1. Lambs with cannulas in the duodenum and ileum were allowed free access to one of four diets: a basal diet of oat hulls and solka floc, or the basal diet supplemented with either urea, urea plus casein or urea plus formaldehyde-treated (HCHO)-casein. Mean nitrogen intake was 1.9 g N/d for the basal diet and 15.0, 32.4 and 36.9 g N/d respectively for the other diets.

2. The rate of irreversible loss of ammonia from the rumen pool estimated using 15NH+4 was highest on the casein diet (33 g NH3-N/d) by comparison with 18 g NH3-N/d for the urea and HCHO-casein diets and 7 g NH3-N/d for the basal diet.

3. The proportions of bacterial and protozoal N in the rumen derived from rumen ammonia did not differ significantly between the supplemented diets and were 0.66 and 0.52 respectively.

4. Estimation of 15N flowing to the duodenum during continuous infusions of 15NH+4 into the rumen indicated considerable ammonia absorption from the rumen on all the diets. Greatest absorption of ammonia (21 g N/d) apparently occurred in animals on the diet supplemented with urea and casein.

5. The estimated microbial non-ammonia-N (NAN) flowing out of the rumen per unit organic matter fermented in the rumen (FOM) was similar on all diets, i.e. 21.3 (±1.09) g N/kg FOM. The requirement for dietary fermentable N for microbial N production on these diets was 1.2 (±0.07) g N/MJ ME.

6. The flow of NAN into the duodenum and throught the ileum, and total N in the faeces was significantly influenced by the form of N supplementation. The flow of NAN into the duodenum for the HCHO-casein diet (27 g N/d) was more than twice that for the other diets (11 g N/d). The flow of NAN through the ileum and excretion of total N in the faeces was also greater with the HCHO-casein diet than with all other diets. The apparent digestibility of NAN in the small intestine ranged between 0.62–0.66 for all diets.

7. Urea and casein supplements were apparently completely degraded in the rumen. In contrast, the HCHO-casein was almost completely resistant to degradation in the rumen and only 65% of the HCHO-casein was digested in the small intestine.

8. Protein absorbed: energy absorbed (expressed as NAN digested in the small intestine/MJ ME) was calculated to be 5.5 (±0.70) for the basal, urea and urea-plus-casein diets, and 11.6 (±1.71) for the urea-plus-HCHO-casein diet.

1. Twenty leaf-protein concentrates (LPC), were produced from different crops and by different processes, the latter being designed to retain maximum nutritional value of the samples.

2. The establishment of conditions for the use of CI Acid Orange 12 in a commercial dye-buffer reagent for the determination of protein and reactive (available) lysine in LPC was investigated.

3. Values for protein by dye-binding correlated well with those for tungstic-acid-precipitated nitrogen (×6.25).

4. Some LPC samples showed a loss of reactive lysine, the greatest loss being associated with the most severe processing conditions.

5. For the LPC samples studied, dye-binding provided a convenient method for the concurrent determination of protein and reactive lysine.

1. Polyethyleneglycol (PEG 4000) was examined for its influence on relative nutritional value (RNV) and available methionine in sorghum (Sorghum ulgare Pers.), field beans (Vicia faba L.) and barley, as measured microbiologically with Streptococcus zymogenes. The results were assessed in relation to the content of tannins in the test samples.

2. In grain of hybrid sorghum the RNV averaged 87 (range 79–92) for six low-tannin varieties and 41 (30–53) for eleven high-tannin varieties. The corresponding available methionine values averaged 17.0 (15.7–18.9) and 8.9 (6.7–11.0) g/kg protein. Addition of PEG 4000 to the test samples increased the average RNV of the high-tannin varieties from 41 to 78, and the average available methionine content from 8.9 to 16.2 g/kg protein.

3. With seed of ten coloured-flowered varieties of field beans, treatment with PEG gave a small but consistent increase in the available methionine content, which resulted from the inactivation of tannins in the testa.

4. In twenty-three samples of barley grain, treatment with PEG had no effect on the values obtained for available methionine.

5. Treatment of high-tannin sorghum grain with ammonia has been reported to inactivate the tannins and increase the nutritional value for rats and chicks. This finding was confirmed. The present study showed that ammonia and PEG 4000 were equally effective in enhancing the nutritional quality as measured in the microbiological tests.

1. Twenty-eight leaf-protein concentrate (LPC) samples, subjected to different thermal treatments, were produced from five curd batches. For these samples, the fluorodinitrobenzene (FDNB)-reactive lysine values gave closer agreement with dye-binding lysine (DBL) than with the dye-binding capacity (DBC).

2. No relationship was established between the dye-bound-after-propionylation (DBAP) and the histidine+arginine value.

3. Comparison of dye-bound-protein values with those for tungstic-acid-precipitated nitrogen ×6.25 for the LPC samples showed the heat-damaged samples to lie below the regression line for the other samples.

4. Reactive-lysine values by dye-binding and by FDNB methods correlated well with total lysine, but the slopes of the regression line indicated closer agreement for values for samples not damaged by heat.

5. The correlation coefficients between DBC and total basic amino acids, DBC and histidine+arginine+DBL, and DBC and histidine+arginine+FDNB-reactive lysine were similar.

6. There was no correlation between the lightness of colour of the LPC samples and the availability of lysine.

1. An experiment was carried out on growing male rats to study the effects of a phosphorus deficiency on voluntary energy intake, estimated by the separate-feeding technique, as well as the consequences on growth and metabolic utilization of energy, protein and minerals. After a preliminary period of P deprivation, three groups of twelve animals were fed separately and simultaneously two dietary rations. A protein ration provided 1.2 g protein/d to which was added one of three levels of P in the form of monosodium phosphate: a normal level of 35.4 mg/d (treatment A), half the normal level (19.1 mg/d, treatment B) or one-quarter the normal level (9.6 mg/d, treatment C). Another protein-free ration was fed ad lib.

2. It was only when the level of P represented one quarter the normal level that a significant decrease in growth rate was noticed, accompanied by a definite decrease in daily energy consumption. The food conversion ratio (g dry matter intake/g body-weight gain) increased whereas the protein efficiency ratio (g body-weight gain/g protein intake) was lower. The nitrogen and energy retentions changed in the same way: both dectreased with treatment C compared to treatment A and B. Independently of the protein supply, the voluntary energy intake was closely related to the intensity of protein retention, which depended on the dietary level of P. The daily retention of P only slightly decreased at the lowest ingestion level (9.6 mg/d in treatment C), compared to that of the higher levels. On the other hand, the amount of calcium retained regularly decreased with the decreasing supply of P. The result of this was a progressive reduction in retained Ca:P as the level of P decreased.

3. From these results it appeared that the primary effect of a P deficiency in the growing rat was a decrease in bone mineralization. At a more advanced stage, the tissue P levels were affected and the resulting metabolic alterations reduced protein deposition and consequently the voluntary energy intake. The level of energy consumption, in separate-feeding, is more generally dependent on the level of protein deposition allowed by the limiting factor for growth, either protein, minerals or vitamins.

1. In order to establish whether or not there is a change in the relative rates of anabolism and catabolism of amino acids in the livers of lambs as they mature, a study has been made in isolated perfused livers obtained from foetal, suckling and ruminating lambs. The livers were perfused in a recirculating system and a mixture of amino acids (casein hydrolysate) was infused as substrate in the presence and absence of glucagon.

2. The oxygen consumption of the livers per unit weight increased as the lambs matured but the uptake of α-amino nitrogen declined. A comparison of the rates of O2 consumption and substrate uptake indicated that in foetal lambs less than 20% of the amino acids could have been oxidized, whereas in ruminating lambs all the amino acids taken up could have been oxidized.

3. In livers obtained from foetal lambs, the rate of urea production per unit weight of liver was approximately double that observed in ruminating lambs. Comparison of the rate of urea production and α-NH2-N uptake indicated that more than 60% of the substrate uptake was used for non-catabolic processes in the foetal lambs, whereas in ruminating animals all the α-NH2-N taken up could be accounted for as urea.

4. Gluconeogenesis could not be detected in lambs at any age studied and glucagon had no effect on any of the parameters studied.

1. Two preceding papers in this series describe the application of microbiological and other in vitro tests in the evaluation of sorghum (Sorghum vulgare Pers.), field beans (Vicia faba L.) and barley, and in assessing the influence of polyethylene glycol (PEG 4000) on the nutritional availability of the methionine. The present paper gives for comparison the results of bioassays on some of the same test samples. Net protein utilization (NPU) in rats was measurd by the nitrogen balance method, and N digestibility in chickens by the ileal analysis procedure.

2. In rat tests on sorghum, N in grain of high-tannin varieties was poorly digested. Supplementation of the test diets with 0.1 g PEG 4000/g protein gave a large improvement, which was partly offset by an apparent decrease in biological value (BV). With chickens N digestibility was even lower, and was similarly improved with PEG 4000. Treatment of high-tannin grain with ammonia solution was also effective in improving N digestibility.

3. With low-tannin sorghum the amino acid digestibilities were uniformly high and were not affected by addition of PEG to the test diet. With high-tannin sorghums they were low and less uniform, and were much improved by PEG 4000.

4. With field beans, the influence of the seed-coat tannin on protein utilization was much less pronounced than with sorghum. In chickens there was a significant effect (P < 0.05) of PEG 4000 on N digestibility in a high-tannin variety. With rats the effect was smaller and not significant.

5. In four samples of barley, N digestibility was high (0.87–0.96) and was not further improved by PEG 4000. The BV of a high-lysine cultivar proved marginally inferior to that of a normal variety. Possible reasons for this are discussed.

6. Over all, the results were closely consistent with those from microbiological tests with Streptococcus zymogenes.

1. Three sheep fitted with duodenal re-entrant cannulas and three with large rumen fistulas were given red clover, perennial ryegrass and a 2:1 (w/w) mixture of grass and clover in two Latin square arrangements. Measurements were made of voluntary intake, digestibility, flow of nutrients into the duodenum and the flow of Cr-EDTA marker through the reticulo-rumen.

2. Organic matter (OM) digestibility was similar for the three feeds but the voluntary intake decreased in the order mixture > red clover > perennial ryegrass. There was an increase in the rate of marker flow from the rumen and a decrease in retention time of the same order. Rumen volume did not change significantly.

3. There was a reduction in the mean particle size of rumen contents in the order perennial ryegrass > clover > mixture. The in vitro digestibility of particles decreased with size; the reduction being more rapid for clover than perennial ryegrass.

4. The proportion of ingested digestible OM appearing at the duodenum increased from 18.4% to 26.7% to 30.0% for perennial ryegrass, clover and the mixture respectively.

5. A higher proportion of digestible cellulose and hemicellulose disappeared over the stomach for the perennial ryegrass feed compared to the clover and the mixture but over 96% of water soluble carbohydrates and starch disappeared over the stomach for all three feeds.

6. The apparent digestibility of nitrogen was similar for all three feeds but the proportion of undigested feed N appearing at the duodenum was calculated to be greater by a factor of 1.71 and 2.52 for clover and mixture feeds compared to grass.

7. It was concluded that the higher nutritive value of red clover compared to perennial ryegrass was due to an increased rate of flow of nutrients througth the reticulo-rumen and an increase in the proportion of digestible OM digested post ruminally.

1. Glucose entry rates were measured with [2−3H]glucose in groups of cattle given sugar-cane diets and between o and 1200 g rice polishings.

2. In the first experiment measurements of glucose metabolism were estimated in four animals (one of each being given 0, 400, 600 and 1000 g supplement) over 24 h using a repeated single injection at 6 h intervals and sampling blood for 3 h.

3. The results indicated that in a short time period of each isotope experiment relatively steady-state conditions existed since the plot of log specific radioactivity v. time was linear with a high correlation coefficient.

4. The pattern of glucose entry rates was variable over the 24 h period being highest shortly after feeding and then declining to quite low levels immediately before the next feed, 24 h later. However, the more rice polishings that were made available to the cattle, the higher the glucose entry rate at 4–7 h, and it remained higher for a longer time.

5. In the second experiment with nineteen animals there was a linear relationship between the glucose entry rate (measured 4–7 h after feeding) and the amount of rice polishings consumed by the animal.

6. The results suggest that glucose is being made available in quite large quantities from the supplement. Using the means of these estimates over 24 h to predict glucose entry rate on a daily basis, it is suggested that at least 50% of the starch in the rice polishings was made available to the animal as glucose.

7. The results are discussed in relation to the suggestion that the availability of glucose may be limiting nutrient in cattle given low-protein diets.

1. Preruminant calves, fitted with abomasal and re-entrant ileal cannulas, were given, at intervals of 2–3 d by infusion into the absomasum, a series of five single experimental feeds containing heated soyabean flour (product B) as the only protein source. The calves were sensitized in this way to a constituent in the soya beans and by the fifth feed showed a number of digestive disturbances. Further test feeds were then given in which heated soya-bean flour was sometimes replaced by soya-bean products prepared under laboratory or commercial conditions by treating I part fat-free raw soya-bean meal with either I part (product M) or 4 parts (product L) ethanol (750 ml/l) at 78–80° and evaporating the whole mixture to dryness, or by extracting I part meal with 4 parts aqueous ethanol under similar conditions (product K). Products M, L and K were heated with steam and finely ground. Feeds prepared from casein and from commerical ethanol-extracted concentrate (product D) were also examined.

2. Measurements were made of transit time through the small intestine, flow rate of ileal digesta, recovery of polyethylene glycol (a water-soluble marker added to the feed) and net nitrogen absorption up to the distal ileum. Compared to feeds based on casein, feeds containing products K, L or M showed some differences in digesta movement and N uptake, but much less disturbance than feeds containing product B. Products prepared by extracting soya-bean meal with ethanol appeared to be slightly superior to those prepared from meal treated with ethanol, but the differences were not significant.

3. Weanling rats were used to assess the nutritive value of soya-bean products by an N balance method. Digestibilities (mean 0.948) and biological values (mean 0.860) obtained for products B, D, K and L did not differ significantly.

4. Results confirmed that extracting soya-bean meal with hot aqueous ethanol improved its value for calf feeding and indicated that at least part of the effect was due to the destruction of a toxic constituent present in the soya bean which probably acted by inducing a gastrointestinal allergy.

1. Sixteen first-calf Friesian heifers were used in a continuous treatment design experiment. For 2 weeks after calving they were given a 750 g concentrate, 250 g hay/kg ration with 169 g crude protein (nitrogen × 6.25; CP)/kg dry matter (DM). They were then divided into two groups of eight and given a high-protein (223 g CP/kg DM) or low-protein (107 g CP/kg DM) ration at the rate of 10.8 kg concentrates+3.6 kg hay for 8 weeks.

2. Milk yield and composition, live weight and blood composition were monitored throughout. A digestibility trial was carried out with six animals on each treatment.

3. The low protein ration reduced DM, organic matter, energy and fibre digestibility significantly (P < 0.001) so that intakes of digestible energy were not equal and the low-protein group lost more weight than the high-protein group.

4. Milk yield and the fat content of milk were lower in heifers given the low-protein ration (P < 0.01). The lactose content of the milk was not affected and protein content only slightly reduced (P < 0.1) by low-protein feeding. When the heifers were all changed onto an adequate protein (190 g CP/kg DM) ration in mid-lactation, those which had previously been under-fed protein appeared to recover in milk yield to the point they might have been expected to reach if given an adequate-protein ration throughout.

5. Concentrations of urea (P < 0.001) and albumin (P < 0.05) were reduced by underfeeding protein, but albumin concentration was affected less by diet than by stage of lactation. Blood concentrations of total protein, glucose, sodium, potassium, calcium, inorganic phosphate, iron, copper, haemoglobin and packed cell volume were unaffected by treatment. Blood magnesium concentration was slightly lower (P < 0.1) with low-protein feeding.

Zinc-deficient (ZD), weight-restricted (WR), pair-fed (PF) and ad lib. -fed (AL) Sprague-Dawley male rats were killed after feeding the respective Zn-deficient and Zn-supplemented diets from 3 to 8 weeks of age. Animals killed at the start of the experiment served as a baseline control (BC).

Four different skeletal muscles – biceps brachii, soleus, plantaris and extensor digitorum longus (EDL) – were studied for changes in weight, the number and diameter of muscle fibres and Zn concentration.

The soleus muscle had the highest concentration of Zn. It was the only muscle to reduce its Zn concentration due to Zn deficiency.

There was a loss of muscle fibres during normal growth (groups BC v. AL) in the soleus muscle (P < 0.05). The estimated length of muscle and the diameter of the muscle fibres in all four muscles increased significantly (P < 0.001). Therefore postweanling growth appears to occur as a result of longitudinal and transverse increases in the dimensions of these muscles.

The reduction in muscle fibre number in ZD rats compared to BC animals may occur within the range of expected fibre loss during normal growth. Fibre loss in ZD rats may be more affected by feeding-pattern-dependent metabolic changes than by a deficiency of Zn per se (groups ZD v. WR). Soleus fibre loss in ZD rats may be related to the high Zn concentration in this muscle.

The effect of Zn deficiency per se on muscle fibre diameter may be inaccurately interpreted by comparing the ZD animals with their PF and AL controls. There was no significant difference in fibre diameter in any of the four muscles when ZD and WF rats were compared.

1. Sheep were injected with varying doses of urea into the rumen and changes in the amount of saliva secreted from one parotid gland were studied. When the dose of urea was 0.1–0.2 g/kg, the secretion under- went no change. When the dose was 0.3 g/kg. the secretion was inhibited. When the dose was 0.4 or 0.5 g/kg, there was a marked inhibition in the secretion.

2. There was a close relationship between the ammonia level of the jugular blood and the inhibition of salivary secretion. When the ammonia level exceeded approximately 0.28 mmol/l, the secretion was inhibited abruptly.

3. Salivary secretion and rumen movement were inhibited when the blood ammonia level exceeded 0.28 mmoljl, after injection of ammonium acetate into the jugular vein.

4. Based on the results mentioned previously, the mechanism of inhibition on the secretion of parotid saliva is discussed in relation to the domestic ruminant in which urea had been injected into the rumen.

1. Heat production and heart rate of seven steers were measured simultaneously using either a calori- metric chamber or head-cage.

2. The relationship between heat production and heart rate for each animal was best described by linear regression.

3. Differences between individual animals made separate ‘calibration equations’ necessary for each animal.

4. Accuracy of prediction of heat production from heart rate was better than ±10% in all instances.

5. It is concluded that frequent measurement of heart rate appears to offer a practical method for esti- mation of heat production of free-range animals.