1. An isotope tracer method for estimating methane production in sheep is described.

2. The technique was used to estimate methane produced in both the upper and lower digestive tract and to determine the routes by which it was excreted.

3. Four Merino ewes given lucerne chaff (33 g every hour) were used.

4. Total methane production rate was 21±1.1 (se) ml/min; production in the rumen accounted for 87±1.2% of the total production; 95±1.4% of the methane produced in the rumen was excreted by eructation.

5. Of the methane produced in the lower digestive tract, 89±2.3% was excreted through the lungs and 11% through the anus.

1. Kinetic experiments were done with pepsin (EC 3.4.4.1) using haemoglobin as a substrate in the presence of different metal cations.

2. The activation of peptic hydrolysis with higher concentrations of cupric ions added to the reaction mixture was determined from turnover-rate curves in experiments with constant substrate concentration. With a Cu2+ concentration greater than 1.67 × 10-4M activation was obtained

3. Nickel ions at a concentration of 8.33 × 10-4 M and at higher concentrations also increased pepsin activity. Additions of ferrous ions and zinc ions had no effect.

4. Experiments were done using variable substrate concentrations in the presence of different Cu2+ concentrations. The concentrations of haemoglobin ([S]) at half maximum velocity were determined. The double-reciprocal plots of [S] v. reaction velocity (v) (i.e. I/[S] v. I/v) had no common intersection point. Therefore the kinetics did not correspond to any of the known kinetics. The activation brought about by Cu2+ cannot easily be explained by the study of the kinetics. Certain simple explanations of the phenomenon can be eliminated.

1. The diets and living conditions of nine Asian boys with biochemical, and in most instances also radiological, signs of rickets were compared with those of nine other boys who appeared to be normal. The groups were matched according to age, religion, place of father's origin and boy's own place of birth.

2. There were no outstanding differences between the diets of the boys with, and of those without signs of rickets. All had adequate to high calcium intakes. Most of the boys had low intakes of vitamin D, and those with signs of rickets generally had lower intakes than the normal boys. The food tables used for making the calculations of vitamin D intakes report the amount of the vitamin in the lipid fraction of milk. If it proves to be true that most of the vitamin D activity of milk is in the aqueous fraction, the boys would have been getting considerably more vitamin D than the results suggested, and their average intake may have been about 3.5 μg/d.

3. It was not possible to make any quantitative measure of the exposure of the boys to sunlight. All Asian boys studied appeared to have their bodies more completely covered than British or West Indian boys.

4. The problem of why nine boys had signs of rickets and nine had none has not been solved. It is suggested that those with signs of rickets may have had higher requirements for vitamin D than the others. When the intake of vitamin D is low and exposure to sunlight is minimal, those with high requirements will be the ones to develop signs of rickets.

1. A low-magnesium diet was fed to four sheep, each of which had been surgically prepared with a rumen fistula, a tube into the cranial one-third of the omasum, a tube to the cranial one-third of the abomasum and a re-entrant duodenal cannula. Mg, as gluconate or acetate, was continuously infused for 12–14 d in turn into (1) the caudal duodenal cannuia, (2) the abo-masum, (3) the omasum, (4) the rumen. A continuous infusion of the chromium-ethylene- diaminetetraacetic acid complex (CrEDTA) was maintained to the rumen. The abomasal effluent which flowed through the cranial duodenal cannula was continually sampled and the flow of Mg calculated from the concentrations of Mg and CrEDTA. Blood and rumen fluid samples were taken and urine and faeces collected during each period of Mg infusion.

2. The Mg infused to either the abomasum or omasum was completely recovered at the duodenum, indicating a lack of net absorption of Mg from these stomach compartments. In contrast, 13.7–18.7 mmol (36–61 %) of the Mg infused to the rumen was not recovered at the duodenum which suggested that a substantial net absorption of the infused Mg occurred from the reticulo-rumen. Absorption of Mg caudal to the pylorus was not related to the site of Mg infusion and averaged 3.28 ±0.56 (sem) mmol/d.

3. Compared with the intraruminal infusion, the post-ruminal infusion of Mg was associated with decreased plasma and rumen fluid Mg concentrations, decreased urinary Mg excretion, decreased Mg balance and increased faecal Mg excretion.

4. It is concluded that no significant absorption of Mg occurs from either the omasum or abomasum in sheep and that the reticulo-rumen is the principal site of Mg absorption before the pylorus. Absorption of Mg post-ruminally is insufficient to maintain normal Mg status in the animal.

1. Experiments were done using 8-d-old kids to determine the metabolic effect of feeding a carbohydrate-free diet, and the effects of supplementation of this diet with a small amount of glycerol, sodium propionate or glucose.

2. The experimental (carbohydrate-deficient) diets permitted growth nearly equal to that with the control diet (cow's milk). The kids given the experimental diets generally had lower levels of blood glucose than those given the control diet.

3. With all experimental diets there were increases in the concentrations of plasma lipid and total liver lipid and a decrease in the concentration of liver glycogen; supplementation of the carbohydrate-free diet with glycerol, sodium propionate or glucose had no additional effect on these values.

4. The ingestion of cow's milk produced hyperglycaemia 2 h after feeding, while in kids given the carbohydrate-free diet there was no increase in blood glucose level. The concentration of plasma free fatty acids in the kids given the carbohydrate-free diet was higher than that in control animals 24 h after feeding, suggesting that the kids given the experimental diet preferentially utilize free fatty acids as an energy source.

1. The decrease in specific radioactivity of individual volatile fatty acids (VFA) after a single injection of tracer was monitored. The results obtained indicated the occurrence of a first-order process.

2. Regression analysis indicated the high flux of VFA through the caecal pool, equivalent to 30% of the maintenance energy requirement of the animal.

3. Interconversion of VFA was monitored, and results indicated substantial synthesis of butyric acid from acetic acid.

4. Results were obtained from animals on two dietary regimens, and these were compared with results reported for other species.

1. The contribution to acidification of the stomach contents of pigs by hydrochloric acid secretion or by lactic acid produced by fermentation was studied in fifteen suckling pigs from six litters born and reared either in a ‘conventional’ environment or in an isolated ‘clean’ environment. Sequential samples of stomach contents obtained during periods of up to 24 h were analysed for their chloride and lactic acid contents, pH and total titratable acidity. These values gave a measure of organic and inorganic acids respectively.

2. Six pigs from two litters born and reared in a ‘clean’ environment had acid secretion in the stomach at 2 d of age, and the concentrations of lactic acid in stomach contents remained low (0-40 mmol/1) throughout the suckling period.

3. Eight pigs from three litters born and reared in a ‘conventional’ environment, and a ninth pig born in this environment but moved to the ‘clean’ environment at 24 h of age, had lactic acid in concentrations of up to 250 mmol/l in stomach contents within the 1st week of life. The pattern of lactic acid production (and hence the acidity of stomach contents) was governed by the frequency of suckling.

4. Both between- and within-litter variation in the age of onset of HCl secretion was evident in the group reared in a ‘conventional’ environment, and when HCl secretion did occur it was usually accompanied by a reduction in lactic acid production.

5. It is concluded: (I) that the environment at birth is important in determining the fermentative ability of the stomach flora; (2) that if lactic acid is produced in large amounts in the stomach, it may partly or completely inhibit acidification by HCl.

1. 14C-labelled lysine, glutamic acid and methionine were each administered as single infusions through catheters in the jugular veins of pigs between 28 and 42 d old, receiving either a low-protein (LP) (140 g protein/kg), or a high-protein (HP) (200 g protein/kg) diet. The pigs received 40 g diet/kg body-weight per d.

2. l-[U-14C]lysine and l-[U-14C]glutamic acid were both rapidly removed from the plasma; 3 min after completion of the infusion less than 10% of the activity from the [14C]-lysine, and between 10 and 20 % of the activity from the [14C]glutamic acid remained in the plasma.

3. In pigs killed 15 min after infusion of either [14C]lysine or [14C]glutamic acid 26% of the activity from the dose of lysine was in the liver of those receiving the LP diet, whereas the corresponding value was only 16% for those which had received the HP diet. The uptake of activity from [14C]glutamic acid by the liver was unaffected by the level of protein in the diet. More activity from [14C]lysine than from [14C]glutamic acid was recovered in the spleen, heart and brain.

4. The recovery of the activity from [14C]lysine as 14CO2 in the 6 h after the infusion of the dose was lower for the pigs on the LP diet (2.7 %) than for those on the HP diet (4.8%). The corresponding values for [14C]glutamic acid infusion were 34 and 52% respectively.

5. Supplementing the LP diet with five successive increments of 1.5 g DL-methionine/kg resulted in an increase from 8 to 17% dose in the recovery of activity as 14CO2 from a dose of l-[I-14C]methionine, whereas with the same supplementation of the HP diet the recovery increased from 8 to 24 % dose.

1. A study has been made by gel-filtration techniques of the soluble copper- and zinc-binding proteins in rat liver after both intraperitoneal injection of Cu and dietary Cu supplementation.

2. Liver Cu and Zn concentrations increased after injection of Cu, both metals accumulating in the cytosol, mainly in a fraction with an apparent molecular weight of (about 12 000)

3. When Zn-deficient rats were injected with Cu, there was little change in liver Zn concentration and the occurrence of Cu in the low-molecular-weight form (about 12 000) was more transient. At most periods after injection, Cu accumulated mainly in a fraction with a molecular weight greater than 65 000.

4. When the rats were Cu-loaded by dietary supplementation, virtually no Cu or Zn was found in the low-molecular-weight form in Zn-deficient rats, although they were found in the Zn-supplemented animals.

5. The results suggest that Zn is essential for the accumulation of Cu in this form, but not for Cu to stimulate production of the metal-binding protein by a process requiring active protein synthesis.

1. Livers from rats fed on a standard diet were perfused with whole blood, and infused continuously with glucose and fructose at equimolar rates.

2. Infusion of fructose increased both the secretion of very-low-density-lipoprotein (VLDL)-triglycerides and the incorporation of free fatty acids (FFA) from the perfusate into VLDL-lipids, but neither of these two processes was affected by infusion of glucose.

3. Infusion of fructose decreased the oxidation and increased the esterification of FFA, but glucose infusion had no effect on these processes. When fructose and glucose were infused together there was a further decrease in oxidation.

4. When fructose was infused alone or together with glucose, blood concentrations rapidly became stabilized at those found in the hepatic portal vein in vivo, with similar rates of hepatic uptake to those found in the intact animal. Infusion of glucose alone resulted in continuously increasing perfusate glucose concentrations, and rates of uptake which were only 20 % of those for fructose. Blood glucose concentrations were reduced, and lactate concentrations were increased by fructose infusion, and when glucose and fructose were infused together there was a greatly increased rate of glucose uptake.

5. Liver glycogen was not affected by the infusion of fructose or glucose alone; however, their combined addition significantly increased its concentration.

6. Uptake of perfusate FFA was not affected by either fructose or glucose infusions.

7. The results are discussed in terms of the differences in nutrition and metabolism between glucose and fructose, with particular reference to the development of hyper- triglyceridaemia.

1. The forms of vitamin B12 were determined in foods, most of which had been prepared for consumption.

2. Five forms were detected: adenosylcobalamin, hydroxocobalamin, methylcobalamin, cyanocobalamin and sulphitocobalamin. Adenosylcobalamin and hydroxocobalamin were the predominant forms.

3. The intestinal absorption of [57Co] sulphitocobalamin was estimated and found to be lower than that of [58Co]cyanocobalamin.

1. Seasonal variations in plasma retinol-binding holoprotein concentration have been found in two groups of entire ewes and in a control group of wethers (castrated rams).

2. In each group retinol-binding holoprotein level was minimal in summer and increased to peak values in September just before the autumn breeding season.