1. Five groups of juvenile turbot (Scophthalmus maximus) which had been given a diet free of fat for 12 weeks were given diets in which the lipid component (g/kg) was: oleic acid alone 50, oleic acid 40+linoleic acid 10, oleic acid 40+linolenic acid 10, oleic acid 40+arachidonic acid 10 or oleic acid 40+cod-liver oil 10. These five experimental diets were given for 16 weeks.

2. Weight gains were highest in the group given the diet containing cod-liver oil and lowest in the groups given diets containing oleic acid alone or oleic acid+linoleic acid. Weight gains in the groups given oleic acid+arachidonic acid or linolenic acid were markedly inferior to those of the group given oleic acid+cod-liver oil. It is concluded that arachidonic acid is inferior to polyunsaturated fatty acids of the ω3 series in maintaining growth rate in turbot.

3. Fatty acid analyses of neutral lipids and phospholipids of liver and extrahepatic tissues did not suggest any evidence of desaturation of dietary oleic acid, linoleic acid or linolenic acid by the turbot. These experiments confirm previous isotopic evidence that turbot lack the necessary microsomal desaturases to perform this metabolic transformation.

1. The effect of a diet containing a trypsin inhibitor on the incorporation of radioactively labelled leucine into the pancreatic proteins secreted during stimulation with cholecystokinin-pancreozymin (CCK) was studied in rats.

2. The total output of protein was significantly greater in the rats given raw soya-bean flour (RSF) compared with those given heat-inactivated soya-bean flour (HSF) (controls) in response to the sub- and supramaximal stimulation with CCK, but similar responses were obtained to maximal stimulation with CCK. Total protein output decreased continuously with time after reaching peak values at 90–120 min after the start of stimulation with CCK.

3. The total output of radioactively labelled protein in RSF-fed rats was not different from that of the controls with sub- and supramaximal dose rats of CCK, but was significantly lower than that of the controls in response to the dose rate of CCK which produced maximal rates of pancreatic secretion.

4. The specific activity of radioactively labelled protein increased continuously, while the output attained a constant rate during stimulation with all doses of CCK.

5. We concluded that feeding the trypsin inhibitor-containing diet led to increased secretion of stored pancreatic protein, while secretion of newly synthesized protein was not altered. During the course of prolonged stimulation with CCK, irrespective of diet, there was increasing secretion of the newly synthesized protein compared with the pre-existing stored proteins of the pancreas, but it was unable to compensate for the decreased secretion of pre-formed protein.

1. The adoption of a meal-eating pattern of feeding by rats altered the alkaline phosphatase (EC 3.1.3.1) activity in serum and liver. It was therefore necessary to regulate the feeding pattern of both magnesium-deficient rats and control animals receiving a Mg-adequate diet in order to study the effect of the deficiency.

2. Mg deficiency decreased the activities of alkaline phosphatase and inorganic pyro-phosphatase (EC 3.6.1.1) in serum, kidney and tibia, but increased them in spleen.

3. Addition of a standard concentration of exogenous Mg to tissue extracts usually increased the activity of corresponding enzymes from Mg-deficient and control rats by the same proportion, indicating that the main effect of the deficiency was on the amount of enzyme present rather than on the efficiency of its operation.

4. Certain quantitative differences in the response to exogenous Mg and the activity ratio, alkaline phosphatase: inorganic pyrophosphatase were found between tissues from Mg-deficient and control rats. The significance of these are discussed in relation to the association of the two enzymic activities with the same protein molecule, and the possible occurrence of isoenzymes.

1. Meals were prepared from the seeds of fifteen varieties of cowpea (Vigna unguiculata), one of lima bean (Phaseolus lunatus) and one of yam bean (Sphenostylis stenocarpa), and their methionine content was determined by six different methods.

2. Total methionine content was determined by two chemical methods (ion-exchange chromatography and a colorimetric procedure) and by two microbiological methods. The ‘available’ methionine content was determined by microbiological assay with Streptococcus zymogenes.

3. All the different methods for total methionine determination gave similar results, with much the same high extent of precision.

4. The values for ‘available’ methionine content were similar to or marginally higher than the corresponding microbiological assay values for total methionine content. There was no indication that the methionine in any of the test samples was not completely available.

1. Thirty-five pigs were fitted with single re-entrant cannulas in either the duodenum, jejunum or ileum. A further twenty-four pigs were used in a conventional digestibility trial.

2. Methods for collecting, sampling and returning digesta were developed.

3. A ‘practical-type’ diet and two purified diets were used, fed twice daily.

4. Flow and pH of digesta were measured hourly in the duodenum and jejunum, and every 6 h in the ileum.

5. In the duodenum and jejunum there were clear flow responses to feeding, while such an effect was not found in the ileum where the flow-rate was much lower and more uniform than in the former sites.

6. In the duodenum and jejunum, and within 6 h periods in the ileum, there was considerable variation in the flow-rate between different pigs within each hour but there was less variation in pH.

7. The pattern of flow in the duodenum and jejunum was similar for each of the diets but the total flow and the average pH in 24 h differed significantly between diets. There were more digesta of a lower pH from the ‘practical-type’ diet than the purified diets.

8. The pH in the duodenum was highest after feeding and decreased with increasing time after feeding. In the jejunum and ileum the pH varied over a much smaller range than in the duodenum.

9. Collections for 6 h periods appeared to be insufficiently long to predict the values obtained in 24 h collections with reasonable accuracy.

A system for collection and removal of urine has been developed, consisting of a peristaltic pump controlled by an electronic switch activated by the presence of urine in a funnel and in tubing. For optimum performance, it is necessary to clean parts at regular intervals.

1. Steers, fitted with simple rumen and duodenal cannulas, were given diets of approximately equal parts of flaked maize and hay (A) (containing 16 g nitrogen/kg dry matter (dm)) or diets of flaked maize and straw supplemented with decorticated groundnut meal (B), fish meal (C), or heated (D) or unheated (E) soya-bean meal (containing 24 g N/kg dm). Chromic oxide was given as a marker with the feeds, and flows of different combined sugars at the duo denum estimated from the values for sugars: marker at this site. Contributions of bacterial constituents to these flows were estimated from amounts of RNA present.

2. Rumen bacteria from steers receiving diet A contained approximately 110 g α-dextran-glucose/kg dm and contributed about 60 g α-dextran-glucose/d at the duodenum; bacteria from steers receiving diets B, C, D or E contained 25–40 g α-dextran-glucose/kg dm and contributed about 20–30 g α-dextran-glucose/d at the duodenum. There were no significant differences between different N supplements. About half the α-dextran-glucose, varying amounts of the mannose and galactose, and nearly all the rhamnose and ribose in duodenal digesta were contributed by the bacteria. Almost all the arabinose, xylose and cellulose-glucose was of dietary origin.

3. For steers receiving diet A, mean coefficients of digestibility between mouth and duodenum, corrected where necessary for bacterial contribution, were 0.96, 0.73, 0.58, 0.22 and 0.53 for starch-glucose, galactose, arabinose, xylose and cellulose-glucose respectively. Corresponding mean values when diets B, C, D and E were given, which did not differ significantly amongst themselves, were 0.98, 0.79, 0.81, 0.59 and 0.58. Most values for galactose, arabinose and xylose were significantly higher than the diet A values.

1. Serum caeruloplasmin (ferroxidase I; EC 1.16.3.1) activity has been used as an indicator of copper status of cattle to survey beef herds in Northern Ireland.

2. The main survey covered some 20000 cows on 1200 farms.

3. The results are reported in the form of a map showing areas where herds of low and very-low Cu status predominate. Clinical signs of Cu deficiency in calves were encountered in only two areas.

1. The effect of age on the flow of duodenal digesta and of pancreatic secretion was studied in preruminant calves fitted with duodenal re-entrant and pancreatic sac cannulas. In Expt 1 a comparison was made at 7, 24 and 63 d of age of Ayrshire calves given whole milk, and in Expt 2 Friesian calves given milk-substitute diets were studied during the period 16–37 d of age.

2. For the Ayrshire calves, ad lib. whole-milk intake increased with age, but whole-milk intake on a per kg metabolic body-weight (W0.75) basis did not alter. As the intake increased with age, the whey fluids were passed out of the abomasum more rapidly.

3. As judged by the mean duodenal pH values and the values for ‘chloride ion minus sodium ion’ concentration in the digesta, and for apparent secretions (total quantity recovered at duodenal cannula during 12 h after feeding minus intake) the duodenal digesta became more acid as the Ayrshire calves became older. There was no change with age in the extent of degradation of the milk proteins as indicated by the protein-nitrogen: total N values for duodenal digesta.

4. The volume of pancreatic fluids secreted by the Ayrshire calves increased markedly with age, but when expressed on a per kg W0.75 the volume did not increase after 24 d of age. In absolute terms and also in relation to whole-milk intake or W0.75 there was a large increase in secretion of total protease, a very large increase in α-amylase (EC 3.2.1.1) but no change in trypsin (EC 3.4.4.4) activities with age.

5. In the Friesian calves secretion of pancreatic fluid and activities of α-chymotrypsin (EC 3.4.4.5), α-amylase, lipase (EC 3.1.1.3) and ribonuclease (EC 2.7.7.16, 2.7.7.17) but not trypsin or total protease increased with age.

6. The extent of the increase in secretion of pancreatic enzymes during the first hour after the Friesian calves were fed milk-substitute diets differed between enzymes.

7. The changes in the quantities of pancreatic enzymes secreted are discussed in relation to the changes in the digestibility of milk-substitute diets.

1. The effect of oven-drying on the heat of combustion of rat carcasses was studied and found to produce losses of 10% of the original energy content. Oven-drying also produced a small loss of nitrogen.

2. A method of carcass preparation not involving oven-drying was tested and found to produce suitably homogeneous samples for analysis without any loss of energy.

1. The role of corticosteroids in determining which clinical features of protein-energy malnutrition develop on a deficient diet has been studied by the administration of cortisone acetate to experimentally malnourished rats fed ad lib. on a mixture containing 31 g protein/kg.

2. Daily administration of 1.25 mg cortisone acetate did not affect dietary intake, which remained the same as in saline (9 g sodium chloride/l)-injected controls. Plasma albumin concentrations, however, increased from a low value of 25.7 g/1 to 47.2 g/l and this was accompanied by an increase both in liver weight and protein content. On the other hand, the protein content of muscle decreased.

3. These changes in the protein contents of liver and muscle were associated with alterations in the corresponding free amino acid pools. The free amino acid content of muscle generally decreased, but in liver many amino acids were increased.

1. A study has been made of the effects of dietary zinc supplementation on the development of copper toxicosis in three groups each of eight 12-week-old lambs.

2. None of the lambs receiving 420 mg Zn/kg diet developed Cu toxicosis in the 24-week experimental period, compared with three in the control group receiving 43 mg Zn/kg and possibly one in the group receiving 220 mg Zn/kg.

3. Liver Cu concentrations were reduced by up to 40% in the Zn-supplemented animals, with concomitant reductions, especially in the early stages of the experiment, in the extent of liver damage, as assessed by measurement of plasma aspartate aminotransferase (EC 2.6.1.1) and arginase (EC 3.5.3.1) activities.

4. Plasma and liver Zn concentrations were increased only slightly in the lambs receiving the Zn-supplemented diets, and the only indication of possible toxic effects of the Zn supplements was the development of a slight anaemia in those animals receiving 420 mg Zn/kg diet.

5. The results suggest that the incidence of Cu toxicosis in sheep may be controlled by increasing their dietary Zn intake.

1. A procedure is described for using pivalic acid as an inert reference substance in determination of changes in concentrations of volatile fatty acids (VFA).

2. Pivalic acid in concentrations of up to 80 mmol/l had no effect on production of methane or VFA by rumen contents.

3. Pivalic acid was inert during incubation with rumen contents from sheep given different diets and with samples taken at different times with respect to feeding.

1. Additional protein given to malnourished rats early in pregnancy was found to increase substantially the weight and cellularity of their foetuses and placentas at term.

2. This observation confirms the hypothesis that protein is stored in early pregnancy for use during the period of rapid foetal growth.

1. Carcass fat was determined by extraction with tetrachloroethylene and measurement of the solvent's change in density. The results were comparable in precision to those of a reference method; the new method extracted storage lipid but little structural lipid.

2. The technique is simple, rapid and appropriate for many nutritional studies.

1. In three series of experiments, Na235SO4 was infused into the rumen of sheep consuming a variety of diets. The specific activity of the sulphur in the rumen H2S pool, rumen bacteria and of the S in bacterial cystine were determined.

2. The results showed that, depending upon the diet, the proportion of total sulphur and cystine sulphur in rumen bacteria originating in the rumen H2S pool could be as low as 0.557 and 0.280 respectively.