to fall exponentially with a half-life of about 24 h.

2. Mixtures of unsaturated long-chain fatty acids infused into the rumen during feeding inhibited the production of methane. The inhibition was greater when the sheep were given hay than when they were given sugar-beet pulp.

3. In general the concentration of soluble carbohydrates in the rumen increased during feeding and fell rapidly to the values found before feeding as soon as the sheep finished eating. The infusion of unsaturated fatty acids during feeding did not result in an accumulation of soluble carbohydrate in the rumen.

4. It is suggested that the rapid methane production during feeding was associated with fermentation of the more soluble part of the diet and that the fermentation of carbohydrate was not inhibited by the infused fatty acids. The results are consistent with specific inhibition of methanogenesis by unsaturated fatty acids.