1. In a comparative slaughter experiment growing lambs were given concentrate diets in which 7, 15 or 22% of the metabolizable energy (me) provided by barley was replaced by sodium and calcium salts of acetic acid, or 22% of me was replaced by Na and Ca salts of propionic or butyric acids.

2. The efficiency of utilization for fattening (kf) of the diets containing 0, 7, 15 or 22% of me as acetate was 57.2, 59.6, 54.1 and 48.8 (se ± 1.8) respectively, the last value being significantly lower (P < 0.001) than the first. The kf for successive increments of acetate was 90, 37 and 19% (se ± 13), the decrease being significant (P < 0.001).

3. The kf values of the diets containing 22% of me as propionate or butyrate respectively were 48.7 and 50.6 (se ± 1.8), both values being significantly lower than the control (P < 0.01). The partial kf of propionate was 19±13, and of butyrate 28 ± 13%.

4. It is concluded that the experiment provided evidence that the efficiency with which acetate is utilized for energy retention is not constant, but varies with its contribution to me. The experiment also provided some evidence that large amounts of propionate and butyrate may be inefficiently utilized by growing lambs, although poor utilization of high levels of volatile fatty acid (VFA) salts per se cannot be entirely excluded.

1. An extract containing ‘unavailable’ small peptides was isolated from an enzymic digest of heat-damaged cod fillet and examined for its influence on uptake of leucine in the rat small intestine, using the everted-sac technique.

2. The extract strongly inhibited the uptake of leucine. It had no effect on uptake of glucose or its metabolism to lactate.

3. The findings are discussed in relation to the concept (Buraczewski, Buraczewska & Ford, 1967) that the accumulation of ‘unavailable peptide’ material in the intestine, found in rats given heat-damaged protein, might hinder the absorption of amino acids by blocking a mechanism involved in their transport across the mucosal barrier.

1. Four methods of vitamin E and selenium supplementation were evaluated using thirty-nine pregnant ewe-lambs fed on a ration containing 0.043 mg Se/kg and 25 mg vitamin E/kg. Treatments were control, fortified mineral mix (ESe salt) (300 mg vitamin E, 3 mg Se), ruminal Se pellets (505 mg Se), drench (300 mg vitamin E, 3 mg Se) and intramuscular injection (600 mg vitamin E, 3 mg Se). Only ewes were supplemented, commencing approximately 50 d before parturition.

2. Birth weights were similar for all treatments and live-weight gains of lambs to 56 d of age were improved in all supplemented groups (P < 0.05). There were no clinical cases of nutritional muscular dystrophy.

3. Se concentrations in whole blood were more than doubled in both lambs and ewes drenched or injected; responses to ESe salt and pellets were much smaller.

4. Plasma tocopherol levels were increased in injected dams and their lambs (P < 0.001).

5. Haemoglobin concentration and erythrocyte counts were significantly higher (P < 0.01) in control ewes and lambs than in treated lambs.

6. Lactate dehydrogenase (EC 1.1.1.27), creatine kinase (EC 2.7.3.2) and aspartate aminotransferase (EC 2.6.1.1) activities were increased in lambs from control, ESe salt and pellet groups (P < 0.001). Glutathione peroxidase (EC 1.1.1.1.9) activity responded to Se supplementation in both ewes and their lambs (P < 0.001) and the response was highest in the injected group, followed, in order, by the drench, pellet, ESe salt and control groups.

7. These studies indicated that in terms of the haematological and blood chemistry changes investigated, the intramuscular injection was most effective, followed by the oral drench. Ruminal pellets and fortified salt were less satisfactory.

1. Two calorimetric experiments were conducted to study the utilization of energy in sheep given diets of grass silage or grass silage and barley. Three silages were investigated. One was made from first-harvest grass in the spring (S) and the others from regrowth cut either early or late in the autumn (E and L respectively). All were of perennial ryegrass (Lolium perenne) and preserved with formic acid. Each silage was given at two levels of feeding, the lower providing approximately a maintenance energy intake. The S and L silages were also given supplemented with barley.

2. The digestibilities of organic matter, cellulose and energy in the silages were high. Measured at maintenance, digestible energy (de) contents (MJ/kg dry matter (dm)) were 11.83, 14.67 and 12.90 for S, E and L respectively. The de contents of the S and E silages were depressed at the higher level of feeding but the effect was offset by changes in the energy losses as methane and urine. Metabolizable energy (me) contents (MJ/kg dm) for the three silages, S, E and L were respectively 9.88, 12.54 and 10.73 at the low level of feeding and 9.91, 11.99 and 11.08 at the high level of feeding. The mean me content of barley calculated by difference was 13.76 MJ/kg dm.

3. The mean efficiencies of utilization of me for maintenance (km) for the S, E and L silages were 0.69, 0.71 and 0.68 respectively. Corresponding values for fattening (kf) were 0.21, 0.57 and 0.59. Excepting the kf for the S silage which was low, observed efficiencies were in broad agreement with those predicted by the equations of the Agricultural Research Council (1965). Similar agreement was obtained with all diets consisting of silage and barley.

1. The changes in a number of metabolic measurements brought about by low-biotin diets associated with high and low incidences of fatty liver and kidney syndrome (FLKS) were studied in healthy 4-week-old broiler chicks.

2. Liver pyruvate carboxylase (pyruvate: CO2 ligase (ADP); EC 6.4.1.1) activity was low in birds fed on a diet causing a high incidence of FLKS but the addition of fat or protein to this diet, to decrease the incidence of FLKS, increased enzyme activity.

3. Liver weights, blood lactate concentrations, plasma lactate dehydrogenase (l-lactate:NAD oxidoreductase; EC 1.1.1.27) activities and values for C16:1:C18:0 fatty acid in liver, adipose tissue and plasma triglyceride were highest in birds fed on the high-FLKS diet and all measurements were negatively correlated with pyruvate carboxylase activity.

4. Birds with high plasma lactate dehydrogenase activity or triglyceride C16:1:C18:0 values were the most likely to develop FLKS when fasted.

5. There was no evidence that increased liver weight was associated with increased activities of certain other liver enzymes.

6. It is concluded that FLKS occurs in birds with little or no hepatic gluconeogenic capacity via pyruvate carboxylase as a result of a dietary insufficiency of biotin but that the initiation of the syndrome is probably associated with the inhibition of other pathways of gluconeogenesis.

1. Amylase (EC 3.2.1.1) activity found in the intestinal tract of chicks posterior to the stomach is of endogenous origin, as amylase in the food is inactivated by the low pH in the stomachs.

2. Ingestion of raw soya-bean diet (RSD) or of heated soya-bean diet (HSD) supplemented with trypsin inhibitors induced higher amylase activities in the lower part of the small intestine and caecum as compared with HSD.

3. Ingestion of RSD after ligation at the end of the duodenum, end of the ileum or one of the caeca, or injection of soya-bean trypsin inhibitor into a ligated caecum, indicated that there is no amylase synthesis by the intestinal tract cells or microflora as a response to the presence of RSD or trypsin inhibitors.

4. It seems that amylase found in the digestive tract of the chick is of pancreatic origin and that RSD or trypsin inhibitors induce higher pancreatic amylase secretion than HSD which (the additional amylase) accumulates mainly in the caeca.

1. The fractional synthetic rates of tissue proteins were studied in growing pigs using the constant-infusion technique of tracer-labelled amino acids ([14C]leucine and [14C]lysine) and the mathetmatical model for calculation, employed in rats by Garlick, Millward & James (1973).

2. During a 6 h infusion, samples were taken from blood and muscle and at the end of the infusion from liver, muscle, pancreas, heart, duodenum, jejunum, ileum, colon, and skin. The specific radioactivity of free and protein-bound leucine and lysine was estimated.

3. A quasi-steady-state in the specific radioactivity of free plasma leucine and lysine was reached within approximately 2 h, the rate-constants being 35 and 48/d respectively.

4. The specific radioactivity of free leucine and lysine in plasma was used to calculate the flux of these amino acids. It was found to be higher than the daily intake.

5. The average fractional rate of protein synthesis in muscle and heart was 8.1 %/d, in small and large intestine the values were 50 and 33 %/d respectively and in liver and pancreas more than 100 %/d.

6. The calculation of protein synthetic rate in pig tissue using the constant-infusion method of labelled amino acids seems to be a suitable tool for study of this species.

1. When lead is administered in drinking-water iron-deficient rats retain more Pb than Fe-replete rats (Six & Goyer, 1972; Klauder & Petering, 1975). In the present study the relationship between the absorption of Pb and Fe was investigated.

2. Adult male rats were transferred to a milk-based diet fed with or without supplementary Fe (180 mg Fe/kg as ferrous sulphate). After 7–9 d the absorption of duodenally-administered 203Pb and 59Fe was measured as uptake of radioactivity from the gastrointestinal tract after 90 min. 59Fe absorption was increased in rats given the unsupplemented diet for 7 d and was further increased in rats kept on the diet for up to 7 weeks. 203Pb absorption was not consistently increased by either short- or long-term Fe deprivation.

3. Much of the 203Pb in homogenates of the upper small intestine was bound to soluble protein of which up to 85% was dialysable. In contrast little 59Fe was dialysable. Only a small proportion of the soluble musosal Pb was associated with ferritin during gel-filtration chromatography although 203Pb precipitated together with carrier rat-liver ferritin with an antibody to rat-liver ferritin.

4. There appeared to be no direct relationship between the transfer of Fe and Pb across the small intestine of the adult rat.

1. Diets containing graded levels of pyridoxine hydrochloride (to supply 0.26–30 mg pyridoxine/kg) were given to seven duplicate groups of turbot (Scophthalmus maximus) for 12 weeks and their growth rate was measured during this period.

2. Good growth was obtained on all treatments except those groups given less than 1.0 mg pyridoxine/kg diet. These fish grew normally until weeks 8–10 but thereafter their weight gain was significantly less than that for other treatments.

3. Measurements of aspartate aminotransferase (EC 2.6.1.1) in muscle and liver and of alanine aminotransferase (EC 2.6.1.2) in liver of the turbot showed that the activities of these enzymes increased with increasing dietary pyridoxine intake up to a level of 2.5 mg pyridoxine/kg. The activities of these enzymes were not further enhanced by additional dietary pyridoxine.

4. Percentage stimulation of these enzymes by pre-incubation of extracts with pyridoxal phosphate was minimal with those groups of turbot given 2.5 mg pyridoxine/kg diet or more.

5. It is concluded that the dietary requirement of turbot for vitamin B6 can be safely met with a diet containing between 1.0 and 2.5 mg pyridoxine/kg.

6. An eighth group of turbot given the pyridoxine antagonist 4-deoxypyridoxine hydrochloride (20 mg/kg) showed retarded growth after 2 weeks, together with a high mortality rate.

1. Physical performance capacity was assessed before and after injection of cyanocobalamin and a placebo for thirty-one Burmese male subjects whose age ranged from 18.7 to 20.8 years.

2. The subjects chosen were free from anaemia and were paired on a ‘weight-age’ basis and divided into two groups.

3. One group received an injection of 1 mg cyanocobalamin and the other was given a placebo injection three times weekly for 6 weeks. This was done on a ‘double-blind’ basis.

4. There was no significant difference between the two groups in any of the criteria measured, before and after administration of either 1 mg cyanocobalamin or placebo injection. So also there was no significant increase in any of the measurements in the subjects after receiving cyanocobalamin injections compared with those receiving the placebo.

1. Naturally-occurring and synthetic analogues of phenylalanine, tyrosine, histidine, arginine, proline, tryptophan and the sulphur amino acids have been tested in rat reticulocytes and in the Reuber H35 hepatoma for effects on protein synthesis and protein degradation and on the heat lability of phosphoenolpyruvate carboxykinase (EC 4.1.1.32) in the hepatoma cells. The experiments were designed to test whether the analogues could be incorporated into mammalian proteins and whether the resultant proteins would be degraded at an accelerated rate.

2. Several analogues, including thiazolylalanine, triazolalanine and selenocystine both stimulated protein synthesis and produced labile protein in reticulocytes. Other analogues, such as dihydroxyphenylalanine, thioproline and pipecolic acid accelerated protein breakdown but probably indirectly via an inhibition of protein synthesis. Azetidine-2-carboxylic acid had the largest effect on protein breakdown in reticulocytes.

3. Labile protein was produced in hepatoma cells incubated in the presence of azetidine-2-carboxylic acid, canavanine, indospicine, triazolalanine, 2-, 3- and 4-fluorophenylalanine. These same analogues, together with 3, 4-dehydroproline, β-2-thienylalanine, dihydroxyphenylalanine, histidinol, 5- and 6-fluorotryptophan, selenocystine and selenomethionine produced heat-labile phosphoenolpyruvate carboxykinase. Enzyme induced in the presence of selenomethionine or indospicine showed the largest increases in heat lability, and for these analogues equimolar concentrations of methionine and arginine respectively were needed to nullify the enzyme abnormality.

4. The toxicity of the same naturally-occurring analogues has been discussed in terms of their ability to be incorporated into cell proteins.

1. Rabbits hand-reared on a diet based on cow's milk frequently experience convulsive and sometimes fatal reactions to their feed. These have been thought to be caused by immunological hypersensitivity to cow's milk.

2. This explanation has been re-examined and found to be untenable.

1. There was a significant increase in oxygen consumption in ten women after small intakes of alcohol.

2. No significant difference was found between the average increase in metabolic rate over 3 h after an isoenergetic meal of food or of food plus alcohol. However, during the last half of the 3 h postprandial period, the increased O2 consumption was significantly greater after the meal including alcohol.

3. Possible explanations for the contradictory results in the literature are discussed.

1. Adsorption of bile salts by dietary fibre is believed to promote their excretion and hence to reduce the serum cholesterol level in man and experimental animals.

2. We have tested a number of plant fibre fractions and other related materials for their ability to adsorb bile salts from aqueous solution. The ‘insoluble’ plant fractions were from ‘dry grain’ (a residue from brewing), apple, wheat bran, lucerne (Medicago sativa), soya beans, mung beans (Phaseolus mungo), chick peas (Cicer arietinum), rolled oats, spinach (Spinacia oleracea), sunflower seeds, sawdust and sheep faeces. The other materials were cholestyramine, pectin and lignins prepared from wheat bran and from sawdust.

3. Only cholestyramine and the fibre from lucerne, soya beans, mung beans, chick peas, spinach, and sunflower seeds adsorbed enough of either sodium cholate or sodium deoxycholate for adsorption to be detectable.

4. This result conflicts with a report that the lignin component of dietary fibre is responsible for adsorption of bile salts.

5. Adsorption of bile salts, when it occurs, may depend on the presence of saponins bound to the fibre.

1. Broilers were kept under environmental temperature regimens of 16, 21, 26 or 31° and given, 22–57 d of age, either a complete diet or free-choice of whole wheat and a higher-protein food containing either 252 or 516 g crude protein (nitrogen × 6.25)/kg.

2. Broilers maintained at 16 and 21° consumed food at a significantly higher rate than those kept at 26° and the latter had a significantly higher food intake rate than broilers kept at 31°, for each feeding treatment. Compared with 21° the 57 d body-weight of broilers kept at 26° and 31° was significantly reduced.

3. When kept under the 16, 21, 26 and 31° regimens, the amount of whole wheat in the food consumed by the broilers choice-fed with wheat and the 252 g crude protein/kg food was 56, 55, 48 and 46% respectively. The corresponding values for the broilers on the second choice-feeding treatment were 80, 76, 79 and 72%.

4. Except for a single instance the choice-fed broilers grew at a significantly slower rate than broilers given the complete diet.

1. Hypovitaminotic C guinea-pigs fed on a high-cholesterol diet for 5 weeks developed gallstones (810 mg cholesterol/g) whereas no concretements were observed in vitamin C-replete animals.

2. Scanning electron microscope studies of the three types of gallstone observed in the gallbladders of vitamin C-deficient animals showed them to be composed of randomly-arranged needle-shaped or laminated crystals of cholesterol.

3. The hepatic bile of gallstone-forming animals had a higher cholesterol concentration and lower bile acid content, the latter being principally due to a reduction in the chenodeoxycholic fraction, than the bile of vitamin C-replete animals.

4. No significant difference was observed between the volume of bile secreted by hypovitaminotic C and vitamin C-replete animals, but due to the qualitative changes in bile composition, gallstone formation was associated with an increased biliary secretion of cholesterol and a reduced secretion of bile acids.

1. Twelve sheep fitted with abomasal cannulas were given ad lib. access to a diet of chopped lucerne (Medicago sativa) hay to ascertain if the amount of digesta being transported by the intestines was limiting intake. If this was the situation, pumping a solution of the bulk-laxative methylcellulose (100 g/kg; MC) into the abomasum should have reduced intake in proportion to the mass of digesta attributable to the MC and associated water. In preliminary experiments faecal water and wet matter ouptuts increased by 6.2 and 7.4 g/g MC powder respectively.

2. The infusion of 2.95 kg MC/d did not affect food intake even though wet faecal output increased from a control value of 2.436 to 4.616 kg/d. The transit time of 51Cr-EDTA through the intestines decreased only slightly during the infusion indicating that MC produced a marked increase in the mass of intestinal contents. Increasing the rate of infusion to 5.336 kg/d increased wet faecal output to 5.437 kg/d, did not change transit time but significantly decreased food intake presumably to protect the intestines from overdistension. After stopping the infusion, food intakes and faecal outputs returned to control values but transit time remained unchanged. The intake of chopped lucerne hay by sheep was not limited by the capacity of the small and large intestines to transport bulk as intake was maintained even though wet faecal output was doubled and the intestines apparently became markedly distended.

1. Early-weaned lambs were used to estimate the concentration of urea required to give the maximum intake and utilization of maize or barley with either a high (HPB) or low (LPB) protein content.

2. Approximately the same concentration of urea (7–11 g urea/kg feed) was required for maximum intake and feed utilization of both HPB and LPB. With maize there was no increase in intake, live weight gain, digestion and feed conversion as a result of adding more than 7 g urea/kg.

3. The proportion of protein degraded in the rumen was estimated by the synthetic fibre bag technique to be 0.69, 0.82 and 0.54 for HPB, LPB and maize respectively. The similarity in concentration of urea required for the optimum utilization of LPB and HPB might be explained by differences in the extent of degradation of protein in the rumen, but the lower concentration of urea required for maize cannot be similarly explained.

4. From estimates of yield of microbial protein in the rumen, the extent of rumen fermentation and the measured extent of protein degradation, theoretical requirements for urea were calculated and compared with other predictions and with the experimentally determined values. For barley, predicted values agreed reasonably well with experimental ones, but for maize all values, including those derived by a new system adopted by the Agricultural Research Council (ARC) Working Party, were too high.

1. Comparisons were made between castrated male Scottish Blackface sheep and red deer (Cervus elaphus) of voluntary forage intake (VFI), digestibility and the mean retention time (MRT) of a particulate-phase marker (103Ru-phenanthroline) in the alimentary tract, when a range of forages: dried-grass pellets, chopped dried grass, fresh-frozen Agrostis-Festuca spp. and heather (Calluna vulgaris, L. Hull) were given at different times of the year.

2. On both the dried-grass-pellet and chopped dried-grass diets the red deer and sheep ate similar quantities. Both species had a higher VFI of dried-grass pellets in July than in November. The sheep digested the dried-grass-pellet diet better than the red deer and this was associated with a longer MRT of the particulate-phase marker in the alimentary tract.

3. The VFI of Agrostis-Festuca spp. and heather by the red deer was twice that of the sheep. The VFI of heather by the sheep increased by 32 % between January and April, and the VFI of both the Agrostis-–Festuca spp. and heather diets by the red deer increased by 65–70 %. The sheep digested the Agrostis–Festuca spp. better than the red deer but the red deer digested the heather slightly better than the sheep. MRT of the particulate-phase marker was greater for the sheep than for the red deer on both diets. The digestibility and MRT of both diets in the red deer did not decrease with the seasonal increase in VFI, suggesting a possible hypertrophy of the alimentary tract.