1. The effects of intravenous trithiomolybdate administration on the fate of 64Cu and on stable Cu metabolism were examined in sheep held in metabolism cages and fed on a low-Cu diet supplying 2·95 mg Cu/animal per d.

2. In Expt 1 the injection of trithiomolybdate, 30 mg molybdenum/sheep per d for 5 d, greatly increased plasma Cu levels and more than doubled the faecal Cu excretion. Urinary Cu excretion was unaffected. The disappearance from plasma of 64Cu injected during the trithiomolybdate administration was slowed although faecal 64Cu excretion was increased more than threefold.

3. In Expt 2 trithiomolybdate, 10 and 30 mg Mo/sheep per d for 3 d, was administered 22 h after the injection of 64Cu. Radioactivity reappeared immediately in plasma and faecal 64Cu excretion was increased.

4. In both experiments the 64Cu and the increased stable Cu in plasma were associated with albumin.

5. The experiments explain the effectiveness of thiomolybdates as ‘decoppering’ agents and provide a model for some of the systemic effects seen in ruminants exposed to increased dietary Mo. The experiments support the view that the thiomolybdates, by causing the appearance of new ligands, alter the distribution of Cu in tissues and cause an overall depletion.

1. Five Greyface wethers (42–45 kg) fed on various fixed amounts of dried grass pellets (either approximately 1·3 times maintenance or 2 times maintenance) by means of belt-type continuous feeders were housed in opencircuit respiration chambers for periods of 45 d. Between days 15 and 35 they received daily oral doses of 1·5 mg of the β-adrenergic agonist clenbuterol (adsorbed on to the feed). Continuous energy and nitrogen balance measurements each of 5 d duration were conducted throughout the chamber confinement.

2. On six occasions (twice during the 15 d pre-clenbuterol period, on days +4, +11 and +18 of clenbuterol administration and once during the post-treatment period) animals were infused with [l-14C]leucine to determine the rates of leucine oxidation and the amounts of leucine available for protein synthesis.

3. Clenbuterol administration caused a marked increase in N retention (2–3 g N/d; P < 0·001) throughout the 20 d treatment period. It also increased (P < 0·001) the energy expenditure of the animals (on average by 1·1 MJ/d over the first 5 d, compared with immediate pretreatment values, and 0·6 MJ/d over the 20 d period, compared with the mean of pre- and post-treatment control values). The effect of treatment was calculated to result, on average, in the daily retention of 19 (SE 1·5) g more protein and 30 (SE 5·5) g less fat.

4. During clenbuterol treatment leucine oxidation was reduced (P < 0·01). However, values for the amounts of leucine available for protein synthesis were equivocal, with an increase (P < 0·001) on day 11 of treatment, but no change on days 4 and 18.

5. Withdrawal of the clenbuterol resulted in rapid alterations of N and energy metabolism towards those expected of control animals of that weight.

1. An experiment was conducted to determine the effect of the abomasal parasite, Haemonchus contortus, on the pattern of digestion and nutrient utilization in Merino sheep. There were three groups of sheep: infected with H. contortus (300 larvae/kg live weight) (n 5), sham-infected by transferring blood from the jugular vein to the abomasum, and uninfected (control) sheep (n 9) which were fed daily rations equal to amounts consumed by ‘paired’ animals in the two other treatment groups. A diet containing (g/kg): lucerne (Medicago sativa) chaff 490, oat chaff 480, ground limestone 10, urea 10, and sodium chloride 10, was given in equal amounts at 3-h intervals.

2. Continuous intrarumen infusions (8 d) of chromium and ytterbium were made in order to measure the flow of digesta through the rumen, duodenum and ileum with 15NH4Cl included in the infusate for the final 3 d. The loss of blood into the gastrointestinal tract was measured using 51Cr-labelled erythrocytes and the rate of irreversible loss of plasma urea was measured with reference to a single intravenous injection of [14C]urea. Samples of rumen fluid were taken for analysis of volatile fatty acid (VFA) concentrations.

3. The infected and sham-infected sheep developed severe anaemia during the period over which digestion and metabolism measurements were made (packed cell volume 0·118 (SE 0·0042) and 0.146 (SE 0·0073) respectively). The corresponding rates of blood loss into the gastrointestinal tracts were 253 (SE 23) and 145 (SE 17) ml/d.

4. The proportions of VFA in rumen fluid were altered (P < 0·05) in the infected group with a decrease in the ratio, acetate: propionate (control 3·28, infected 2·58, standard error of difference (SED)(0·21). There was also an increase in rumen fluid outflow rate (P < 0·01) from 4·05 litres/d in the control group to 5.53 litres/d in the infected group (SED) 0·43). Water intake was higher (P < 0·05) in the infected than in the control animals (2·25 and 1·84 litres/d respectively; SED 0·14).

5. There was a decrease (P < 0·05) in apparent digestion of organic matter in the forestomachs of infected sheep (0·32 compared with 0·39 in the control, SED 0·02). There was also a decrease (P < 0·05) in the apparent digestion of organic matter across the whole digestive tract (0·65 control, 0·61 infected, SED 0·013).

6. There was a loss of 2·6 and 1·8 g blood nitrogen/d into the gastrointestinal tract of the infected and sham-infected sheep respectively. In the infected sheep approximately 50 % of this N was accounted for as additional ammonia leaving the abomasum compared with 20% in the sham-infected group. The additional non-ammonia-N (NAN) entering the duodenum of parasitized or sham-infected animals was reabsorbed before the ileum. There was no effect of infection or sham-infection on the synthesis or digestion of microbial NAN.

7. There was a higher (P < 0·001) rate of plasma urea irreversible loss in the infected sheep (8·9 control, 12·2 infected, 10·9 sham-infected, SED (control v. treated) 0·87 g N/d). This was apparently due to increased absorption of ammonia and increased urea excretion and transfer to the gut.

8. The results show that in sheep infected with H. contortus there was a considerable increase in the amount of additional endogenous N entering the duodenum. Although the extra N lost into the gastrointestinal tract was reabsorbed before the digesta reached the ileum the animals suffered a net loss of amino acids since part of the reabsorbed N was in the form of ammonia and reabsorbed NAN was apparently ineffectively utilized.

1. The present study concerns the question whether the hypercholesterolaemic effect of casein, a phosphorylated protein, is modified in species differing both in glycine-taurine conjugation of bile acids and in intestinal alkaline phosphatase (EC 3.1.3.1).

2. Since these two variables are entirely different in rabbits and rats, identical (cholesterol-free) semi-purified diets containing either casein or soya-bean protein were given to both species.

3. In rabbits casein, as compared with soya-bean protein, did not affect calcium absorption but immediately increased phosphate absorption and decreased faecal excretion of bile acids. These effects preceded the accumulation of apo B-cholesterol in serum, which indicates a cause-and-effect relation.

4. In contrast, none of these casein-specific effects were observed in rats.

5. These results suggest that the hypercholesterolaemic potential of casein is expressed mainly in species (like the rabbit) with a low activity of intestinal phosphatase and with a high glycine conjugation of bile acids. This might explain why species (like rat and man) are rather insensitive to dietary casein.

1. The nature of the digestion-inhibiting substance in Kikuyu grass (Pennisetum clandestinum, Hochst), containing high levels of nitrate, was investigated using in vitro digestibility techniques.

2. Nitrite, which accumulated during the reduction of nitrate to ammonia, seemed to be the primary factor reducing digestibility. Nitrate and ammonia did not affect digestion in vitro.

3. Nitrite caused a reduction in the cellulolytic, xylanolytic and total microbial population, with a concomitant reduction in cellulase and xylanase activity of the digesta.

4. The mode of action of nitrite on rumen microbial growth was investigated.

5. The possibility that the growth of cellulolytic rumen microbes was depressed by a reduction in concentration of essential branched-chain volatile fatty acids by nitrite was discounted.

6. Although nitrite caused a marked increase in the redox potential, due to its oxidizing properties, the more-positive redox potential did not reduce the digestibility of the grass.

7. The growth of three of the four major cellulolytic bacteria commonly found in the rumen was severely depressed by nitrite, while some rumen bacteria were relatively insensitive to nitrite.

8. Growth inhibition seemed to depend primarily on the extent to which these microbes derive their energy from electron-transport-mediated processes.

9. It was suggested that, due to the sensitivity of some rumen bacteria to nitrite, digestibility and therefore animal performance could be affected long before clinical symptoms of nitrite toxicity become apparent.

1. Wistar rats were fed on a control semi-synthetic diet throughout pregnancy, or a control diet in the first 2 weeks and a marginal-zinc diet in the 3rd week of pregnancy. On day 20, after an overnight fast, half the animals in each group were given glucose by gavage and the 0–30 min rise in blood glucose measured in tail blood. After 60 min blood was taken by cardiac puncture for glucose and insulin assay. Maternal pancreases were removed and the Zn contents measured. Fetuses from each litter were combined for wet/dry weights, protein and DNA determinations.

2. Plasma insulin concentration was higher, and glucose concentration and pancreatic Zn content lower, in pregnant v. non-pregnant animals of similar age, fed on the same diet. Pancreatic Zn content was lowest in the marginal-Zn group of pregnant rats. Fetuses from mothers fed on the marginal-Zn diet during the last week of pregnancy were slightly heavier than controls and had a significantly higher protein: DNA ratio. The 0–30 min rise in blood glucose was significantly greater in the marginal-Zn animals.

3. In a second experiment, pregnant rats were given similar diets to those used in the first study, but the marginal-Zn diet was given for a shorter period (days 15–19 of pregnancy). On day 19 the rats were meal-fed and on day 20, after an overnight fast, an oral glucose dose was administered. Tail-blood was taken at timed intervals up to 60 min post-dosing for glucose assay. Both maternal and fetal blood glucose and insulin concentration was measured 70 min post-dosing.

4. Values for maternal and fetal blood glucose and plasma insulin, measured 70 min after the administration of a glucose dose, were similar in the two groups, but the initial rise in blood glucose concentration was again significantly higher in pregnant rats given the marginal-Zn diet towards term.

5. It is suggested that the change in growth and composition, observed in fetuses from rats given a marginal-Zn diet in later pregnancy, is associated with altered maternal carbohydrate metabolism.

1. Branched-chain amino acid aminotransferase (EC 2.6.1.42; BCAAT) and branched-chain α-keto acid dehydrogenase (EC 1.2.4.4; BCKDH) activities were measured in preruminant lamb liver, longissimus dorsi muscle, kidney, jejunum and adipose tissue, 2 h after a meal with or without an excess of leucine.

2. Skeletal muscle contained about 70% of the total basal BCAAT activities of the tissues studied whereas liver contained about 60% of the total BCKDH activities of these tissues.

3. BCAAT activities were very low in preruminant lamb tissues. BCKDH was more phosphorylated in tissues of preruminant lambs than in rats, especially in liver. These low catalytic potentialities might contribute to a low rate of branched-chain amino acid catabolism in sheep.

4. Ingestion of an excess of leucine led to an increase in liver and jejunum BCAAT activities and activation of BCKDH in jejunum.

1. Two experiments are reported in which the effect of alteration in growth rate on the levels of avian skeletal muscle calcium-activated neutral proteinase (EC 3.4.22. 17) (CANP or calpain) and its specific inhibitor (calpastatin), a system thought to be implicated in myofibrillar catabolism, was studied by means of manipulation of dietary protein concentration.

2. In Expt 1 broiler chicks were given free access to diets containing 105, 149, 197 and 212 g protein/kg for 20 d. In Expt 2 the four dietary treatments were 119, 141, 182 and 227 g protein/kg diet given for 16 d. Chick growth rate and total leg skeletal muscle weight significantly increased (P < 0·001) with increasing dietary protein concentration in both experiments. Total skeletal muscle protein increased with the level of dietary protein, the effect being significant (P < 0·01 and P < 0·001 in Expts 1 and 2 respectively).

3. Minced leg muscle was homogenized in low-salt buffers, and the extract chromatographed on DEAE-cellulose to separate proteinase and inhibitor activity. The partially purified CANP enzyme and inhibitor proteins were present at a concentration broadly consistent with literature reports, and their elution characteristics and Ca2+ concentration dependence were not varied by dietary protein concentration.

4. Both the muscle CANP and CANP inhibitor activities (units/kg muscle) exhibited upward trends with growth rate and increased muscle weight. However, these differences were not statistically significant (P > 0·05) and were not present at all when the results were expressed as units/g muscle protein.

1. The uptake of 5-methyltetrahydrofolate (MTHF) and folic acid (pteroylmonoglutamate) by enterocytes and brush-border-membrane vesicles prepared from the small intestine of the 6-d-old male goat was determined using a rapid-filtration assay.

2. Both MTHF and folic acid were taken up by membrane vesicles at 25° and enterocytes at 37° by a pH-dependent mechanism with maximum uptake when the pH of the incubation medium was 5·0.

3. Experiments in which the osmotic pressure of the medium was raised in successive increments with the non-absorbable sugar cellobiose indicated that transport rather than membrane binding was the main component of uptake.

4. Experiments at pH 5·0 showed that uptake of MTHF and folic acid was saturable and that the characteristics of folate transport were similar in both tissue preparations: (a) transport rates of both MTHF and folic acid were constant during the first 1-2 min for a given folate concentration, then declined to reach a steady-state in 10-30 min; (b) initial velocities of transport of MTHF and folic acid increased in proportion to their concentrations up to 7-10 μM, but the rate of increase slowed thereafter until saturation was reached at 20-25 μM (Km for brushborder-membrane vesicles 40·8 and 62·9 μM, Km for enterocytes 50·9 and 55·2 μM for MTHF and folic acid respectively). Values of Vmax for membrane vesicles (pmol/mg protein per min) were 46·5 MTHF or 40·3 folic acid; enterocytes Vmax (pmol/107 cells per min) 15·9 MTHF or 30·6 folic acid; (c) uptake of MTHF and folic acid by brush-border-membrane vesicles and enterocytes measured under steady-state conditions approached saturation at 50 μM for each analogue (Km for membrane vesicles 58·1 and 55·2 μM, Km for enterocytes 43·1 and 49·4 μM for MTHF and folic acid respectively; Vmax for membrane vesicles 49·7 and 77·8 pmol/mg protein, for enterocytes 52·8 and 54·7 pmol/107 cells for MTHF and folic acid respectively).

5. It was concluded that transport of MTHF and folic acid was by a similar pH-dependent mechanism both in brush-border-membrane vesicles and in intact enterocytes. At pH 5·0, transport involved a saturable carrier-mediated process located in the brush-border membrane.

1. Cellular and humoral immune responses were studied in guinea-pigs fed on zinc-deficient (ZnD), Zn-adequate (control) and Zn-replete diets containing 1·25, 50 and 100 mg Zn/kg diet respectively.

2. It was found that the ZnD guinea-pigs had significantly decreased ability to elicit delayed-type hypersensitivity (DTH) response against sheep erythrocytes as compared with controls on the 9th day of immunization. This was further substantiated by histological examination of DTH-positive skin sections.

3. A significant reduction in direct splenic plaque-forming-cell response and haemagglutinating-antibody titre was also observed in ZnD guinea-pigs.

4. Serum electrophoretic studies revealed a highly disordered protein profile with a significantly depressed value for γ-globulin.

5. Zn repletion of the previously ZnD group resulted in marked, though incomplete, restoration of immunological responses.

1. In vitro leucine catabolism in adipose tissue, skeletal muscle, kidney and liver homogenates was studied in sheep.

2. In Expt 1, Suffolk × Targhee ram lambs were slaughtered at 1, 28, 56, 84, 112, 140, 168, 196, 224 and 365 d of age. In Expt 2, 5-month-old crossbred wethers were fed on 80, 120 or 180 g crude protein (nitrogen × 6·25) /kg diets for 4 weeks or fed on 120 g crude protein/kg for 4 weeks and then fasted for 48 or 96 h before slaughter. Leucine catabolism was assayed in tissue homogenates for Expts 1 and 2.

3. Leucine deamination (per unit protein) was highest in skeletal muscle at day 1 and then declined; liver exhibited an activity pattern akin to muscle while kidney activity tended to rise over the duration of the study. Adipose tissue in vitro leucine deamination was higher at all ages studied and 9- to 50-fold higher than all other tissues at 365 d. Leucine decarboxylation (per unit protein) was highest at day 1 in muscle and declined to low levels (P < 0·01) after 28 d; liver and kidney decarboxylation activities were higher than muscle at all ages with kidney showing the highest activity. Whilst adipose had high initial activity it declined significantly (P < 0·01) by day 28 and remained low.

4. Dietary protein intake had no effect on leucine deamination in any tissue. Leucine decarboxylation tended to increase with protein intake for all tissues except kidney. Length of fast (96 h) resulted in a variable decline in leucine deamination; leucine decarboxylation was significantly lower in kidney, liver and adipose tissue after a 96 h fast.

5. When these in vitro enzyme activity results are related to questions concerning the role of skeletal muscle in leucine catabolism in sheep, the present findings indicate that in grown sheep, skeletal muscle has a small to moderate role in total body leucine deamination but plays a very minor role in leucine decarboxylation. Adipose tissue appears to be a major site of leucine deamination in grown sheep. These results are not in agreement with the idea that during fasting leucine becomes an important energy substrate and is oxidized in skeletal muscle as has been shown in rodents.

1. Whole-body protein synthetic rates in non-pregnant ewes were determined by the continuous infusion of L-[15N]- and [1-13C]leucine and measuring the plasma enrichment of leucine, α-ketoisocaproate (α-KIC) and expired carbon dioxide by gas–liquid chromatography–mass spectrometry.

2. The mean whole-body protein synthesis estimated from plasma leucine flux corrected for oxidation was 5·38 (SE 0·54) g/kg per d.

3. Under the conditions of the present study leucine oxidation was 0·323 (SE 0·067) mmol/kg per d and accounted for 10·71 (SE 2·26) % of plasma [13C]leucine flux. Deamination of leucine was 0·55 (SE 0·035) mmol/kg per d and accounted for approximately 17% of plasma [15N]leucine flux.

4. The rate of α-KIC reamination to leucine, calculated by subtracting 13C flux from 15N flux, was 0·228 (SE 0·101) mmol/kg per d.

5. The rate of whole-body protein degradation was 4·49 (SE 0·54) g/kg per d and there was a net protein gain of 0·89 (SE 0·21) g/kg per d.

1. Studies of gastric function were made in preruminant calves fitted with a single abomasal cannula, re-entrant cannulas in the duodenum close to the pylorus and recording electrodes on the pyloric antrum and proximal duodenum.

2. Simultaneous measurements were made of gastric emptying of a saline (9 g sodium chloride/1) meal, myoelectric activity of antral muscle and plasma concentration of somatostatin in jugular blood whilst infusing the duodenum with different solutions. The duodenal infusates were isotonic sodium bicarbonate (300 mosmol/kg), hyperosmolar solutions of NaCl (1000 mosmol/kg), sodium carbonate (500 mosmol/kg), sucrose (1000 mosmol/kg), 41 g emulsified butterfat/kg or 60 mM-hydrochloric acid.

3. Infusing the duodenum with isotonic NaHCO3 stimulated intense myoelectric activity of the antral smooth muscle and rapid emptying of the test meal. In contrast, infusions of 60 mM-HCl reduced antral motility and inhibited gastric emptying of digesta. This inhibitory response to HCl infusion was related to a significant (P < 0·05) increase of somatostatin in peripheral venous blood.

4. The Na2CO3 infusate, like HC1, inhibited gastric motor activity and digesta emptying, but the concentration of circulating somatostatin was only slightly elevated above pre-infusion levels.

5. Compared with the effects of infusing HCl, infusions of emulsified butterfat or hyperosmolar NaCl and sucrose induced a greater intensity of antral motor activity and faster outflow of gastric effluent, although not to the same extent as with isotonic NaHCO3. However, as with isotonic NaHCO3, these infusates did not evoke the release of somatostatin.

6. The results support the concept of duodenal receptors which, in response to a variety of stimuli in gastric chyme, modulate stomach emptying of digesta through actions on contractile processes of antral smooth muscle. Activation of such receptors by fat or osmotic stimuli, both ionic and non-ionic, do not appear to involve the release of somatostatin. However, the hormone appears to have an entero-gastrone role in mediating the inhibitory action of HCI on gastric motor function.

1. The influence of goat's-milk folate-binding protein (FBP) on the uptake of 5-methyltetrahydrofolate (MTHF) by brush-border-membrane vesicles prepared from the small intestine of the 6-d-old goat was investigated using a rapid-filtration assay.

2. Uptake of MTHF by the membrane vesicles was strongly enhanced by FBP within the pH range 4·5-6·5, with an optimum at pH 5-5·5.

3. Both the initial rate of MTHF uptake and uptake of MTHF at equilibrium were markedly increased in the presence of FBP.

4. Uptake of MTHF by brush-border-membrane vesicles was maximal when the molar ratio FBP: MTHF was 1·0-2·5.

5. The relation between pH and 125I-labelled FBP binding to the membranes was similar to that for uptake of MTHF, with an optimum at pH 5.

6. In experiments in which the osmotic pressure of the incubation medium was progressively increased with cellobiose, 125I-labelled FBP was found to be taken up primarily by binding to the brush-border-membrane surface.

7. Uptake of 125I-labelled FBP was time-dependent and saturable, with a Km of 0·39 (SE 0·07) μM and Vmax of 6·73 (SE 0·92) μg/mg protein.

8. Experiments in which various milk proteins (cow FBP, goat FBP, α-lactalbumin, β-lactoglobulin, bovine serum albumin and lactoferrin) were allowed to compete in turn with 125I-labelled FBP for uptake by brush-border-membrane vesicles indicated that high-affinity binding was probably specific to FBP, although lactoferrin reduced uptake possibly by non-specific coating of the mucosal surface.

9. It was concluded that a folate transport mechanism mediated by the FBP in milk exists at the intestinal brush border of neonatal goats. It is suggested that this may reinforce the developing endogenous transport system.

1. Increases in plasma tocopherol concentrations were compared in sheep after a single oral administration of (per kg body-weight): 67 mg D- and 91 mg DL-epimers of α-tocopherol, and 74 mg D- and 100 mg DL-epimers of α-tocopheryl acetate, or intravenous administration of DL-α-tocopherol and DL-epimers of DL-α-tocopheryl acetate.

2. The results showed that biological availability was higher after D-α-tocopherol dosing than after the other forms. Intravenous administration of D-α-tocopherol acetate was a more effective way of dosing in sheep than equivalent intravenous amounts of DL-α-tocopheryl acetate or DL-α-tocopherol.

1. Over- or undernutrition of newborn mice was caused by suckling in litters consisting initially of four or eighteen pups. After weaning mice were fed ad lib. At 13 weeks of age some mice from large litters received gold thioglucose (GTG: 600 mg/kg intraperitoneally) to induce hyperphagia, and mice were killed at 13, 19·5, 26, 39 and 52 weeks.

2. Total carcass lipid and the size and number of adipocytes in the inguinal subcutaneous, genital, perirenal and mesenteric depots were determined.

3. Mice, both male and female, raised in small litters were heavier and had more carcass fat at all ages than mice raised in large litters. After GTG-treatment mice from large litters were heavier and fatter than mice raised in small litters.

4. Fat distribution between the depots was related to carcass lipid content and not to treatment. The order of depot development was subcutaneous, parametrial, perirenal and mesenteric in females and epididymal, subcutaneous, perirenal and mesenteric in males. At 13 weeks the depots in males were more developed than those in females.

5. Litter size had no effect on adipocyte volume in female mice at 13 weeks but by 52 weeks small-litter mice had larger cells in all depots and more cells in the parametrial and perirenal depots.

6. Male mice from small litters had bigger cells at 13 weeks in all depots compared with males from large litters but by 52 weeks no significant differences remained. Greater numbers of cells were present only in the perirenal and mesenteric depots of small-litter males at some ages.

7. Depots of GTG-treated large-litter female mice had larger cells than those of small-litter females, while a similar number of cells was found by 52 weeks in all but the perirenal depot, which had significantly more cells.

8. GTG treatment of male mice from large litters also caused bigger cells than in small-litter mice, and an increased depot cell number at earlier ages in all but the epididymal depot. By 52 weeks cell numbers were similar in depots from small-litter and GTG-treated large-litter mice, except for the epididymal depot from the latter which had fewer cells.

9. Increases in cell numbers with age in different depots occurred independently of existing cell mean volume and even of tissue growth, suggesting the presence of an in-built chronology, at least in older mice.

10. We suppose that the differences in response to the level of preweaning nutrition in males and females result from a greater effect on the hypothalamic appetite centre in the latter. Whereas the cellular changes in large-litter males occur in the late-developing depots and are reversed naturally with time, those in the large-litter females are more extensive and require induction of hyperphagia for reversal.