1. Single meals of protein (24.3 mg nitrogen/100 g body-weight) were fed with and without carbohydrate (167 mg/100 g body-weight) to groups of rats kept in anticoprophagy cages after an 18 h fast. The contents of the gastro-intestinal tract were collected and analysed and the rises in plasma amino acid concentrations were also determined.

2. After ingestion of different proteins with sucrose, the passage of protein from the stomach was delayed compared with that when the meal was of protein alone: the initial stomach emptying was little affected by the nature of the protein in the diet, but subsequently the relative rates of evacuation of different proteins were similar to those when the proteins were given alone.

3. When proteins were given with different carbohydrates the subsequent digestion and absorption of the meal was modified in a way which could be explained by the observed properties of the carbohydrates given alone, particularly with regard to solubilization in the stomach.

4. The rises in concentration of plasma free amino acid were lower after ingestion of proteins with carbohydrate than when the proteins were eaten alone, and different carbohydrates affected these rises to different degrees.

1. The mechanisms by which an oral dose of glucose can stimulate the uptake of essential amino acids from serum was found to be operative even in children with severe, untreated kwashiorkor.

2. Although the percentage fall in the concentration of the essential amino acids in response to glucose was the same before and after treatment, the absolute fall was greater on discharge. The results indicated that the magnitude of this fall might depend on the initial fasting concentration of each individual amino acid.

3. These results have been discussed on the basis of possible long-term pathological effects of a distorted serum amino acid pattern typified by low concentrations of valine, leucine and threonine. The protein-sparing action of carbohydrate, achieved by the preferential synthesis of muscle protein in response to insulin secretion, might be less effective because of substrate limitation.

4. Of the non-essential amino acids, the concentrations of alanine and glycine also fell markedly before treatment, but this did not occur on discharge. The significance of this difference is also discussed.

5. The results also indicate that slightly high, spurious amino acid ratios can be obtained if a child is given a drink containing sugar before a blood sample is taken.

1. Duodenal contents were collected from cannulated sheep that were fed on dried grass cubes. After high-speed centrifugation, the distribution of long-chain unesterified fatty acids between the aqueous and particulate fractions of the digesta was examined.

2. The unesterified fatty acids of the digesta were found to be predominantly associated with the particulate matter.

3. When gall-bladder bile was added to the digesta at 37° and pH 4.0, in vitro, it was observed that unesterified fatty acids were transferred from the particulate matter to micellar solution. This transfer was due largely to the solubilizing effect of bile salts acting together with biliary phospholipids.

4. These findings are discussed in relation to the absorption of unesterified fatty acids by the sheep.

1. The yeast grown on normal paraffins (British Petroleum Proteins Ltd, London) contained62% crude protein and, except for lower content of methionine, its amino acid compositionwas similar to that of white fish meal.

2. The value to growing pigs of yeast + methionine as a protein supplement to diets based on barley and fine wheat offal was compared with that of white fish meal. The two protein supplements supplied the same amount of total nitrogen and were compared at a ‘standard’ level, commonly used in practice, and at a ‘low’ level. Two experiments were conducted: a feeding trial covering the live-weight range from 20 to 90 kg, and a metabolic trial (20–60 kg live weight) in which N retention and digestibility were measured.

3. There was a small but significant difference in favour of the yeast treatment for growth rate and feed conversion ratio, but there were no consistent differences in the linear measurements of the carcasses due to protein source.

4. In the metabolic trial there was no significant difference in performance, N retention,apparent N digestibility or linear carcass measurements and no consistent difference in tissuecomponents, between the diets supplemented with yeast or fish meal.

5. In pigs given the ‘low’-protein diets, performance and most of the other variables measured were significantly poorer than in those given the ‘standard’ protein diets, irrespective of whether yeast or fish meal was the source of supplementary protein.

6. It is concluded that yeast (+ methionine) may be closely equated with high-quality fishmeal as a protein supplement in diets for growing pigs. The small differences found are discussed in relation to possible differences in availability of amino acids and energy values in the diets.

1. The responses of serum lipids of weanling and adult male rats to different diets have been examined. Total cholesterol, phospholipids and triglycerides were measured. The proteins used in the diets were casein and wheat gluten, the carbohydrates were starch and sucrose, and the main lipid source was groundnut oil supplemented with either gluten oil or maize oil.

2. In general, the type of carbohydrate did not influence the experimental results, whereas the type of protein had a marked effect. Compared with casein, gluten caused an increase in concentration of serum triglycerides, phospholipids and cholesterol in weanling rats, but there was no change in adult animals. Much of this ‘gluten effect’ in weanlings was not ob- served when the diet was supplemented with 0.7% L-lysine hydrochloride.

3. When 1% cholesterol was added to the gluten diets, the serum cholesterol concentrations were only slightly and variably affected in weanlings. Serum triglycerides and phospholipids were not altered in adult rats by the dietary cholesterol, whereas there were reductions in these lipid components in the weanlings, whether the protein was supplemented with L-lysine hydrochloride or not.

4. Gluten oil was not shown to be responsible for any major portion of the differences observed between gluten and casein in their effects upon the lipids of rat serum.

1. Vitamin B12 activity in the milk of rats on various diets was measured by microbiological assay at intervals throughout lactation. The concentration of sodium and calcium in the milk was also determined.

2. At all stages of lactation the milk of rats fed on commercial rat cake contained much more vitamin B12 activity than that of rats receiving a semi-synthetic diet containing at least as much vitamin B12 as the rat cake. The milk of the latter group of animals contained more vitamin B12 than that from rats fed on the same diet without added cyanocobalamin. The levels of sodium and calcium were much less variable than those of vitamin B12 and the changes did not appear to be related to differences in diet, stage of lactation or litter size.

1. Erythrocytes from Ugandan children with untreated kwashiorkor had membranes containing larger amounts of lecithin than erythrocytes collected during the recovery phase.

2. The passive permeability of the erythrocyte membrane to glycerol and thiourea was reduced in kwashiorkor and returned to a more normal value on treatment.

3. The results are discussed in the light of similar findings of high erythrocyte lecithin concentrations in various liver diseases.

1. The effect of preventing rumen fermentation of feed on the utilization of energy and protein by growing lambs has been studied by theoretical means.

2. Initially, the differences in feed utilization resulting from microbial fermentation compared with digestion by host enzymes were estimated. It was assumed that a diet containing 85% of unspecified carbohydrate and 15% casein was placed directly into the rumen (ruminant lamb) or abomasum (non-ruminant lamb) of animals weighing 20 kg, and that in both instances the diet was completely digested. In the non-ruminant lamb from 39 to 45% more net energy was available for maintenance, and from 22 to 61% more net energywas available for production, than in the ruminant lamb. The smaller differences applied to concentrate diets and the larger differences to highly fibrous diets. When dietary protein was completely degraded by microbes approximately 50% less protein was absorbed from the small intestine in the ruminant lamb than in the non-ruminant lamb. It is suggested that this may significantly reduce tissue synthesis and growth in early-weaned lambs weighing less than 30 kg, but it may not limit growth in heavier animals.

3. Because part of the food of ruminants generally escapes fermentation and is digested by enzymes in the small intestine, and because part of the food of non-ruminants is fermented in the hind-gut, the estimates were adjusted accordingly. In this situation the utilization of digested energy in the non-ruminant lamb was from 30 to 45 % more efficient for maintenance and from 10 to 60 % more efficient for production than in the ruminant lamb. Some dietary proteins are so resistant to microbial degradation that a lower efficiency of utilization in the ruminant lamb when these proteins are given could only result from a limit in availability of energy.

4. Since ruminants digest crude fibre more efficiently than non-ruminants, it was calculated that the level of dietary crude fibre must exceed at least 22%, and in some instances 35%, of the dry matter before the ruminant digestive system results in a better utilization of dietary energy in lambs. Thus, many common feeding-stuffs would be more efficiently used by lambs if they by-passed the rumen. The possible limitations to the adoption of this procedure are discussed.

5. The present techniques available for reducing the degradation of food within the rumen are outlined. It is suggested that an improvement in food utilization in ruminants could be achieved by feeding fats or formaldehyde-treated fat-casein complexes in solid diets, or alternatively, by feeding liquid diets which activate the reticular groove.

1. Rates of disappearance of glucose from ligated loops of small intestine in lambs, adult sheep and young rats were studied. The concentration of glucose in the lumen decreased exponentially with time, suggesting that within a range of concentrations of 166–277 m-moles/l glucose was absorbed mainly by passive diffusion.

2. The rate of absorption of glucose from a 166 mM-solution based on either zero or first order kinetics and expressed as m-moles/m small intestine per h decreased along the intestine from the duodenum to the ileum in lambs and rats. The decrease was slight in adult sheep.

3. The total absorptive capacity of the small intestine of adult grazing sheep for glucose from 166 mM-solutions (06 m-moles/kg body-weight per h) was approximately 25% of that for lambs less than 1 week of age.

4. Young rats had a greater absorptive capacity of the small intestine (12.9m-moles/kg body-weight per h) than adult sheep of about 40 kg body-weight (0.6 m-moles/kg body-weight per h) and this largely reflected a longer small intestine per unit body-weight.

5. The absorptive capacity of lambs for glucose was greater when the level of voluntary lactose intake was increased before an experiment. The absorptive capacity of the ileum of adult sheep given wheat was greater than that of grazing adult sheep.

6. Developmental changes in glucose absorption are discussed in relation to normal changes in diet and to changes in the morphology of the small intestine with age.

1. Concentrations of nucleic acid nitrogen and other nitrogenous constituents were estimated in digesta taken from the proximal duodenum of calves which were given, either, one of a number of stall diets or pasture. These concentrations were compared, using polyethylene glycol (PEG) as a non-absorbed marker, with corresponding concentrations in rumen fluid and ileal contents.

2. There was little net change in amounts of RNA or DNA between rumen and duodenum relative to PEG, but there was a marked increase in amounts of total-N. In duodenal digesta, for any one animal given most diets, nucleic acid-N formed a fairly constant percentage (8–11 for different animals) of the total non-ammonia-N. This value was lower (by about 3) than the corresponding percentage in rumen fluid. Comparison of nucleic acid-N: total-N ratios in duodenal contents and bacteria suggested that, for these diets, about 40–55% of the non-ammonia-N in duodenal contents was of microbial origin.

3. During passage of digesta between the duodenum and ileum the mean percentage disappearances of total-N, RNA and DNA were estimated to be about 67, 85 and 75 respectively. There was evidence that these values varied with the amounts of the constituents entering the duodenum.

4. Ammonia was absorbed in the omasum-abomasum only when concentrations in rumen fluid were high (40 mM), but even moderate concentrations of ammonia entering the duodenum (3 mM) were efficiently absorbed (about 90%) in the small intestine.

1. A technique for the separation and colorimetric estimation of 2, 4-diaminopimelic acid (DAP) using automated ion-exchange chromatography coupled with an acid ninhydrin detection system is described.

2. Only traces of DAP were found in rumen protozoa and no DAP was detected in rumen fluid prepared by ultracentrifugation or dialysis.

3. The concentration of DAP in rumen bacteria from sheep on a constant feeding regimen, and the ratio of nitrogen to DAP for these bacteria were found to be constant over a 3-month period.

4. The method has proved suitable for the estimation of bacterial N in the duodenal digesta of ruminants.

5. The contribution of bacterial N to the total N leaving the abomasum of a lactating cow fitted with a permanent re-entrant cannula in the duodenum was found to be 50%.

1. Iodine metabolism was studied using labelled sodium iodide in subjects with endemic goitre which is prevalent in the south-west part of Ceylon, where the iodine content of the drinking water was shown to be low. The study was confined mostly to children of school age.

2. The patients showed raised thyroidal uptake of 181I and 48 h serum protein-bound radio-active iodine, lowered plasma inorganic iodide and urinary iodide.

3. These findings suggest that the goitre which is endemic in Ceylon is due to environmental iodine deficiency rather than to a goitrogen.

1. Baby pigs were removed from the sow 36–48 h after birth and reared on a diet of reconstituted whole-milk powder until 28 d of age. The whole milk was either mildly or severely heated before spray-drying; the severe heating completely denatured the whey proteins.

2. When the two milks were given at a high level of intake, either at hourly intervals or twice daily, severe scouring and some deaths occurred, the incidence being higher among pigs receiving the severely heated milk. The severe heat treatment also reduced the nutritive value of the milk powder as measured by the performance of the pigs during the 1st week of life. However, no difference in the nutritive value of the two milks was apparent for the surviving pigs over the whole experimental period.

3. There were no deaths when the two milks were given at a moderate level of intake and at hourly intervals. The effect of heat treatment on performance was similar to that at the high level of intake.

4. The apparent digestibility of the nitrogen in the diet was similar for both milks. However, balance trials could not be carried out when scouring occurred, when differences between the milks were most likely to be apparent. The N retention was similar with both milks at 7 d of age, although retention was higher when the severely heated milk was given to pigs between 14 and 21 d of age.

5. The digestion of the two milks was studied in 28-d-old pigs. The ability of the severely heated milk to clot in the stomach was greatly reduced compared with that of the mildly heated milk, but the performance of the pigs was unaffected. No other differences in the digestion of the milks were found. The ability of the diet to clot in the stomach appeared to be unimportant at this age.

6. It is possible that a reduction in the clotting ability of the severely heated milk was responsible for the decreased efficiency of digestion during the 1st week of life.

1. The effects of ingestion of diets deficient in both copper and iron on storage of these elements and on the red cell indices have been studied in rats.

2. Injection of Cu into rats whose stores of Cu had been virtually exhausted resulted in a temporary increase in the concentration of plasma Fe and depletion of the Fe stored in the liver. Storage of Fe in the spleen seemed to be affected somewhat differently from that in the liver.

3. Fe injected into Cu-deficient rats was transported to storage sites but, although the plasma Fe concentration was presumably transiently increased thereby, there was no lasting effect.

4. The hypotheses that Cu mediates in the release of Fe from ferritin and that of Osaki, Johnson & Frieden (1966) that caeruloplasmin promotes the rate of Fe-saturation of apotransferrin are discussed.

1. The technique for the quantitative estimation of lignin by digestion with 72% H2S04 has been investigated. Two methods of pretreatment designed to eliminate interference products of carbohydrates and proteins were compared, namely (a) acid and pepsin and (b) acid detergent. The latter technique gave low lignin yields owing to the colloidal dispersion of lignin in the acid detergent treatment. Erroneous results arise from an inadequate digestion in 72% H2SO4. It was found preferable to filter the product lignin without prior dilution of the acid since white particles of material, assumed to be cellulose, flocculated from solution on dilution. Also there is some loss due to colloidal dispersion of lignin during refluxing in dilute acid.

2. Analysis of soda lignin and sulphuric acid lignin preparations from hay, duodenal contents and faeces of sheep with exteriorized flow through a re-entrant duodenal fistula provided evidence for the degradation of lignin by digestive processes. Demethoxylation of lignin occurred mainly in the stomach, suggesting that this was the main site of breakdown.

3. A new displacement method of measuring duodenal flow is described. Quantitative results obtained also indicate that lignin is degraded mainly in the stomach to the extent of about 10%.

4. These results suggest that faecal lignin is an adequate marker for the estimation of duodenal flow, and hence of the extent of changes in the stomach and intestines respectively.

1. The effects of dietary supplements of heather at different stages of growth on the breeding of captive red grouse were studied.

2. A supplement of heather which was beginning to grow in spring stimulated captive red grouse to lay more eggs and to lay at a faster rate than birds given a supplement of dormant winter heather.

3. Although laying was stimulated, no significant effect on the date of laying, the hatchability of the eggs or the survival of the young was demonstrated; however, the possibility of such effects occurring in the wild is not ruled out.

4. The experimental effect occurred although the heather formed only a small proportion of a largely artificial diet, which provided a high plane of nutrition in terms of known nutrients.

5. The effect is attributed to an unidentified factor contained in the new growth.