1. The influence of dietary meat and meat stock intake on urinary excretion of 3-methylhistidine (3MH) was examined in human adults.

2. In the absence of 3MH ingestion for 48 h, the study subjects adjusted to an intrinsic urinary 3MH: creatinine value. If the meat and meat stock-free diet was maintained on subsequent days, only minute diurnal variations occurred, and the values of random urine samples during the day were representative of the 24 h 3MH: creatinine value.

3. The mean 3MH: creatinine value (SD) for a group of adults (n 7) was 0·105 ± 0·023 (μmol of 3MH/mg creatinine), which is approximately 35% lower than the corresponding value in healthy growing infants (0·148 ± 0·039) (Seashore et al. 1981).

4. Ingestion of meat soup and meat causes different patterns of urinary excretion of 3MH which are consistent with the finding that meat extracts, such as soup and stock, contain considerable amounts of 3MH. The 3MH contents of beef, chicken and turkey were 3·8 ± 0·15, 3·0 ± 0·09 and 2·3 ± 0·29 μmol/g dry wt meat respectively. All three meats contained a water-soluble 3MH-fraction (% total 3MH: beef 8, chicken 21, turkey 23). Amino acid analysis of the soluble fraction with or without hydrochloric acid hydrolysis demonstrated free 3MH in chicken and turkey (5·2 and 2·8% of the total respectively) but not in beef.

5. Patients undergoing urinary 3MH measurements should maintain a diet that is free not only of solid meats, but also of meat stock. The ingestion of commercial food products (e.g. frozen or canned meals, sauces, pizza, etc.) may impair the validity of such measurements because of their meat-stock content.

6. A dietary regimen is presented which is based on a shorter 12 h urine collection. The shorter collection time is satisfactory in the light of the steady rate of 3MH-excretion after 2 d of a diet free of meat and meat stock.

1. Fluoride content in ninety-three individual food items from a hospital in a fluoridated area was determined by ashing (total fluoride) v. unashing (inorganic fluoride) analysis.

2. No discrepancy between the two methods was found by food group but two dry cereals and black pepper did show significantly more fluoride after ashing. The reason for the unavailability before ashing was not determined.

3. Daily fluoride intake was estimated at 1·783 mg which is midway between the 1·211 and 2·201 mg reported from studies in which composite diets were analysed.

4. Daily intake from food at 0·4 mg was one-quarter of the daily total intake of 1·8 mg; a ratio consistent with those previously reported in serum, urine and bone between residents from a non-fluoridated v. fluoridated community.

1. Male Wistar rats were fed on semi-synthetic diets containing cooked white kidney beans (Phaseolus vulgaris) or equivalent levels of protein and carbohydrate.

2. No change was observed in over-all nitrogen balance in animals fed on the bean diet, but there was a two-to three-fold increase in their faecal excretion, compared with control rats. This was compensated by a decrease in urinary-N excretion.

3. Homogenized small intestinal mucosa, prepared from bean-fed animals, showed at 28%increase in protein content compared with control material.

4. Measurements of 3H-labelled thymidine turnover indicated that mucosal cell exfoliation was increased by approximately 35% in the small intestines of bean-fed rats compared with controls.

5. It is concluded that though a diet rich in cooked P. vulgaris leads to someincrease in mucosal cell turnover in the small intestine of rats, the consequent increasein mucosal protein loss could not account for the increased faecal-N excretion seen in these animals.

1. Four groups of rats were fed for 49 d on one of four semi-purified diets, without added cholesterol and containing 230 g/kg of the following isolated proteins: casein, whey, soya-bean or sunflower.

2. Whey, soya-bean and sunflower proteins, when compared with casein, decreased the level of serum high-density-lipoprotein (HDL)-cholesterol. These low cholesterol levels were accompanied by an increase in the daily faecal excretion of neutral sterols and bile acids in the case of soya-bean protein, and by a decrease in the liver cholesterol content, when rats were fed on whey protein.

3. Considering the amino acid composition of the four purified proteins, we observed that serum total and HDL-cholesterol levels had a significant positive correlation with tyrosine and glutamic acid, and a negative correlation with cystine and alanine.

4. The present study showed that the hypocholesterolaemic effect of dietary proteins was not related to their animal or vegetable origin.

1. In order to test the suggestion that a dietary excess of leucine may be a precipitating factor in pellagra, rats were fed on diets that provided 15 g leucine/kg in excess of requirements for 7 weeks from weaning. This led to a significant reduction in the concentrations of nicotinamide nucleotides in liver and blood. The effect was only apparent when the diets provided less than a minimally adequate amount of nicotinamide, so that the animals were dependent on the synthesis of nicotinamide nucleotides from tryptophan to meet all or part of their requirements.

2. Urinary excretion of N1-methyl nicotinamide was not a useful indicator of tissue concentrations of nicotinamide nucleotides, and seemed not to be adequately sensitive to differentiate between minimal adequacy and marginal deficiency, as demonstrated by changes in concentrations of nicotinamide nucleotides in liver and blood.

3. The addition of leucine to incubation media for the measurement of enzyme activity in tissue homogenates at concentrations within the physiological range, led to a significant activation of tryptophan oxygenase (L-tryptophan: oxygen oxidoreductase (decyclizing), EC 1.13.11.11) and significant inhibition of kynureninase (L-kynurenine hydrolase, EC 3.7.1.3). The effect on tryptophan oxygenase may not be physiologically significant, in view of the considerable range of activity of this enzyme under normal conditions. However, the inhibition of kynureninase, which was primarily competitive with respect to the substrate, probably is physiologically significant, and was enough for this enzyme to become a probable rate-limiting step in tryptophan metabolism and nicotinamide nucleotide synthesis. Other enzymes of the tryptophan – nicotinamide nucleotide pathway were not affected by the addition of leucine to the incubation medium.

4. Feeding 15 g leucine/kg diet in excess of minimum requirements had no effect on the activities of tryptophan oxygenase or kynureninase in liver homogenates. This may reflect the reversible competitive nature of the inhibition of kynureninase by leucine, and hence be an artefact of the incubation procedure. Rats fed on the high-leucine diets excreted significantly more kynurenine than did control animals, which is evidence of inhibition of kynureninase in vivo.

5. It appears that a dietary excess of leucine, of the order of 15 g/kg above requirements, may be a precipitating factor in pellagra when there is reliance on the synthesis of nicotinamide nucleotides from tryptophan to meet a part or all of the requirements, but not when minimally adequate niacin is available from the diet.

1. Non-haem iron absorption from a variety of vegetable meals was studied in parous Indian Women, using the erythrocyte utilization of radioactive Fe method.

2. The studies were undertaken to establish whether Fe absorption could be correlatedwith the chemical composition of the foodstuff.

3. Addition of the following organic acids commonly found in vegetables, improved the geometric mean Fe absorption from a basic rice meal as follows: from 0·028 to 0·085 with 1 g citric acid, from 0·031 to 0·081 with 15 mg ascorbic acid, from 0·048 to 0·095 with 1 g L-malic acid, from 0·041 to 0·096 with 1 g tartaric acid. The only exception was oxalic acid; the addition of 1 g calciumoxalate to cabbage (Brassica oleraceae) was associated with some depression in Fe absorption from 0·320 to 0·195.

4. There was a marked inhibition of the geometric mean absorption when 500 mg tannic acid was added to a broccoli (Brassica oleraceae) meal (0·015 v. 0·297). Sodium phytate (2 g) caused a similar, though less profound inhibition (0·035 to 0·152).

5. When 3 mg ferrous sulphate was added to different vegetables the geometric mean absorption varied widely. Vegetables of low Fe bioavailability were wheat germ (Triticum aestivum) 0·007, aubergine (Solanum melongena) 0·007, butter beans (Phaseolus lunatus) 0·012, spinach (Spinacea oleraceae) 0·014, brown lentils (Lens culinaris) 0·024, beetroot greens (Beta vulgaris) 0·024 and green lentils (Lens culinaris) 0·032. In contrast, bioavailability was moderate or good with carrot (Daucus carota) 0·098, potato (Solanum tuberosum) 0·115, beetroot (Beta vulgaris) 0·185, pumpkin (Cucurbita mixta) 0·206, broccoli 0·260, tomato (Lycopersicon esculentum) 0·224, cauliflower (Brassica oleraceae) 0·263, cabbage 0·320, turnip (Brassica rapa) 0·327 and sauerkraut 0·327.

6. All the vegetables associated with moderate or good Fe bioavailability contained appreciable amounts of one or more of the organic acids, malic, citric and ascorbic acids.

7. Poor Fe bioavailability was noted in vegetables with high phytate contents (e.g. wheat germ 0·007, butter beans 0·012, brown lentils 0·024 and green lentils 0·032).

8. The fact that a number of vegetables associated with low Fe-absorption turned bluish-black when Fe was added to them, suggested that the total polyphenol content in them was high. The vegetables included aubergine spinach, brown lentils, green lentils and beetroot greens. When the total polyphenol content in all the vegetables tested was formally measured, there was a significant inverse correlation (r 0·859, P < 0·001) between it and Fe absorption. The inverse correlation between the non-hydrolysable polyphenol content and Fe absorption was r 0·901 (P < 0·001).

9. The major relevance of these findings is the fact that the total absorption of non-haem-Fe from a mixed diet may be profoundly influenced by the presence of single vegetables with either marked enhancing or inhibiting effects on Fe bioavailability.

1. Whole-milk powders containing 25 g water/kg were stored for up to 9 weeks in sealed aluminium containers at elevated temperatures. Lysine and other essential amino acids were measured by chemical and microbiological methods.

2. Storage at 60° resulted in the progressive formation of lactulosyl-lysine. After 9 weeks, 30% of the lysine groups were present in this form. The powders still retained their natural colour and the levels of tryptophan, methionine, cyst(e)ine and leucine remained unchanged.

3. Storage at 70° resulted in the formation of lactulosyl-lysine followed by its complete degradation with the development of browning. Available tryptophan, methione, leucine and isoleucine decreased progressively during storage.

4. The different methods for lysine determination gave widely dissimilar results. The direct fluorodinitrobenzene (FDNB) technique and reactive lysine from furosine were considered to be the most reliable methods. The FDNB-difference, dye-binding lysine, Tetrahymena and Pediococcus methods all seriously underestimated reactive or available lysine in heat-damaged milk powders. Tetrahymena and Pediococcus appeared to utilize lactulosyl-lysine as a source of lysine.

5. The results are discussed in relation to storage and distribution of milk powders in hot climates.

1. Storage of milk powder under unfavourable conditions accelerates the normally slow deterioration in nutritional quality. The effects of such storage on the water-soluble vitamin composition were examined.

2. (a) Spray-dried whole milk containing 25 g water/kg was stored at 60° and 70° and sampled weekly to 9 weeks. (b) Spray-dried whole milk and skimmed milk were adjusted to contain 40 and 100 g water/kg and stored at 37° in nitrogenand in oxygen. Samples were taken for analysis at intervals during storage.

3. The samples were analysed for eight B-complex vitamins and ascorbic acid, and also for total lysine, ‘reactive lysine’ and ‘lysine as lactulosyl-lysine’.

4. Storage at 60° caused rapid destruction of folic acid (53% loss at 4 weeks) and slower loss of thiamin, vitamin B6 and pantothenic acid (18% at 8 weeks). There was no change in the content of riboflavin, biotin, nicotinic acid and vitamin B12. At 70° the rate of destruction of the four labile vitamins was much increased; 18% or less survived at 4 weeks.

5. At 37° and 40 g water/kg there was little change in total and ‘reactive’ lysine during storage for 57 d. Lactulosyl-lysine was demonstrably present butatlow concentration. There was considerable loss of folate (72%) and ascorbate (91%) during storage for 30 d in O2, but no significant loss in N2. Thiamin fell by approximately 12% in 57 d, equally in O2 and N2. The content of the remaining vitamins was unchanged. At 100 g water/kg there were progressive Maillard changes. During 27 d in N2 the colour changed from cream to palebrown, but in O2 there was no perceptible colour change. Total lysine fell by 20% in 27 d, and ‘reactive lysine’ by 30%. Folate was stable during 16 d in N2, but largely (94%) destroyed in O2. Ascorbic acid was also destroyed in N2 as in O2. Thiamin fell by 41% in 27 d, equally in O2 and N2. Vitamin B6 was more labile, especially in N2, falling by 71% in 16d.

6. With skimmed-milk powder containing 100 g water/kg, storage at 37° in O2 and N2 gave much the same results as for the corresponding whole-milk powder. The presence of milk fat had no marked effect on the stability of the water-soluble vitamins.

7. Destruction of vitamins was clearly linked to the progress of Maillard-type reactions and was strongly influenced by time and temperature of storage, moisture content and, in some instances, by the presence of O2.

1. Mature Merino ewes were given either a low-zinc diet (4 mg/kg) or an adequate-Zn diet (50 mg/kg) for all or part of pregnancy.

2. The ewes consuming the low-Zn diet consumed 25% less feed than those given the adequate-Zn diet during the last 115 d of pregnancy.

3.Zn concentration in the plasma of Zn-deficient pregnant ewes declined from 0·7 to 0·3 mg/1.

4. The lambs born to Zn-deficient ewes weighed less and had reduced concentrations ofZn or less total Zn, or both, in the whole carcass, liver and pancreas.

5. A reduction in activity of alkaline phosphatase (EC 3.1.3.1) in the liver and a slight reduction in thymidine kinase (EC 2.7.1.21) activity in the thymus was also observed in Zn-deficient lambs.

6. The Zn-deficient ewes deposited approximately 63 mg Zn into each single-born lamb;this indicates that during the last third of pregnancy the developing foetuses were accumulating the equivalent of 35% of the total dietary Zn intake of the ewes.

1. In three experiments, mature Blackface wethers were given freeze-stored Agrostis festuca herbage by continuous feeder.

2. In Expt 1, on separate occasions [U-14C]threonine, [U-14C]glucose and NaH14CO3 were infused over 12 h periods to obtain estimates of irreversible loss rate (ILR) of threonine, glucose and carbon dioxide in the plasma and of the exchange of C between these metabolites.

3. In Expts 2 and 3, during periods when glucose and threonine metabolism were examined, glucose loss across the kidneys (23–29 g/d) was induced by infusion of phloridzin.

4. Results from the four sheep used in Expts 1 and 3 are presented as three-pool models. They indicate that threonine ILR (7·8 g/d; 3·1 g C/d) was approximately three times the estimated rate of absorption of exogenous threonine (1 g C/d). Glucose ILR was approximately 76 g/d (mean ± SE; 30·3 ± 0·57 g C/d). Only 0·3% of the glucose-C (0·09 g/d) was derived directly from threonine-C (i.e. 3% of the threonine-C ILR). Bicarbonate ILR was 170 ± 7·3 g C/d, and glucose contributed 11·1 ± 3·52 g C/d to this, accounting for 51 ± 4·4% of glucose-C ILR. Threonine contributed 0·20 ± 0·026 g C/d to the bicarbonate-C ILR, accounting for only 6·4 ± 0·87% of the threonine-C ILR.

5. When, in Expts 2 and 3, phloridzin was infused, glucose ILR was increased by 28 ± 1·5% and bicarbonate ILR was increased by 13 ± 2·4%. Threonine ILR (3·1 g C/d) was not increased, but the metabolic distribution of threonine-C was altered. The transfer of threonine-C into glucose and CO2 was increased by 39 and 69% respectively to 0·125 and 0·45 g C/d, accounting for 4 and 13% of the threonine ILR respectively.

6. Both technical and metabolic considerations which affect interpretation of these results in terms of rates of catabolism of threonine and of quantitative estimates of gluconeogenesis from threonine are discussed.

1. The irreversible loss rate (ILR) of glucose, bicarbonate and threonine were determined in six twin- and triplet-bearing ewes on three occasions during the last 6 weeks of gestation.

2. Three of the ewes (group S) were given conventional rations of hay plus concentrates so that their blood ketone levels did not rise over this period. The other three ewes (group H) were given a fixed intake of hay throughout; their blood ketone levels rose, but remained at subclinical levels.

3. The results are presented in the form of three-pool open-compartment models for each period. There was an increase in the glucose ILR for both groups over the 6-week period, but the over-all increase (mean ± SE) was much greater (p < 0·001) in group S (35·1 ± 2·43 g carbon/d) than in group H (11·3 ± 1·28 g C/d). Similarly, increases in bicarbonate ILR were also higher in group S (161 ± 11·2 g C/d) than in group H (63 ± 21·7 g C/d). However, whereas with group S ewes, receiving supplementary feed, this increase was progressive throughout the 6 weeks, with the group H ewesthe increase which occurred over the last 3 weeks of gestation (56 ± 26·3 gC/d) was much greater than that which occurred over the preceding 3 weeks (7 ±4·7 g C/d). This pattern was also evident in the oxidation of glucose to CO2.

4. In contrast to the previously mentioned findings, neither threonine ILR nor the amount of threonine converted to glucose or catabolized to CO2 changed significantly over the 6-week period.

5. The results are discussed in the light of findings presented in the previous paper that the amount of threonine used in catabolic processes can alter if a glucose-only sinkis created in wether sheep.

1. The apparent absorption values of individual amino acids from two samples of feather meal (FM) were determined in the lower ileum of chicks fed on diets containing magnesium ferrite as a marker.

2. The average absorption values for FM amino acids were low, approximately 0.50, as compared with approximately 0.85 for soya bean, used as a control. Values for individual amino acids from FM differed distinctly, ranging from 0.20 to 0.70. Low values were obtained for aspartic acid, histidine, lysine, glutamic acid and cystine.

3. An indication of the low absorption of the previously-mentioned amino acids was obtained by analysing the amino acid composition of the FM residues undigested by pepsin or pancreatin.

4. The reasons for testing the apparent rather than the true absorption are discussed.

1. Six pigs, initially of 35 kg mean live weight, were each fitted with a re-entrant cannula. This was formed on either side of a short pouch of duodenum into which the pancreatic duct opened and which contained a simple cannula linked to the centre of the re-entrant cannula.

2. Each pig received two diets: diet A was based on wheat starch, sucrose and casein, while diet B was based on barley and soya-bean meal. The diets were given in equal amounts at 12 h intervals.

3. Digesta and pancreatic juice were collected continuously during three 12 h periods for each pig on each diet.

4. Mean duodenal output: dietary intake values for diets A and B respectively were: digesta 1·80, 2·86; dry matter 1·05, 1·03; nitrogen 1·05, 1·06; trichloroacetic acid (TCA)-soluble N 7·69, 9·10; glucose 0·97, 0·89. For diet A the proportion of TCA-soluble N in total N rose from 13 to 50% during 12 h, while it was approximately 50% throughout 12 h for diet B.

5. Mean total pepsin (EC 3.4.23.1) activities (units/24 h) were 760449 (diet A) and 1466571 (diet B).

6. Salivary and gastric secretions were calculated to be approximately 4 and 8 kg/24 h for diets A and B respectively.

7. Mean flows in pancreatic juice (g/24 h) for diets A and B respectively were: juice 1204, 2182; protein 10·94, 12·10; N 1·98, 2·14; ash 9·46, 17·31; sodium 3·88, 6·91; potassium 0·23, 0·54: calcium 0·031, 0·046; phosphorus 0·024, 0·026.

8. Mean total enzyme activities (units × 10−3/24 h) for diets A and B respectively were: trypsin (EC 3.4.21.4) 138, 114; chymotrypsin (EC 3.4.21.1) 84, 84; carboxypeptidase A (EC 3.4.2.1) 5, 4; carboxypeptidase B (EC 3.4.2.2) 15, 17; amylase (EC 3.2.1.1) 1061, 981.

9. It was calculated that the minimum amount of endogenous N from saliva and gastric secretion was 0·3–0·6 g in 24 h. This assumes no absorption of N occurred anterior to the duodenal cannula.

1. The effects of feeding either high-protein (HP) or low-protein (LP) diets between 1.8 and 15 kg live weight (LW) and a low-energy (LE) or high-energy (HE) intake subsequently on the cellularity of muscle and adipose tissue in pigs growing to 75 kg LW were investigated.

2. The effects of the nutritional treatments on muscle tissue were assessed from the weight and DNA content of the m. adductor. For adipose tissue the total DNA content and fat cell size of the subcutaneous adipose tissue contained in the left shoulder joint were determined.

3. Feeding the LP diets in early life reduced the weight and DNA content of the m. adductor (P < 0.01) and increased fat cell size (P < 0.01) at 15 kg LW.

4. Subsequent to 15 kg there was an almost linear increase in muscle DNA with increasing LW, and the difference between pigs from the initial protein treatments progressively diminished and was no longer apparent at 60 kg LW.

5. At 30 kg LW, pigs given the LP diets before 15 kg LW contained less DNA in the subcutaneous adipose tissue from the shoulder joint (P < 0.01) and had larger fat cells (P < 0.05) than pigs given the HP diets initially. However, adipose DNA and fat cell size increased with increasing LW and the differences resulting from the initial protein treatments progressively diminished. On the LE and HE treatments subsequent to 15 kg these differences were no longer evident at 45 and 60 kg respectively.

6. Pigs given the HE intake subsequent to 15 kg, contained less DNA in muscle tissue (P < 0·05) at 60 and 75 kg LW and had larger fat cells (P < 0·05) at 45, 60 and 75 kg LW, than pigs on the LE treatment.

1. Six wether sheep were each provided with a permanent cannula in the rumen and re-entrant cannulas in the proximal duodenum.

2. In a preliminary study, the sheep consumed 200 g hay and 400 g concentrates supplemented with up to 40 g linseed oil, coconut oil or cod-liver oil daily. Feed was refused at higher levels of supplementation.

3. Five of the sheep were used in a 5 × 5 Latin-square experiment. They were given 200 g hay and 400 g concentrates alone (B) or supplemented with 40 g linseed oil (L), coconut oil (C), protected linseed oil or protected coconut oil daily. The protected oils were prepared by emulsifying the free oils with formaldehyde-treated sodium caseinate. Formaldehyde-treated sodium caseinate was also included in the other three diets.

4. Digestion in the stomach was measured by spot sampling duodenal digesta, using chromic oxide-impregnated paper as the marker. Microbial flow at the duodenum was measured by use of both diaminopimelic acid (DAPA) and RNA as microbial markers.

5. Both the free oils had broadly similar effects despite their very different fatty acid compositions. Digestion in the stomach of organic matter (OM) was reduced from 0·48 (diet B) to 0·29 (diets L and C) and that of neutral-detergent fibre from 0·50 (diet B) to 0·19 (diet L) and 0·12 (diet C). The molar proportions of acetic acid and n-butyric acid were decreased and that of propionic acid was increased. Protozoal numbers were reduced by 78% (diet L) and 90% (diet C). The flow of total nitrogen and microbial N was increased by both oils and the efficiency of microbial protein synthesis (g N/kg OM apparently digested in the rumen) was increased from 30 (diet B) to 85 (diet L) and 74 (diet C) when based on DAPA and from 41 (diet B) to 94 (diet L) and 81 (diet C) when based on RNA. The efficiency when based on true digestion of OM (g N/kg OM truly digested in the rumen) was increased from 23 (diet B) to 46 (diet L) and 44 (diet C) when based on DAPA and from 29 (diet B) to 49 (diet L) and 46 (diet C) when based on RNA. The amounts of microbial OM (g/d) at the duodenum were increased from 68 (diet B) to 124 (diet L) and 106 (diet C) when based on DAPA and from 92 (diet B) to 136 (diet L) and 115 (diet C, non-significant) when based on RNA.

6. When the oils were given in the protected form, the effects on digestion in the stomach were reduced but not eliminated. No significant increases in the amount of total N or microbial N at the duodenum were established, though there was a tendency for an increase in the efficiency of microbial protein synthesis with protected linseed oil. The results suggested that the method of protection used reduced the effects of the oils on rumen digestion and synthesis but was only partially successful in preventing hydrogenation of the fatty acids.

7. It is concluded that free oils can markedly increase the efficiency of microbial protein synthesis, possibly by their defaunating effect, and that this may enhance the potential for using non-protein-N on oil-supplemented diets.

1. Sheep fitted with rumen and re-entrant duodenal cannulas were given diets of approximately 200 g hay and 400 g concentrate mixture alone, or supplemented daily with 40 g linseed or coconut oils free or protected with formaldehyde-casein in a 5 × 5 Latin-square arrangement. Chromic oxide paper was given as a marker at feeding time and passage to the duodenum of neutral-detergent fibre (NDF) and different sugars were estimated from the values for c0nstituent:marker at the duodenum. Contributions of microbial carbohydrates to these flows were estimated from amounts of RNA present.

2. The carbohydrate composition of mixed rumen bacteria from sheep rumen digesta were similar regardless of diet. Of the sugars entering the duodenum all the rhamnose and ribose and 0·51, 0·24 and 0·35 of the mannose, galactose and starch-glucose respectively, were contributed by the microbes. Virtually all the arabinose, xylose and cellulose-glucose were contributed by the diet.

3. For sheep receiving the basal ration, coefficients of digestibility between mouth and duodenum, corrected where necessary for microbial contribution, were 095,0·66,0·67,0·62,0·45 and 0·51 for starch-glucose, mannose, arabinose, galactose, xylose and cellulose-glucose respectively. Corresponding values when free-oil-supplemented diets were given were 0·95,035,0·38,0·55,0·01 and –0·02 respectively. Values for diets supplemented with linseed oil or coconut oil did not differ significantly. Addition of protected oils to the basal feed also resulted in depressed digestibilities of dietary structural sugars but to a far lesser extent than those observed with the free oils.

4. Apparent digestibility of NDF was altered in the same direction as those of the main structural sugars, averaging 0·50,0· 17 and 0·29 in animals receiving the basal, free-oil-supplemented or protected-oil-supplemented diets respectively. The reasons for the difference between NDF and discrete carbohydrate analytical totals are discussed.

1. The incorporation of uniformly-labelled [14C]glucose into fatty acids and glycogen of adipose tissue and liver was used to assess the effects of zinc deficiency on glucose metabolism in meal-fed rats.

2. Throughout the study, identical feeding regimens were maintained between each of the Zn-deficient groups and their appropriate controls. The feeding regimens were either meal-feeding or ad lib. feeding.

3. Zn deficiency reduced [14C]glucose incorporation into fatty acids of epididymal fat pads of meal-fed rats by 75% when compared with meal-fed controls.

4. Zn deficiency caused a slight but significant decrease in [14C]glucose incorporation into liver fatty acids of meal-fed fats when compared with meal-fed controls.

5. Zn deficiency significantly increased [14C]glucose incorporation into liver glycogen of meal-fed rats in Expt. 2 but not in Expt 1.

6. Some effects of Zn deficiency on glucose metabolism were shown to be independent of the feeding regimen when a single daily meal was given to both Zn deficient and control groups. This method of feeding may be a useful approach to study the effects of Zn on glucose metabolism in the rat.

1. Protein synthesis in liver and jejunal mucosa was measured in 19-d-old germ-free (GF) and conventional (CV) chicks fed on a semi-purified casein–gelatin (SCG) diet using a massive-dose single injection of [U-14C]phenylalanine. The effect of subsequent feeding for 9 d either a nitrogen-free (NF) diet or an NF diet supplemented with L-methionine (5 g/kg) and L-arginine hydrochloride (2 g/kg) (MA diet) was investigated in both types of chick.

2. In the liver, apart from the amount of DNA, the values for wet weight, protein, RNA, fractional synthesis rate (FSR) and the amount of protein synthesized were reduced after feeding the NF diet and, to a lesser extent, the MA diet. Except that the total amount of liver DNA was higher in the CV chicks than in their GF counterparts (P < 0·01), no environmental effect was significant. When expressed on a unit body-weight basis, liver weight, protein, RNA and DNA were significantly higher in the CV than in the GF chicks.

3. In the jejunal mucosa, the values for wet weight, protein and RNA tended to be reduced after the NF treatment but increased after the MA treatment. Mucosal DNA and the amount of protein synthesized (μg/mm per d) were significantly reduced after the NF diet but were less affected after the MA diet. Mucosal protein FSR and the amount of protein synthesized per mg RNA were significantly reduced after both dietary treatments. No difference was found among dietary treatments in the amount of protein synthesized per mg DNA in jejunal mucosa. Mucosal DNA was significantly higher in the CV chicks and the reverse was true for mucosal protein: DNA.

4. It was suggested that the increased protein synthesis in jejunal mucosa and possibly in liver on supplementation of an NF diet with methionine and arginine would partly, ifnot completely, account for the N-sparing effect of these amino acids.

5. Although the protein: DNA value was smaller in CV chicks, the FSR and the amount ofprotein synthesized tended to be higher than in their GF counterparts irrespective of nutritional status. This might imply that protein degradation rate is greater in the CV state.

1. Two rumen cannulated steers consuming 5·5 kg air-dry lucerne (Medicago sativa) hay/d given at two-hourly intervals were used to study the kinetics in the rumen of the two particulate markers, 103Ru-labelled Tris-(1,10-phenanthroline) ruthenium II chloride ([103Ru]P) and dysprosium (Dy). Provision of markers was achieved by allowing the steers to eat separatedstems of the hay on to which had been sprayed solutions of the markers.

2. The intake of large-particle (retained by a 3·2 mm mesh screen) dry matter (DM) in boluses and the rumen large-particle pool size measured by emptying the rumen wereused to calculate the turnover rate-constant of this pool (1·02 and 1·19/d for steers A and B respectively).

3. The decline with time of both [103Ru]P and Dy associated with large-particle DM in raft digesta was best described by two-compartmental kinetics. The first compartment apparently reflected a combination of the processes of mixing of labelled particles throughout the rumen contents, physical migration of marker from the labelled hay, and physical breakdown of large particles to small particles.

4. The disappearance with time of [103Ru]P and Dy associated with small particles from the raft, ventral digesta and faeces from 3 to 8 d was well described by a single kinetic compartment with a rate constant similar to that of the second compartment of the large particles from the raft.

5. [103Ru]P was rapidly distributed through both the raft and ventral digesta of the rumen. This observation, taken together with measurements of migration of [103Ru]P, suggested that on entering the rumen much of the [103Ru]P did not remain associated with the original feed material.

6. The majority (63–64%) of Dy entered the raft digesta and mixed only slowly through the rumen contents. Some Dy (18–27%) apparently migrated rapidly from large particles and to small particles immediately after ingestion and there was also evidence for some slow migration from small to large particles.

7. When used under the conditions described for this experiment neither [103Ru]P nor Dy was satisfactory as a marker to trace the passage through the rumen of a particular meal.

1. The calcium and phosphorus concentrations in foetal tissue or the placental transfer of 45Ca and 32P, or both, were studied in fifty-five control or 1α-hydroxycholecalciferol (1α-(OH)D3)-treated (0·1 μg/kg body-weight per d for 12 d) ewes between 77 and 140 d of gestation.

2. Treatment resulted in a significant increase in the concentration of Ca and P in foetal tissues at all stages of gestation except at 140 d when, it is suggested, foetal mineralization may approach a maximum value.

3. This increase in Ca and P concentration in foetal tissues was associated with an increased placental transfer of Ca, though at 111 and 120 d gestation this increase was not significant. P transfer, which was only measured at 140 d gestation, was also significantly higher in treated animals.

4. The concentrations of Ca and P in both maternal and foetal plasma were increased significantly by the 1α-(OH)D3 treatment.

5. Whereas the concentration of Ca in the plasma of foetuses was always greater than in their dams, the concentration of plasma P in treated animals, unlike controls, was lower in foetuses than dams. This suggests that the increased placental transfer of P, unlike that of Ca, may be a passive rather than an active process.