Age-correlation of protein utilization to saccharide intake

Male Wistar rats aged 30, 90, 150 and 360 days were fed ad libitum on diets with an optimum protein and fat content for their respective ages and an increasing saccharide content. Net protein utilization (NPU) was determined from the body nitrogen and protein intake values and the course of gluconeogenesis in the liver was measured by specific phosphoenolpyruvate carboxykinase (PEPCK) activity. According to the growth curve for the standard diet, animals aged 30 and 90 days have a high growth rate (3.245 g/day), 150-day-old rats grow more slowly (1.856 g/day) and 360-day-old animals put on scarcely any weight at all (277 mg/day). In 30-day-old rats, NPU attains maximum values in the presence of a 36% saccharide content in the diet, in 3- and 5-month-old animals in the presence of 51% saccharides and in one-year-old animals in the presence of 41% saccharides in their food. The course of gluconeogenesis also corresponds to these values. PEPCK activity in the youngest age group is greatest in the presence of 31% saccharides in the food, at 90 days it is stimulated in the presence of 31-46% saccharides, at 150 days the decisive concentration is 41 and 46% and at one year proteins are used for saccharide synthesis in diet with a 31 and 36% saccharide concentration. For optimum saccharide values, PEPCK activity is reduced in every age group; together with the maximum NPU values, this indicates that proteins are used for growth and building of the organism at an early age and for the renewal of tissues and organs and maintenance of the organism in adulthood.     

Determination of the optimum doses of nutrients in a diet.

For 14 days, SPF male Wistar rats with an initial weight of 60 g were given isocaloric diets (1.7 MJ/100 g diet) containing 10% protein (casein) and 5, 10, 25 and 40% fat (margarine). Two utilization parameters of the protein biological value--net protein utilization (NPU) and liver protein utilization (LPU)--were determined from protein intake and body and liver nitrogen. These results were supplemented by a study of the course of the antithetical processes of gluconeogenesis and glycolysis, of the citric acid cycle and transamination processes and of the liver and muscle amino acid spectrum. A high (40%) fat diet significantly reduced the protein biological value parameters NPU and LPU and liver and muscle amino acid values, stimulated gluconeogenesis and inhibited glycolysis and the citric acid cycle, together with associated transamination processes in the liver. Activation of these processes in the muscles provided substrates for increased gluconeogenesis. The negative effect of a low fat + high carbohydrate diet was less marked. The optimum diet for weaned rats is thus a diet containing 10% protein and 10--25% fat. The study, which submits several possible ways of determining optimum nutrient intakes under different physiological conditions shows that diets with more detailed nutrient concentrations should be used.     

Determination of the optimum dose of fats in the food of rats of different ages

Over a 14-day period, male SPF Wistar rats with an initial weight of 60, 200 and 250 g (ages 30, 75 and 90 days) were given diets with a constant protein content (10% casein) and a mounting fat content (10, 15, 20, 25, 30, 40 and 50% margarine, at the expense of the saccharides in the standard diet). The utilization parameter of protein biological value (NPU) for the various diets was determined from protein intake and the body nitrogen values. The reciprocal relation of the intake of the two nutrients was determined on the basis of linearity between th growth parameter NPR and protein and fat intake and, after substituting the optimum protein intake, was used to compute the optimum fat content of the diet. From the aspect of the maximum NPU value the optimum fat contents were 30% for 30-day-old, 15% for 75-day-old and 10% for 90-day-old animals. In all three age groups (according to the growth curve for the standard Larsen diet animals with an equal growth rate of 3 g/day), protein utilization under optimum nutritional conditions was the same. The optimum fat content of the diet computed from the reciprocal relationship of fat and protein intake is in agreement with the value obtained by the biological method - 29.4% (49.5 energy %) for 30-day-old animals, 15,8% (30.4% of the total energy value of the diet) for 75-day-old animals and 11.83% (23.7% of total energy) for 90-day-old rats. By using a biological and a mathematical method, this study contributes to the determination of optimum physiological doses of nutrients.     

Effect of a high fat intake on protein utilization during ontogenetic development

Male rats (Wistar strain, Velaz, Prague) aged 30, 90 and 150 days were fed 14 days ad libitum on a high fat diet (containing 40% margarine) and their growth (PER, NPR) and utilization (NPU, LPU) parameters of protein (casein) biological value were compared with those of animals given a standard gel containing 10% margarine (the diets were isoenergetic). The course of gluconeogenesis in their liver was also determined by measuring phosphoenolpyruvate carboxykinase (PEPCK) activity. A high fat intake had a negative effect on the growth parameters of protein biological value, PER and NPR, in all three age groups and on the utilization parameters NPU and LPU in 30- and 90-day-old rats. The nonsignificant increase in NPU and LPU in the oldest animals was evidently related to the equal protein intake compared with the control, indicating that proteins need to be utilized more economically in the presence of a raised fat intake; owing to their far lower fat intake compared with 90-day-old animals on a high fat diet, the fat had a less negative effect on their protein utilization than in the younger age group. The negative effect of a high fat intake was confirmed by high activation of gluconeogenesis in 30- and 90-day-old animals and by raised phosphoenolpyruvate carboxykinase activity in 150-day-old rats, in which the supposition that gluconeogenesis would be highly activated if the diet were administered for a period other than 14 days cannot be ignored. The biological and biochemical methods employed in this study can be used with a wider perceptual range of dietary nutrients to determine optimum nutrient values under different conditions.     

Determination of optimum fat intake

In a 14-day experiment, adult rats weighting 250-260 g were given ad libitum diets with a constant protein content [casein - 10 %] and a mounting fat content [margarine - 0, 10, 20, 30 and 40 % - added at the expense of carbohydrates]. The growth parameters of protein biological value - PER and NPR - were determined and together with weight increments in correlation to protein an fat intake [a linear correlation] they were used on the basis of their regression equations to calculate the reciprocal relationships of fat and protein intake [for equality y]. By substituting the optimum protein intake [43.3 g/14 days - according to NPU], the optimum fat intake for adult rats was found to correspond to dietary fat concentrations of 9.72 % [y = weight increments], 12,82 % [y = PER] and 11.83 % [y = NPR]. These results wee verified in a biological experiment in which adult animals, for 14 days, were given a limited amount [31 g/animal per day] of diets containing 10 % protein [casein] an d9, 10, 11, 12, and 13 % fat [margarine - at the expense of carbohydrates] with the aim of studying the effect of a mounting fat intake on optimum protein intake [43.4 g/14 days]. The correctness of the mathematical method for determining the optimum fat intake was verified by a biological method [the optimum net protein utilization , NPU, which is highest in diets containing 11 % fats, i.e. 22.5 % of the total energy value of the diet]. It was also found that this method, both along and in conjunction with other methods [especially the one using the NPR parameter], was suitable for the determination of optimum nutrient values.     

Effects of protein level, methionine supplementation and carbohydrate type of the diet on liver lipid and plasma free threonine contents in the lactating rat

Eight groups of 13-15 female rats were fed purified diets after littering. Four groups received a low protein (8% casein) diet (groups 8) and the others, a normal protein (20% casein) diet (groups 20). Carbohydrates were supplied either as starch (groups S) or as starch plus 40% fructose (groups F). Half the animals received a 0.4% methionine supplementation (groups M). Four or five dams per group were sacrificed on days 2, 7 and 14 after littering. The diet intake was increased by methionine supplementation, substitution of starch for fructose and increased protein content, mainly during the second week of lactation. This influenced weight variation of the dams and litter growth. On all days, the plasma levels of cholesterol esters, triglycerides and phospholipids were positively correlated with the dietary protein level. On days 7 and 14, the liver neutral lipid content was increased in rats fed the low protein diets supplemented with methionine (groups 8SM and 8FM) and the normal protein diets containing 40% fructose (groups 20F and 20FM). The plasma free threonine content was positively correlated with the protein level in the diet. On day 14, rats fed a low protein diet had a threonine deficiency, except those in groups 8S and 8F. The plasma free threonine content of these rats was not reduced, possibly due to an impaired utilization of this amino acid. The liver lipidosis observed during lactation, in contrast to that observed during growth with a low protein diet, was not due to a threonine deficiency.     

The regulation of N-acetylglutamate synthetase in rat liver by protein intake

Urea cycle enzymes are subjected to regulation by dietary proteins. We have shown that this is also the case for N-acetylglutamate synthetase (EC 2.3.1.1.) (NAGS). Four different groups (n = 7) of male Wistar rats received either a low protein (8.7%) or a high (32% and 51%) protein diet and a control diet of 17% protein. The NAGS-activity in the liver, assayed after 15 days of feeding the different diets, increased from 25 +/- 7 (controls, 17% protein) to 31 +/- 5 (32% protein) and to 52 +/- 17 (51% protein) nmoles.min-1.g-1 wet weight. It decreased in the group with low protein diet (8.7%) to 5 +/- 3. The ratio of the arginine stimulated to the unstimulated enzyme activity remained constant over the range of protein intake. Similar changes were observed for carbamylphosphate synthetase, ornithine carbamyltransferase and arginase. As it is known for these enzymes adaptive mechanisms in relation to variations in dietary protein consumption also could be demonstrated for the enzyme NAGS.     

Protein utilization in correlation to protein intake

In a 14-day experiment, weaned and adult rats were given ad libitum isocaloric diets with a mounting casein content (5, 10, 15, 25 and 40% by weight) and growth parameters of protein biological value, PER and NPR, and the utilization parameters NPU (body protein) and LPU (liver protein) were determined together with phosphoenolpyruvate carboxykinase (gluconeogenetic enzyme) and pyruvate kinase (glycolytic enzyme) activity in the animals' liver. The decrease in all the biological value parameters in weaned rats on 25% and 40% casein diets and in adult rats on 15%, 25% and 40% casein diets shows that these concentrations are too high for the organism. The decrease in PER and diminished weight and body and liver nitrogen increments in both age groups in animals with a low protein intake is evidence that 5% casein is an inadequate concentration. The optimum diet for weaned rats is thus a 15% casein diet and for adult rats a 10% casein diet, as confirmed by the linear correlation between weight increments, body and liver nitrogen and protein intake and also by gluconeogenetic enzyme activity. Under the given experimental conditions the study is a contribution to the determination of optimum physiological doses of proteins.     

The relationship between protein retention and energy requirements in rats of different ages

Male Wistar rats aged 30, 75 and 150 days were fed for 14 days ad libitum on diets with an optimum protein content (15% for 30-day-old, 12.5% for 75-day-old and 10% for 150-day-old animals) and a mounting fat content (from 5 to 40%), supplemented by saccharides (from 76 to 41%). Net protein utilization was determined for each of the diets from the body nitrogen and protein intake values. Protein retention values were determined from protein intake on the basis of net protein utilization (NPU). Energy intake was computed from fat and saccharide intake, using energy coefficients. The optimum fat content of the diet, evaluated from the maximum protein retention value per day and the minimum amount of energy needed for the retention of 1 g protein, is 30% at 30 days, 15% at 75 days and 10% at 150 days. Protein retention per kg body weight falls with advancing age--mildly at 75 days compared with 30 days, but markedly at 150 days. From their smaller weight increments and NPU values and also from their lower protein retention, 150-day-old animals are characterized by slower growth and higher protein requirements for maintenance of their organism likewise demonstrated by the growth parameter net protein ratio (NPR). Energy requirements for total protein retention/day per kg body weight diminish with age. In old age a small amount of energy is needed only for the maintenance of body functions. This study contributes to the expression of the interrelationship of energy requirements and protein retention.     

Influence of the time of intake of a high fat diet on gluconeogenesis

Male Wistar rats aged 75 and 150 days were given high fat diet (36.5 weight % and 30 weight % fat) over a period of 14 days. The growth (PER, NPR) and utilization (NPU, LPU) parameters of protein biological value and liver phosphoenolpyruvate carboxykinase (PEPCK) activity were determined. In another experiment, the time dependence of liver gluconeogenesis enzyme (PEPCK and fructose-1,6-diphosphatase /FDP-ase/) and transaminase (alanine and aspartate aminotransferase /ALT, AST/) activities during 24 days' administration of the diet were determined. A 14 days' high fat intake had a negative effect on protein utilization in the organism of 75- and 150-day-old animals, which was more pronounced in the younger age group (a bigger drop in net protein utilization /NPU/ and greater stimulation of PEPCK activity). In 150-day-old animals the negative effect of a high fat intake was already manifested on the 6th to 10th day of the diet to the same degree as in the younger animals on the 14th day, as seen from the increase in all the enzyme activities. The paper presents findings on differences in the degree of the negative effect of a high fat intake on protein utilization with reference to age.     

Inter-organ relationships between glucose, lactate and amino acids in rats fed on high-carbohydrate or high-protein diets

1. Inter-organ relationships between glucose, lactate and amino acids were studied by determination of plasma concentrations in different blood vessels of anaesthetized rats fed on either a high-carbohydrate diet [13% (w/w) casein, 79% (w/w) starch] or a high-protein diet [50% (w/w) casein, 42% (w/w) starch]. The period of food intake was limited (09:00-17:00h), and blood was collected 4h after the start of this period (13:00h). 2. Glucose absorption was considerable only in rats fed on a high-carbohydrate diet. Portal-vein-artery differences in plasma lactate concentration were higher in rats fed on this diet, but not proportional to glucose absorption. Aspartate, glutamate and glutamine were apparently converted into alanine, but when dietary protein intake was high, a net absorption of glutamine occurred. 3. The liver removed glucose from the blood in rats fed on a high-carbohydrate diet, but glucose was released into the blood in rats fed on the high-protein diet, probably as a result of gluconeogenesis. Lactate uptake was very low when amino acid availability was high. 4. In rats on a high-protein diet, increased uptake of amino acids, except for ornithine, was associated with a rise in portal-vein plasma concentrations, and in many cases with a decrease in hepatic concentrations. 5. Hepatic concentrations of pyruvate and 2-oxo-glutarate decreased without a concomitant change in the concentrations of lactate and malate in rats fed on the high-protein diet, in spite of an increased supply of pyruvate precursors (e.g. alanine, serine, glycine), suggesting increased pyruvate transport into mitochondria. 6. High postprandial concentrations of plasma glucose and lactate resulted in high uptakes of these metabolites in peripheral tissues of rats on both diets. Glutamine was released peripherally in both cases, whereas alanine was taken up in rats fed on a high-carbohydrate diet, but released when the amino acid supply increased. 7. It is concluded that: the small intestine is the main site of lactate production, and the peripheral tissues are the main site for lactate utilization; during increased ureogenesis in fed rats, lactate is poorly utilized by the liver; the gut is the main site of alanine production in rats fed on a high-carbohydrate diet and the liver utilizes most of the alanine introduced into the portal-vein plasma in both cases.     

Effect of water temperature and dietary starch on growth and metabolic utilization of diets in gilthead sea bream (Sparus aurata) juveniles

We evaluated the effect of dietary starch level on growth performance, feed utilization, whole-body composition and activity of selected key enzymes of intermediary metabolism in gilthead sea bream juveniles reared at 18 and 25 degrees C. A diet was formulated to contain 48% crude protein, 12% lipids and 30% gelatinized maize starch (diet 30GS). Two other diets were formulated to include the same level of ingredients as diet 30GS except for the gelatinized starch, which was included at 20% (diet 20GS) or 10% (diet 10GS). No adjustment to diet composition was otherwise made. Each diet was fed to triplicate groups of gilthead sea bream (30 g initial mass) for 8 weeks, on a pair-feeding scheme. The higher temperature improved growth performance but the opposite was true for feed efficiency and protein efficiency ratio. Independently of temperature, growth performance, feed efficiency and protein efficiency ratio were lower in fish fed diet 30GS. No effect of temperature or dietary starch level on whole-body composition was noticed. Hepatosomatic index and liver glycogen were higher at 18 degrees C and, within each temperature, in fish fed diet 30GS. Glycemia was not affected by temperature, but was lower in fish fed diet 10GS. Data on enzyme activities showed that increasing water temperature enhances liver glucokinase (GK) and pyruvate kinase (PK) activities, suggesting that gilthead sea bream is more apt to use dietary starch at higher temperatures. No effect of temperature was noticed on hexokinase (HK), fructose-1,6-bisphosphatase (FBPase), glucose-6-phosphate dehydrogenase (G6PD) and glutamate dehydrogenase (GDH) activities. Dietary starch enhanced PK and FBPase activities while depressed GDH activity, suggesting a lack of significant regulation of hepatic glucose utilization and production in this species. HK, GK and G6PD activities were unaffected by dietary composition. Irrespectively of water temperature, gelatinized starch may be included up to 20% in diets for gilthead sea bream juveniles; at higher dietary levels, growth and efficiency of feed utilization are depressed.     

Response of hexokinase enzymes and the insulin system to dietary carbohydrates in the common carp, Cyprinus carpio

The response of the common carp to diets with varying amounts of digestible starch, provided either as pea meal (LP, HP, 30 and 46% peas, respectively) or as cereal (LW, HW, 30 and 46% wheat, respectively), was studied and compared with the response to a carbohydrate-free protein-rich diet (CF). Here we focused on the utilisation of dietary carbohydrates by examining the relationship between dietary starch intake, hepatic hexokinase activities, circulating insulin and muscle insulin receptor system. Plasma glucose concentration and hepatic high Km hexokinase (glucokinase, GK) activity were not affected by the content of digestible starch, but 6 h after feeding enzyme activity was higher in the fish fed carbohydrate diets. Similarly, low Km hexokinase (HK) activity was also higher in the fish 24 h after feeding. Fat gain and protein retention were significantly improved by increased digestible starch intake, especially in the HP group, which in turn, presented the highest plasma insulin levels. Glycogen stores were moderately increased by the ingestion of digestible starch. The number of insulin receptors was greater in the CF group than in fish on carbohydrates, except the HP group. Our results confirmed that the common carp uses dietary carbohydrates efficiently, especially when there are provided by peas. This efficiency might be related to the enhanced response of postprandial insulin observed in the HP group.     

Effect of normal and waxy maize starch on growth, food utilization and hepatic glucose metabolism in European sea bass (Dicentrarchus labrax) juveniles

We determined the effect of dietary starch on growth performance and feed utilization in European sea bass juveniles. Data on the dietary regulation of key hepatic enzymes of the glycolytic, gluconeogenic, lipogenic and amino acid metabolic pathways (hexokinase, HK; glucokinase, GK; pyruvate kinase, PK; fructose-1,6-bisphosphatase, FBPase; glucose-6-phosphatase, G6Pase; glucose-6-phosphate dehydrogenase, G6PD; alanine aminotransferase, ALAT; aspartate aminotransferase, ASAT and glutamate dehydrogenase, GDH) were also measured. Five isonitrogenous (48% crude protein) and isolipidic (14% crude lipids) diets were formulated to contain 10% normal starch (diet NS10), 10% waxy starch (diet WS10), 20% normal starch (diet NS20), 20% waxy starch (diet WS20) or no starch (control diet). Another diet was formulated with no carbohydrate, and contained 68% crude protein and 14% crude lipids (diet HP). Each experimental diet was fed to triplicate groups of 30 fish (initial weight: 23.3 g) on an equivalent feeding scheme for 12 weeks. The best growth performance and feed efficiency were achieved with fish fed the HP diet. Neither the level nor the nature of starch had measurable effects on growth performance of sea bass juveniles. Digestibility of starch was higher with waxy starch and decreased with increasing levels of starch in the diet. Whole-body composition and plasma metabolites, mainly glycemia, were not affected by the level and nature of the dietary starch. Data on enzyme activities suggest that dietary carbohydrates significantly improve protein utilization associated with increased glycolytic enzyme activities (GK and PK), as well as decreased gluconeogenic (FBPase) and amino acid catabolic (GDH) enzyme activities. The nature of dietary carbohydrates tested had little influence on performance criteria.     

Increasing protein at the expense of carbohydrate in the diet down-regulates glucose utilization as glucose sparing effect in rats

High protein (HP) diet could serve as a good strategy against obesity, provoking the changes in energy metabolic pathways. However, those modifications differ during a dietary adaptation. To better understand the mechanisms involved in effect of high protein diet (HP) on limiting adiposity in rats we studied in parallel the gene expression of enzymes involved in protein and energy metabolism and the profiles of nutrients oxidation. Eighty male Wistar rats were fed a normal protein diet (NP, 14% of protein) for one week, then either maintained on NP diet or assigned to a HP diet (50% of protein) for 1, 3, 6 and 14 days. mRNA levels of genes involved in carbohydrate and lipid metabolism were measured in liver, adipose tissues, kidney and muscles by real time PCR. Energy expenditure (EE) and substrate oxidation were measured by indirect calorimetry. Liver glycogen and plasma glucose and hormones were assayed. In liver, HP feeding 1) decreased mRNA encoding glycolysis enzymes (GK, L-PK) and lipogenesis enzymes(ACC, FAS), 2) increased mRNA encoding gluconeogenesis enzymes (PEPCK), 3) first lowered, then restored mRNA encoding glycogen synthesis enzyme (GS), 4) did not change mRNA encoding β-oxidation enzymes (CPT1, ACOX1, βHAD). Few changes were seen in other organs. In parallel, indirect calorimetry confirmed that following HP feeding, glucose oxidation was reduced and fat oxidation was stable, except during the 1(st) day of adaptation where lipid oxidation was increased. Finally, this study showed that plasma insulin was lowered and hepatic glucose uptake was decreased. Taken together, these results demonstrate that following HP feeding, CHO utilization was increased above the increase in carbohydrate intake while lipogenesis was decreased thus giving a potential explanation for the fat lowering effect of HP diets.     

Comparison of copper status in rats when dietary fructose is replaced by either cornstarch or glucose

The purpose of this study was to determine what levels of starch or glucose replacement for fructose in the copper-deficient diet (copper) can minimize the fructose-copper interaction. Experimental diets contained either 100% fructose as the carbohydrate source, or the fructose was partially replaced with 50% starch, 50% glucose, 75% starch, or 75% glucose. Diets were either copper adequate (7-8 ppm) or inadequate (less than 1 ppm). Male weanling rats were fed their respective diet for 5 weeks and then fasted overnight. After decapitation, blood was collected and liver and heart were removed. Plasma copper was significantly reduced and ceruloplasmin was not detected in all copper-deficient groups. Copper deficiency increased plasma cholesterol, as well as heart and liver weight in the glucose groups, but not in the starch groups. Those organ weights were heavier in glucose-copper than starch-copper rats. Erythrocyte copper-zinc-superoxide dismutase activity was greater in starch-copper rats. Erythrocyte copper-zinc-superoxide dismutase activity was greater in starch-copper than glucose-copper rats regardless of carbohydrate amount. Hepatic copper concentration of the group fed starch-copper was twice levels observed in glucose-copper. The 50% glucose rats had lower hepatic copper than the 75% glucose rats. Hepatic copper-zinc-superoxide dismutase activity showed patterns similar to hepatic copper. Cardiac copper was greater in starch-copper than glucose-copper rats. Cardiac copper-zinc-superoxide dismutase activity was equally reduced in all copper-deficient groups. The 50% starch-replaced diet was more effective in minimizing copper deficiency than the 75% glucose-replaced diet. This poorer improvement of copper deficiency by glucose than starch may partially be due to a more severe reduction of food intake in glucose than in starch diets.     

Effects of long-term feeding of high-protein or high-fat diets on the response to exercise in the rat

The aim of this work was to find by which mechanisms an increased availability of plasma free fatty acids (FFA) reduced carbohydrate utilization during exercise. Rats were fed high-protein medium-chain triglycerides (MCT), high-protein long-chain triglycerides (LCT), carbohydrate (CHO) or high-protein low-fat (HP) diets for 5 weeks, and liver and muscle glycogen, gluconeogenesis and FFA oxidation were studied in rested and trained runner rats. In the rested state the hepatic glycogen store was decreased by fat and protein feeding, whereas soleus muscle glycogen concentration was only affected by high-protein diets. The percentage decrease in liver and muscle glycogen stores, after running, was similar in fat-fed, high-protein and CHO-fed rats. The fact that plasma glucose did not drastically change during exercise could be explained by a stimulation of hepatic gluconeogenesis: the activity of phosphoenolpyruvate carboxykinase (PEPCK) and liver phosphoenolpyruvate (PEP) concentration increased as well as cyclic adenosine monophosphate (AMPc) while liver fructose 2,6-bisphosphate decreased and plasma FFA rose. In contrast, the stimulation of gluconeogenesis in rested HP-, MCT- and LCT-fed rats appears to be independent of cyclic AMP.     

On the Relationship between Food Composition and Serine Dehydrase Activity in Rat Liver

Relationship between serine dehydrase activity in rat liver and dietary protein and carbohydrate levels, using casein and wheat starch, was investigated. Between 10% to 50% of dietary protein levels the enzyme activity sharply increased with increase of protein level. The enzyme activity was also increased by the restriction of carbohydrate intake, even when protein intake was equal in amount. Apparently enzyme activity is controlled by dietary protein level and also by carbohydrate level. In the case of high protein or low carbohydrate diet these changes may be mainly acting for utilization of protein as caloric source.     

Marine ash‐products influence growth and feed utilization when Atlantic cod Gadus morhua L. are fed plant‐based diets

Atlantic cod Gadus morhua L. were fed high plant protein diets added to either shrimp‐shell meal or crab‐shell meal. The aims were to investigate if diluting dietary energy would reduce the liver index (HSI) and if marine ash would add value to plant protein‐based diets. Two control diets were used: a high plant protein control diet (PP) with no marine ash addition, and a fishmeal‐based diet (FM) with no marine ash addition. All diets were evaluated in small cod (initial weight 79 ± 15g) and in market‐size cod (initial weight 1579 ± 20 g). Addition of crab‐shell meal up to 20% and shrimp‐shell meal up to 10% did not influence liver size in either small or market‐size cod. An addition of up to 20% crab‐shell meal and 10% shrimp‐shell meal improved growth compared to the PP control diet, and stimulated increased feed intake. However, 10% shrimp‐shell meal and 20% crab‐shell meal diets resulted in a similar intake of energy and protein as the control groups. Increasing shrimp‐shell meal to 20% resulted in reductions in feed intake, fat digestibility and growth, and in altered gut histology. All diets, except the 20% shrimp added diet, resulted in normal ranges of plasma nutrients and blood hematological values, showing good fish health with or without the marine ash addition.     

Developmental physiology of cestodes. XIV. Roughage and carbohydrate content of host diet for optimal growth and development of Hymenolepis diminuta.

Diets of rats infected with Hymenolepis diminuta (CESTODA: Cyclophyllidea) were altered with respect to carbohydrate content and to roughage, and the effects on worm growth and development were studied. Compared to worms from rats fed a 56% glucose diet, those on a 56% starch diet were heavier at 10 and 15 days and had more immature proglottids at 5 days, mature prglottids at 10 days, and mature and gravid proglottids at 15 days postinfection. In addition, worms from rats fed the starch diet contained a higher carbohydrate concentration and a lower lipid concentration from those fed the glucose diet. Worms from rats fed diets with combinations of carbohydrates such as 51% starch-5% sucrose and 51% starch-5% lactose were not different from those fed the 56% starch diet. If rats were fed a pellet diet (Purina Laboratory Chow), the worms grew substantially larger than those from rats fed the 56% starch or combination diets. The differences could be overcome if a 6% roughage component were included in the 56% starch diet. Therefore, the starch-roughage diet here presented is recommended as the optimal defined diet for studies of the development of H. diminuta in the definitive host.