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 When food was withdrawn for 5 d the concentrations of both hormones declined.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. Evaluation of the germ meal (CGM) of carob seed (Ceratonia siliqua) and its protein isolate was carried out with weanling rats. Comparisons were made with casein, soya-bean meal, whole defatted egg and a soya-bean protein isolate (Promine-D) as protein sources. The growth-promoting effects and certain biological indices were evaluated using the protein efficiency ratio (PER), biological value (BV) and net protein utilization (NPU) bioassay procedures.

2. The unsupplemented CGM had a PER of 1.66 ± 0.09 and an NPU of 0.58 ± 0.013. Addition of DL-methionine at 4, 8 and 12 g/kg diet resulted in a PER of 1.95 ± 0.11, 2.01 ± 0.11 and 1.90 ± 0.11 respectively. The corresponding BV values were 0.80 ± 0.003, 0.78 ± 0.015 and 0.74 ± 0.011, and those for NPU 0.69 ± 0.013, 0.66 ± 0.026 and 0.63 ± 0.020 respectively. The addition of amino acids improved the PER (2.24–2.59), BV (0.78–0.79) and NPU (0.71–0.73) values.

3. The BV and NPU assays for the unsupplemented carob germ isolate were low (BV 0.36 ± 0.016, NPU 0.35 ± 0.015). Supplementation with amino acids resulted in a positive increase with values of 0.66 ± 0.013 and 0.64 ± 0.013 for BV and NPU respectively.

1. Serum prealbumin, transferrin and iron concentrations were measured in ninety-two north Cameroonian children under 5 years of age. The results were grouped according to the blood haemoglobin concentration range in order to show the interactions of anaemia with prealbumin and transferrin concentrations.

2. Transferrin concentration showed a significant negative correlation with serum Fe and percentage saturation of transferrin values. Prealbumin concentration showed a significant direct correlation with haemoglobin but did not correlate with either serum Fe or percentage saturation of transferrin.

3. It is concluded that in regions where Fe-deficiency anaemia is endemic transferrin concentration may be of little value in determining nutritional status. On the contrary, prealbumin seems to be more useful.

1. The rates of entry of urea into plasma, of urea degradation in the gastrointestinal tract, and the partition of that degradation between the rumen and post-ruminal tract were determined by use of [14C]urea and NaH14CO3 in Hereford steers receiving hay diets with or without sucrose. The concentrations of plasma urea and rumen ammonia were varied by infusions of urea into the rumen or abomasum.

2. For all diets, plasma urea concentration was related to urea entry rate, to degradation of urea in the whole gastrointestinal tract, and to its degradation in the post-ruminal tract, but the relationship with its degradation in the rumen was poor.

3. Degradation of urea in the rumen was related in a multiple regression in a curvilinear manner in three groups of diets (pasture-hay alone, pasture-hay–lucerne (Medicago sativa) mixtures, diets with sucrose), and negatively to rumen ammonia concentration for pasture-hay diets, and diets with sucrose.

4. Ruminal clearance of urea (rate of urea degradation per plasma urea concentration) was negatively related to the rumen ammonia concentration for steers given diets with sucrose, of pasture-hay with or without urea infusions. Provision of sucrose in the diet significantly increased clearance.

5. Enhanced urea degradation in the rumen associated with dietary sucrose supplements accounted for 0.4 of additional microbial N synthesis in the rumen.

6. The partition of transfer of urea to the rumen via saliva and through the rumen wall is discussed.

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. The levels of the brush-border enzymes sucrase (sucrose glucohydrolase, EC 3.2.1.48), isomaltase (oligo-1,6-glucosidase, EC 3.2.1.10), maltases 2 and 3 (glucoamylase, EC 3.2.1.3), lactase (β-galactosidase, EC 3.2.1.23) and trehalase (EC 3.2.1.28) and adsorbed pancreatic α-amylase (EC 3.2.1.1) have been measured at twenty-one positions along the small intestines of eighty-four pigs of different ages ranging from 3 weeks to 4.5 years. The state of dilation of the intestine at the sampling points was noted.

2. The levels of sucrase and isomaltase increased with age throughout the age-range studied. Trehalase and the glucoamylases increased with age up to 200–300 d of age. Lactase decreased with age over the whole age range.

3. For the pigs above 10 weeks of age, the distribution pattern of the brush-border enzymes along the intestine did not change with age. Each enzyme had a characteristic distribution curve, with low values at the proximal and distal ends and a peak which was proximal in the instance of lactase and trehalase and approximately mid-way along the gut with sucrase, isomaltase and the glucoamylases.

4. The pattern of distribution of the brush-border enzymes altered with age in the piglets, but approached the adult pattern by 8 weeks.

5. Piglets weaned at 3 weeks had higher levels of sucrase, isomaltase and glucoamylases at 5 weeks than piglets left on the sow. At 8 weeks of age the piglets weaned at 3 weeks still had higher sucrase and isomaltase levels than those on the sow.

6. There was a very close correlation between the sucrase and isomaltase levels, and between the maltase 2 and maltase 3 levels in all the samples, and a fairly close correlation between all these four enzymes.

7. The level of α-amylase increased with age but showed no regular distribution pattern, its irregular fluctuations being related to the presence or absence of dilation of the intestine at the time of slaughter rather than to the position along the intestine.

1. α2HS-glycoprotein accumulates in bone and dentine and its plasma levels could vary in conditions in which the rate of bone formation is altered.

2. The plasma concentration of this protein was found to be lower in thirteen children suffering from protein–energy malnutrition compared with age-matched healthy preschool children.

3. This finding might be associated with the phenomenon of stunting in protein–energy malnutrition.

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. Large intestine electromyograms were recorded from four pigs receiving successively three diets containing different amounts of fibre (standard cereal diet, milk substitute and milk plus 170 g bran/kg). For each diet the mean retention time of a marker added to one meal was determined. Three occurrences of spontaneous constipation were also studied.

2. Slow waves were observed in the colon only during 10% of the recording time at a frequency of 10.3 ± 1.1/min. Two kinds of spiking activity were recorded on the colon: short spike bursts of 0.5–2 s duration and long spike bursts of approximately 7 s duration. Long spike bursts alone were recorded on the caecum.

3. The mean retention time of the marker was 40 h on the standard diet, 120 h on the milk-substitute diet, and 66 h on the milk plus bran diet.

4. On the standard diet, approximately 1500 colonic long spike bursts were recorded daily and short spike bursts occupied 15% of the recording time. On the milk diet, the number of long spike bursts decreased significantly (P < 0.01) to 500/d and the short spike bursts increased significantly (P < 0.05) to take up to 21% of the time. Intermediate values (1100/d and 19%) were observed when bran was added to the milk diet. The lowest values for long spike bursts (300/d) and highest values for short spike bursts (44% of the time) were observed in constipation.

5. It is concluded that long spike bursts are associated with propulsion of intestinal contents and that short spike bursts are non-propulsive.

Tissue ascorbic acid (AA) contents of approximately 12 and 100% saturation respectively were produced in two groups of guinea-pigs. The ‘low-AA’ group had significantly lower muscle carnitine concentrations than the ‘high-AA’group. There was no concomitant emergence of the symptoms customarily regarded as characteristic of hypovitaminosis C. It is concluded that muscle carnitine (β-OH-γ-(trimethylamino) butyric acid) is a highly-sensitive indicator of tissue AA contents; this could account for the lassitude and fatigue reported to precede the emergence of frank scurvy in man.

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. [U-14C]glucose was infused intravenously into conscious lactating goats exposed to thermoneutral or cold environments for a total of 24 h. The irreversible loss of glucose from the whole body and uptake of glucose by the mammary gland was measured and glucose utilization in the udder was studied by measuring the incorporation of radioactivity into carbon dioxide in mammary venous blood, into milk lactose and milk triglyceride-glycerol.

2. Exposure to cold increased the circulating level of glucose and slightly, though not significantly, increased the non-mammary irreversible loss of glucose.

3. The extraction of glucose from the circulation by the udder fell, the secretion of lactose by the udder also fell and this correlated closely with the reduced secretion of milk in the cold.

4. Simultaneous measurements of the concentrations of insulin, growth hormone and corticosteroids in the arterial plasma were made.

5. The plasma concentration of corticosteroids increased significantly in the cold.

6. It is concluded that reduced glucose uptake and lactose synthesis by the udder are important factors which reduce milk secretion during cold exposure.

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.

1. Dry matter and crude protein (nitrogen × 6.25) digestibility of four poultry diets determined by an in vitro method using the intestinal fluid of pigs was significantly correlated with corresponding in vivo digestibility values obtained with hens.

2. The intestinal fluid could be lyophilized and stored for at least 35 d without losing its activity on digestion.

1. Refection, resulting in an increased supply of riboflavin to riboflavin-deficient rats through coprophagy, was demonstrated on a sucrose-based diet when sensitive biochemical tests of riboflavin status were employed: these included measurements of NAD(P)H2:glutathione oxidoreductase (EC 1.6.4.2); succinate:(acceptor) oxidoreductase (EC 1.3.99.1) and NADH:(acceptor) oxidoreductase (EC 1.6.99.3).

2. The use of tail-cups to eliminate coprophagy, and hence refection, resulted in a more rapid and reproducible progress into severe deficiency.

3. The occurrence of refection on a sucrose-based diet may account for hitherto unexplained differences between previous publications on the biochemical effects of riboflavin deficiency.

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.

1. Circulating concentrations of some hormones and metabolites and nitrogen balance were measured in lactating beef and dairy cows given daily injections of growth hormone (GH) and were compared to values before injection. Changes in milk yield and composition were recorded in these cows and in additional cows injected with GH fragments.

2. GH, but not GH fragments, raised milk yield while milk composition did not change. GH injection caused a large, rapid increase in the level of the hormone in blood and slower, smaller increases in the concentrations of insulin, prolactin and thyroxine. Blood metabolite levels were unaltered except for a rise in glucose concentration in beef cows during GH injection and a fall in 3-hydroxybutyrate concentration in the same cows after the injections ceased. An increase in N output in milk was partly balanced by a reduction in urinary N so that N retention did not change significantly.

3. GH caused a reduction in food intake in the beef cows.

4. The results are discussed in relation to control of partition of nutrients in the lactating cow, where GH is considered to play an important role. It was concluded that this role may be in increasing the supply of energy metabolites for milk synthesis, rather than a direct effect on the activity of the mammary gland.