1. The rate of proteolysis of fraction 1 (18S) leaf protein in the rumen of sheep and cattle was affected by diet and the rate on fresh lucerne (Medicago sativa L) was three to nine times the rate on a hay + concentrate diet.

2. Simultaneous rumen fermentations in vivo and in an artificial rumen showed that the rates of proteolysis of fraction I in vitro was approximately 80% of the rates in sheep.

3. Using 14C uniformly-labelled fraction I protein at low concentrations, proteolysis exhibited 1st-order kinetics. Over a wide range of protein concentrations the velocity v. substrate concentration curve showed Michaelis–Menten characteristics typical of an enzyme-catalysed reaction. With rumen fluid from a hay + concentrate-fed sheep the maximum velocity was 2.6 mg protein nitrogen/1 per min and the Michaelis constant was 75 mg nitrogen/1.

4. Rapid adsorption of 14C-labelled fraction I protein onto bacterial cells preceded proteolysis.

5. Sucrose-density-gradient analysis showed initial incorporation of 14C from protein into rumen bacteria followed by partial transfer to rumen protozoa.

6. No peptides were detected during proteoiysis showing that the rate-limiting step occurred during the initial stages of proteolysis. Only small amounts of free amino acids were released except for leucine, isoleucine, valine and ornithine, which showed significantly increased levels.

7. Volatile fatty acids were the main 14C-labelied end products and were rapidly produced in descending concentrations: acetate > propionate > 3-methyl + 2-methyl butyrate > butyrate > isobutyrate > valerate.

1. Rats were deprived of food for periods of from 0 to 40 h and then given 203Pb, 203Hg. 59Fe, 64Cu. 64Zn or 45Ca by stomach tube. The absorption and retention of these metals in tissues was measured 1 h and 2 d after dosing.

2. After 16–24 h of food deprivation between two and ten times more metal was retained than after 0–12 h.

3. The effects of length of fast on metal uptake by the intestinal mucosa were greatest in the duodenum.

4. Lactale production by duodenal mucosa was halved after 12 h of food deprivation but galactose absorption was little changed after a 40 h fast.

1. Dry matter (DM), organic matter (OM), nitrogenous constituents, carbohydrate constituents and pH were estimated in digesta taken from eight different sites in the small intestines of slaughtered steers given different diets. Amounts of constituents passing different sites were compared using cellulose as a non-digestibte marker.

2. Amounts of the different constituents entering the small intestines varied with the type of diet given but the patterns of removal of each constituent were similar regardless of diet.

3. DM and OM were removed uniformly down the length of the small intestines. Net digestibilities of 0·62 and 0·63 for DM and OM respectively of the amounts measured in segment 1 digesta (first 3 m post-pylorus) were found at the terminal ileum. DM and OM contents of segment 1 digesta were 5 and 8% higher respectively than in abomasal digesta. Significantly smaller amounts of digesta were found in the proximal quarter of the small intestines than in more distal sections. There was a 10% addition of water to digesta in segment 1 compared with abomasal digesta. Of the water entering the small intestines a net 65% was absorbed therein, most absorption occurring in the first half.

4. Ammonia nitrogen was removed uniformly down the length of the small intestines to a net extent of 75% of that in segment 1 digesta. There was an apparent increase of approximately 18% in the total N (TN) content of segment 1 digesta compared with abomasal digesta. There was an approximate net removal of 80% of the TN measured in segment 1 digesta during passage down the small intestines. Over 95% of the digestible TN was removed in the section of tract between 3 and 15 m from the pylorus. Net removal of nucleic acid N (NA–N) up to the distal ileum was 78% of that in segment 1 digesta, most removal occurred in the proximal quarter of the small intestine. Little or no net loss of diaminopimelic acid–N (DAP–N) occurred in the small intestine.

5. Of the carbohydrates entering the small intestines, there was little or no removal of rhamnose, arabinose or xylose. Net removal of ribose, mannose, galactose and ‘starch’ glucose up to the distal ileum was 82, 76, 54 and 70% respectively of the amounts found in segment 1 digesta. All disappeared uniformly down the length of the small intestine.

1. Four pelleted diets were prepared containing milk or isolated soya-bean protein (ISP) as the major protein source. The milk and ISP were given either as intact proteins or partially (0·65) hydrolyzed with papain before feeding.

2. The diets were given ad lib. to thirty-two pigs from 7–28 d of age. The pigs were slaughtered at 28 d of age.

3. Weight gains, food conversion ratios and nitrogen balances of pigs given diets containing milk protein were better than those of diets containing ISP (231 g/d, 0·80 and 11·5 g/d compared to 209 g/d, 0·88 and 9·00 g/d respectively)

4. Partial hydrolysis of proteins before feeding did not affect the performance of the pigs.

5. Apparent digestibilities of N before the ileum and in the whole tract were 0·78 and 0.94 for the pigs given the ISP diets and 0·86 and 0·97 for the pigs given the milk-protein diets.

6. Retention time of ISP diets in the whole digestive tract was 1475 min and that of the milk-protein diets was 1089min.

7. pH of digesta in the stomach was 5·0–5·3 for all diets and increased to 6·9–7.1 in the ileum.

8. There were no differences in flows of total N and protein N to the ileum and lower digestive tract between the pigs given the intact- and hydrolyzed-protein diets.

9. Apparent absorptions of N in the stomach, duodenum and jejenum were greater in the pigs given diets containing hydrolyzed proteins than in those given diets containing the intact proteins.

10. Flows of total N and protein N to the ileum tract were greater when the pigs were given the ISP diets than when they were given the milk-protein diets.

11. Hydrolysis of proteins before feeding resulted in a reduced trypsin and chymotrypsin activity in the duodenum and pancreas.

12. Retention of dietary N in the carcass was greater in pigs given the milk-protein diets (0·79) than in those given the ISP diets (0·68).

1. Eight insulin-dependent and eight insulin-independent diabetic patients and twenty-eight non-diabetic essential hypertensive patients were given a high-fibre, high-unrefined carbohydrate and low-fat diet for 3 months duration.

2. The effects of this dietary regimen on the patients' fasting blood glucose, hypoglycaemic therapy and weight was observed.

3. Fasting lipid profiles were obtained before and after 3 months on the dietary regimen, and total serum lipids and lipoprotein fractions were analysed.

4. The insulin-dependent and insulin-independent diabetic patients showed a reduction in hypoglycaemic therapy, with no significant change in fasting blood glucose. The insulin-independent and non-diabetic groups both showed significant weight loss.

5. The three groups of patients showed a significant reduction in cardiovascular risk factors with either an elevation of high-density lipoprotein (HDL)-cholesterol or a fall in low-density lipoprotein (LDL)-cholesterol and a reduction in the total cholesterol: HDL-cholesterol value.

1. Q-strain mice selected for high (QLF) or low (QSC) body-weight at 6 weeks of age were compared with respect to their body-weight increases, gross body compositions and food intakes.

2. DNA, RNA, protein and hydroxyproline contents were measured.

3. QLF animals were larger at all stages of development but ate more food and gained more body-weight per unit food intake with an apparently improved efficiency of utilization compared with QSC mice.

4. The efficiency of deposition of dietary energy in Q-strain mice was found to be significantly lower than that of other growing mammals receiving similar energy intakes.

5. Body water, protein and fat of both strains were similar at birth and at 42 d of age but the contribution of fat to body-weight in the preweaning phase was greater for QLF while QSC accreted more fat per unit weight gain in the postweaning period.

6. An increase in cell number made a greater contribution to the growth post partum of the QLF mice, but by 42 d of age little difference between the number of cells per unit weight in the two strains was evident.

7. Despite increases in RNA concentrations at all stages of development, of QLF mice compared with QSC, measurements of body composition do not indicate any accompanying increases of protein concentration in these animals.

1. An experiment is reported in which the effects of giving copper sulphate-supplemented diets and control unsupplemented pair-fed diets to laying hens were compared.

2. The level of food intake significantly adversely affected mean body-weight, egg number, egg weight, liver, kidney, oviduct and ovary weights. Gizzard weight/kg body-weight was significantly increased both with decreasing levels of food intake and increased CuSO4 supplementation.

3. There was evidence of a depressing effect of CuSO4per se on egg production and possibly on oviduct and ovary weight.

4. Liver lipid concentration was significantly decreased with decreasing levels of food intake and the results also suggest a depressing effect of CuSO4.

5. The Cu concentrations and total contents in liver and kidneys were significantly increased by dietary added CuSO4. Liver and kidney Zn and Fe concentrations were increased with decreasing levels of food intake rather than by CuSO4. addition.

1. The relative potencies of three lysine, one tryptophan and six methionine analogues to their corresponding L-amino acids were determined.

2. Male poults, 9 d of age, were used in five 14 d experiments. Experimental diets were formed by adding increasing levels of an amino acid (L-isomer) or its analogues to a basal diet deficient in the test amino acid. Multiple-regression analyses of body-weight gain v. level of added or amount of consumed amino acid supplement were computed. Relative potencies of the analogues were calculated using the slope-ratio technique.

3. Type of independent variable used in the regression analyses did not significantly affect relative potency values.

4. From regression analyses with level of added amino acid supplement as the independent variable, relative potencies (with 95% confidence intervals) on a molar basis of each analogue as a percentage of the respective amino acid were: hydroxymethyl-L-tryptophan monohydrate 9 (−12, 22), DL-methionine sulphone 3 (−68, 36), DL-methionine hydantoin −10 (−63, 29), L-cystine 8 (−31. 40), DL-methionine sulphoxide 59 (24, 95) and 46 (18, 74), oleoyl-DL-methionine 77 (37, 138), methionine hydroxy analogue calcium 93 (65, 128), dicocoyl-L-lysine 23 (5, 41). bis-hydroxymethyl-L-lysine-calcium 69 (54, 82) and 41 (−1, 80), mono-hydroxymethyl-L-lysine-calcium 89(77, 101) and 99(65, 134).

5. The first four analogues appeared to have little or no amino acid activity. DL-methionine sulphoxide, dicocoyl-L-lysine, and bis-hydroxymethyl-L-lysine-calcium were partially active. Relative potencies of oleoyl-DL-methionine, methionine hydroxy analogue calcium, and mono-hydroxytmethyl-L-lysine-calcium were not significantly different from those of their corresponding amino acids.

1. A study was carried out to determine the effects of varying the level of energy intake on nitrogen balance in preschool children receiving the safe requirement level of protein, determined in an earlier study.

2. Seven preschool children received four energy levels, i.e. 293, 334, 376 and 418kJ/kg body-weight at the safe level of protein intake of 1·75 g/kg body-weight and N balance determined.

3. The N balance decreased with a decrease in energy intake. However, the N balance was positive at all levels of energy intake studied.

4. Results indicated that at a protein intake of 1·75 g/kg body-weight the minimum level of energy intake for a retention of 40 mg N/kg body-weight in these children was found to be 326·2±45·5 (mean ± SD) kJ/kg body-weight. Below this energy intake the safe level of protein intake became inadequate.

1. Six sows were housed in solid-floored farrowing pens and fed daily with approximately 200 μCi 198Au, three of them from 3 d before farrowing until their piglets were 10 d old and three from 10 d after farrowing until their piglets were weaned at 21 d.

2. The sows' faeces and sawdust bedding became radioactive but their milk remained free of radioactivity. The piglets' radioactivity was measured daily in a whole-body counter after they had been washed to remove external contamination.

3. The piglets' mean whole-body radioactivity was equivalent to 20·9 ± 2·5 g (range 5·7–85 g) of faeces and bedding. If the average passage time of the digesta through the gastrointestinal tract is assumed to be 24 h these values are equal to the average daily intake of faeces and bedding by the piglets.

4. This intake of faeces could possibly prevent the piglets becoming anaemic if the sow's diet were supplemented with iron to increase the Fe concentration of her faeces to approximately 2 mg Fe/g fresh faeces.

1. Three series of nitrogen balance experiments were performed with growing rats to test the effect of type and level of protein, fibre and starch on N excretion patterns. The design involved eighteen treatments in a 3×3×2 factorial experiment with five rats per dietary treatment. The eighteen treatments resulted from a combination of three protein treatments, three fibre treatments and two starch treatments. Protein treatments consisted of onelevel (15 g N/kg DM) of casein fortified with methionine, a protein of high digestibility, and two levels (15 and 20 g N/kg DM) of autoclaved brown beans (Phaseolus vulgaris), a protein source of low digestibility. The fibre treatments were two levels of cellulose powder and one level of barley hulls. The two starch treatments were autoclaved potato starch and autoclaved and raw potato starch (1:1, w/w).

2. The inclusion of raw potato starch reduced true protein digestibility markedly when the protein source was casein, but the corresponding biological values were increased significantly with this treatment. This strongly indicated a movement of urea from the blood to the intestines. This assumption was also supported by significantly lower blood urea concentrations in animals given raw starch. The influence of raw starch on true protein digestibility was, however, significantly less when cellulose and barley hulls were included. This is probably due to reduced transit time from fibre inclusion. The nature of the gut contents also supported this hypothesis.

3. The inclusion of raw potato starch when brown beans were the source of protein had much less effect on true protein digestibility and biological value than when casein was the protein source. This was probably due to the low digestibility of DM and protein in this food leaving sufficient energy and protein for maximum microbial growth. The inclusion of fibre also had little effect on N excretion patterns with the brown-bean diets.

4. An increase in the level of brown bean inclusion reduced true protein digestibility only on the diets containing raw starch whereas the biological value was consistently reduced regardless of starch treatment. The lower biological values were associated with significantly higher blood urea concentrations. Increasing the level of brown bean inclusion also resulted in higher fresh weights of caecum, colon and contents.

5. The present work proves that, through dietary manipulation, it is possible to affect nitrogen excretion patterns in rats.

1. The results of nine estimates of the efficiency of utilization of supplements of free lysine by growing pigs fed once daily and reported by Batterham (1974) and Batterham & O'Neill (1978) were re-analysed using carcass rather than live-weight values as the criteria of response.

2. The efficiency of utilization of free lysine with once daily feeding relative to frequent feeding was 0·53 using carcass gain as the criterion of response (P < 0·001), and 0·56 using food conversion efficiency on a carcass basis (P < 0·001). These estimates were lower than estimates of 0·67 using live-weight gain (P < 0·01) and 0·77 using food conversion ratio on a live-weight basis (P < 0·05).

3. The results indicate that current estimates of the lysine requirements of pigs that are based on responses to supplements of free lysine under once daily feeding regimens may be 10–30% over-estimated, as a result of incomplete utilization of the free lysine.

1. Twenty-six sheep were used in experiments designed to test the effectiveness of ammonium tetrathiomolybdate in the prevention and treatment of chronic copper poisoning.

2. Intravenous injections of 100 mg ammonium tetrathiomolybdate twice weekly (a) prevented the occurrence of haemolytic crisis in sheep repeatedly dosed with copper sulphate and (b) minimized tissue damage and prevented further haemolytic crisis when given to sheep already in haemolysis.

3. Thiomolybdate prevented excessive depostion of Cu in the liver of sheep receiving orally large amounts of Cu and decreased liver Cu levels in sheep that were not given additional Cu. In the latter sheep, 50 mg ammonium tetrathiomolybdate given twice weekly did not produce histologically-detectable tissue damage even though liver and kidneys contained high levels of molybdenum, and kidneys contained elevated levels of Cu.

4. It is concluded that chronic Cu poisoning can be successfully prevented or treated by intravenous injection of appropriate doses of ammonium tetrathiomolybdate.

1. Two experiments with male weanling rats were conducted in which they received individually and restrictedly either a basal semi-purified diet containing starch as the principal carbohydrate or the same diet to which mixed aflatoxins were added in quantities providing from 0·13 to 0·4 mg aflatoxin B1 /kg diet. Various natural ingredients, or semi-purified sources of dietary fibre were substituted for a portion of the starch in the basal diet containing aflaloxin. The diets were fed for 13–14 weeks after which the rats were given ad lib. a commercial rodent diet until they were killed at 109 weeks of age.

2. Two further experiments were conducted in which twenty-four rats in each experimentreceived the basal diet plus aflatoxin, or diets in which a portion of the starch was replaced by gum arabic or by wheat offal. After 13 or more weeksthe absorption, retention and excretion of 14C-labelled aflaloxin B1 was measured in each rat.

3. The addition of gum arabic or wheat bran to the diet decreased the effects of the toxin in the first two experiments, but as measured by several characteristics, only wheat bran provided an effect which persisted during the period when neither it nor the toxin was given. The effects included an apparent reduction in tumour incidence. The change in the content of starch in the basal diet, occurring as a consequence of adding the test ingredients is also considered to be an associated cause of the effects observed

4. In comparison to starch, wheat offal increased the total 14C in the faeces and the proportion of the total found during the first 48 h after dosing. Rats receiving starch excreted more 14C in their urine and retained more 14C in their livers. The differences between gum arabic and starch were not significant as measured by 14C excretion and retention. Liver size as a proportion of carcass weight was less in rats receiving wheat offal or gum arabic, and rats receiving wheat offal had a lower incidence of fat-loaded hepatocytes.

5. The interaction of dietary toxins, or drugs, with the ingredient composition of diet may affect animal response even when the diets are adequate and similar in nutrient composition. This may be of significance both in drug-safety studies and in animal production.

1. There is controversy regarding the capacity of the cat to convert 18:2ω6 to 20:4ω6 and the ability of the essential fatty acid (EFA)-deficient cat to produce 20:3ω9.

2. This paper reports the isolation and identification of 20: 3ω9 from kidney phospholipids of EFA-deficient cats.

3. The results suggest that the cat is capable of limited synthesis of 20:4ω6 using a Δ5- and Δ8-desaturase.

1. Fourteen sheep were dosed repeatedly with a solution of copper sulphate (2 g/l) in order to induce chronic copper poisoning and four similar undosed animals acted as controls.

2. Thiomolybdate (TM) was intravenously administered to all control sheep and to all except two of the test sheep. A variety of biochemical factors were studied before and after injections of TM.

3. The direct-reacting Cu, whole-blood Cu and plasma Cu concentrations were elevated in animals given TM injections and at the ‘haemolytic crisis’ of untreated chronic Cu-poisoned animals. But most of the increased Cu observed on injecting TM was insoluble in trichloroacetic acid (TCA) and did not enter erythrocytes. The results indicate that uptake of Cu by erythrocytes is essential for haemolysis to occur and that for this to happen the Cu must be in a direct reacting, TCA-soluble form.

4. Increased amounts of Cu were excreted in the urine at haemolysis and at the commencement of TM injections. High levels of direct-reacting Cu were found in plasma at these times.

5. Marked changes were not found in caeruloplasmin activity, packed cell volume or the osmotic fragility of erythrocytes except at haemolysis. TM injections did not alter these factors in any of the sheep studied.

1. Three adult dairy cows were fitted with cannulas in a mesenteric, portal, hepatic and jugular vein and a carotid artery. They received infusions of step-wise increasing amounts of ammonia as ammonium acetate via a mesenteric vein until NH3 intoxication occurred. Sodium acetate was used in control infusions. The maximum rate of uptake of NH3 by the liver and the concentrations of glucose, urea, lactate, acetate and bilirubin in blood were measured.

2. During the infusions of ammonium acetate the liver extracted almost all the NH3 present in the portal vein until an infusion rate of approximately 15·0 mmol/min was reached. The maximum capacity of the liver to remove NH3 during its first pass was on average 1·84 mmol/min per kg wet weight. The cows became intoxicated when arterial plasma ammonia concentrations reached 0·8 mmol/1. Concentrations of NH3 in jugular venous blood were between 66 and 74% of those in the carotid.

1. The eating and ruminating activity of four rams given long-chopped silage ad lib. in two daily meals was studied by jaw movement recordings. The events of rumination and pseudo-rumination were observed by fluoroscopy and by cineradiography.

2. The rate of eating was highest at the beginning of the main meal and then declined gradually.

3. The silage intake level was low.

4. The swallowed silage did not accumulate at the cardiac region but was forced into the dorsal sac of the rumen by the contractions of the reticulum and cranial sac of the rumen. For regurgitation the solid particles had to return via the ventral and cranial sac of the rumen into the reticulum.

5. Liquid reticular contents with floating solid particles were aspirated into the oesophagus during the maximum of the regurgitation contraction of the reticulum.

6. The rumination activity during the day presented a high proportion of pseudo-rumination cycles whereas during the night the rumination became progressively normal.

7. Pseudo-rumination was caused by delayed return of the fibrous silage particles into the reticulum. Thus in pseudo-rumination the regurgitated material consisted predominantly of fluid containing only a small quantity of solid particles.

8. The results explain why long-chopped silage intake is associated with pseudo-rumination, a lower breakdown of particles and a waste of digestion time.

1. The supply and utilisation of acetate has been estimated simultaneously in the whole animal and tissues of sheep using a combination of isotope-dilution and arteriovenous-difference techniques. Animals were made alloxandiabetic and acetate metabolism was compared when stabilized to normal metabolite levels with insulin (ITA sheep) and when food and insulin had been withdrawn for 36 h (fasted, diabetic sheep).

2. Acetate was simultaneously produced and utilized by all tissues. The exogenous (or gut) supply of acetate was the most important determinant of circulating acetate level. Endogenous acetate was produced mainly in the liver; 77 and 94% in fasted, diabetic and ITA sheep respectively. The production of endogenous acetate remained fairly constant and was not related to ketogenesis, which supports the idea that circulating acetate is largely a product of fermentation. The liver, gut and muscle utilized 17, 25 and 54% respectively (96% total) of the acetate entry rate in ITA sheep; a similar percentage utilization was found in fasted, diabetic sheep.

3. Acetate is largely oxidized to carbon dioxide in the gut and muscles of sheep and may account for 30–40% of their oxidative metabolism. This figure is similar to that for the whole animal. The total acetate taken up by the liver could account for 30% of the oxygen consumption; however, the liver may not directly oxidize all the utilized acetate.

4. The over-all conclusion from this study is that acetate is largely of dietary origin and the major factor determining its rate of utilization is the arterial concentration.

1. Both albumin and transferrin have been suggested as carriers of zinc in plasma. Their relative importance in Zn transport was therefore investigated as a preliminary to a study of the rates of passage of Zn through plasma.

2. The apparent log stability constant for Zn binding to human apotransferrin at pH 7·4 was estimated to be approximately 5·9 which is substantially lower than previous reports of 7·0 for the corresponding value for Zn binding to albumin (Giroux & Henkin, 1972).

3. When the relative abilities of human albumin and apotransferrin to compete for Zn with low-molecular-weight chelators were compared at the same relative concentrations of these proteins as are found in plasma, albumin retained substantially more Zn than transferrin.

4. It seems likely that albumin acts as the major transport protein for Zn in plasma of most species, Zn also being present firmly bound to α2-macroglobulin.

5. In porcine plasma or serum however, there were three major Zn-binding proteins, two of which were probably albumin and α2-macroglobulin. The nature of the third component remains unknown but it appeared to have a molecular weight of between 100000–140000, it was precipitated by 2·2 M-ammonium sulphate and by 150 gpolyethylene glycol/l.

6. There were no significant differences in Zn distribution in plasma of porcine blood obtained from the aorta, the posterior vena cava or from the hepatic portal vein but use of heparin as an anticoagulant altered the normal pattern of distribution of Zn in plasma.