Mechanistic rumen models of Baldwin (1995), Danfæer (1990) and Dijkstra et al. (1992) were compared on identical inputs that were derived from trials with lactating dairy cows fed on grass herbage. Consistent differences were detected between models and between predicted and observed outputs. None of the models seemed to predict all nutrient flows best. The models particularly differed in the representation of microbial metabolism: degradation of insoluble substrate, fermentation of substrate into volatile fatty acids, and incorporation of substrate into microbial matter. Differences amongst models in the prediction of these processes compensated for each other and consequently all models predicted the duodenal flow of non-NH3 N, microbial N and organic matter reasonably well. Large differences remained in the prediction of individual nutrient flows, however, and it was stressed that in order to enhance prediction of the profile of nutrient flows, the mechanisms of microbial metabolism need to be tested on their ability to describe the intraruminal transactions. However, this requires more-detailed information on individual nutrient flows and on the microbial or non-microbial origin of duodenal contents. Parameter inputs for physical and chemical feed properties were identified that are improperly defined in extant models or susceptible to error. The description of these feed characteristics needs to be developed further and become identifiable for a wide range of dietary conditions.

Samples and extracts of foliage from African multipurpose trees were screened for their effects on rumen protozoa and bacteria with a view to predicting their safety as feed supplements and for identifying species with potential antiprotozoal activity. The species tested were Acacia aneura, Charnaecytisus palmensis, Brachychiton populneum, Flindersia maculosa, Sesbania sesban, Leucaena leucocephala and Vernonia amyedalina. Antimicrobial effects were mild except for S. sesban, which was highly toxic to rumen protozoa in vitro, and A. aneura, which was toxic to rumen bacteria. The antiprotozoal factor in S. sesban was apparently associated with the fraction of the plant containing saponins. When S. sesban was fed to sheep, protozoal numbers fell by 60 % after 4 d, but the population recovered after a further 10 d. In vitro experiments demonstrated that washed protozoa from later times were no more resistant to S. sesban than on initial exposure, suggesting that other micro-organisms, probably the bacteria, adapted to detoxify the antiprotozoal agent. Thus S. sesban may be useful in suppressing protozoa and thereby improving protein flow from the rumen, but only if the bacterial metabolism of the antiprotozoal factor can be avoided.

The effect of exogenous glucose supply by either intrajugular (IJG) or intraduodenal (IDG) infusion at 2.0 mg glucose/kg body weight per min was investigated in four wether sheep (average weight 44 (sd 4) kg) chronically catheterized in the carotid artery and portal veins. Sheep were fed on a dried grass pellet diet hourly using continuous belt feeders. Whole-body glucose irreversible loss (IL) rate, measured with [6-3H[glucose, was increased by 0.5 and 0.8 of exogenous supply for IJG and IDG infusions respectively. Portal glucose utilization, measured by isotope dilution across the portal-drained viscera, was unaffected by additional glucose regardless of the route of glucose supply (P = 0.76 for control ν. glucose infusions) and was a constant proportion of glucose IL (0.28) for all treatments. Portal plasma flow was higher during IDG infusions compared with IJG infusions (1.65 ν. 1.44 litres/min, P=0.055). Circulating total free amino acid concentrations fell during glucose infusions (2146, 1808 and 1683 μmol/l for control, IJG and IDG treatments respectively, P=0.067 for treatment effect) but net portal absorption was not affected by increased glucose supply. Recovery in the portal vein of [1-13C[leucine infused into the duodenum averaged 0.65 and was not affected by increasing glucose supply to the gut tissues. The results show that glucose utilization by gut tissues is responsive to changes in both vascular and luminal glucose supply. The effects of changing gut tissue use of glucose and increased whole body glucose IL on metabolism of nutrients is discussed.

The relationships of N input or protein status and the concentrations of serum insulin-like growth factor-1 (IGF-1), plasma fibronectin (FN) and total protein (TP) were examined in three experiments with steers and sheep nourished by intragastric infusion of nutrients. In Expt 1, three steers (340 kg live weight) were infused with three levels of volatile fatty acids (0, 300 and 600 kJ/kg metabolic weight (W0.75) per d) and six levels of casein (0, 200, 400, 650, 1500 and 2500 mg N/kg W0.75 per d). Each N treatment was imposed for 5 d. In Expts 2 and 3, five groups of sheep (about 35 kg live weight) were infused with casein at 500 mg N/kg W0.75 per d for 2 weeks followed by 1500, 500 or 50 mg N/kg W0.75 per d in Expt 2, and in Expt 3, with 100 mg N/kg W0.75 per d for 6 weeks or 10 mg N/kg W0.75 per d for 4 weeks. Non-protein energy was maintained constant at 500 kJ/kg W0.75 per d throughout. Daily N balance and total body N content at the end were measured, and protein status was defined as a percentage of cumulative N accretion or depletion in relation to the total body N content at maintenance. It was found that IGF-1 and FN responded rapidly and substantially to altered N input, and that when daily N input was maintained constantly at sub-maintenance, their continuous declines were related closely to progressive protein depletion in the sheep. Plasma TP concentration was independent of N input when N input was altered acutely in the steers, but declined significantly and gradually with severe, chronic body protein depletion in the sheep. Plasma content of TP in the sheep however reduced acutely with a reduction in N input. Plasma volume fell substantially over the first 2 weeks of protein depletion, compensating for the declines in TP content and maintaining TP concentration plateau. The possible implications of the changes in TP concentration and content (concentration x volume) to body protein loss in sheep are discussed.

In 1986, in her paper, ‘Animals in the service of human nutrition’, celebrating the award of the E. V. McCollum International Lectureship in Nutrition, Dr Elsie Widdowson observed: ‘Animals have served human nutrition well over the past century.... They are still of great service in human nutrition and may be more essential in the future as proper animal models for human diseases are discovered’. Ten years on, those animal models are an integral part of nutrition research and are providing fundamental tools to study the effects of diet on many of the major diseases of the Western world, including cardiovascular disease, obesity and cancer. Many of these models have been developed through the use of recombinant DNA technology and the expression of normal or mutated genes in the genome of transgenic mice.

Three ruminally and duodenally cannulated non-lactating Finnish Ayrshire cows were used to investigate ruminal and intestinal digestion of cell-wall carbohydrates by a combined in situ method. Five grasses cut at 10 d intervals were incubated in the rumen for 0, 6, 12, 24, 48, 72 and 96 h, and the undegraded residues were exposed to intestinal digestion. With advancing maturity of grass both the rate and extent of cell-wall digestion decreased. At early stages of growth the decreases were faster for the rate of digestion and at late stages of growth for the extent of digestion. Applying a passage rate of 0.02/h in one compartmental rumen model resulted in digestibility values markedly lower than typically observed in vivo. However, applying a rumen model incorporating a selective retention of particles and time-dependent release of particles from the non-escapable pool resulted in much higher digestibility values. Recovery of lignin after 96 h ruminal incubation with a subsequent mobile-bag incubation was very low (from 244 to 460 mg/g). Intestinal disappearance of neutral-detergent fibre (NDF) and hemicellulose decreased with advancing maturity of grass and with increasing length of preceding ruminal incubation period, i.e. with decreasing potential digestibility of the material. Disappearance of hemicellulose was much greater than that of cellulose for intact grasses but the difference diminished with increasing length of preceding rumen incubation period. On average, 195 mg/g of potentially digestible NDF disappeared from the mobile bags in the intestines. The post-ruminal digestion as a proportion of the total NDF digestibility varied between 0.034 and 0.058. Despite methodological problems both in ruminal in situ and intestinal mobile bag techniques, these methods can be used to investigate ruminal and intestinal cell-wall digestion and to partition cell-wall digestibility between ruminal and post-ruminal digestion providing that appropriate rumen models are used.

To investigate Fe nutritional indices in malaria infection in children, haematology (blood haemoglobin, plasma ferritin, transferrin, Fe, and transferrin saturation), acute phase markers (albumin and caeruloplasmin) and liver function tests were studied in fifty consecutive cases of severe and mild falciparum malaria, fifty matched controls and twenty-three cases of asymptomatic malaria. Blood haemoglobin and transferrin were lower, while ferritin and transferrin saturation were higher, in groups with symptomatic malaria in comparison with the control group. The differences were greatest with the severest form of the disease. There were no differences between any of the groups in plasma Fe. Plasma transferrin correlated directly with albumin in asymptomatic, mild and severe malaria groups (r 0.48, 0.65 and 0.83; P < 0.05, P < 0.01 and P < 0.001 respectively), and inversely with caeruloplasmin (r −0.65, −0.34 and −0.43; P < 0.01, P < 0.05 and P < 0.01 respectively). For ferritin, the correlation was inverse with albumin (r −0.65, −0.57 and −0.64; P < 0.01, P < 0.001 and P < 0.001 respectively and direct with caeruloplasmin (r 0.83, 0.21 and 0.49, P < 0.001, NS and P < 0.001 respectively). Multiple regression analysis on data from all patients combined indicated that albumin, and to a lesser extent alanine aminotransferase (EC 2.6.1.2) activity, explained 62 % of the variance in transferrin. Caeruloplasmin, parasite count and albumin explained 59 % of the variance in ferritin, and transferrin and unconjugated bilirubin explained 62 % of the variance in Fe values. In conclusion, these data suggest that low transferrin and high ferritin values are primarily due to the acute phase response. High transferrin saturation and lack of differences in plasma Fe between the groups are probably due to Fe released from lysed erythrocytes. Finally, in both symptomatic and asymptomatic malaria, indices of Fe status can be misleading and may be especially problematic in community studies in malaria-endemic areas where asymptomatic malaria may be common.

Meat has been identified, often wrongly, as a food having a high fat content and an undesirable balance of fatty acids. In fact lean meat is very low in fat (20–50g/kg), pork and poultry have a favourable balance between polyunsaturated and saturated fatty acids (P:S) and grazing ruminants produce muscle with a desirable n–6:n–3 polyunsaturated fatty acid ratio. In all species, meat fatty acid composition can be changed via the diet, more easily in single-stomached pigs and poultry where the linoleic, α-linolenic and long-chain polyunsaturated fatty acid content responds quickly to raised dietary concentrations. Recent work in pigs has attempted to manipulate the n–6:n–3 ratio by feeding higher levels of α-linolenic acid (e.g. in rapeseed) or its products eicosapentaenoic acid (20:5) and docosahexaenoic acid (22:6) present in fish oils. In ruminants the challenge is to increase the P:S ratio whilst retaining values for n–6: n–3 found in cattle and sheep fed on forage diets. The saturating effect of the rumen can be overcome by feeding polyunsaturated fatty acids which are protected either chemically, by processing, or naturally e.g. within the seed coat. Some protection occurs when grain-based or grass-based diets are fed normally, leading to relatively more n–6 or n–3 fatty acids respectively. These produce different flavours in cooked meat due to the different oxidative changes occurring during storage and cooking. In pigs and poultry, high n–3 fatty acid concentrations in meat are associated with fishy flavours whose development can be prevented with high dietary (supranutritional) levels of the antioxidant vitamin E. In ruminants, supranutritional vitamin E delays the oxidative change of oxymyoglobin to brown metmyoglobin and may also influence the characteristic flavours of beef and lamb.

The nutritional regulation of glucose transporter GLUT4 was studied in eight muscles and four adipose tissues from two groups of preruminant (PR) or ruminant (R) calves of similar age (170d), empty body weight (194kg) at slaughter, and level of net energy intake from birth onwards. Isocitrate dehydrogenase (EC 1.1.1.41) activity in muscles was not different between PR and R except in masseter muscle from the cheek (+71 % in R; P<0·003), which becomes almost constantly active at weaning for food chewing. Basal and maximally-insulin-stimulated glucose transport rate (GTR) per g tissue wet weight in rectus abdominis muscle were significantly higher in R calves (+31 and 41 % respectively; P<0·05). GLUT4 protein contents did not differ in muscles from PR and R except in masseter (+74 % in R; P<0·05) indicating that the increased GTR in rectus ubdominis cannot be accounted for by an enhanced GLUT4 expression. GLUT4 mRNAlevels did not differ between the two groups of animals in all muscles suggesting a regulation of GLUT4 at the protein level in masseter. GLUT4 number expressed on a per cell basis was lower in adipose tissue from R calves (-39 % P<0·05) and higher in internal than in peripheral adipose tissues. In summary, the regulation of GLUT4 in calves at weaning differs markedly from that previously described in rodents (for review, see Girard et al. 1992). Furthermore, significant inter-individual variations were shown for metabolic activities in muscle and for biochemical variables in adipose tissue.

Daily secretion of pancreatic juice, including postprandial responses to food, was investigated in two groups of calves: preruminant (fed with liquid food) and ruminant (fed with solid food). Male Friesian calves (1 week old and 6 weeks old) were surgically fitted with a pancreatic duct catheter, duodenal cannula and two duodenal electrodes. Continuous 24 h collections of pancreatic juice and myoelectrical recordings were performed with minimal restraint and disturbance of animals. In both groups of calves clear periodic fluctuations in pancreatic juice secretion (volume, protein output and trypsin activity) coinciding with duodenal migrating myoelectric complexes (MMC) were recorded. Secretion of juice per cycle and per day was greater in ruminant calves, but the frequency and amplitude of cycles were lower in this group. There were no differences between day and night-time preprandial pancreatic cycles and duodenal MMC in preruminant calves, whilst in ruminant calves, evening MMC were longer than morning MMC. The pancreatic cephalic phase (increase of volume flow, protein output and trypsin activity during and just after food intake) was significant only in preruminant calves following morning feeding. Postprandial pancreatic cycles did not differ from preprandial cycles, except the pancreatic cycle (juice volume and trypsin activity) in which food was offered in preruminant calves. No gastric or intestinal phase was observed in either group of calves. In conclusion, biological cycles of the gastrointestinal tract are present in both preruminant and ruminant calves, and these cycles evolve along with the change from liquid to solid food.

It has been suggested that decreased immune responsiveness in the elderly may be counteracted by the antioxidant vitamin E. In a 3-month double-blind placebo-controlled intervention trial among elderly subjects aged 65 years and over we studied the effects of a daily dose of 100 mg dl-α-tocopheryl acetate on the cellular immune responsiveness (n 52) measured by the in vitro response of peripheral blood mononuclear cells (PBMC) to the mitogens concanavalin A (ConA) and phytohaemagglutinin (PHA). Also effects on the humoral immune responsiveness (n 74) were investigated by measuring immunoglobulin (Ig)G, IgG4 and IgA antibody concentrations against various common antigens. In the vitamin E group plasma α-tocopherol increased by 51 % (P = 0.0001) during intervention whereas no significant changes were observed in the control group. Initial proliferative PBMC responses differed between the vitamin E group and the control group whereas all other baseline characteristics were comparable. No significant changes were observed in cellular immune responsiveness when adjusted for initial values in either the control group or the vitamin E group and, after the trial period, responses in the two groups were not significantly different. Similarly, in the vitamin E group no significant changes were found in levels of IgG and IgA raised against Penicillium or IgG4 raised against egg, milk, or wheat proteins. In the control group small but significant increases in IgG anti-Penicillium (P <0.05) and decreases in IgG4 against milk proteins (P < 0.05) were observed. Thus, the results of this study performed with the relatively low dose of 100 mg dl-α-tocopheryl acetate do not support the claims of a beneficial effect of vitamin E intake on the overall immune responsiveness of elderly subjects.

The nutritional manipulation of the diets of laying hens to include sources of n–3 fatty acids promotes the deposition of these nutrients into egg yolk. n–3 Fatty acid-rich eggs may provide an exciting alternative food source for enhancing consumer intake of these proposed healthful fatty acids. Care must be taken when designing n–3 fatty acid-rich poultry rations, however, to assure that the resulting egg fatty acid profile is useful for promoting consumer health yet maintaining egg sensory quality. In study 1 laying hens were fed on diets supplemented with graded levels of menhaden oil (MO), rich in both eicosapentaenoic acid (EPA; 20:5n–3) and docosahexaenoic acid (DHA; 22: 6n–3), for 4 weeks to determine maximal yolk fatty acid deposition attainable without sensory compromise. Yolk fatty acids were analysed for an additional 4 weeks, post-MO removal, to investigate yolk n–3 fatty acid tenacity. Dietary MO levels between 15 and 30g/kg yielded the greatest yolk n–3 fatty acid content; however, only eggs from birds fed with 15g MO/kg were considered acceptable by trained flavour panelists. Evaluation of eggs from hens fed with 15g MO/kg during storage verified that the shelf-life of enriched eggs was comparable with that of typical eggs. In study 2, graded levels of whole or ground flaxseed were used for the deposition of linolenic acid (LNA; 18:3n–3) and to determine in vivo production of DHA from dietary LNA for yolk deposition. Flaxseed form influenced yolk n–3 fatty acids only when given at 150 g/kg diet. In vivo production of DHA, while significant, was not enhanced by increasing the level of dietary flaxseed nor by grinding the seed. In the third study, a DHA-rich natural marine alga (MA) was investigated as an n–3 fatty acid supplement. Despite similar DHA profiles, dietary MA was found to be more efficient for yolk DHA deposition than dietary MO. These studies suggest that there are numerous viable n–3 fatty acid supplements for poultry rations. It must be realized, however, that the fatty acid profile of the final product varies substantially depending on which supplement is fed.

Rapeseed and rapeseed press cake were tested in four long-term experiments with a total of ninety-eight pigs. Rapeseed contained 20 and rapeseed press cake 19 mmol glucosinolates/kg DM. The proportion of the tested rapeseed products in feed amounted to 0 (control), 50, 100 and 150 g/kg diet. Moist-heat-treated rapeseed and rapeseed press cake with an extremely low glucosinolate content were also given at 150 g/kg diet. Each dietary rapeseed product level was given with 125 or 250 μg supplementary I/kg diet. Reduced feed intake and growth retardation were found in groups receiving 150 g rapeseed products/kg diet; in the case of rapeseed the impairments were significant. Rapeseed products ≥ 100 g/kg diet increased the thyroid weight and decreased the serum thyroxine (T4) concentration. Higher I dosage brought the serum T4 concentration to the level of the control group and retarded thyroid enlargement. Intake of rapeseed products lowered the I content of the thyroid; however, there was no significant difference between groups given 0·9 mmol glucosinolates/ kg diet and those receiving three times as much. Degrading glucosinolates by moisture and heat prevented feed intake depression and growth retardation. In the case of treated rapeseed the decreased serum T4 concentration and increased thyroid weight persisted, indicating formation of some antithyroid compounds due to myrosinase (EC 3.2.3.1) activation. A maximal glucosinolate content of 2 mmol/kg diet and additional I application are a prerequisite for using rapeseed products in pig feeding.

Zoo animal nutritionists need to make decisions about diet composition for a wide variety of vertebrate species, including those with very specialized diets (dietary specialists). For some zoo species it is common to refer to the published literature on the nutrient requirements of analogous domestic animals, such as cattle, horses and cats, as well as human beings (Allen & Oftedal, 1996). When this information is combined with knowledge of natural history, feeding patterns, composition of foods consumed in the wild and gastrointestinal tract morphology, it is possible to develop a sound foundation for a successful feeding programme for many zoo animals.

The effects of acidogenic conditions, a high S level and the addition of thiamin on the rumen microbial metabolism of thiamin were investigated in vitro in a semi-continuous fermenter (RUSITEC), using a factorial design. Acidogenic conditions were obtained by simultaneously increasing the starch: cellulose ratio and the amount of solid substrate fed, and by decreasing the buffering capacity of the liquid phase of the fermenter. S in the form of sulfate was supplied at two levels, one corresponding to a control amount of S (2 g/kg dietary DM), the second to an excess (5 g/ kg DM) which is sufficient to trigger cerebrocortical necrosis (CCN) when used in vivo. Acidogenic conditions decreased the pH of the fermenters, CH4 production and cellulose digestibility, increased the short-chain fatty acid production, but had no effect on thiamin production. The high S level enhanced the production of sulfide considerably, had no effect on the microbial metabolism of energy and N, and decreased thiamin production (326 ν. 266 nmol/d). The added thiamin was rapidly converted into phosphorylated compounds which largely decreased the apparent synthesis of this vitamin by the rumen microflora. The total thiamin flow was increased by added thiamin. In no case was thiaminase activity in the fermenter liquid phase significantly modified. The high level of S induced only a limited decrease of total thiamin flow. Consequently, it is unlikely that the investigated factors could be considered to be high risk factors for the thiamin-dependent CCN.

The effect of body fat content on the protein metabolism of energy-restricted sheep has been studied in two experiments. In the first experiment, six Suffolk-cross wether sheep, three weighing about 39 kg and three of about 61 kg, were given progressively increasing amounts of casein-N from 0 to 3000 mg N/kg metabolic body weight (W0·75) daily with constant energy, 91 kJ/kg W0·75 daily, from a high-propionic acid mixture of volatile fatty acids (VFA). In the second experiment, two lean and two fat sheep of similar body weights were given progressively increasing amounts of casein with the same VFA mixture. All the animals attained a positive N balance when they were in negative energy balance. N balance was not affected by body fatness of the magnitude studied, although lean animals utilized increasing levels of standard VFA (acetate-propionate-butyrate 65:25:10, molar proportions) infusion for N accretion more efficiently than fat animals. Endogenous energy was utilized for protein accretion with an efficiency of 0·56. Supply of glucogenic VFA equivalent to 28 mmol glucose/kg W0·75 reduced fasting N excretion by 39%. Fasting heat production decreased from 335 to 300 kJ/kg W0·75 with the infusion of casein and glucogenic VFA. It is argued that fasting induces additional heat losses due to raised protein metabolism and is unsuited as a baseline for dietary assessment.

Recent evidence suggests that plasma lutein is better correlated than either β-carotene or lycopene with its respective carotenoid intake and therefore may be a better marker of vegetable intake than either β-carotene or lycopene. In the study reported in this paper, measurements of plasma carotenes and retinol were made in infants from two villages near Peshawar in the North West Frontier Province, Pakistan, in July and November 1993. The approximate age at the start was 14 months, and 101 boys and ninety girls completed the study. Of the usual plasma carotenes, only lutein was measurable in all samples and was correlated with retinol in both boys (r 0.38, P < 0.0001; r 0.35, P < 0.001) and girls (r 0.21, P = 0.038; r 0.307, P = 0.003) at the two time points respectively. In addition, the change in lutein was even more strongly correlated with the change in retinol in both boys (r 0.453, P <0.0001) and girls (r 0.439, P < 0.0001). In August β-carotene was measurable in approximately 8 % of samples and this increased to 31 % in November but there was no correlation between β-carotene and retinol at any time. There were negligible amounts of lycopene and β-cryptoxanthin in plasma at both time points. The mean concentration of plasma retinol in the infants was 0.66 μmol/l at baseline and 59 % of the infants had retinol concentrations < 0.7 μmol/l. In addition, there were fifteen infants whose levels were below 0.35 μmol/l suggesting that vitamin A status in the population was marginal. Food intake of the infants was not monitored in the present study but breast feeding continues for up to 2 years in this part of Pakistan and most infants would be weaned onto selected foods eaten by the family. The close correlation between plasma lutein and retinol suggests that the increase in retinol over the summer season may be attributable to an increased availability of green vegetables to the families. The source of lutein to the infants is most likely to be the breast milk since such vegetables are unlikely to be given to infants except to suck as a weaning food. The results may indicate the potential usefulness of plasma lutein as a marker of changes in vegetable intake and changes in vitamin A status in Third World infants and children.

Following 10 weeks of fat supplementation a group of aerobically trained thoroughbred horses exhibited a significant decrease in postprandial plasma triacylglycerol concentration. This decrease was associated with a mean 50% increase in plasma total lipase activity following pentosan polysulfate administration and an increase in postprandial plasma cholesterol concentration. A significant increase in the activity of muscle citrate synthase (EC 4.1.3.7), expressed as a ratio to the total fractional area occupied by type I and type IIa muscle fibres, was also observed. No significant change in the concentration of resting muscle glycogen or triacylglycerol occurred as a result of fat supplementation. These results suggest that there was improved management of the fat load and that the triacylglycerol-clearing capacity of the horses was increased as a result of fat supplementation. It is suggested that the increase in plasma total lipase activity following pentosan polysulfate administration may have reflected an increase in muscle lipoprotein lipase (EC 3.1.1.34) activity, which would increase the capacity of muscle for free fatty acid uptake from circulating triacylglycerol-rich plasma lipoproteins. Fat supplementation may also enhance the oxidative capacity of muscle, as suggested by the significant increase in muscle citrate synthase and the trend towards an increase in β-hydroxyacyl CoA dehydrogenase (EC 1.1.1.35) following 10 weeks of fat supplementation.

One-day-old broiler chickens were fed on a control diet based on maize and maize starch or diets containing 30g/kg of 89 % deacetylated chitin (chitosan) or low-methoxyl (34 % degree of esterification) pectin. Feeding of the chitosan diet to chickens significantly reduced body weights and feed intakes compared with animals fed on control or pectin diets on days 5 and 11 of the experiment. On day 12, significant reductions in total plasma cholesterol and HDL-cholesterol concentrations were observed among birds fed on the chitosan but not the pectin diet in relation to control-fed animals. A concomitant increase in the plasma HDL-cholesterol:total cholesterol ratio was observed among chitosan-fed chickens. The generally reduced concentrations of primary and total bile acids in the duodenum of birds fed on the fibre-containing diets on day 13 may have been an indication of a delay in the production and/or secretion of bile. Viscosity of the three broiler-chicken diets was measured after suspension in water, acidification and finally neutralization of the suspensions, in an attempt to simulate the effect of changes in pH and dilution of diets occurring in the gizzard and small intestine of chickens. Viscosity of the chitosan diet was significantly elevated after acidification and significantly reduced at neutralization in comparison with the control and pectin-containingdiets suggesting that the hypolipidaemic influence of chitosan observed in the present study may be due to interruption of enterohepatic bile acid circulation rather than increased viscosity in the small intestine of chickens. The low viscosity of the pectin diet in vitro together with the absence of a hypocholesterolaemic effect of this diet when fed in vivo precludes any conclusion regarding the hypocholesterolaemic mechanism of pectin observed in earlier studies.

The effects of L-carnitine supplementation (50–500 mg/kg diet) of a practical layer diet, based on maize, soyabean and wheat, on the performance of laying hens and some indices of egg quality were studied for 8 weeks, using 65-week-old hens kept in cages. Albumen quality (albumen height and Haugh (1937) unit score) was improved, while yolk index and yolk colour score were not affected by dietary L-carnitine. The percentage of egg-white increased and that of egg yolk decreased in response to dietary supplementation of L-carnitine. Dietary L-carnitine did not influence laying performance (egg production rate, mean egg weight, daily feed intake, daily egg mass and feed conversion) or external egg quality measured by egg weight, egg-shape index or by eggshell quality, either measured directly as shell breaking strength or indirectly as shell weight, shell thickness or shell weight per unit surface area. Based on the results of the present study, L-carnitine had a beneficial effect on albumen quality and could modify the components of the edible part of the egg, during the late laying period.