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. Phospholipid content of brains of 3- or 8-week-old undernourished rats was 7–9 % less than that for the corresponding control animals and this deficit could not be made up by rehabilitation. Phosphatidyl ethanolamine and plasmalogen were the components most affected in brains of undernourished rats.

2. Incorporation of 32P into phospholipids by brain homogenates was 28% higher in 3-week-old undernourished rats. It is suggested that enhanced phospholipid metabolism in undernourished animals may be related to behavioural alterations noted previously (Sobotka, Cook & Brodie, 1974).

3. Ganglioside concentrations in 3- and 8-week-old undernourished animals were 14% and 11.5% less respectively than those of the control animals and this difference could be made up by rehabilitation. [14C]Glucosamine incorporation in vivo into brain gangliosides was not affected by undernutrition.

1. The role of the starch component of cereals and legumes on the utilization of casein-protein was studied.

2. In comparison with maize starch the legume and potato starches caused a significant lowering of net protein utilization (npu). And this reduction in npu could be partially restored by cooking the diets before they were fed to the rats.

3. It is suggested that in npu studies involving rats the experimental diet should always be cooked so that the conclusions drawn may be applicable to human diets.

1. The concentrations of vitamin B12 and folate in the serum and folate in the erythrocytes were determined and full blood counts made on a series of caucasian vegans and omnivore controls.

2. The blood counts and films were normal in all the vegans and no subject had a haemoglobin concentration below the lower limit of normality.

3. Although within the normal range, male but not female vegans had lower values for erythrocyte counts and higher values for mean corpuscular volume and mean corpuscular haemoglobin than their controls regardless of whether they were taking vitamin B12 supplements or not.

4. The mean serum vitamin B12 concentration was lower in the vegans not taking vitamin B12 supplements and in those using foods supplemented with the vitamin than in the controls, but in no subject was it below 80 ng/l.

5. The serum folate concentrations were higher in the vegans than in their controls. The mean value for erythrocyte folate tended to be greater in the vegans not taking vitamin B12 supplements. No subject had an erythrocyte folate concentration of less than 100μg/l.

6. It is concluded that megaloblastic anaemia is very rare in caucasian vegans and that a diet consisting entirely of plant foods is generally adequate to promote normal blood formation providing it is composed of a mixture of unrefined cereals, pulses, nuts, fruit and vegetables and is supplemented with vitamin B12.

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. The heat losses and energy balances of thirty-eight individually housed pigs (initial body-weights 21–38 kg) were measured continuously for periods of 14 d when they were maintained at environmental temperatures of 10, 15, 20, 25 or 30°. At each temperature four levels of feeding were given approximating to once, twice and three times the maintenance energy intake and the ad lib. level. The minimal maintenance energy requirement (M) was calculated to be 440 kJ metabolizable energy (me)/kg0.75 per d at 25°.

2. me intake at the ad lib. level decreased from 1965 kJ/kg0.75 per d at 10° to 1202 at 30°.

3. Heat loss calculated from multiple regression analysis decreased to minimum levels between 20 and 25° 30° was within the hyperthermic zone at each plane of nutrition.

4. The partition of heat loss into its sensible and evaporative components showed that evaporation increased from 25% at 10° to 78% at 30°.

5. Critical temperature was dependent upon food intake and decreased from 23.1° at M to 20.7° at 2M, 18.0° at 3M and 16.7° at 4M.

6. The extra food required to meet extra thermoregulatory heat production per 1° below the effective critical temperature was 0.65 g/kg body-weight per d.

1. Measurements of energy and nitrogen balances were made on thirty-eight individually housed pigs (initial body-weights 21–38 kg) at environmental temperatures of 10, 15, 20, 25 and 30° with four levels of feeding at each temperature. Values for energy retention (ER), protein (P) and fat (F) deposition and body weight gain (δW) were calculated at each temperature at metabolizable energy (me) intakes equivalent to once (M; 440 kJ/kg0.75 per d), twice (2M), three (3M) and four (4M) times the thermoneutral maintenance energy requirement.

2. ER at each plane of nutrition increased with temperature to maximal values between approximately 20 and 25° ER was negative at four of the five environmental temperatures at M.

3. P increased significantly with increase in me intake but was dependent on environmental temperatures only at intakes of M and 2M. The increase in P per unit increment in me intake decreased from 0.16 at 10° to 0.12 at 30°. The net efficiency of protein utilization also decreased with increase in environmental temperature from 0.54 at 10° to 0.39 at 30°.

4. F increased significantly with increase in me intake, but was more temperature-dependent than P, increasing to maximum values estimated to be between 20 and 25° at each level of intake; F at 30° was less than that at 25°. The increase in F per unit increment in me intake decreased from 0.63 at 10° to 0.51 at 30°.

5. The optimum temperature for ΔW was dependent upon me intake, varying from above 30° at M to less than 20° at 4M. The reduction in ΔW per 1° at 15° was also dependent upon the level of intake decreasing from 1.63 g/kg0.75 per d at M to -0.09 at 4M.

6. For a 35 kg pig the reduction in P, as a result of a 1° decrease in temperature at 15° at an intake corresponding to 2.5M, was equivalent to a 4 g/d reduction in food intake; the corresponding equivalent for F was 28 g/d.

1. The effect on calcium and phosphorus metabolism of a high rate of Ca infused directly into the blood of Ca-deficient wethers, already receiving an adequate Ca intake, has been studied by a combination of balance and radioisotope techniques.

2. The rate of Ca retention, which was already high, increased only slightly during the infusion before it reached a maximum. The surplus Ca was compensated for by a decrease in the rate of absorption and an increase in the rate of urinary Ca excretion.

3. These findings support the theory that at maximum retention the rate of Ca absorption becomes regulated according to the rate at which Ca can be stored in bone.

4. Results suggest that the decreased absorption was due to a decrease in the rate of active absorption and that the low rate remaining was due to diffusion.

5. The rate of P retention was increased by the Ca infusion, possibly as a result of the increased Ca retention.

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. From the relation between metabolizable energy (me) intake and heat loss (H), energy retention (ER), protein (P) and fat (F) deposition the energy costs of maintenance (MEm) and the partial efficiencies of energy retention (k) and protein (kp) and fat (kf) retention were determined in growing pigs at environmental temperatures of 10, 15, 20, 25 or 30°.

2. k decreased with increase in environmental temperature from 0.79 at 10° to 0.63 at 30° with 0.67 at the thermally-neutral temperature of 25°. Each 0.04 decrease in k was associated with a 100 kJ/kg0.75 per d decrease in mem Analysis, within several ranges of environmental temperature, suggested a curvilinear relation between ER and me intake indicating a decrease in k with increase in level of feeding, particularly at thermally-neutral temperatures.

3. Both kp and kf were similar at each environmental temperature and decreased from 0.78 at 10° to 0.63 at 30°. These values are discussed in relation to those predicted from experimentation and it is suggested that the wide range of predicted estimates of kp could be attributed to differences in the rate of protein turnover.

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. Eight protein concentrates were compared on a total lysine basis in lysine-deficient diets for pigs during the 20–45 kg growth phase. Each diet was also supplemented with free lysine to verify that lysine was the first limiting amino acid.

2. With fish meal, skim-milk powder, rapeseed meal and soya-bean meal growth rates and feed conversion efficiencies were similar and superior (P < 0.05) to those produced with cottonseed meal, two meat meals and sunflower meal.

3. The response to added free lysine confirmed that lysine was the first limiting amino acid in all diets except skim milk, where the growth response was not significant (P < 0.05).

4. The growth response of the pigs indicated that the availability of lysine in cottonseed meal, the two meat meals and sunflower meal was reduced by approximately 60% compared to that in the other protein concentrates.

5. Rat bio-assay estimates of the availability of lysine in the protein concentrates were in general agreement with those calculated from the response of pigs. There was little relationship between the Silcock estimates for lysine availability for the cottonseed, meat meals or sunflower meal relative to either the rat bio-assay estimates or the response of pigs.

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. The fatty acids of the triacylglycerols of subcutaneous adipose tissue of cattle, sheep, goats and red deer (Cervus elaphus) which consumed either herbage or a barley-rich diet were analysed for their content of branched-chain components.

2. Whereas the consumption of the barley-rich diet by sheep and goats was associated with the occurrence of relatively high proportions of branched-chain fatty acids, it was not in cattle and red deer.

1. Serum albumin levels have been estimated in healthy adult Nigerians. The average level of albumin was 41.4 g/l and there was no sex difference, but the findings differed from that of a previous survey in Ibadan. The importance of serum albumin measurement in relation to the socio-economic and dietary habits of the population has been reviewed.

2. It is concluded that socio-economic, dietary and cultural changes associated with Western education could be responsible for the increased level of serum albumin in this healthy population.

3. It is suggested that similar surveys should be done by locally-practising chemical pathologists.

1. Seven isonitrogenous diets were prepared containing soya-bean meal and dried grass either unsupplemented, or supplemented with wheat starch or paper or equal mixtures of both.

2. The diets were allocated according to a balanced incomplete block design to seven Clun Forest wether sheep, each fitted with a re-entrant duodenal cannula.

3. After each sheep had received a diet for 6 d, daily samples of digesta were collected automatically for the next 3 d.

4. The amounts of dry matter, gross energy and major nitrogenous components consumed in the diet, passing into the duodenum and excreted in the urine and faeces were determined.

5. A novel method was applied to estimate the proportion of the total amino acids passing into the duodenum which was of microbial origin.

6. The amounts of microbial total amino acids synthesized were compared with the amounts of energy disappearing in the rumen for each of the seven diets tested. For the starch- and paper-containing diets an average of 14.7 g microbial total amino acid passed into the duodenum per MJ energy disappearing in the rumen, whilst for the diets containing either paper or starch alone the mean value, 6.1 g/MJ, was significantly lower (P < 0.05).

7. The results of the experiment suggested that the energy released from a mixture of starch and paper was utilized more efficiently for microbial protein synthesis than when the energy was provided by supplements of either paper or starch alone.

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.