1. Changes in total retinol-binding protein (RBP), the holoprotein (holoRBP) and prealbumin (PA) concentrations have been monitored in plasma of thirty protein- and vitamin A-deficient preschool children from within a few hours up to 7 weeks after treatment with retinol and a good-quality protein diet.

2. The children were classified into groups according to nutritional status as having either kwashiorkor, marasmus-kwashiorkor or marasmus, and given formula diets whose protein and energy contents increased stepwise from 1 g and 105 kJ/kg body-weight respectively up to 4 g and 733 kJ/kg body-weight after 4 weeks. Retinol was administered in the forms of retinyl palmitate either orally or intramuscularly.

3. PA and total RBP were determined by electroimmunoassay procedures and the holoRBP by its fluorescence after separation from other plasma proteins.

4. RBP in plasma of the vitamin A-deficient child is largely denatured and incapable of binding administered retinol, which must first be taken up by the liver before native holoRBP is released. An increased pool of native apoprotein accumulates in the liver during vitamin A deficiency which is released into plasma quickly after retinol uptake to form peak concentrations of total and holoRBP approximately 3 h after dosing intramuscularly and 6 h orally.

5. The accumulated pool of RBP was highest in livers from the marasmus group and lowest in those from the kwashiorkor group, reflecting their relative capacities to synthesize plasma proteins.

6. The mean plasma concentrations of total and holoRBP for the various groups were minimal 24–48 h after dosing with retinol and then improved almost linearly over the following week.

7. Mean plasma PA concentrations of the various groups on admission were also in order of the severity of their malnutrition. There was little or no change in this protein concentration over the first 24 h after dosing with retinol, but thereafter the mean values rose almost linearly over 2 weeks. Albumin on the other hand changed little during the first week. The results show that PA is the more sensitive measurement of protein nutritional status.

1. Rats which have been maintained for ten to twelve generations on diets of low protein value were rehabilitated in utero (group P), from birth (group F) and from 4 weeks of age (group W).

2. Group W showed little change in physique, behaviour or learning, indicating that for recovery to be effective refeeding must begin earlier.

3. Group F just failed to attain full physical recovery (90%) whereas group P overgrew by 18.6% in weight and 8.5%; in length.

4. In a test designed to evaluate learning ability rehabilitated rats of groups P and F were significantly less successful than normal rats, but more successful than rats of group W or rats of the original undernourished colony.

5. Rehabilitation for a further two generations in groups F and P corrected any residual physical and behavioural defects but produced no further improvement on the Lashley (I 938) jumping platform.

1. The proportion of iron liberated from twenty foods was measured after incubation in vitro with human gastric juice.

2. Results with samples of gastric juice obtained from one subject on ten occasions and from sixteen subjects on a single occasion showed good agreement, the proportions of Fe liberated covering the entire range from zero for egg to 1.0 for wine.

3. Where there were small variations between the results obtained with different samples of gastric juice attempts were made to correlate these with peptic activity, various proteins and mucoproteins, pH and total and free acid; the only factors that varied with the proportions of Fe solubilized were the various measures of acidity.

4. The results correlated highly with those of Layrisse et al. (1969) for the in vivo absorption of Fe from similar foods, although the samples used were not the same.

5. The amounts of Fe solubilized when the foods were mixed with bran, oats or egg (known to reduce the in vivo absorption of Fe from foods) were less than calculated from the sum of each, with two exceptions.

6. The results obtained with human gastric juice differed from those obtained with in vitro methods prcviously reported, namely treatment with dilute hydrochloric acid and double incubation with pepsin plus HCI at pH 2.5 followed by adjustment to pH 7.5.

7. The amount of Fe solubilized from soya-bean flour by gastric juice was compared with that solubilized by pepsin plus HCI; both systems were shown to be pH dependent but the amount of Fe liberated with pepsin- HCI was much greater than that known to be absorbed by man in vivo.

8. It is suggested that incubation with human gastric juice may permit in vitro analyses of ‘chemically- available’ Fe in foods and thus be of value in food composition tables in terms of ‘Fe equivalents’ even though the amounts absorbed in vivo are subsequently influenced by other ingredients of the diet and by the Fe status of the individual.

1. The effect of supplementing barley diets with urea (U), extracted, decorticated groundnut meal (GNM) or Peruvian fish meal (PFM) on rumen bacterial protein synthesis and the proportion of undegraded food protein passing to the duodenum of sheep has been examined.

2. Three wethers were given isonitrogenous, isoenergetic diets containing (g/kg dry matter (DM)): U 20, GNM 106 or PFM 78, the crude protein (nitrogen × 6.25) contents being 139, 145 and 148 respectively. The sheep were fed hourly, the mean daily intake of DM being 0.634 kg.

3. Rumen bacterial protein synthesis was determined using 35S and diaminopimelic acid (DAPA) as bacterial markers and polyethylene glycol (PEG) and chromic oxide as markers of digesta flow. Rumen volatile fatty acid (VFA) production rate was determined by a continuous infusion of [I-14C]acetate. 4. and DAPA gave similar estimates of the proportion of bacterial N in the trichloroacetic acid- precipitable nitrogen of the rumen digesta, the mean value being 0.86. The VFA production rate did not vary significantly between diets, the mean being 5.8 mol/24 h. The flow of bacterial N from the rumen was calculated from the PEG and Cr2O3, estimates of flow and the 35S and DAPA estimates of the proportion of bacterial N in the rumen. and DAPA gave similar values (mean 12.5 g/24 h) and Cr2O3, gave a slightly lower value (11.5 g/24 h) than PEG (13.5 g/24 h). Dietary effects, averaged over the four methods, were not significant; the values were 13.0, 13.4 and I 1–0 g/24 h for the U, GNM and PFM diets respectively.

5. Duodenal samples were taken from two 12h continuous collections from re-entrant cannulas and the DM flow adjusted to total recovery of Cr2O3,. The mean recovery of Cr203 at the duodenum was 0.798. The rates of flow of DM were 0.296,0.311 and 0.334 kg/24 h and of non-ammonia-N (NAN) 13.5, 15.2 and 15.4 g/24 h on the U, GNM and PFM diets respectively.

6. The concentrationsof the essential amino acids in duodenal digestaweregenerally higher with the PFM diet than with either of the other two diets. The flow of most amino acids through the duodenum was generally higher on the PFM and GNM diets than on the U diet.

7. The energetic efficiency of bacterial protein synthesis was calculated to be 2.1 g bacterial N/mol VFA or 28 g bacterial N/kg organic matter fermented in the rumen.

8. From the estimates of bacterial N flow from the rumen and NAN flow through the duodenum it was calculated that 0.22 and 0.69 of the supplemental N from GNM and PFM respectively passed through the rumen undegraded.

1. Transfer potentials were obtained from everted jejunal sacs prepared from fed euthyroid, fasted euthyroid, fed hypothyroid and fasted hypothyroid rats by addition of serial concentrations of the dietary sugars glucose and galactose and the glucalogues 3-O-methyl glucose, α-methyl glucoside and 6-deoxy-D-glucose to the incubation fluids. The kinetic parameters of ‘apparent Michaelis constant’ (apparent Km) and maximum transfer potential difference (pdmax) obtained from the results were used to characterize the changes in the electrogenic transfer mechanisms for these substrates.

2. Analysis of the significant differential changes in values for ‘apparent Km’ and pdmax for the two dietary sugars and the three glucalogues indicated heterogeneity in the mechanisms for sugar transfer across the intestine and suggested a minimum of four possible carriers.

3. The validity of using glucalogues to characterize changes in the transfer mechanisms for the dietary sugars in different dietary and hormonal states was assessed. None of the kinetic parameters for electrogenic glucalogue transfer matched those for the dietary sugars in all the experimental conditions. The employment of glucalogues to assess changes in electrogenic transfer mechanisms for dietary sugars can thus lead to invalid conclusions.

4. Fasting decreased the ‘apparent Km’ of the dietary sugars and the glucalogues. However, the pdmax values for glucose, galactose, and α-methyl glucoside decreased whereas those for 3-O-methyl glucose and 6-deoxy-D-glucose did not.

5. Hypothyroidism showed different effects in fed and fasted intestine. Because hypothyroidism induced a reduction in food intake, separation of the direct effects of the condition on electrogenic transfer from reduced food intake effects was not possible.

1. Measurements were made of the nitrogen and energy balances of pigs of 30, 60 and 90 kg given a conventional diet at various daily rates.

2. Body protein synthesis was estimated from the irreversible loss of leucine from the blood following the infusion of [1-14C]leucine, and from the oxidation of the labelled amino acid.

3. Protein synthesis (g/d) increased by 2.17 for each 1 g increase in daily protein accretion and by 1.55 for each 1 g increase in daily protein intake.

4. At 30 kg, pigs close to energy equilibrium synthesized 270 g protein daily compared with 406 g and 512 g when their ration supplied twice and three times their maintenance requirement.

5. There was a close correlation between the daily urinary excretion of urea + ammonia and total amino acid catabolism estimated from the catabolism of leucine, but the latter underestimated the observed excretion by 2.5 g N/d.

6. The results imply that protein turnover accounts for only a proportion of the heat production associated with protein deposition.

1. Semi-synthetic diets containing 200 g protein/kg were meal-fed for 1.5 h to groups of rats. The contents of the whole small intestinal tract were collected and the amount of soluble calcium was determined.

2. In the rats given 200 g casein/kg diet, formation of a fraction containing macrophosphopeptide in the small intestine was confirmed by gelfiltration of the intestinal contents on Sephadex G-25. However, this macrophosphopeptide fraction was not found when casein alone was fed.

3. In the intestinal contents at 2.5 h after ingestion, the amounts of both soluble Ca and phosphorus were significantly higher in rats fed the casein diet than in those fed diets containing egg albumin, isolated soyabean protein or an amino acid mixture. However, the amount of insoluble Ca was least in rats fed the casein diet.

Two experiments were conducted to study the digestion of nitrogenous constituents in the rumen, small intestine and caecum and colon of sheep given diets of grass silage or grass silage and barley. Three silages were used. One was made from first-harvest grass in the spring and the others from regrowth grass cut in either early autumn or late autumn. All were of perennial ryegrass (Lolium perenne) and were preserved with formic acid.

Expt 1 involved a comparison between the spring silage given alone (644 g dry matter (DM)/d) and the spring silage supplemented with barley (151 g DM/d). The intakes (g/d) of total nitrogen for the silage diet and for the supplemented diet were 14.89 and 17.36. Corresponding values (g/d) for N passage were 15.55 and 18.53 (P < 0.01) at the duodenum, 6.01 and 7.09 at the ileum and 5.06 and 5.52 in the faeces. The barley supplement had no significant (P < 0.05) effect on rumen ammonia-N- concentration.

Expt 2 involved a comparison between the two autumn-cut silages each offered at a level of feeding of approximately 700 g DM/d. The intakes (g/d) of total N for the early-cut silage and for the late-cut silage were 21.67 and 15.62 respectively. Corresponding values (g/d) for N passage were 17.10 and 16.96 at the duodenum, 6.65 and 6.80 at the ileum and 4.5 and 5.22 in the faeces. The concentration of NH3-N in the rumen was significantly (P < 0.001) higher with the early-cut silage than with the late-cut silage.

In both experiments the rates of bacterial crude protein (N × 6.25) synthesis in the rumen, estimated using α, ε-diaminopimelic acid as a marker, were low, 142 and 161 g crude protein/kg organic matter apparently digested in the rumen for the spring silage and the spring silage and barley diets respectively, and 68 and 103 g crude protein/kg organic matter apparently digested in the rumen for the early-cut autumn silage and the late-cut autumn silage respectively. For all diets there was a relatively low contribution of bacterial crude protein to the duodenal passage of crude protein and the amounts of individual amino acids ingested in the diets had a marked influence on the amino acids passing to the duodenum and as a consequence on the mixture of amino acids taken up from the small intestine.

The results are discussed in relation to the nutritive value of silage N for ruminants.

Two experiments were conducted to study the digestion of organic matter, gross energy and carbohydrate constituents in the rumen, small intestine and caecum and colon of sheep given grass silage diets. Three silages made from perennial ryegrass (Lolium perenne) with formic acid as an additive were used. One was made from first-harvest grass in the spring and the others from regrowth grass cut from a single sward in either early autumn or late autumn. Expt I involved a comparison between the spring silage given alone or supplemented with barley (silage:barley, 4:I dry matter (DM) basis). Expt 2 involved a comparison between the early-cut and late-cut autumn silages.

In Expt I, supplementation of the silage with barley resulted in a non-significant (P > 0.05) reduction in the proportion of digestible energy (DE) and digestible organic matter digested in the rumen and an increase in the proportions digested in the small intestine. There were also pronounced effects of barley on ruminal cellulolysis and the proportion of digestible cellulose broken down in the rumen was reduced (P < 0.05) from 0.90 to 0.77. There was an increased passage of α-linked glucose polymers to the duodenum but even with the supplemented diet 0.91 of the dietary polymers were digested in the rumen. The molar proportion of propionic acid in the rumen tended to be reduced and there were increases in the proportions of butyric acid (P < 0.01) and acetic acid.

In Expt 2, the digestibility of organic matter, gross energy and cellulose in the early-cut silage was higher (P < 0.01) than in the late-cut silage but there were no significant (P < 0.05) differences between silages in the sites of digestion of these constituents. However, the molar proportion of acetic acid in the rumen was higher (P < 0.01) and the molar proportion of propionic acid was lower (P < 0.01) with the late-cut silage than with the early-cut silage.

The results are discussed in relation to the voluntary intake and utilization of high-digestibility silages.

The daily rates of synthesis of protein by the whole body and by the individual tissues were determined in two Hereford × Friesian heifers (236 kg and 263 kg live weight), and a dry Friesian cow (628 kg live weight).

The rate of whole-body protein synthesis (g protein/d) was estimated from the total flux through the blood of [3H]leucine and [3H]tyrosine following infusion at a constant rate for 8 h.

The fractional rates of protein synthesis (ks) in the tissues (g synthesized/d per g tissue protein) were obtained after slaughter of the animals at the end of the infusion period. The fractional rate of protein synthesis was calculated assuming that the specific radioactivity of free tyrosine in either the blood (to give ks, b) or the tissue homogenate (to give ks, h) defined closely the specific radioactivity of the amino acid precursor for protein synthesis. Total protein synthesis (As, b or As, h; g/d) in an individual tissue was calculated as the product of ks, b) (or ks, h) × protein content.

Based on the total leucine flux, i.e. without correction for oxidation, 1.6 kg protein were synthesized daily in the heifers; for the cow this value was 2.0 kg/d.

The sum of the daily total synthesis in the major tissues (muscle+bone+brain, gastrointestinal tract (GIT), liver, hide) gave values of 1.4–1.9 kg/d based on As, b, and 2.2–3.0 kg/d based on As, h.

The percentage contributions of the individual tissues to the total protein synthesis were similar in all three animals, for example based on As, h muscle was 12–16; carcass (muscle+bone+brain) 32–33; GIT 38–46; liver 7–8; skin 14–21%.

The contribution of muscle to total synthesis estimated from the leucine flux was 19–22%; this value is in agreement with those calculated on the same basis for other species.

The energy cost of protein synthesis was estimated to account for a maximum of 30% of heat production.

A simple procedure using 35S incorporation for the measurement of microbial protein in abomasal or duodenal digesta of ruminants was developed and tested.

Microbial protein synthesized in the rumen was labelled with 35S by intraruminal infusion of 35SO4 and a microbial fraction was isolated by differential centrifugation.

35S not bound by micro-organisms and present as inorganic 35S in whole digesta and in microbial fractions was oxidized to 35SO4 and the samples were brought into solution by acid-hydrolysis. 35SO4 was precipitated as Ba35SO4.

The proportion of microbial non-ammonia-nitrogen (NAN) in digesta NAN was determined as 35S:NAN (digesta) ÷ 35S:NAN (microbial).

In sheep offered grass nuts at maintenance level of feeding, 48% of NAN flowing through the abomasum was of microbial origin. NAN flow to the small intestine was estimated using chromic oxide as a marker and it was calculated that 49% of the grass N was degraded in the rumen.

1. The effect of acute duodenal infusion of 99Mo-labelled sodium tetrathiomolybdate on caeruloplasmin (ferroxidase; EC 1.16.3.1) was examined in sheep. The diamine oxidase activity of this enzyme with respect to two substrates, p-phenylenediamine and o-dianisidine (both at their apparent Km concentrations) was inhibited.

2. The 99Mo appeared rapidly in plasma and was at first present predominantly in a trichloroacetic acid insoluble form; inhibition of oxidase activity was related to the levels of TCA-insoluble Mo. The behaviour of the copper prosthetic groups of caeruloplasmin was altered since some plasma Cu precipitated with the protein fraction after TCA treatment. The appearance of TCA insoluble Cu was related to the level of TCA-insoluble 99Mo and corresponded to the inhibition of diamine oxidase activity.

1. The rate of utilization (k) of labelled thyroxine increased when energy intake, given as standard pig meal, was doubled from 20 to 40 g/kg body-weight per d. When the bulk of food was increased, but not its energy content, the value of k did not change. Ambient temperature was constant throughout the experiment.

2. Groups of pigs were given pig meal at 20 g/kg body-weight, 40 g/kg body-weight or 20 g/kg body-weight plus a supplement. The supplement was of equivalent energy content to 20 g pig meal/kg body-weight and consisted of coconut (high-fat), fish meal (high-protein) or glucose. The values of k were similar on diets (g/kg body-weight) of 40 pig meal, 20 pig meal plus coconut, and 20 pig meal plus fish meal. When the supplement was glucose however the values of k were similar to that for 20 g pig meal/kg body-weight.

The plasma concentrations of T4, and triiodothyronine were not affected by eating a meal, or by changing the energy intake presented as pig meal. A comparison between pigs given 20 g pig meal/kg body-weight plus supplements of bran, coconut, fish meal or glucose revealed differences in the concentration of both hormones. When food was withdrawn for 5 d the concentrations of both hormones declined.

1. Vitamin D-depleted, housed sheep were given diets providing fixed intakes of cholecalciferol ranging from 0.0 to 0.8 μg/kg body-wt per d for 220 d. Thereafter they were shorn, deprived of dietary cholecalciferol and turned out from 30 June to 30 November. The concentration of 25-hydroxyvitamin D (25-OHD) in serum was determined at frequent intervals.

2. The serum concentrations of 25-OHD took approximately 10 weeks to stabilize after which they reflected dietary intake over the range 0.1–0.4 μg/kg body-wt per d. For intakes of 0.4 and 0.8 μg/kg body-wt per d the mean maximum concentrations were similar, but the rates of increase differed. The latter was proportional to the logarithm of intake over the range studied.

3. Changes in serum 25-OHD due to insolation were similar in all sheep regardless of their starting values, and consequently in some animals reached levels considerably greater than from the dietary source.

4. Although the response of serum 25-OHD to the higher dietary intakes appeared to be limited there was no evidence of any such control over the response to endogenously-synthesized vitamin.

1. Three experiments were conducted to investigate the relationships between blood pyruvate carboxylase (pyruvate: carbon dioxide ligase (ADP-forming), EC 6.4.1.1; PC) activity, growth performance and dietary biotin level in broilers under different husbandry conditions. Blood PC activity was also used to gain information on the ingestion of biotin of faecal origin by birds housed on wood shavings and the effect of steam-pelleting on the biotin content of diets.

2. Blood PC activity and relationship to dietary biotin level were similar in birds kept under different husbandry conditions.

3. Biotin requirement for growth was higher in birds kept under conditions that allowed them to reach their growth potential more fully.

4. The contribution of biotin of faecal origin to the biotin intake of birds housed on wood shavings was negligible at 3 weeks of age but by 7 weeks was equivalent to approximately 0.01 mg/kg diet.

5. Steam-pelleting did not affect the stability or availability of biotin of natural or synthetic origin in diets.

6. It is concluded that blood PC activity is a good criterion of biotin status and requirement in fast-growing

1. Cereal-based diets containing 0, 500, 1000 or 2000 mg added copper/kg were offered ad lib. to laying hens for 8 weeks. All the hens were subsequently offered the control diet (no added Cu, 7.5 mg Cu/kg).

2. Hens from each treatment were killed at 0, 2, 4, 6 and 8 weeks after removal of the Cu-supplemented diets. Records were kept of body-weight, food consumption and egg production.

3. After slaughter, blood haemoglobin, packed cell volume, serum Cu and aspartate aminotransferase (AAT; EC 2.6.1.1) were assayed. The liver, kidneys, oviduct, ovary, gizzard, caeca and bile duct were weighed.

4. Mean Cu, zinc and iron concentration of liver, kidneys and caecal contents were determined.

5. The adverse effects of Cu on body-weight, food intake, egg production and liver, oviduct, ovary, gizzard and bile weights were rapidly reversed by removal of added Cu from the diets.

6. Greatly enhanced liver Cu concentration resulted from feeding the high-Cu diets but this effect was rapidly reversed on removal of added Cu from the diets. Liver Fe concentration showed a less marked but similar effect.

7. The Cu concentration of caecal contents was increased by Cu supplementation and rapidly reduced after withdrawal of the Cu-containing diets.

1. Zinc deficiency in young rats reduced both the total alkaline phosphatase (EC 3.1.3.1) activity and Zn concentration in serum, kidney, small intestine and femur.

2. Addition of 0.01 mM-exogenous Zn had no greater activating effect with extracts of kidney, small intestine and femur from Zn-deficient than control rats, indicating that the main effect of the deficiency was on the amount of enzyme present rather than the efficiency of its operation. Exogenous Zn increased the activity of enzyme in serum of Zn-deficient rats, but it was still lower than in the serum of control animals.

3. Electrophoresis on polyacrylamide gel separated the alkaline phosphatase activity from all tissues into two bands. The bands had similar electrophoretic mobilities and appeared to be qualitatively identical in corresponding tissues from Zn-deficient and control rats.

4. Zn deficiency eliminated the first band found in serum from control rats and it had selective effects on the activity of individual bands in other tissues. The major inhibitory effect was on the first bands of enzyme activity in kidney and femur, but in small intestine only the second band was affected. In liver the activity of the first band was increased and that of the second band decreased by similar amounts.

The effect of varying dietary levels of maize oil and tripalmitin (0–250 g fat/kg) on hepatic lipogenesis and the levels of hepatic fatty acid synthetase (FAS), glucose-6-phosphate dehydrogenase (EC 1.1.1.49; G6PD), malic enzyme (EC 1.1.1.38, 1.1.1.39, 1.1.1.40; ME) and glucokinase (EC 2.7.1.2; GK) was examined in meal-fed mice.

2. Meal-fed mice compared to mice fed ad lib. show enhanced hepatic lipogenesis as demonstrated by an increased rate of in vivo fatty acid synthesis and increased levels of FAS, ME and G6PD. The level of GK in meal-fed mice was unchanged by meal feeding.

3. Maize oil more effectively reduced in vivo hepatic lipogenesis than tripalmitin in meal-fed mice.

4. Maize oil more effectively reduced the hepatic levels of FAS, G6PD, ME and GK than tripalmitin in meal-fed mice.

5. The increased inhibition by maize oil is observed at all levels of fat in the diet investigated and has been shown not to be due to decreased carbohydrate intake nor to differences between the absorption of maize oil and tripalmitin.