1. Serum amino acid ratios and urinary hydroxyproline indices have been studied in three groups of children from different parts of Uganda. The results of these biochemical investigations are compared with clinical assessments and anthropometric measurements made at the same time.

2. In Buganda, an area where protein deficiency is prevalent, a high incidence of both abnormal hydroxyproline indices and amino acid ratios was found. In Karamoja, where a drought had caused a widespread shortage of food, the hydroxyproline indices were particularly low but the amino acid ratios were relatively normal. In Bukedi the dietary pattern was changing and becoming more like that in Buganda; this was reflected by the biochemical results obtained which were similar in the two areas.

3. The biochemical results confirmed earlier investigations, carried out in more severely ill children in a metabolic ward, which had indicated that these two tests can differentiate between primary protein deficiency and total calorie deficiency.

4. The biochemical tests confirmed the anthropometric measurements in a quantitative way, and also indicated the reason for the nutritional difficulties which could otherwise only have been surmised from the food habits of the area.

1. The use of chromic oxide (Cr2O3) as an indigestible marker for studies on intestinal digestion in sheep has been examined. The sheep used were equipped with a cannula into the rumen and a re-entrant cannula in the proximal duodenum; some also had a re-entrant cannula in the terminal ileum. The marker was administered twice daily in the form of Cr2O3-impregnated paper, through the rumen cannula.

2. Recovery of Cr2O3 in the faeces, based on 7-day collection periods, was satisfactory, the mean recovery for all seven experiments being 99.6 ± 0.7%. In seventeen 24 h collections of digesta entering the proximal duodenum, the mean recovery of the daily dose of marker was 83.7% (range 63.6-148.4%); in eleven such collections at the terminal ileum the mean recovery was 77.3% (54.0-90.0%).

3. Detailed examination of the concentrations of Cr2O3 in dry matter was made with individual samples taken during single 24 h periods for five duodenal and three ileal collection periods. There were always marked variations in these concentrations. It is concluded that use of short collection periods to give mean values for the flow of digesta throughout the 24 h, at particular points along the tract, may lead to large errors.

1. The interrelationship between cholesterol and vitamin A metabolism has been studied in rats.

2. The effect of cholesterol feeding in increasing the liver storage of cholesterol w-as enhanced during vitamin A deficiency.

3. This effect was due to an increased rate of absorption of cholesterol and not due to a decreased turnover rate.

4. Feeding of high levels of vitamin A markedly depressed the cholesterol absorption; however, its turnover was unaffected.

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. 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. 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. 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. In Expt 1, five groups of four dry non-pregant ewes were given 1 kg/day of a semi-purified diet containing either 0.05, 0.10 or 0.15% magnesium with 0 or 4.44% added potassium. Plasma Mg Concentrations were reduced by increasing the K intake (P < 0.001) and by reducing the Mg intake (P < 0.1). The effects were additive and, at the lowest Mg intake, supplementary K induced two cases of hypomagnesaemic tetany.

2. Expt 2 was similar to Expt 1 except that the ewes were suckling single lambs, they were given 2 kg food/day and the lowest dietary Mg concentration was 0.075%. K again lowered plasma Mg values and induced two cases of tetany but reductions in Mg intake had no effect.

3. After repletion on the basal diet, sixteen lactating ewes from Expt 2 were transferred to a diet containing 0.05% Mg with 0, 2.22 or 4.44% added K. Plasma Mg concentrations fell rapidly on each treatment; the effect was greatest in K-supplemented groups ( P < 0.05) and two cases of hypomagnesaemic tetany were induced at the highest K intake.

4. In each experiment the K supplements caused a rapid increase in plasma K concentrations to a relatively constant level some 5 mg/100 ml above the resting value of 18.0 mg/100 ml.

5. Some sheep refused K-supplemented diets at first and there was a tendency for refusals to be greatest at the lowest Mg intakes.

6. The results are discussed in relation to the aetiology of hypomagnesaemic tetany.

1. Rats were made severely iron-deficient by feeding with Fe-deficient diets, which contained adequate amounts of zinc.

2. Ten days after an oral dose of 250 μg65Zn the Fe-deficient rats had retained 17% whereas control rats had retained only 8% of the dose.

3. When unlabelled Zn was given intravenously to the Fe-deficient and control rats there was a reduction in retention of the orally administered 65Zn. This effect was not produced when Fe was given before the oral dose of 65Zn.

4. Total body Zn, whole blood Zn and plasma Zn concentrations of the rats were measured by atomic absorption spectrophotometry. Both the Fe-deficient rats and the control rats had the same total body Zn calculated as a proportion of body-weight. The plasma Zn concentrations were normal in all the animals. Blood cell Zn concentrations in the Fe-deficient animals were raised.

5. The blood cell Zn concentration was directly related to the reticulocyte count in all the rats.

6. It was concluded that Fe and Zn are absorbed by different metabolic pathways, and that there is an increased turnover of Zn in the Fe-deficient rats, possibly related to the short lifespan and increased Zn concentration of Fe-deficient rat erythrocytes. In the rat abnormalities of Zn concentration can only be considered significant if Fe status is also known.

1. An isotope dilution method, known to be satisfactory for measurement of volatile fatty acid (VFA) production in the rumen under steady-state conditions, was tested for its applicability where the VFA pool in the rumen could vary irregularly. The method indicated mean production rates closely similar to those obtained when the pool size was virtually constant. Tests carried out in a model rumen confirmed this finding and the method was accepted as suitable for measurement of VFA production in grazing sheep.

2. The method, modified to allow continuous sampling of rumen acids by dialysis, was applied to sheep grazing a mixed pasture. Mean rates of VFA production determined in seven sheep during fourteen 3-day periods throughout winter, spring and summer months ranged from 3.4 to 5.3 moles daily, production increasing during the period of growth of the pasture, and declining again with its drying-off.

3. The pasture was at all times abundant; the findings are therefore considered to represent the pasture's full potential yield of VFA to the sheep and so to indicate its changing value in this respect as the seasons progressed.

4. Results from sheep given roughages and from the grazing sheep indicated that, despite irregular intake, good predictions of mean VFA production rates could be made from mean VFA concentrations in the rumen fluid.

1. The biological evaluation of solvent and prepress-solvent processed rapeseed meals RM(S) and RM(PS) was carried out with the weanling (phase 1) and the mature (phase 2) rat. The nutritional indices measured were compared with those for diets containing soyabean meal SM and casein CS.

2. The true nitrogen digestibility (td(N)) for RM(S), RM(PS), SM and CS in the weanling rat was (%) 78.9 f±1.2, 77.9±2.7, 90.4±0.9 and 96.0±0.6 (P < 0.01) respectively. Net protein utilization was (%) 68.9±10.1, 65.6±3.5, 80.6±4.8 and 81.7±3.1 (P < 0.05) respectively. Biological value was (%) 83.0±7.9, 84.1±5.6, 8.90±5.1 and 85.0±3.4 (P < 0.05) respectively. The same indices when measured in the mature rat showed an increase over those obtained in the weanling rat.

3. The growth-promoting effects of the test diets were evaluated over a period of 8 weeks with ad lib. feeding between phases 1 and 2. Protein efficiency ratio averaged 2.0±0.14, 1.9±0.35, 2.4±0.39 and 2.3±0.25 for the RM(S), RM(PS), SM and CS treatments respectively.

4. The daily endogenous urinary N excretion was 1.58±0.14 mg N/basal kcal or 254 mg N/kg body-weight for the weanling rat and 0.16 mg N/basal kcal or 18 mg N/kg body-weight for the mature rat. Metabolic faecal N excretion was 98.0±9.3 mg N/kg body-weight, or 27.9% of the total N output for the weanling rat, and 37.9±7.2 mg N/kg body-weight, or 67.3% of the total N output for the mature rat during the ‘protein-free’ feeding periods.

5. The fresh weight of the thyroid gland per kg metabolic body size was 70, 90, 40 and 40 mg respectively for the RM(S), RM(PS), SM and CS dietary treatments.

6. The moisture content of the carcasses was 66.9±3.1, 63.6±2.3 and 64.2±2.2 and the protein content on a dry-matter basis was 55.9±9.6, 50.2±6.4 and 53.1±4.9 for the RM (S and PS), SM and CS diets respectively. The results suggest an increased lean body mass in the rats receiving the rapeseed meal treatments.

7. Under the conditions of this experiment solvent-extracted rapeseed meal was superior to prepress-solvent meal on the basis of rat growth response and of results for nutritional indices. Both rapeseed meals were inferior to soya-bean meal and casein.

1. Seven groups of male rabbits (thirteen to fifteen per group) were given ad lib. a diet consisting of 80 parts of a low-fat basal ration to which were added 20 parts of fat in the form of butterfat, maize oil or various mixtures of the two.

2. After 40 weeks, samples of blood were taken and the animals were killed. The concentrations of total cholesterol and phospholipid in the plasma and the fatty acid compositions of the plasma cholesteryl esters and phospholipids were determined. The degree of atheromatous degeneration was determined in the aortas.

3. Little aortic atherosis was observed in the rabbits given the diets containing 0, 10 and 12% butterfat, but as the butterfat content of the diet was increased above 12%, pronounced increases occurred in the extent of atheromatous degeneration of the aorta. The concentration of cholesterol in the plasma increased progressively as the butterfat content of the diet was increased and the maize oil content was decreased. There was an inverse curvilinear relationship between the degree of aortic atherosis and the phospholipid: cholesterol ratio in the plasma.

4. The concentration of linoleic acid in the plasma cholesteryl esters was inversely related to the concentration of cholesterol in the plasma, and the concentration of linoleic acid in the plasma phospholipids was inversely related to the concentration of phospholipids in the plasma. There was a positive linear relationship between the stearic: palmitic acid ratio and the linoleic: oleic acid ratio in the plasma phospholipids.

1. [I-3H]Cholecalciferol and [I-3H]cholecalciferol palmitate in amounts equivalent to 2 μg cholecalciferol were injected into rachitic rats as aqueous preparations (intravenously) or in arachis oil (intramuscularly).

2. The radioactive faecal metabolites collected for up to 17 days were fractionated according to their polarity. The same pattern of excreted radioactivity was seen with intravenous and intramuscular cholecalciferol and intravenous cholecalciferol palmitate. Intramuscular chole-calciferol palmitate produced a higher proportion of the most polar metabolites in faeces.

3. Parenterally administered cholecalciferol palmitate in a rickets-healing biological assay had activity equivalent to unesterified cholecalciferol.

4. Vitamin D ester synthesized in vivo is considered to be eventually metabolized as vita- min D alcohol and to be available to vitamin D-requiring processes.

1. The fatty acid compositions of the plasma cholesteryl esters, phospholipids, triglycerides and unesterified fatty acids were determined in three sheep at various times after they had been given intra-abomasal infusions of emulsions of linseed oil, maize oil or linoleic acid.

2. The concentrations of linolenic acid or linoleic acid in the plasma triglycerides began to increase 1.5 h after infusion of the emulsions had begun. As the concentration of linolenic or linoleic acids in the plasma triglycerides increased, the concentrations of palmitic and stearic acids decreased, hut there were no appreciable changes in the concentrations of oleic acid.

3. The concentrations of linolenic or linoleic acid in the plasma phospholipids and cholesteryl esters did not begin to increase until 8–9 h and 24–25 h respectively after the infusions of the emulsions had begun.

4. It is suggested that, after absorption from the small intestine of the sheep, linolenic and linoleic acids are transported in triglyceride form to the liver where the triglycerides are partially or completely hydrolysed. These C18 polyunsaturated acids are then preferentially utilized for the synthesis of phospholipids and cholesteryl esters but not for the re-synthesis of triglycerides.

1. An experiment was performed to study the effect of sodium acetoacetate on urinary excretion of santhurenic acid and other tryptophan metabolites in male albino rats.

2. Animals were fed on a nicotinic acid-deficient diet for a period of 3 weeks. The animals were then divided into two groups and, after the basal urinary excretion of the tryptophan metabolites had been estimated, the rats of both the groups were force-fed with L-tryptophan (100 mg per rat), the rats of the second group being simultaneously injected intraperitoncally with acetoacetate (200 mg/kg body-weight), and the urine samples during the following 24 h were collected and analysed.

3. Acetoacetate-treated rats given tryptophan were found to excrete significantly greater amounts of kynurenine, hydroxykynurenine and xanthurenic acid than the corresponding control rats. There was no ditference between the amounts of kynurenic acid excreted by the animals in the two groups.

1. Artificial emulsions of nine synthetic triglycerides ranging from tripropionin to triolein were given as continuous infusions into the jugular vein of lactating cows for periods of 2 days. The effects of these infusions on the composition of blood lipids and on the secretion of the component fatty acids in milk were examined.

2. Tricaproin, tricaprylin, tripelargonin, tricaprin, trilaurin, trimyristin and triolein, in contrast to tripropionin and tributyrin, increased the yields in milk of the acid contained in the triglyceride. The increased yield of acid was positively correlated with chain length of the infused triglyceride, and with triglycerides above tricaprin the transfer of fatty acid to milk was sufficiently large to give consistently increased yields of total milk fat.

3. The infusions increased the concentrations in blood plasma of cholesterol, phospholipid and in some experiments also of triglyceride. Concentrations of these lipids returned to normal by 2 days after the infusion. The fatty acid compositions of the plasma triglycerides were not affected by the infusion of triglycerides up to tripelargonin but with triglycerides longer than this the plasma triglycerides were altered in composition towards that of the infused triglyceride.

4. Short- and intermediate-chain fatty acids of the infused triglycerides were elongated by the successive addition of two carbon units to give increased yields in milk of acids ranging up to C15 and C16 when they contained acids with an even and odd number of carbon atoms respectively. Possible interference with the conversion of stearic into oleic acid in the mammary gland owing to the infused emulsions is also discussed.

1. The effects of intravenous infusions of emulsified cod-liver oil, Ethive (British Codliver Oils (Hull & Grimsby) Ltd; ethyl ester fraction of cod-liver oil rich in polyunsaturated acids) and soya-bean oil on the secretion of milk fat and the composition of blood lipids in the dairy cow were investigated.

2. Soya-bean oil increased the yield of total fat, by increasing the secretion of unsaturated C18 acids in milk and also increased the proportions of oleic and linoleic acids in the blood plasma triglycerides.

3. Cod-liver oil and Ethive both decreased the yield of total fat and the yields of C14 to C18 acids but had no effect on the yields of C4 to C12 acids in milk. Although the emulsions contained considerable quantities of C20 to C22 acids, which were incorporated into the blood plasma triglycerides, these acids were not secreted in the milk fat.

4. It is concluded that, if the polyunsaturated C20 and C22 acids in cod-liver oil are not hydrogenated in the rumen before their absorption from the digestive tract, they can act directly on the mammary gland, possibly through the inhibition of lipoprotein lipase, to reduce the secretion of long-chain acids in milk. In addition, cod-liver oil may have an indirect effect, through changed volatile fatty acid production in the rumen, on the secretion of short-chain acids in milk.