1. Two groups of ewes were fed on a cobalt-deficient diet throughout pregnancy; one group (group A) was given the diet from the beginning of pregnancy, whilst the other (group B) received the diet for 16 weeks before mating. The ewes in group A continued to receive the diet for 12 weeks post-partum.

2. The vitamin B12 content of serum was estimated on three occasions before parturition and, for group A ewes, at 12 weeks post partum. Urinary concentration of methylmalonic acid was also determined at intervals before the lambs were born.

3. Serum values for vitamin B12 indicated that the ewes in both groups were depleted of the vitamin, though those in group B were more severely affected, as was evidenced by the high incidence of perinatal mortality among the lambs born to these ewes. Perinatal mortality appeared to be associated with abnormally-high values for urinary concentration of methylmalonic acid.

4. Analysis of liver lipids and adipose tissue triacylglycerols of some of the vitamin B12-deprived lambs which died before, or within 1 d of, birth showed that, compared with the corresponding tissues of control lambs, these lipids contained unusually high proportions of odd-numbered fatty acids (mostly 15:0, 17:0 and 19:0). This observation is discussed in relation to the likelihood that, in vitmain B12-deprived lambs, propionate becomes available as a primer unit for fatty acid synthesis when the metabolism of its carboxylation product, methylmalonic acid, is impaired due to partlal lack of a vitamin B12-containing enzyme system.

1. The excretion of 75Se and stable Se in bile and urine was measured in four steers during 6 h after intravenous injections of 75Se as either selenite or selenate containing either 5 or 5000 μg carrier Se.

2. When 5000 μg Se were given, the rate of urinary excretion and plasma clearance of 75Se was similar for both salts. Approximately 23% was excreted in urine and plasma clearance was triexponential, the mean half-life (t½) of the successive components, α, β and γ, being 2·3, 15·2 and 465 min respectively. The amount of 75Se excreted in bile was small; 1·94% of the 75SeO32− and 0·86% of the 75SeO42− dose.

3. When 5 μg Se were given the plasma clearance of 75Se was initially biexponential but the entry of 75Se-labelled protein from the liver caused an increase in plasma radioactivity after 30–40 min. The effect was most marked after 5 μg 75SeO32− when plasma 75Se radioactivity returned to 60% of the activity present at 2 min. Values for t½ of the two components of clearance for 75SeO32− and 75SeO42− were respectively α 2·6 and 2·5 min, and β 15·9 and 36·6 min. Similar amounts of 75Se appeared in bile (0·2% of the dose) after injections of either salt but much less 75Se was excreted in urine after 75SeO32− (6%) than after 75SeO42− (37%).

4. At low dosage rates (5 μg) Se is more readily incorporated into tissues from SeO32− than from SeO42−.

1. The rates of transport of zinc through plasma have been investigated in normal and endotoxin-stressed pigs.

2. 65Zn added to porcine plasma in vitro rapidly equilibrated with the Zn originally present.

3. 65Zn bound to albumin and injected intravascularly into pigs rapidly equilibrated with two kinetically distinguishable pools. The first of these pools was mainly associated with the plasma but was significantly larger than the plasma volume and substantially so in Zn-deficient pigs. The second pool appeared to represent a summation of the rapidly-exchangeable Zn within the extravascular tissues.

4. In non-stressed animals, the flux of Zn from the plasma of Zn-deficient pigs was only half that in Zn-supplemented animals.

5. Administration of endotoxin reduced the plasma Zn concentration of Zn-supplemented pigs but not of Zn-deficient animals. The fractional turnover rates of Zn were not altered in either of the two pools following endotoxin.

6. At 10 h after giving endotoxin neither the Zn content of the two pools nor the flux of Zn through them differed significantly between Zn-deficient and control pigs.

7. Intravascular infusion of Zn at a rate which essentially prevented the usual depression in plasma Zn concentration following endotoxin failed to alleviate the effects of endotoxin on Zn-supplemented pigs.

8. The reduction in plasma Zn concentration following endotoxin stress appears to be a normal physiological response which is not indicative of an increased metabolic requirement for Zn.

1. Rainbow trout (Salmo gairdneri) of mean initial weight 15 g were given either a low-manganese or control diet containing 1·3 and 33 mg Mn/kg dry diet respectively.

2. Weight gains over a 24-week feeding period were the same for both groups of trout.

3. Hepatosomalic index, blood packed cell volume and haemoglobin concentration, plasma protein and the activities of aspartic aminotransferase(EC 2.6.1.1)and alanine aminotransferase(EC 2.6.1.2) were unaffected by dietary Mn intake.

4. Plasma potassium and iron levels were increased in the trout given the low-Mn diet.

5. The hepatic levels of magnesium, sodium, K, zinc, copper, Mn and phosphorus were significantly reduced in the fish given the low-Mn diet.

6. In those trout given the low-Mn diet the levels of Mn and calcium in the vertebral ash were significantly reduced.

7. The hepatic activity of Cu-Zn superoxide dismutase (EC 1.15.1.1; Cu–ZnSOD) and of Mn superoxide dismutase (EC 1.15.1.1; MnSOD) in cardiac muscle and liver was reduced in the group of trout given the low-Mn diet. The fall in Cu–ZnSOD and MnSOD activities coincided with reduced tissue levels of their respective metal components.

1. Glutathione peroxidase activity (EC1.11.1.9) and erythrocyte stability were measured in Friesian bull calves which were given for 36 weeks semi-purified diets either adequate or low in selenium or vitamin E or both.

2. Dietary Se or vitamin E content had no effect on growth rate and haematological vaiues. None of the calves exhibited clinical deficiency symptoms and serum aspartate amino transferase (EC 2.6.1.1) and creatine phosphokinase (EC 2.7.3.2) activities remained normal. Heart and skeletal muscles of all calves appeared macroscopically and microscopically normal at autopsy.

3. Glutathione peroxidase activity in plasma, blood and other tissues, except the testis, was significantly lower in calves receiving low dietary Se but was independent of dietary vitamin E content.

4. Plasma vitamin E levels decreased rapidly and to very low levels in calves given low vitamin E diets irrespective of the Se content of the diet.

5. A low dietary vitamin E intake increased the susceptibility of erythrocytes to auto- and peroxidative haemolysis whereas a low Se intake in the presence of adequate vitamin E did not. However, erythrocytes from calves receiving low Se and low vitamin E were more susceptible to peroxidative haemolysis than erythrocytes from calves receiving low vitamin E and adequate Se. The effect of dietary vitamin E content on osmotic haemolysis induced by hypotonic saline was variable.

6. The results suggest that measurement of blood glutathione peroxidase activity and the susceptibility of erythrocytes to auto- or peroxidative haemolysis could be used for the differential diagnosis of subclinical Se and vitamin E deficiency in ruminants.

1. A long-term experiment was made with the Rumen Simulation Technique (Rusitec), in which the fermentation of a mixed ration of hay (1Og/d) and bruised barley (5g/d) was compared with the fermentation of the same diet in the presence of 2, 10 and 50 mg monensin/d.

2. Monensin depressed the production of acetic and butyric acids, markedly increased the production of propionic acid and virtually eliminated the production of isovaleric acid. The production of methane was decreased in the presence of monensin, but this decrease could be accounted for entirely by the changes in the production of volatile fatty acids and redistribution of metabolic hydrogen.

3. The digestibility of dry matter (DM) in the rations declined in the presence of monensin. Determinations of the rates of digestion showed that the digestion of the readily-fermented food in the initial stages was not affected by monensin, but that at 24 h digestion had been inhibited by monensin. The inhibition was due entirely to its effect on the digestion of the fibrous components. Digestion of non-fibrous material was not affected.

4. The efficiency of microbial growth, expressed as g dry weight/mol ATP formed (YATP) and in terms of dm digested, tended to be increased by monensin. This however occurred only at high, non-practical doses.

5. Urease (EC 3.5.1.5) was induced by the addition of urea to the fermentation, but monensin had no effect on urease activity. Although monensin increased the activity of protease in washed suspensions, more food protein apparently escaped degradation. This may have been due to decreased deaminative activity.

6. Monensin altered the mircroscopic appearance of the fermentation fluid, and changed the activity of some enzymes in sonicated extracts, including alkaline phosphatase (EC 3.1.3.1), acetate kinase (EC 2.7.2.1) and succinate dehydrogenase (EC 1.3.9.1). These results are discussed in terms of known sensitivities of rumen microbes to monensin and their contribution to the fermentation as a whole.

1. Surgical removal of the forestomach, the caecum or both the forestomach and the caecum, was performed on growing male golden hamsters (Mesocricetus auratus) given a low-or high-fibre diet.

2. In Expt J, 18 d after surgery, the hamsters which were given a concentrate before surgery were given an experimental low-fibre diet containing urea or [15N]urea (10 g/kg diet) for 9 d. In Expt 2, 5 d after surgery, the hamsters which were given a forage diet before surgery were adapted to an experimental high-fibre diet containing urea (10 g/kg) and dried Italian ryegrass (Lolium italicum) powder (400 g/kg diet) for 5 d, and 10 d after surgery, given a diet containing [l5N]urea (10 g/kg diet) for 9 d.

3. In both experiments, removal of the caecum resulted in a significant lowering of both weight-gain and the digestibility of the dry matter, and removal of the forestomach resulted in a significant decrease of both accumulation of 15N in the body protein and proportion of l5N retained in the body protein as a proportion of the administered dosage.

4. The effect of removal of the caecum on the utilization of [15N]urea was not apparent in Expt 1, but the utilization of [15N]urea was significantly lowered by removal of the caecum in Expt 2.

5. These results suggest that the caecum may play a more important role in food utilization than the forestomach. However, the forestomach of the golden hamster plays a significant role in the utilization of dietary urea. It is presumed that the role of the caecum in the utilization of urea may vary under different dietary conditions.

1. Primary growths of Italian ryegrass and timothy were harvested in late May, high-temperature dried and either retained in the chopped form or ground through a 2 mm sieve and pelleted. All diets were fed to four sheep fitted with re-entrant cannulas into the proximal duodenum and measurements of the sites of energy and protein digestion and the synthesis of volatile fatty acids (VFA) and microbial protein were made.

2. Grinding and pelleting significantly reduced rumen digestion of organic matter and structural carbohydrate(P < 0·05) and the synthesis of rumen VFA (P < 0·01), whilst significantly more digestion occurred in the hind gut, although this was not sufficient to prevent a decline in over-all digestibility on the pelleted diets (P < 0·05). The magnitude of all responses was much larger on the Italian ryegrass diet.

3. Net microbial protein synthesis was 15% less on the pelleted diets but efficiency of microbial protein synthesis was unaffected (mean 188g/kg rumen digested organic matter). Pelleting reduced the degradation of dietary protein from 69% to 47%, and dietary protein represented significantly more of the total protein flowing to the duodenum on the pelleted diets (chopped 28%, pelleted 41%).

4. Over-all, grinding and pelleting reduced total absorbed energy supply by 10% but increased absorbed protein supply by 1 5% which may contribute to some of the improvements seen, in the net energy value of pelleted dlets.

1. Experiments were undertaken to examine the kinetics of large ciliate protozoa in the rumen of cattle on sugar-cane diets.

2. Three Zebu bulls were fed once daily on a diet of sugar cane and wheat bran. The diurnal patterns of volatile fatty acids and ammonia concentrations, and the numbers of protozoa in rumen fluid were determined. The numbers of protozoa reached values of 5 × 104/ml for holotrichs (large ciliates) mainly Isoiricha and Dasytricha spp and 4 × 105 for smaller protozoa, mainiy Entodinia (small ciliates)

3. A method was developed which allowed large ciliate protozoa in rumen fluid to be separated from plant material and bacteria and concentrated in a relatively uncontaminated form. Analysis of these protozoa indicated that 1.8 × 105 large ciliates contained 1 mg nitrogen and approximately 32 mg dry matter

4. A labelled preparation consisting mainly of large ciliates (principally Isotricha spp.) was obtained by incubating isolated protozoa in rumen fluid (free of plant materials) containing [14C-methyl]choline and then isolating them by sedimentation and differential centrifugation

5. A portion of the preparation containing labelled protozoa was incubated in vitro with rumen fluid to determine the turnover of 14C-labelled metabolites. There was no apparent dilution of the label in the protozoa over a 22 h period

6. A major portion of the preparation containing labelled protozoa was returned to the rumen of each of the donor cattle as a single injection. The specific radioactivity in the large protozoa (μCi/mg N) was monitored frequently for over 30 h, and thereafter daily for a further 12 d. The kinetics of tracer dilution were analyzed to give estimates of the size of the pool of these large ciliates in the rumen (24–46 g N), and of their apparent rate of turnover

7. In contrast to the slow turnover of the large ciliates, the rate of turnover of the rumen fluid pool (approximately 54 l), estimated from the rate of dilution of polyethylene glycol, was considerably faster. Large ciliates were therefore selectively retained within the rumen

1. Endogenous levels of amino acids in ileal digests were determined as the output from pigs given protein-free diets and by extrapolation to zero intake of linear regressions of ileal amino acid output v. dietary amino acid intake. The protein-free diets included 0 or 50 g cellulose/kg and extrapolations were made from two series of four diets which contained graded levels of wheat or barley as the only source of protein. Within each series, dietary fibre level (mg/g) was maintained at approximately 140 or 190 neutral-detergent fibre (NDF) respectively. Endogenous amino acid levels in faeces were also determined.

2. Endogenous amino acid output in faeces was linearly related to dietary fibre level; endogenous ileal output increased with dietary fibre up to approximately 100 mg NDF/g, after which endogenous output no longer increased.

3. The amino acid composition of endogenous ileal protein varied little among levels of output and among different experiments. The composition appears to be determined by the predominance of mucin protein, the slow absorption of some amino acids and the methods commonly used to measure output. The very high levels of proline and glycine in ileal digesta seemed characteristic only of protein-free and low-protein diets.

4. The amino acid composition of endogenous faecal protein also varied little among different estimates, but was considerably different from that of endogenous ileal protein. Furthermore, the similarity of bacterial and faecal proteins suggested that much of the endogenous faecal protein was of bacterial origin.

1. A slope-ratio assay was developed to determine the availability of lysine in protein concentrates for chicks, Two protein concentrates were assessed per assay, using three levels of incorporation into the basal diet.

2. Availability of lysine, expressed as a proportion of total lysine in five protein concentrates was: cottonseed meal 0·83, fish meal 1·00, meat-and-bone meal 0·86, soya-bean meal 0·93, sunflower meal 1·01.

3. The five protein concentrates had previously been assayed for available lysine with slope-ratio assays for pies and rats (Batterham et al. 1979; Batterharn et al. 1981), There was little relationship between the results for chicks and those for pigs and rats. For pigs, availability estimates ranged from 0·43 for cottonseed meal to 0·89 for fish meal. For rats, availability estimates ranged from 0·49 for sunflower meal to 1·04 for fish meal.

4. The results for chicks were in closer agreement with values obtained using the Silcock available-lysine assay (Roach et al. 1967) and the direct 1-fluoro-2,4-dinitrobenzene procedure (Carpenter, 1960). By contrast, there was litlle relationship between the chemical tests and results for pigs or rats.

1. Pigs prepared with re-entrant ileal cannulas were used to determine the ileal availability of amino acids in nine cereal grains including five wheats, sorghum (Sorghum vulgare Pers.), maize, barley and Triticale.

2. The average true availability of amino acids in these grains was 0·88 but there were consistent differences in availability among amino acids. Generally, lysine and threonine were among the least available amino acids while glutamic acid and arginine were among the most available amino acids in cereal protein.

3. There was as much variation in amino acid availability within a grain species (wheat) as among the other grains.

1. Male lambs that had been born in autumn and wintered on forage diets were cannulated in the abomasum, confined indoors in individual pens, and fed on fresh primary growth ryegrass (Lolium perenne) – clover (Trifolium repens) pasture ad lib, for a 12-week period during spring. Mean diet organic matter digestibility (OMD) was 0/76, nitrogen content 29 g/kg dry matter (DM) and metabolizable energy (ME) content 11.1 MJ/kg DM. Thirteen lambs were infused into the abomasum with 44 g sodium caseinate +0/5 g L-methionine/d and 12 lambs were similarly infused with equivalent amounts of inorganic sodium and phosphorus. Initial live weight was 16/5 kg.

2. The twenty-five treatment lambs were slaughtered at the end of the experiment, and thirteen similar lambs were slaughtered when the experiment commenced. Body composition was determined and rates of protein, fat and energy deposition were calculated using comparative slaughter procedures.

3. Voluntary herbage DOM intakes tended to be slightly greater for control than protein-infused lambs, but calculated ME intakes including that infused as amino acids were similar for the two groups. Live-weight gains were 79 and 99 g/d for control and protein-infused lambs respectively (P < 0/05) and corresponding values for carcass gain: live-weight gain were 0/44 and 0/50 (P < 0/01), Wool growth was markedly increased by the amino acid infusion.

4. Carcass and whole body protein content was increased 10 g/kg by the protein infusion (P < 0/01) and fat content depressed approximately 25 g/kg (P < 0/05). Rates of protein deposition in both carcass and wool-free whole body were markedly increased by protein infusion, and total deposition including wool was 12.6 and 21.0 g/d for control and protein-infused lambs (P < 0/001). Energy deposited in protein as a proportion of total energy deposition was 0/27 and 0/41 for control and protein-infused lambs (P < 0/001), but total energy retention and the efficiency of utilization of ME for growth did not differ between the two groups of lambs.

5. It was estimated that 60 and 100 g total amino acids/d were absorbed from the small intestine in the control and protein-infused lambs respectively, corresponding to 0.16 and 0/25 of total ME intake. It was concluded that absorption of protein from the small intestine was limiting protein deposition in the growing lambs fed on fresh ryegrass-based spring pasture in this study. Absorption of cystine+methionine was specifically shown to be limiting. However, the protein deficiency was not a major factor in the low value for the efficiency of utilization of ME for growth for this diet (0/30).

1. The rates of transfer of plasma urea to the rumen of six sheep given brome grass (Bromus inermis) pellets alone or with supplements of sucrose or urea were determined using [14C]urea and 14C-labelled sodium bicarbonate infusions during three periods.

2. The sheep were slaughtered after the third period and samples of rumen epithelium were taken for assessment of numbers of adherent bacteria.

3. Maximum transfer (0·31 g nitrogen/h) of urea to the rumen was observed for sheep given supplements of 150 g sucrose/d plus 20 g urea/d. Maximum clearance of plasma urea to the rumen (rate of urea transfer to the rumen per unit plasma urea concentration, 5·8 1/h) was observed for sheep given 300 g sucrose/d.

4. Urea clearance to the rumen was negatively related to rumen ammonia concentration; the slope of the relationship was increased with each addition of sucrose to the diet.

5. Numbers of facultative bacteria adherent to the rumen epithelium were increased by urea and sucrose supplements.

6. The results are discussed in relation to a hypothesis which relates the ureolytic capability of the bacteria adherent to the rumen epithelium to the control of the rate of transfer of urea into the rumen.

1. Availability values for amino acids in nine cereal grains determined by faecal analyses with pigs and by the Silcock available lysine test (Roach et al. 1967) and an in vitro digestibility assay were compared with ileal availability values for the same grains determined with pigs by Taverner et al. (1981b).

2. There was a significant canonical correlation of ileal and faecal availability values. On average, apparent faecal availability of the indispensable amino acids was 4·2% greater than apparent ileal availability, but the difference was up to 12·6% for threonine. Furthermore, the difference appeared to increase as the digestibility of the grain decreased.

3. Silcock available-lysine values for the cereal grains were unrelated to the lysine truly absorbed by the pig.

4. There were close relationships of ileal protein and lysine availability values on nitrogen digestibility determined by an in vitro assay using pronase enzyme.

1. The incidence of diarrhoea, digestibilities of nutrients and the faecal bacterial flora were compared among three groups of Holstein male calves up to 3 weeks of age. Two groups of four calves were given a milk-substitute containing tallow by nipple-pail (group TN) and by open-bucket (group TB). The third group of four calves was nipple-fed a milk-substitute containing soya-bean oil (group SN). Each of the milk-substitutes contained approximately 300 g milk-protein and 100 g fat/kg dry matter (DM).

2. Mean faecal DM contents (g/kg) were 217, 185 and 112 for groups TN, TB and SN respectively and the corresponding pH values were 7·21, 7·00 and 6·50. The difference between groups TN and SN was statistically significant (P < 0·05).

3. No difference was observed between groups TN and SN in the apparent digestibilities of DM, crude protein (CP; nitrogen × 6·25), diethyl ether extract (EE) and total reducing sugars. But in the group TB, the digestibility of EE was significantly lower (P < 0·05), and that of CP tended to be, though not significantly, lower than in the other two groups.

4. Bacterial flora in faeces showed considerably wide quantitative variations among individual calves, but there was a tendency for increased viable counts of Lactobacilli in faeces of group SN.

5. The present results suggested that an appreciable difference in the mechanism would exist between diarrhoea occurring when milk-substitute was offered by bucket and when highly-unsaturated vegetable oils were contained in it. Possible mechanisms were also discussed.

1. Protein digestibility and lysine availability were determined in a range of grain samples using an in vitro digestibility assay calibrated with ileal digestibility values.

2. Mean(± SE) values predicted for nitrogen digestibility were 0·92±0·011 in wheat and 0·88±0·021 in barley, and the predicted lysine availability in wheat was 0·86±0·021.

3. Chemical and physical characteristics of the grains were determined and those most closely associated with protein digestibility for wheat were the contents of hemicellulose, neutral-detergent fibre, the bulk density, and to a lesser extent, N and acid-detergent fibre contents. These relationships were used to determine prediction equations for the available lysine content of wheat.

1. The uptake, transport and secretion of calcium into the gastrointestinal tract of germ-free (GF) and conventional (CV) chicks was determined by a variety of in vivo and in vitro techniques using 45Ca as a marker following a standard fast-feed regimen.

2. Following an oral dose of Ca in conscious chicks, the transit time of digesta in the GF birds was appreciably faster than in the CV controls.

3. Although the proportion of the Ca dose absorbed was similar in both groups of chicks, the accumulation of Ca in the intestinal wall was much greater in CV birds. Distribution of the labelled Ca in plasma and bone was similar in both groups.

4. Following intravenous Ca injection in conscious chicks the Ca secretion into the intestinal lumen was similar in both groups, but the amount appearing in the gut wall was appreciably greater in CV chicks.

5. There were regional differences in the ability of the gut to absorb Ca. There was a tendency for Ca uptake to be greater in the GF chicks but only in the proximal ileum did this approach significance.

6. When the Ca was confined to an intestinal loop the uptake/g tissue was similar in the proximal ileum of both groups but significantly greater in the distal ileum of the GF group. Uptake/10 mm gut was similar in both groups at both the proximal and the distal site.

7. It is suggested that the absence of a microbial load does not affect the ability of the enterocyte to absorb Ca but the subsequent removal of the absorbed load from the intestinal wall is appreciably slower in the CV group.