1. The serum immunoreactive insulin (IRI) concentrations, and glucose disappearance rate-constants after intravenous glucose administration were measured on admission and during recovery in children suffering from protein-energy malnutrition (PEM).

2. A high potassium intake resulted in a considerable increase in the serum IRI levels early in the treatment period. There was a definite relationship between potassium depletion and many measurements of insulin secretion.

3. The results are consistent with the hypothesis that impaired insulin release in children suffering from PEM is partly the result of potassium depletion.

1. The effects of seasonal conditions and nutrition on serum proteins and serum urea concentrations were studied in female reindeer and reindeer calves in Finland. With the exception of one group in winter, the reindeer were roaming wild in the forests. This one group was kept in captivity, out of doors, on a comparatively high nutritional plane. One group lived wild during the winter in very poor nutritional conditions.

2. A very clear seasonal variation in the serum protein and urea concentration was found. The serum protein concentration was low in late winter and increased rapidly during the summer, being high in the autumn. The serum urea concentration was also low in the winter and high in the summer. In the autumn, however, the serum urea concentration was again low.

3. Changes in the serum protein concentration were normally associated with the serum globulins. Only in the very poor-nutrition group did the albumin content decrease significantly. As a result of the large changes in the concentration of serum globulins, there were also considerable changes in the albumin: globulin ratio.

4. The serum protein concentration was much lower in the reindeer calves than in the adult reindeer. The concentration of globulins in particular was much lower than in the adults.

1. The flow of digesta through the duodenum and the concurrent secretion of the pancreas were studied in four Friesian calves given four milk-substitute diets. The diets were: reconstituted, ‘mildly’ pre-heated, spray-dried skim-milk powder with (SKF) or without (SK) margarine fat or with 50% of the skim-milk powder in diet SKF replaced by soya-bean flour (ASKF) or fish-protein concentrate (BSKF), together with dried whey. The diets were given ad lib. twice daily from 13 to 37 d of age, each diet being given for 6 consecutive days. Collections of duodenal digesta and pancreatic secretions, from cannulas, were made for 12 h after feeding the 6th and 12th meals (‘experimental’ meals) for each diet

2. The diets fed as ‘experimental’ meals contained polyethylene glycol (PEG) as a fluid (whey) marker and goat's milk containing [3H]lysine as a marker for total protein; β-carotene was added as a lipid marker to the three diets containing margarine fat

3. Over the 12 h postprandial period, the patterns of duodenal digesta flow and secretion of pancreatic fluid did not differ markedly between the four diets. The abomasal outflow of both nitrogen and lipid in a 12 h postprandial period was related to their intakes from the ‘penultimate’(5th and 11th) meals for diets SKF and SK but to their intakes at the ‘experimental meals’ for diets ASKF and BSKF. Secretion of pancreatic enzyme activity was highest during the 1st hour after feeding but the main outflow from the abomasum of total N and lipid occurred 5–10 h after feeding

4. The time required for all the whey marker (PEG) to pass through the duodenum was similar for diets SKF and SK, but only 53 and 42% respectively of the ingested protein marker passed through the duodenum in the 12 h after feeding. More acid appeared to be secreted by the abomasum when diet SK was given; also less undigested protein passed out of the abomasum after giving this diet. It is concluded that the physical absence of fat globules in the abomasal clot increases the degree of proteolysis

5. The secretions of pancreatic fluid and pancreatic enzyme activity were all markedly lower for diet SK than for diet SKF

6. With diets containing non-milk proteins (ASKF and BSKF), abomasal proteolysis was less efficient and the ingested protein passed out of the abomasum more rapidly than for diet SKF. There was no difference in the rate of abomasal outflow of the whey fluids between diets SKF, ASKF and BSKF

7. In comparison with diet SKF, diets ASKF and BSKF tended to induce less pancreatic enzyme secretion over a 12 h postprandial period, with the exception of lipase

8. There appeared to be no direct relationship between the quantities of any of the pancreatic enzymes secreted during a postprandial period and either the concurrent flow of duodenal digesta or the total quantities of dietary constituents passing through the duodenum.

1. Sheep fed on a maintenance ration of wheaten-hay chaff or of wheaten-hay chaff–lucerne-hay chaff (1:1, w/w) became deficient or incipiently deficient in vitamin E.

2. Degenerative changes were observed in bone marrow and muscle, and liver function was impaired in some animals. These abnormalities were not influenced by the vitamin B12 status of the animals or by a shortage of cobalt in the rumen.

3. Plasma ascorbic acid levels may not have been optimum, and folic acid may not have been fully utilized by some sheep.

4. Liver function responded fairly rapidly to α-tocopheryl acetate, but skeletal muscle had not returned to normal after 28 weeks of treatment. A variable trend towards normal cellularity was found in bone marrow following supplementation with α-tocopheryl acetate.

5. A secondary deficiency or, alternatively, inefficient excretion or metabolism of a toxic material, may occur in vitamin E deficiency as a result of degenerative changes in the absorptive or excretory areas of the intestinal tract and be responsible for the bone marrow abnormality.

1. The effects of perinatal malnutrition on behavioural development and adult shuttle-box avoidance performance were studied in Swiss white mice.

2. Mice were malnourished (a) from the 7th day of gestation until birth, (b) from birth until weaning, or (c) during both gestation and the sucking period.

3. Pups born of protein-restricted mothers had reduced birth weights, retarded development and poor adult avoidance performance, even if reared from birth by well-nourished mothers.

4. Postnatal malnutrition, induced either by restricting maternal diet or by rearing in large litters, retarded development during the second half of lactation and lowered subsequent adult avoidance performance.

1. The effects of retinol and retinoic acid supplementation of retinol-deficient rats were studied for a variety of metabolic processes shown to be affected by retinol deficiency.

2. Retinol-deficient rats were found to have decreased body-weight, liver and testes weights, a degeneration of testicular germinal cells, an increased incorporation of labelled choline into liver and testes phospholipids, an increased protein synthetic activity (in vitro) of liver ribosomes, an increased transfer-RNA methyltransferase activity in liver and a decreased activity in testes, an increased DNA content of testicular nuclei, and a decreased uptake of [3H]thymidine by testicular nuclear DNA.

3. In retinol-deficient rats supplemented for 8 weeks with retinol these changes were reversed, measurements returning to control levels.

4. In retinol-deficient rats supplemented for 8 weeks with retinoic acid all changes were reversed except those in the testes.

5. Testicular signs of retinol deficiency appeared to be delayed when retinoic acid was added to the retinol-deficient diet of weanling rats. This suggests a sparing action of retinoic acid on the rat's utilization of retinol.

6. Suggestions are offered as to why retinoic acid will support growth and development but not spermatogenesis in the rat.

1. The digestion of three foods favoured by ptarmigan (Lagopus mutus) in the wild was studied using captive birds

2. Bulbils of Polygonum viviparum L. were a good source of metabolizable energy, protein and phosphorus, but were deficient in sodium. Berries of Vaccinium myrtillus L. were the most digestible of the three foods, contained enough protein and P for maintenance, but were probably deficient in Na. A diet of Empetrum sp. berries caused the birds to be in negative nitrogen and P balance, but provided adequate Na. Both species of berries were rich sources of soluble carbohydrate

3. In the wild, ptarmigan eat a mixed diet, which presumably provides adequate Na, protein and P

4. The relative proportions of the various end-products of N metabolism varied according to the protein content of the food. With the diet of Vaccinium berries (11 g N/kg dry matter) roughly equal amounts of ammonium salts and urates were excreted. With Polygonum bulbils (29 g N/kg dry matter) the quantities of ammonium salts and urates excreted were similar to those with Vaccinium berries, but some urea was also excreted and about half the N in the birds' droppings was in an unidentified form

5. When eating Empetrum berries, ptarmigan digested lignin and tannins and excreted ornithurates. The benzoic acid moiety of the ornithuric acid molecule may have been derived partly from the digested lignin and tannins.

1. The changes in the solubility of calcium, magnesium and phosphorus in digesta flowing along the intestinal tract and the net movement across the intestinal wall of these elements were determined in six rams, each equipped with three T-shaped cannulas; cannulas were placed in a total of six different sites of the small intestine. Cr2O3 was used as a marker substance to measure the rate of flow of the digesta.

2. The concentrations of soluble Ca, Mg and P decreased as digesta moved along the intestine. The greatest fall in soluble Ca occurred after the first 3 m of the intestine, while a significant decrease in soluble Mg was found only at 15 and 25 m from the pylorus. The concentration of soluble P in digesta decreased until the 7 m site and then remained stable. In the faeces, the level of soluble Mg was approximately 4 times higher than, and that of Ca equal to, the levels of Mg and Ca found in digesta flowing through the upper intestine. Unlike Ca and Mg, a very low concentration of soluble P was found in the faeces.

3. In the duodenum, 84, 78 and 62% of the total Ca, Mg and P respectively were soluble, whereas in the digesta flowing through the terminal ileum the corresponding values were 3·2, 7·2 and 19% for Ca, Mg and P respectively.

4. The forestomachs and the colon were found to be the main sites of Mg net absorption; 1·12 mmol/h was apparently absorbed from the stomach and 1·05 mmol/h from the colon. The upper small intestine (1–3 m from the pylorus) appeared to be the major site of Ca and P absorption.

5. In the last 10 m of the small intestine, considerable amounts of minerals were secreted; 4·70, 0·96 and 1·85 mmol Ca, Mg and P/h respectively were added to the digesta flowing between 15 and 25 m from the pylorus. The effect of the increase in the pH of digesta along the small intestine on the solubility of these minerals is discussed.

1. Rats were given moderate-selenium (4·5 mg/kg) or low-Se (0·5 mg/kg) diets during gestation and lactation. Their young were given diets with high (10 mg/kg), moderate or low Se contents from weaning, and groups of rats were killed at intervals during the 14-week experimental period.

2. Compared with young rats which received the low-Se diet, those which received the moderate- or high-Se diets had a high incidence of liver lesions and there were changes in liver Se content, haemoglobin concentration, packed cell volume, prothrombin activity, fibrinogen content, spleen weight, body water and serum glutamic–oxaloacetic and glutamic–pyruvic transaminase (L-aspartate: 2-oxoglutarate aminotransferase; EC 2.6.I.I and L-alanine: 2-oxoglutarate aminotransferase; EC 2.6.I.2 respectively) and alkaline phosphatase (EC 3.I.3.I) activities. In those rats which received the high-Se diet the changes were more pronounced than in those which received the moderate-Se diet.

3. In young rats from dams given moderate-Se diets, which were themselves given the moderate-Se diet, the liver Se content decreased continuously, whereas rats given the same diet but from dams which had received the low-Se diet, the liver Se content increased continuously. There was a slight improvement of symptoms of Se toxicity in all groups by the 5th week of the experimental period.

4. The results suggest that there was an adaptation to chronic Se intake.

1. Young steers were fed either 3–4 or 20 h before exposure to a thermoneutral or a moderately cold environment. Measurements were made of total oxygen consumption (total Vo2), respiratory quotient (RQ), blood packed cell volume (PCV), and hind-leg blood flow (leg Q) and oxygen uptake (leg Vo2). The arteriovenous differences in whole blood glucose, lactate and pyruvate, and individual plasma amino acid and urea concentrations across the leg were also measured. Net exchange and fractional uptake of these metabolites by the leg were calculated from these results

2. Cold exposure doubled total Vo2, significantly decreased RQ and significantly increased PCV. Leg Q and leg Vo2 increased 3- to 5-fold and 4- to 13-fold respectively in both feeding groups. Arterial blood glucose increased slightly but significantly in both 20 h- and 3 h-fed steers. There was a substantial increase in mean net leg uptake of glucose in both feeding groups. This was much greater in the 20 h-fed group because of the significant increase in fractional uptake occurring only in this group. Cold did not significantly affect arterial blood lactate or pyruvate levels, but the net leg output of lactate found in both feeding groups in thermoneutrality was increased in the 20 h-fed steers, and reversed to a net uptake in the 3 h-fed animals. Cold caused a small but significant decrease in the total plasma amino acid level in the 20 h-fed but not in the 3 h-fed group; individual amino acid levels or leg uptakes were not affected

3. Feeding before the experiment caused a significant increase in RQ. Leg Q, leg uptake of glucose and leg output of lactate increased after feeding in the thermoneutral environment only. Arterial pyruvate increased significantly, but net leg output was not significantly affected by feeding. Arterial plasma concentration of several individual, but not of total amino acids, increased significantly in both environments, and the net output of many individual amino acids in the 20 h-fed steers was decreased or reversed to a net uptake in the 3 h-fed group in thermoneutrality only

4. The results suggest that blood glucose could be a significant fuel for oxidation in shivering skeletal muscle in young steers, and that output of amino acids from skeletal muscle could not contribute significantly to this increased glucose supply by hepatic gluconeogenesis.

1. The effects of dietary energy level and dietary energy source on protein utilization by plaice (Pleuronectes platessa) were examined by giving diets containing 400 g crude protein/kg to nine groups of fish. Five of these diets contained only lipid as a source of energy (in addition to protein) and their energy contents were varied by increasing the lipid level in a step-wise manner from 56 to 176 g/kg. The remaining four diets contained both lipid and carbohydrate (glucose+dextrin) together as energy sources: two levels of carbohydrate (100 and 200 g/kg) being used at each of two (56 and 86 g/kg) lipid levels

2. Weight gains of plaice given the diets containing only lipid as an energy source did not differ significantly from each other. Weight gains of plaice given diets containing carbohydrate as well as protein and lipid were superior to those given diets lacking carbohydrate

3. Values obtained for protein efficiency ratio (PER) and net protein utilization (NPU) increased with increasing dietary energy level in both those fish given the diets containing carbohydrate and those given diets lacking it. Both PER and NPU values were greater for plaice given diets containing carbohydrate than for fish diets without carbohydrate even when the total energy content of the diets was approximately the same

4. Liver glycogen levels were significantly higher in plaice given diets containing 200 g carbohydrate/kg than in plaice given diets without carbohydrate. Blood glucose levels and hepatic hexokinase (EC 2.7.I.I) levels were not significantly different in plaice given these diets. No glucokinase (EC 2.7.I.2) was detected in plaice given either diet

5. The metabolic fate of glucose carbon in plaice was investigated by injecting the fish intraperitoneally with [U-14C]glucose and examining, 18 h afterwards, the distribution of radioactivity in different biochemical fractions from the fish

6. Glucose was respired much less rapidly in the carnivorous plaice, irrespective of dietary treatment, than in omnivorous mammals (mouse and rat). The rate of production of 14CO2 from [U-14C]glucose by plaice given diets containing carbohydrate was not significantly greater than that by plaice given diets lacking carbohydrate

7. More glucose was incorporated into liver glycogen when plaice were given carbohydrate in their food than when it was absent. Otherwise no differences were apparent in the fate of glucose C by plaice which could be related to the diets used

8. No mortalities occurred nor was any histopathology observed in the plaice as a consequence of the inclusion of carbohydrate in the food.

1. Results of 298 nitrogen balance studies from experiments with male cross-bred lambs, ranging in weight from 3 to 38 kg, which had been either fasted, or fed entirely on liquid diets of varying protein content at various energy intakes up to ad lib. intake, were used to quantitatively describe the effects of the amount and quality of absorbed protein, energy intake and live weight on N balance and total N requirement of lambs.

2. When N intake was less than the amount required, N balance was independent of energy intake, but linearly related to absorbed N and metabolic body-weight (live weight0·75). In the fitted relationship, the coefficient of absorbed N was shown to be an estimate of the biological value of absorbed protein and the coefficient of metabolic body-weight was an estimate of the loss of endogenous N in both urine and faeces. For the milk-based diets used in the experiment biological value was 0·72 and the total endogenous N loss in urine and faeces was 148 mg N/kg0·75 per d.

3. When N intake was in excess of the amount required, N balance in lambs of a constant live weight increased linearly with metabolizable energy (ME) intake, at a rate that decreased with increasing live weight. Similarly at constant ME intake, N balance was a curvilinear decreasing function of metabolic body-weight. When N balance was expressed per unit metabolic body-weight, it was constant for lambs of all weights when ME intake was about 0·23 MJ/kg0·75 per d, but it decreased linearly with increasing metabolic body-weight for ME intakes above this level.

4. N balance of fasted lambs was several times less than predicted by either of the relationships established for fed animals, and was found to be linearly related to metabolic body-weight.

5. The effects of energy intake and live weight on the total N requirement of lambs were determined. When total N requirement was expressed per unit of energy intake, it was found to be constant at 0·9 g N/MJ ME for all lambs irrespective of live weight when ME intake was 0·23 MJ/kg0·7 per d. However, as ME intake/unit metabolic body-weight was raised above this level, N requirement/unit ME intake increased for lambs weighing less than c. 23 kg, but decreased for heavier animals.

1. An intestinal perfusion technique was used in six normal human subjects to study absorption of sixteen individual amino acids from an amino acid mixture simulating casein and from an enzymic hydrolysate of casein, prepared for oral administration to these subjects, which consisted of a mixture of oligopeptides and free amino acids.

2. Total absorption of α-amino nitrogen was greater from the casein hydrolysate than from the amino acid mixture, and the considerable variation in percentage absorption of individual amino acids from the amino acid mixture was much reduced when the enzymic hydrolysate solution was perfused, as a number of amino acids which were poorly absorbed from the amino acid mixture were absorbed to a greater extent from the casein hydrolysate.

3. These findings indicate that after extensive intestinal resections or in malabsorption there might be significant nutritional advantages in the administration of protein hydrolysates rather than amino acid mixtures.

1. Measurement of the vitamin B12 content of baboon tissues showed that the liver contained the highest concentration, followed by the pituitary, kidney, heart, spleen and pancreas.

2. The dietary vitamin B12 requirement of the baboon for the maintenance of satisfactory body stores was between 1 and 2 μg/d.

3. Satisfactory liver vitamin B12 stores were invariably associated with serum levels above 125 pg/ml, whereas liver levels were usually low when the serum level was below 50 pg/ml.

4. Increased methylmalonic acid (MMA) excretion after a valine load occurred when the liver vitamin B12 level was less than 0·40 μg/g. L- and DL-valine were approximately equally effective as precursors of MMA, whereas sodium propionate, whether given orally or intra-peritoneally, was less effective.

5. The distribution of radioactivity along the wall of the intestinal tract after an oral dose of [57Co]cyanocobalamin suggested that the distal half of the small intestine was the main site of vitamin B12 absorption. However, the utilization of vitamin B12 put direct into the middle part of the small intestine was much lower than that of an oral dose.

6. The unsaturated vitamin B12-binding capacity of baboon serum was not related to the serum vitamin B12 level. There was a significant difference between the unsaturated vitamin B12-binding capacities of the two subspecies of baboon (Papio cynocephalus cynocephalus and P. cynocephalus anubis) studied.

1. A study has been made of pure proteins heated either alone or in contact with sugars, so as to cause a severe fall in their reactive lysine contents, and also of commercial protein concentrates.

2. For unheated materials, and for bovine plasma albumin and fat-extracted, dried chicken muscle severely heated in the absence of sugar, Acid Orange 12 binding values (mmol bound dye/kg crude protein (nitrogen × 6·25)) were close to the sum of total histidine, total arginine and reactive lysine contents (mmol/kg crude protein (N × 6·25)), which we have termed HARL values. The dye-binding values and the HARL values were reduced similarly by heat treatment.

3. For materials in which protein and glucose had reacted under mild conditions (37°), the dye-binding capacity with Acid Orange 12 was unchanged even though the HARL value of these materials was considerably reduced. When protein and glucose or sucrose were heated more severely, the dye-binding capacity was slightly lowered but not to the same extent as the reduction in the basic amino acids.

4. Animal feeding-stuffs, whether unheated, industrially processed or deliberately heated, appeared to react with Acid Orange 12 in the same way as the model systems (selected to represent three types of heat damage: ‘advanced’ and ‘early’ Maillard and protein–protein damage).

5. Remazol blue binding values and fluorodinitrobenzene (FDNB)-reactive lysine values were similarly reduced in materials that had been severely heated, either with or without added sugars; however, when protein and glucose had reacted under mild conditions the fall in Remazol blue binding was less than that in FDNB-reactive lysine.

6. For the model materials, binding with cresol red was, in general, higher for heated samples but the results showed no correlation with FDNB-reactive lysine values. For meat and groundnut meals, changes in values after heat treatment were smaller than those that have been reported for soya-bean meals.

1. Colonies of rats have been maintained for twelve generations on diets adequate (dietary-protein energy:total metabolizable energy (NDp:E) 0·I) or marginally deficient in protein (NDp:E 0·068)

2. In the malnourished colony, the proportion of ‘small-for-gestational-age’ offspring was ten times as high as amongst the well-nourished colony, growth was slow, sexual maturation delayed, especially in the females, and, when adult, both sexes were significantly lighter and shorter than adults of the well-nourished colony. Organs, other than the eye, weighed less than those of well-nourished ‘age’ controls, but when expressed relative to body-weight, the brain, pituitary, thyroid, adrenals, testes, thymus and eyes were larger, the pancreas unchanged and the kidneys smaller than those of the well-nourished ‘age’ controls. The relative weight of the liver showed little change, being slightly increased in the males and, like the ovaries, slightly reduced in the females. On a body-weight basis, the brains were about 50% heavier than normal, but in absolute terms were 5–5·5% lighter than those of the well-nourished animals, the cerebellum (10·5% lighter in males and 12·9% lighter in females) being more severely affected than the cerebrum (4% lighter)

3. The young malnourished rats showed increased exploratory activity, transient head tremors and an increased sensitivity to noise, the latter being long-lasting if not permanent. When adult, they showed marked differences in behaviour and learning patterns and it was difficult to attract and hold their attention. In situations demanding a choice the animals were very excited, emitted loud squeals and tried to escape from what was clearly a stressful situation. However, a casual examination of the malnourished adults revealed a rather small, badly groomed, excitable rat without gross abnormalities

4. The findings are discussed in relation to changes found in malnourished human communities.

1. A series of digestibility trials was done using four animals of each of the following species: Friesian cattle (Bos taurus), Boran zebu cattle (Bos indicus), Corriedale sheep, fattailed sheep, eland (Taurotragus oryx Pallas), Coke's hartebeest (Alcelaphus buselaphus cokei Günther), Thomson's gazelle (Gazella thomsonii Günther) and bush duiker (Sylvicapra grimmia L.)

2. Two batches of pelleted food were prepared from ground maize cobs, cassava, wheat bran, maize bran and decorticated cottonseed cake. For each batch, five diets (A–E) were prepared containing 65 (A)–135 (E) g crude protein (nitrogen × 6·25)/kg dry matter. The crude-fibre contents of all the diets were similar (120–138 g/kg dry matter)

3. The animals were given the high-protein diet (E), then given diets with decreasing protein contents finishing with the low-protein diet (A). The antelope and half the sheep were given diets from the first batch of pelleted food, the other four sheep and all the cattle were given diets from the second batch of food

4. In sheep, there were significant differences in digestibility between the two batches of food

5. There were no significant differences in the over-all mean digestibilities of all diets when given to cattle (both species) and sheep. However, with diet E, dry-matter digestibility was higher in sheep than in cattle (P < 0·05): the reverse was true with diet A (P < 0·001). Crude-fibre and crude-protein digestibilities followed a similar pattern. The differences between Corriedale and fat-tailed sheep were not significant. The only significant difference between the two species of cattle was the higher digestibility of crude protein in Borans given diet E (P < 0·05)

6. The over-all mean digestibility of the dry matter was higher (P < 0·001) in hartebeest and duiker than in sheep; in Thomson's gazelle (P < 0·01) and eland (P < 0·001) it was lower than in sheep. The values for crude-fibre digestibilities varied in a similar way

7. The mean apparent digestibility of crude protein was higher (P < 0·001) in eland, hartebeest and duiker than in sheep and gazelle

8. The results are discussed in relation to the feeding habits and digestive physiology of the various species.

1. The extent of propionate metabolism during absorption from the gut and the amounts of L-lactate formed and glucose utilized by the portal-drained viscera were determined in conscious sheep from measurements of portal venous blood flow and portal venous and aortic metabolite concentrations. The sheep were fasted overnight and given primed continuous intraruminal infusions of volatile fatty acids (VFA) at two rates, supplying propionate at 40·0 and 79·9 mmol/h. Measurements were made during the 5th and 6th hours of the infusion, when rumen liquor VFA concentrations were constant.

2. The rate of L-lactate formation by the portal-drained viscera was not affected by the VFA infusions and accounted for approximately 15 % of the probable total lactate entry rate.

3. Considerable amounts of glucose were taken up by the portal-drained viscera, amounting to approximately 35 % of the probable glucose entry rate. If this glucose was metabolized through the glycolytic pathway, this would at all times have accounted for the amounts of L-lactate formed.

4. Portal venous blood flow was positively correlated with VFA infusion rates and with the net amount of propionate appearing in the portal blood.

5. It is concluded that although propionate may be metabolized by the rumen epithelium, the unique pathway of L-lactate formation from propionate is of limited quantitative significance to the animal, although it may be of importance to the rumen epithelium itself.

1. Extended feeding of an essential fatty acid (EFA)-deficient diet to laying hens increased liver size and liver lipid concentration.

2. The specific activities of hepatic lipogenic and glutamate-metabolizing enzymes were increased by feeding the EFA-deficient diet.

3. Restriction of daily food intake to 75 % of ad lib. intake did not affect the response to dietary fat concentration.

4. Hepatic enzyme activities in hens fed on restricted amounts of food and killed just before, or after, the normal daily feeding time indicated no reduced capacity for lipogenesis at the earlier time.