1. In three separate experiments, four groups of five to eight young male rats were fed either (i) a high-protein diet, for which the net dietary protein: total metabolizable energy ratio (NDp:E) was 0.1 (HP diet); or (ii) a low-protein diet, for which NDP:E was 0.04 (LP diet). In both these groups, food intake was ad lib In group (iii) the HP diet was given in an amount approximately equal to that taken by the LP group fed ad lib. (HP-restricted). In group (iv) rats were fasted for 48 h after receiving the HP diet (HP-fasted). Each experiment lasted 4 weeks.

2. In the LP and HP-restricted groups, food intake was about 50% of that of the HP rats, while body-weight, after 4 weeks on diet was about 35% and 55% of that of HP rats, for LP and HP-restricted respectively. Both groups of malnourished rats gained some weight during the experiment.

3. Measurements of oral glucose tolerance and plasma insulin levels were made in the fourth week. LP and HP-restricted rats both showed low fasting insulin levels and low insulin to glucose ratios during the glucose tolerance tests; the LP rats were more seriously affected.

4. At the end of the fourth week the rats were killed and blood, liver and gastrocnemius muscle were analysed. LP rats showed specifically and consistently low values for haemoglobin and plasma protein concentration, and low activities of hepatic glucose-6-phosphatase (EC 3.1.3.9) and of alanine aminotransferase (EC 2.6.1.2) in liver and muscle. The activity of hepatic aspartate aminotransferase (EC 2.6.1.1) was, if anything, increased. The plasma amino acid concentrations and ratios showed a specific fall in branched-chain amino acids. Liver fat concentration was consistently elevated. The HP-restricted rats had normal values for haemoglobin, plasma protein and liver fat, and near-normal values for plasma amino acids. Hepatic alanine aminotransferase showed increased activity compared with HP rats, but muscle alanine aminotransferase showed reduced activity. The HP-fasted rats had increased haemoglobin, plasma protein and liver fat concentration, and very low liver glycogen concentrations. Hepatic alanine aminotransferase activity was elevated. Plasma alanine concentration was specifically reduced.

5. The results are consistent with suppression of gluconeogenesis, liver dysfunction and essential amino acid deprivation in LP rats. These biochemical changes found in rats on a low intake of a diet of low protein and high carbohydrate value are similar to those found in kwashiorkor. An equally low intake of a diet of good protein value (HP-restricted) led to marginally better growth, accompanied by biochemical signs of increased gluconeogenesis, analogous to those reported for nutritional marasmus. This nutritional state was not biochemically identical with that of acute fasting.

6. The results are discussed in terms of the consistency of the rat model, and its contribution to understanding biochemical changes found in infant malnutrition.

1. Twenty-four energy and nitrogen balances were determined using twenty-four crossbred cows (Brown Swiss × Sahiwal) during their midstage of lactation. Energy balances were estimated by subtracting milk energy and heat production from the metabolizable energy (me) intake. Heat production was estimated by indirect calorimetry, by collection and analysis of respiratory gases. The cows were given amounts corresponding to 90, 110 and 130 % of the me and 90 and 110% of the digestible crude protein (DCP) standards of the (US) National Research Council (1966).

2. Energy requirements were estimated by partitioning the me intake for maintenance, milk production and energy gain or loss by multiple regression of energy balance values. Heat production (and thus energy balance) was corrected for excess N intake.

3. Energy requirements for maintenance were 585.18, 580.17 and 574.41 kJ me/kg body-weight0.75 per d for cows in negative balance, cows in positive balance and for all cows, respectively.

4. The efficiency of utilization of me for milk production was 68.52, 65.48 and 66.12% respectively, for cows in negative balance, for cows in positive balance and all cows. Energy required per kg fat-corrected milk production was 4.580, 4.791 and 4.746 MJ me for the respective groups of cows.

5. The efficiency of utilization of me for tissue gain was 67.67 and 64.86 % for cows in positive balance and for all cows respectively.

1. Pullets were given from 1-d-old diets containing 1.6, 4.1, 8.1 and 12.0 g Mg/kg. Only small effects of these diets on live weight, food consumption, egg number, egg weights or egg-shell thickness were observed except at the highest level (12.0 g Mg/kg) which caused diarrhoea and an appreciable lowering of the live weight of growing pullets. A further group was given from point-of-lay a diet containing 9.3 g Mg/kg.

2. Eggs laid on 3 consecutive days from each of eighteen hens were collected at intervals of 3 weeks until the birds were 68.5 weeks old. Eggs laid on the 3rd day were used to determine the initial proportion of thick egg-white present and also the concentration of Mg, Ca, Na and K in the thick egg-white. Eggs laid on the 1st and 2nd days were stored at 20° for 20 d to establish the proportion of thick egg-white remaining after storage.

3. With the unsupplemented diet the proportion of residual thick egg-white after storage of eggs for 20 d at 20° was 306, 161 and 305 mg/g total egg-white when the hens were 26.5, 53.5 and 68.5 weeks of age respectively. When the diet containing 9.3 g Mg/kg was given, the proportion of thick egg-white after storage remained approximately 400 mg/g throughout the period of the trial.

4. The mean Mg concentration in the thick egg-white of eggs laid by hens given unsupplemented diets was 5.77 mm. The addition of extra Mg to the diet increased the content of Mg in the thick egg-white, for example when the diet contained 9.3 g Mg/kg the mean concentration rose to 7.69 mm.

1. A comparison was made of the composition of milk from front and rear teats in four sows. There were small and not significant differences in fat, protein and lactose contents, and in the fatty-acid composition of the milk fat with the exception of the 18:3 acid where the difference was also small but significant.

2. The effects of intravenous infusions of glucose and insulin in lactating sows on milk secretion and blood composition were investigated in two sows.

3. Intravenous infusion of glucose had no effect on blood plasma glucose concentration but increased the yields of lactose, protein and water.

4. Intravenous infusion of insulin depressed plasma glucose concentration and the yields of lactose and water. The yield of protein was unaffected.

5. It is concluded that differences between the non-ruminant (the sow) and the ruminant in the responses in milk secretion to glucose infusion may be related to differences in the sensitivity to insulin of mammary tissue.

1. Samples of rumen digesta were taken at different times after giving calves various dried forage or hay and cereal diets and mixed bacteria were separated.

2. For calves receiving dried forage only, the carbohydrate content of mixed bacteria varied with time after feeding, reaching a maximum of approximately 140 g/kg dry matter (DM) after 0.5-1 h, decreasing to about 60 g/kg DM after 4 h.

3. Replacement of part of the dried forage with glucose to give a similar metabolizable energy intake but approximately half as much nitrogen, produced a similar pattern of change with time after feeding but resulted in a markedly increased maximum bacterial carbohydrate content (approximately 230 g/kg DM). Addition of urea to this diet reduced the bacterial accumulation of carbohydrate to approximately the same level as was found in samples from calves receiving forage only diets. For the forage diets the carbohydrate content fell to 60-100 g/kg DM 4 h after feeding. For the hay and cereal diet the value was 170 g/kg DM at this time.

4. Changes in bacterial carbohydrate content were largely a result of changes in storage polysaccharide (α-dextran) content.

5. Crude protein (N × 6.25) and ash contents of mixed bacteria decreased after feeding with all-forage diets, but returned to approximately fasting levels within 4 h. At this time samples from calves receiving dried forage and glucose diets contained less CP and more ash (approximately 450 and 220 g/kg DM respectively) than those from calves given diets of dried forage only (approximately 525 and 180 g/kg DM respectively).

6. CP, total carbohydrate and ash content of mixed rumen bacteria contributed approximately 0.80 g/g DM.

7. Sodium, potassium, calcium, magnesium and phosphate accounted for approximately 0.50 g/g bacterial ash.

1. A study was made in goats of the response in terms of milk production, nitrogen utilization, plasma amino acids and amino acid uptake by the mammary gland, to postruminal infusion of casein. Goats in early lactation, housed in metabolism cages, were fed on 2.5 kg basal ration/d (containing 111 g crude protein (N × 6.25)/kg) and were given, by infusion into the abomasum, 0, 15, 30 or 45 g casein/d.

2. Milk production increased from 2.41 kg/d on the basal ration to 2.52, 2.80 and 2.94 kg/d in response to infusions of 15, 30 and 45 g casein/d respectively. Milk composition was unaffected except for milk fat, which was slightly decreased during infusions of the higher levels of casein.

3. The goats were found to be in positive N balance on the basal ration. Milk N output increased with casein infusion; the increase was equivalent to a maximum of 49% of the infused N.

4. The concentration of glucose in arterial blood plasma was decreased at the highest level of casein infusion, but that of plasma urea N was unaffected by treatments.

5. Casein infusions increased the concentrations of total indispensable amino acids and the ratio, indispensable: dispensable amino acids in arterial plasma. Arterial concentrations and mammary extractions of most indispensable amino acids were increased, but only a few increases were statistically significant (P < 0.05).

6. Comparison of individual indispensable amino acids absorbed from the intestine with output in milk indicated that methionine was probably the first limiting amino acid.

7. The results of the experiment were compared to those of similar experiments with cows that have been reported by other workers. The possible ways in which the infused casein may have caused the responses were discussed. However, no firm conclusions regarding the mechanism involved could be drawn from the results of the present study.

1. The comparative effects of raw soya beans on food intake, growth, digestive organ weight, and enzyme activities in goslings and chicks were studied.

2. Goslings were more affected than chicks by the ingestion of a raw soya-bean diet (RSD) in the following ways: reduction in food intake and growth rate; increase in relative weight of the digestive organs; reduction in specific activities of lipase (EC 3.1.1.3), amylase (EC 3.2.1.1) and chymotrypsin (EC 3.4.4.5) in the pancreas (not affected in chicks); greater inhibition of trypsin (EC 3.4.4.4), chymotrypsin and amylase in the intestinal contents of goslings than of chicks.

3. Addition of methionine to the RSD improved food intake and growth rate more in goslings than in chicks.

4. The interrelationships between enzyme activities, food passage rate, nutrient absorption and food intake regulation are discussed.

1. Young male rats were used in five experiments to study the utilization for growth of methionine sulphoxide, and the relationship between the sulphoxide content in the diet and the level of microbiologically determined methionine activity in blood or blood plasma. In one nitrogen-balance experiment methionine and methionine sulphoxide were compared as supplements to a casein diet and a fish-meal diet.

2. Methionine sulphoxide was poorly utilized for growth when tested as the sole sulphur amino acid in an amino acid diet. Substitution of one-third of the sulphoxide with cystine improved utilization so that it approached that of methionine.

3. Methionine alone and in combination with methionine sulphoxide were added to a soya-bean-meal diet. The sulphoxide showed no adverse effect on growth.

4. Fish meal in which methionine had been oxidized to methionine sulphoxide was tested alone and in combinations with unoxidized fish meal. Only when the oxidized meal was given alone was there an appreciable effect on growth. The fish meals used were low in cystine.

5. Whereas both methionine and methionine sulphoxide improved the N balance when a casein diet was given, there was no effect when a fish-meal diet was given.

6. There was a linear relationship between methionine sulphoxide content in the amino acid diets and the methionine activity in the blood plasma. Methionine sulphoxide added to a soya-bean-meal diet or present in oxidized fish meal gave a curvilinear relationship, and the observed activities were lower than with the amino acid diets. Methionine activity in blood could not be used as an indicator of moderate amounts of methionine sulphoxide in protein-containing diets.

1. Balances of twenty trace elements (silver, arsenic, gold, bromine, cadmium, cobalt, chromium, caesium, copper, iron, mercury, lanthanum, molybdenum, rubidium, antimony, scandium, selenium, samarium, tungsten and zinc) have been determined in four male patients during total parenteral nutrition including fat emulsion and a special solution for addition of Fe, Zn, manganese, Cu, fluorine and iodine, besides calcium and magnesium, to the infusion solutions.

2. The analyses for trace elements were made with the aid of an ion-exchange technique based on neutron activation, and combined with subsequent gamma spectrometry.

3. The intended intravenous supply of trace elements corresponded approximately to the analysed supply. However, all the other trace elements determined were found to be unintentionally administered in small amounts.

4. There was a substantial retention of Fe. Other elements retained were Ag, Co, Cr, Cu, Sb, Sc and W.

5. Particularly Br and Rb were lost by the patients, but negative balances were also found for As, Au, Cd, Cs, Mo, Se and Zn. However, Zn was retained by one patient with short bowel syndrome.

6. The serum concentrations of thirteen (Ag, Br, Co, Cs, Cu, Fe, Hg, Mo, Rb, Sc, Se, W and Zn) of the trace elements were found to have some decrease during the period of total parenteral nutrition, mostly in accordance with the corresponding balance values. Fe, in particular, was found to have the directional change in concentration.

7. The administration of trace elements is recommended in long-term total parenteral nutrition.

1. From 5 weeks of age, control and experimental rats were given diets containing 210 and 31 g protein/kg respectively, and killed for analysis at 0, 2, 5, 8, 12 and 20 d after the start of the experiment. At these times estimates were made of plasma albumin concentration, plasma volume and total vascular and extravascular albumin mass.

2. Plasma albumin concentrations were significantly lower in the experimental animals when compared to controls at 8, 12 and 20 d but plasma volumes (ml/kg body-weight) tended to be greater in the former animals. Total vascular albumin mass (g/kg body-weight) was significantly less in experimental animals compared to controls at 8 and 20 d, but was significantly reduced below values at 0 d only at 20 d.

3. Extravascular albumin mass (g/kg body-weight) was significantly lower in experimental animals in comparison with controls at 2, 5, 8, 12 and 20 d and significantly reduced below values at 0 d at 5, 8, 12 and 20 d.

4. Whole-body albumin mass was significantly reduced at 5, 8, 12 and 20 d when compared both with controls killed at the same time and animals killed at 0 d. Measurement of the ratio, extravascular albumin mass: vascular albumin mass indicated a significant redistribution of whole-body albumin mass at 5 and 20 d and mean values for this ratio were always lower in experimental animals than in controls.

5. It was concluded that measurement of plasma albumin concentration does not indicate the true extent of whole-body albumin losses in protein deficiency since total vascular albumin mass is, to some extent, maintained at the expense of extravascular albumin mass.

1. The incidence of colchicine-induced lesions in the germinal epithelium of the rat duodenum was studied in young rats in an early stage of zinc deficiency and in their pair-fed controls. At both dose levels of colchicine used, a marked increase in the amount of cell damage was observed in the duodenum of Zn-deficient rats as compared with the pair-fed, control (Zn-supplemented) rats.

2. No statistical interaction between Zn and colchicine was demonstrable, and no lesions were found in the duodenum of animals that had not been treated with colchicine.

3. The results are discussed in relation to the effects of Zn deficiency in animals and the possible involvement of Zn in the maintenance of the integrity of microtubular structures.