1. Zinc deficiency was produced experimentally in guinea-pigs fed on a diet containing 1.25 mg Zn/kg diet over a period of 60 d. In addition, the response of the Zn-deficient (ZnD) animals to Zn supplementation was studied for 15 d.

2. In the ZnD group a significant reduction was found in serum Zn and protein concentrations and in alkaline phosphatase (EC 3. 1. 3. 1; AP) activity from day 24 onwards.

3. Paper electrophoretic studies on serum revealed a significant decrease in relative values, as well as absolute values, of albumin and γ-globulin and an increase in β-globulin.

4. Albumin:globulin increased on day 24 but decreased significantly from day 48 onwards.

5. The kidney and testis of the ZnD group showed a reduction in Zn and protein contents, and AP activity.

6. Zn supplementation of the previously ZnD group resulted in marked although incomplete improvement in the biochemical indices studied.

1. In Expt 1, the effects on laying hens of diets supplemented with zinc oxide providing up to 20 gadded zinc/kg were compared. In Expt 2 the diets contained up to 6 g added Zn/kg.

2. In both experiments, food intake, body-weight, egg number, and liver, oviduct and ovary weights/kg body-weight were significantly reduced by added ZnO; gizzard weight/kg body-weight was significantly increased. In Expt 2, pancreas weight was significantly reduced by added ZnO.

3. Liver, kidney and pancreatic Zn and iron concentrations were significantly elevated in both experiments.

4. In both experiments, liver, kidneys and pancreatic copper concentrations gave quadratic responses to added ZnO.

1. Ten Friesian male calves of about 100 kg and 3 months old were reared similarly and were worm-free. From 13 weeks of age five calves received a dose of 640 infective larvae (L3) of lungworms (Dictyocuulus viviparus) twice weekly for 8 weeks to simulate continuous infection. Animals not infected were fed to the same level as the infected animals (about 1.2–1.3 kg concentrates and 14–1.5 kg good-quality hay/d).

2. Heat production was measured twice weekly during 48 h (days 2 and 3, and days 5 and 6) in each group of experimental animals.

3. Infection caused considerable damage to the lungs, increased respiration frequency and clearly produced antibody titres against D. viviparus.

4. Animals infected with lungworms had on average a lower rate of weight gain, reduced by 70 g/d per animal. Digestibility was not affected. Nitrogen retention was much lower in infected animals (12.0 v. 14.6 g/d per animal in controls).

5. Metabolizability of energy was slightly reduced in infected animals. Heat production as found in infected animals may be associated with an increased maintenance energy requirement of 30 kJ/kg live weight0.75 per d or reduced partial efficiency of feed conversion above maintenance in animals infected with lungworms (58.5 v. 64.1 % in the control animals).

6. It was concluded that the depression in rate of gain was related to reduced intake of feed and to decreased N retention.

1. Hyperplastic growth of adipose tissue in Japanese quail (Coturnix coturnix japonica) was examined in relation to sexual maturity to determine whether fat cell number is fixed in mature individuals of this species.

2. Total DNA concentrations in the lipid (lipocyte) and non-lipid (stroma) fractions of collagenase (EC 3. 4. 24. 3)-digested abdominal (retroperitoneal) fat depots were determined on a chronological-age basis from 28 to 240 d of age. The in vivo incorporation of [methyl-3H]thymidine into DNA of both the lipocyte and stroma fractions of abdominal fat from both ad lib. and restricted-fed (75% of ad lib.) females was also examined at ages before and subsequent to sexual maturity.

3. In both males and females, significant increases in abdominal fat weights at ages beyond sexual maturity were associated with increased lipocyte DNA. Regardless of the feeding regimen and stage of maturity, substantial radioactivity was recovered from both the stromal and lipocyte fractions of abdominal fat when female quail were examined 24 h after the administration of tritiated thymidine. When examined 5 d post-injection, the majority of the radioactivity was contained in the lipid fraction of collagenase-digested adipose tissue.

4. Both the total DNA content of adipose tissue and the incorporation of tritiated thymidine into adipose tissue indicated that lipocyte hyperplasia contributes to postmaturational increases in fat deposition.

1. Vegetative secondary growth Lotus pedunculatus was cut daily, and fed fresh at hourly intervals (600 g dry matter (DM)/d) to three groups each of three sheep fitted with permanent cannulas into the rumen and duodenum. Lotus fed to two of the groups was sprayed with low and high rates of polyethylene glycol (PEG; molecular weight 3350), which specifically binds the condensed tannins (CT). Nutrient intake and faecal excretion were measured directly, duodenal flows estimated from continuous intraruminal infusion of inert ruthenium phenanthroline (Ru-P) and CrEDTA markers, and rumen pool sizes measured at slaughter.

2. Dietary concentrations of total reactive CT (i.e. that not bound to PEG) were 95, 45 and 14 g/kg DM, whilst the corresponding values for free CT were 15, 5 and 2 g/kg DM.

3. Increasing dietary reactive CT concentration linearly increased duodenal flows of non-ammonia nitrogen, but linearly decreased the apparent digestibility of energy and organic matter, and rumen digestion of hemicellulose but not of cellulose. Rumen digestion as a proportion of total digestion was increased by the higher PEG rate for organic matter, energy, pectin and lignin.

4. High dietary CT concentration was associated with increased N retention. Rumen ammonia concentration and pool size showed only a slight decline on this diet, indicating that there must have been increased recycling of N into the rumen.

5. Increasing dietary reactive CT concentration had no effect on the rate at which carbohydrate constituents were degraded in the rumen per unit time (FDR), but increased the rate at which their undegraded residues (FOR) left the rumen per unit time. The latter appeared to be the principal mechanism by which rumen digestion as a proportion of total digestion was reduced at high dietary CT concentrations. From a comparison of FDR and FOR of carbohydrate components in lotus and Brassica oleracea diets, it was concluded that hemicellulose digestion was rate-limiting for rumen cell-wall digestion, probably due to bonding with lignin. However, the considerable post-rumen digestion of hemicellulose was not associated with post-rumen lignin digestion.

6. It was concluded that a desired concentration of CT in Lotus sp. should represent a balance between the positive effect of CT in improving the efficiency of N digestion and their negative effect in depressing rumen carbohydrate digestion. A recommended concentration is 3WOg/kg DM.

1. Records of metabolic measurements on cattle by open-circuit indirect calorimetry have been examined to determine the practical significance in the calculation of heat production of including measurements of carbon dioxide and methane in addition to the measurement of oxygen.

2. It was found that the combined effects of CO2 and CH4 made only a small contribution to the total estimation of heat production which could be calculated with approximately ± 1 % accuracy from analysis of O2 alone.

1. The effects of ‘cafeteria feeding’ on primiparous Wistar rats during lactation have been studied by measuring circulating levels of glucose, amino acids, lactate, urea and ammonia as well as glycogen levels in liver and muscle.

2. No significant changes in glucose levels were observed despite alterations in blood glucose compartmentation.

3. Compared with controls, the dams given the cafeteria diet had higher liver glycogen stores which were more easily mobilized at the peak of lactation.

4. Rats given the cafeteria diet showed a lower amino acid utilization than controls and adequately maintained circulating levels, as determined by the lower circulating levels of ammonia and urea.

5. No significant differences in body-weight were observed in the period studied despite increasing dam weight after weaning in the cafeteria-fed group.

6. The size of pups of cafeteria-fed dams was greater than that of controls, and the differences were marked after weaning, when the metabolic machinery of the cafeteria pup maintained high protein accretion and body build-up using fat as the main energy substrate characteristic of the preweaning stage. The controls, however, changed to greater utilization of amino acids as an energy substrate and adapted to high-protein (low- biological-quality) diets with a significantly different pattern of circulating nitrogen distribution.

1. Rams, fauna-free from birth and initially of 48–65 kg live weight, were allocated to two groups of ten each and given a diet containing 14 μg copper/g dry matter; five additional rams were killed and their livers were analysed for Cu.

2. One group (faunated) was inoculated with a mixed population of ciliate protozoa, and contained between 60x105 and 195 x 105 protozoa/ml rumen fluid throughout the 184 d experiment. The other group remained fauna-free. Following blood sampling, three rams in each group were killed on day 63, two on day 125 and four on day 184. One sheep in each group died during the experiment.

3. Faunated rams showed higher weight gains and feed consumption than fauna-free rams.

4. Plasma Cu concentration (μg/ml) increased from an initial 0.82to a final 1.00 in faunated and 1.36 in fauna-free rams. Liver Cu concentration (μg/g dry matter) increased from an initial 745 to a final 962 and 1684 in faunated and in fauna-free sheep respectively, representing a 4.3-fold greater increase in the fauna-free than in the faunated group. The absorption and retention of Cu was 38–50% higher in the fauna-free than in the faunated rams.

5. It was suggested that rumen ciliate protozoa increased rumen production of sulphide (through increased breakdown of soluble proteins) which complexed part of the Cu, making it unavailable for absorption and utilization. Therefore, ciliate protozoa could determine susceptibility to chronic Cu toxicity in sheep.

1. The activity of peptidase enzyme(s) was measured in homogenates of mucosa taken at slaughter from sites along the length of sheep small intestine.

2. The activity of the homogenate towards six dipeptides showed a similar pattern of distribution for each substrate. Activity was lowest in the proximal duodenum, rising through the jejunum to peak in the mid-ileum and declining towards the terminal ileum. The distribution of activity towards two tripeptides was similar.

3. Studies using the inhibitor p-hydroxymercuribenzoate showed that the activity towards the dipeptides was mainly localized in the cytosol fraction, while that towards the tripeptides was evenly distributed between the cytosol and the brush-border and activity towards a tetrapeptide was mainly associated with the brush-border.

4. The results are discussed in relation to the site and mechanism of protein digestion and absorption in the ruminant small intestine.

1. The effect of supplementing with methionine alone or in combination with arginine on whole-body protein synthesis and degradation was studied in protein-starved chicks, fed on a protein-free (PF) diet, by a massive-dose injection of L-[4-3H]phenylalanine.

2. Methionine or methionine and arginine (MA) supplementation reduced body-weight loss and improved N balance compared with unsupplemented controls.

3. Whole-body protein synthesis was significantly increased both in terms of fractional rate and absolute amounts by methionine and MA addition, whereas the fractional degradation rate was unchanged.

4. No significant difference was found between methionine and MA supplementation except for energy balance of the birds.

5. It was concluded that the N-sparing effect of methionine or MA when added to a PF diet was primarily brought about by enhanced whole-body protein synthesis.

1. Gel filtration on Sephadex G 75 was used to separate the medium-molecular-weight zinc-binding proteins from the soluble fractions from the duodenal and jejuno-ileal segments of the rat gut at 30 min after the intragastric administration of a tracer dose of 65Zn. These proteins were resolved by ion-exchange chromatography on DEAE cellulose.

2. In both the duodenum and jejuno-ileal segment an appreciable fraction of the total soluble Zn was bound in a protein fraction that resembled metallothionein [MT] in its behaviour on gel filtration. These fractions, however, were not homogeneous, but contained several medium-molecular-weight Zn-binding proteins. In the duodenum, but not in the jejuno-ileal segment, two ofthese proteins appeared to be the isometallothioneins, ZnMT-I and ZnMT-11.

3. These results suggest a possible role for MT in the binding of newly-absorbed Zn in the duodenal mucosal cells. They also show that gel filtration alone is insufficient for the identification of MT in the intestine.

1. The metabolism of dehydroretinyl ester has been studied in vitamin-A-deficient white leghorn chicks. Dehydroretinyl ester was metabolized to 3-hydroxyretinol diester, 3-hydroxyanhydroretinol and rehydrovitamin A2 which were isolated from the intestines and livers of chicks.

2. The metabolism of 3-hydroxyretinol diester and 3-hydroxyanhydroretinol, which were immediate metabolites of dehydroretinol, was studied in chicks.

3. Retinol was not detected in these experiments.

1. Four ruminating bull calves were provided with cannulas in the rumen and abomasum and a sleeve sutured at the omosal-abomasal orifice that permitted digesta flowing from the omasum to be diverted and collected.

2. The calves were each given in turn a high-roughage (HR) and high-concentrate (HC) diet consisting mainly of dried grass and flaked maize in the proportions 3:2 and 1:2 by weight respectively. Water-soluble non-absorbable marker (polyethylene glycol) was also given and the diets were sometimes supplemented with magnesium sulphate. For each diet (HR(0), HR(Mg), HC(0), HC(Mg)), collections were made from the rumen, reticulum, omasal outflow and abomasum, and flows of water, sodium, potassium and chloride calculated at these sites relative to intakes.

3. The general pattern of net exchange was similar for all the diets. Substantial additions of water and Na, a small addition of K and a small absorption of CI occurred between mouth and reticulum. Substantial (approximately 40–60%) absorption of water and Na, a small absorption of K and considerable secretion of Cl occurred in the omasum. Quantitative comparisons indicated that addition of water and Na up to the reticulum, presumably in saliva, was significantly greater for the HR than the HC diets. Addition of Mg appeared to stimulate absorption of Na and water up to the reticulum for unknown reasons. Re-absorption of these components in the omasum varied for different calves and diets but appeared to be influenced primarily by a positive linear relation between amounts of digesta flowing into the omasum and amounts of water and Na absorbed from it. The proportion of water absorbed also increased with increasing entry rates of water.

4. Other findings showed that pH values rose slightly (about 0.2 pH units) but significantly in the reticulum compared with the rumen and that the value fell again by about the same amount during the passage of digesta through the omasum. Changes between omasal outflow and the abomasum were as expected, with marked additions of Cl, Na and water and a fall in pH.

1. Saponins are steroid or triterpene glycosides which occur in a number of important food plants, including such staples as soya beans (Glycine max) and chickpeas (Cicer arietinurn). They are known to be hypocholesterolaemic.

2. Some saponins form an insoluble complex with cholesterol which prevents its absorption from the small intestine. Others cause an increase in the faecal excretion of bile acids, an indirect route for elimination of cholesterol.

3. We have investigated the effects of different saponins on absorption of the bile salt sodium cholate from perfused loops of small intestine, in vivo, in the rat. Purified saponins from soapwort (Suponaria Officinalis), soya beans and quillaia (Quillata suponaria) reduced the rate of absorption of the bile salt; soya-bean and soapwort saponins substantially so but quillaia saponin to a much lesser extent.

4. These results were explained by the formation of large mixed micelles by bile acid and saponin molecules in aqueous solution. These aggregates can have molecular weights in excess of 106 daltons, consequently the bile acid molecules incorporated in them are not available for absorption.

5. Control of plasma cholesterol and nutrient absorption through dietary saponins could provide substantial health and nutritional benefits in humans.

1. Piglets were weaned at 3 d of age and reared to 2.5 kg on a liquid diet in which the protein was supplied by dried skim milk and a mixture of free amino acids. The oxidation of L-[l-14C]phenyIalanine was measured as an indication of the partition of amino acids between retention and catabolism in pigs (2.5 kg) offered meals containing vaned concentrations of crude protein (nitrogen x 6.25).

2. The dietary protein concentration was varied either by increasing the inclusion of a mixture of free amino acids in a series of diets containing 100 g protein/kg from skim milk, or by increasing the level of inclusion of the skim milk in a series of diets containing the equivalent of 100 g protein/kg from the free amino acid mixture.

3. The oxidation of phenylalanine was minimized by dietary protein concentrations of 240 and 258 g/kg for the diets containing increasing concentrations of free amino acids or skim milk respectively.

4. These results show that a mixture of free amino acids is used more effectively than intact protein for promoting retention of essential amino acids.

5. The recovery of radioactivity in expired carbon dioxide was inversely related to the recovery of radioactivity in liver tissue when the concentration of dietary crude protein was increased from deficient to adequate, demonstrating that the fractional oxidation of the indicator amino acid was inversely related to protein synthesis.

1. Two experiments were conducted to determine the effects of heat on the nutritional value of lupin (Lupinus ungustifolius cv. Uniharvest and Unicrop)-seed meal, relative to soya-bean meal, for growing pigs.

2. In both experiments, values for carcass gain/d and food conversion ratio (FCR) on a carcass basis of pigs fed on the diets containing lupin-seed meal were inferior (P < 0.05) to those produced by pigs fed on soya-bean meal.

3. In the first experiment, heating lupin seed at temperatures from 105 to 150° for 15 min resulted in a linear depression in carcass gain/d, a quadratic increase in carcass FCR, a linear decrease in lean in the ham and a linear increase in backfat thickness. In the second experiment, autoclaving lupin seed from 5 to 45 min at 121° resulted in a linear depression in carcass gain/d and a linear increase in carcass FCR.

4. The addition of L-lysine to the diets containing lupin-seed meal verified that lysine was limiting in both experiments. The additions of L-lysine did not overcome the differences in carcass gains/d of pigs fed on lupin-seed meal relative to those fed on diets containing soya-bean meal.

5. It is concluded that the low lysine availability in lupin-seed meal for pigs is not due to the presence of heat-labile anti-nutritional factors in the seed.

1. Six rumen and abomasal cannulated heifers were used to study the effects of intake on the fractional outflow rates (FOR) of chromium-mordanted cotton-seed meal (Cr-CSM) and meat meal (Cr-MM), CrEDTA, ytterbium and lignin from the rumen. Values of FOR of Cr-CSM and Cr-MM were combined with values of nitrogen disappearance from the protein supplements, placed in porous synthetic (nylon) bags and incubated within the rumen (P), to calculate effective degradation (D)of CSM and MM when fed to heifers eating sodium hydroxide-treated straw. Also, N degradation in vivo (V) was measured as the difference between abomasal N flow and the sum of flows of microbial and endogenous N.

2. FOR were positively related to intake and differences between supplements were significant (p <0.01). FOR pertaining to high and low intakes respectively were 0.073 and 0.052 for Cr-CSM, 0.082 and 0.071 for Cr-MM, 0.030 and 0.023 for lignin, 0.082 and 0.073 for CrEDTA and 0, 044 and 0.035 for Yb.

3. A rise of 28.8 and 13.4% in FOR of Cr-CSM and Cr-MM respectively, associated with an increase in intake from maintenance to 1.5 times maintenance, resulted in 10.7 and 2.2% reductions in D, 24 h after feeding, for CSM and MM respectively.

4. With the exception of CSM at the high intake, estimates of V were underestimated by D and were 8.6–25.0% greater than the D values when time of incubation (t)= ∞. The two techniques, however, ranked the degradation of the two supplements in the same order at both levels of intake.

5. Underestimation of V by D may be attributable to underestimation of P, overestimation of FOR (both resulting in underestimation of D) or overestimation of V due to biases associated with the estimation of this part of the comparison. The relative importance of these factors remains to be determined.

1. Pigs (n 195) between 21 and 49 d of age were given a basal diet containing wheat, wheat gluten and cotton-seed meal which was supplemented with one of nine protein concentrates or free L-lysine. The diets were given ad lib. in two experiments.

2. Increasing the lysine content of the diets from 6.9 to 10.1 g/kg increased the weight gains of the pigs from 89 to 317 g/d in the first experiment. In the second experiment the weight gains were increased from 68 to 213 g/d by increasing the lysine content of the diets from 5.9 to 9.5 g/kg.

3. The utilization of lysine from the protein concentrates was compared with the utilization of free L-lysine.

4. The utilization of lysine for weight gain compared with free lysine was 0.86–0.88 for meat meals, 0.95–0.99 for soya-bean meal, 0, 69–0.75 for cotton-seed meal, 0.90 for lupins (Lupinus augustifoh) and 0.99 for milk.

1. The catabolism of L-[ l-14C]phenylalanine was used to indicate the effects of single amino acid supplementation of an inadequate protein diet (200 g crude protein (nitrogen x 6.25)/kg) on the utilization of dietary amino acids in pigs of 2.5 kg body-weight reared on an adequate protein diet (240 g crude protein/kg) containing skim milk and a mixture of free amino acids.

2. The oxidation of phenylalanine was decreased by the addition of proline or arginine to the inadequate protein diet but not by the addition of threonine, methionine, lysine or a mixture of essential amino acids, indicating that proline and arginine were limiting the utilization of dietary amino acids in the inadequate protein diet.

3. Dietary proline concentrations of 13.9 and 14.2 g/kg minimized phenylalanine oxidation in diets containing 200 or 260 g protein/kg. This indicates a dietary proline requirement of 14 g/kg.

4. Increasing the dietary arginine concentration in a diet containing 240 g protein/kg showed that an arginine concentration of 5.1 g/kg minimized phenylalanine oxidation. However, increasing the arginine concentration in a diet containing 200 g protein/kg increased phenylalanine oxidation, suggesting an amino acid imbalance involving arginine at this lower level of protein.

1. Four mature sheep were offered perennial ryegrass (Lolium perenne, cv. S23) silage (885 g dry matter/d) at hourly intervals. The silage was well fermented with a pH of 4.0, a lactic acid content of 139 g/kg dry matter and an organic matter digestibility of 0.766.

2. Continuous intraruminal infusions of 14C-labelled sodium salts of [U-14C]acetic acid, [2-14C]propionic acid, [2-14C]butyric acid and D- and L-[U-14C]lactic acid and an intravenous infusion of [U-14C]glucose were made on separate occasions to estimate the fluxes of rumen acetate, propionate, butyrate and lactate as well as plasma glucose. The data were resolved by the use of appropriate four-compartment (rumen) and three-compartment (rumen-plasma) models.

3. Irreversible loss rate (g C/h) of rumen acetate (5.32 g C/h) was considerably greater than values obtained for propionate (2.58), butyrate (2.80) and lactate (2.91).

4. Total flux of lactate (1.83 mol/d) exceeded the amount of lactate consumed in the diet (1.37 mol/d) indicating a net synthesis of 0.46 mol lactate/d. Approximately 0.90 of total lactate flux was metabolized in the rumen, with 1.00 mol/d converted to acetate, 0.57 to propionate and 0.08 to butyrate. The flux to acetate was significantly (P < 0.05) greater than that to propionate. Both the D- and L-isomers appeared to have similar metabolic fates.

5. Lactate appeared to make no direct contribution to glucose flux in the animal, but 0.10 of total lactate was converted to glucose through propionate.

6. The results are discussed in relation to overall lactate metabolism, and it is suggested that almost 0.30 of ruminally digested organic matter may be fermented via lactate.