Nutritional and metabolic responses in common dentex (Dentex dentex) fed on different types and levels of carbohydrates

Effect of digestible protein on intermediate metabolism, hepatic enzyme activities, energy reserves, and growth performance of pacu (Piaractus mesopotamicus) in the finishing growth phase

This study investigated the effect of different levels of digestible protein (DP) on blood metabolites, hepatic enzyme activity of glycolysis and amino acid metabolism, energy reserves, and the production characteristics of pacu (Piaractus mesopotamicus) during the finishing growth phase. Six semi purified and isoenergetic diets, containing 16.3, 20.1, 23.8, 27.2, 31.5, and 34.8% of balanced DP, provided with essential amino acid balance, were hand-fed to pacu (1100.0 ± 10.3 g, initial weight) three times daily for 7 weeks. The experiment consisted of six treatments, with three randomly arranged replicates (tanks) per treatment. The data obtained from this experiment were analyzed by one-way analysis of variance (ANOVA), and significant differences (p < 0.05) between treatments were determined using Tukey's test. Blood metabolites, except serum ammonia and the hepatic enzymes activities of glycolysis and amino acid metabolism, except hexokinase activity were affected (p < 0.05) by balanced DP. The energy reserve indices, except hepatic total lipid content, were also found associated (p < 0.05) with balanced DP. The test diets significantly (p < 0.05) affected growth performance parameters. Higher dietary proteins led to a greater energy uptake by fish from the protein in feed. Overall, fish fed the intermediate level (23.8%) of balanced DP with digestible energy of 17.95 MJ kg-1 showed better production traits and physio-biochemical health markers. This information could help nutritionists and farmers to develop nutritionally balanced and economically and environmentally sustainable aquafeed for promoting healthy and sustainable production of pacu in intensive culture systems.

Metabolic adaptation to high-starch diet in largemouth bass (Micropterus salmoides) was associated with the restoration of metabolic functions via inflammation, bile acid synthesis and energy metabolism

A short-term 2-week (2w) and long-term 8-week (8w) feeding trial was conducted to investigate the effects of low-starch (LS) and high-starch (HS) diets on the growth performance, metabolism and liver health of largemouth bass (Micropterus salmoides). Two isonitrogenous and isolipidic diets containing two levels of starch (LS, 9·06 %; HS, 13·56 %) were fed to largemouth bass. The results indicated that HS diet had no significant effects on specific growth rate during 2w, whereas significantly lowered specific growth rate at 8w. HS diet significantly increased hepatic glycolysis and gluconeogenesis at postprandial 24 h in 2w. The hepatosomatic index, plasma alkaline phosphatase, total bile acid (TBA) levels, and hepatic glycogen, TAG, total cholesterol, TBA, and NEFA contents were significantly increased in the HS group at 2w. Moreover, HS diet up-regulated fatty acid and TAG synthesis-related genes and down-regulated TAG hydrolysis and β-oxidation-related genes. Therefore, the glucolipid metabolism disorders resulted in metabolic liver disease induced by HS diet at 2w. However, the up-regulation of bile acid synthesis, inflammation and energy metabolism-related genes in 2w indicated that largemouth bass was still in a state of 'self-repair' response. Interestingly, all the metabolic parameters were returned to homoeostasis, with up-regulation of intestinal glucose uptake and transport-related genes, even hepatic histopathological analysis showed no obvious abnormality in the HS group in 8w. In conclusion, HS feed induced short-term acute metabolic disorder, but long-term metabolic adaptation to HS diet was related to repairing metabolism disorders via improving inflammatory responses, bile acid synthesis and energy metabolism. These results strongly indicated that the largemouth bass owned certain adaptability to HS diet.

Corn substitution by mesquite bean flour (Prosopis juliflora) maintains growth and improves protein metabolism of Nile tilapia juveniles (Oreochromis niloticus)

The objective of this study was to evaluate the potential of mesquite bean flour (Prosopis juliflora) as an energy ingredient in extruded diets for juvenile Nile tilapia (Oreochromis niloticus). Two experiments were carried out: the first consisted of a study to evaluate the chemical composition and digestibility of the energy and nutrients of MBF; the second consisted of a growth test, in which juveniles consumed diets containing different proportions of corn substitution by MBF, in which zootechnical, hematological, physiological, and metabolic variables were evaluated. It was observed that MBF has a chemical composition similar to corn, as well as the apparent digestibility of energy and nutrients. The higher sucrose/starch ratio of the ingredient stands out, as well as the difference in digestibility (p < 0.05) between the predominant carbohydrates 87.63 and 99.25% for starch and sucrose, respectively. In the growth assay, no difference was observed between zootechnical variables (p > 0.05), and sucrase and alkaline phosphatase activities were increased (p < 0.05), which was not observed for amylase and lipase (p > 0.05). The hematological variables did not change (p > 0.05). Metabolic variables indicate a reduction in gluconeogenesis from amino acids, as can be seen by the reduction in liver transaminase levels (ALT and AST) and glutamate dehydrogenase (GDH), as well as the greater availability of free amino acids in plasmas (p < 0.05). Thus, it can be said that MBF has a high nutritional value and can totally replace corn in diets for juvenile tilapia and the metabolic findings indicate a potential protein-sparing effect.

Effects of dietary glucose and starch levels on the growth, apparent digestibility, and skin-associated mucosal non-specific immune parameters in juvenile blunt snout bream (Megalobrama amblycephala)

A 10-week feeding trial was performed to evaluate the effects of different types and levels of carbohydrates in growth performance, apparent digestibility coefficients and skin-associated mucosal non-specific immune parameters in blunt snout bream (Megalobrama amblycephala). Fish were randomly fed four diets containing two carbohydrates (glucose and starch) diets and two carbohydrates levels (330 and 440 g kg^-1). High carbohydrate levels remarkably increased the weight gain rate (WGR), apparent digestibility of dry matters, protein and carbohydrates, body crud protein content, plasma levels of aspartate transaminase (AST), and skin-associated mucosal levels of immunoglobulin M (IgM), HDL cholesterol, lysozyme (LZM), advanced the transcriptions of mucin 2 (Muc2), mucin 5b (Muc5b) and apolipoprotein A-I (apoA-I), whereas the opposite was true for feed conversion ratio (FCR), plasma levels of IgM, skin-associated mucosal levels of major histocompatibility complex (MHC) and β-Defensins, and the transcriptions of heat shock protein 60 (Hsp60). In addition, carbohydrate types of glucose remarkably increased the survival rate, apparent digestibility of dry matters, protein and carbohydartes, body crud ash, plasma levels of total protein (TP), globulin (GLB), immunoglobulin M (IgM), complement C3 and complement C4 and the transcriptions of Muc5b. Whereas the carbohydrate types of starch remarkably increased viscerosomatic index (VSI), hepatosomatic index (HSI), condition factor (CF), abdominal fat percentage (AFP), apparent digestibility of liquid, advanced the transcriptions of Muc2, apoA-I and heat shock protein 70 (Hsp70). Significant interactions between different types and levels of dietary carbohydrates were also observed in WGR, apparent digestibility of dry matters, protein and liquid, body crud ash, plasma levels of TP, albumin (ALB) and AST, skin-associated mucosal levels of major histocompatibility complex (MHC) and β-Defensins, and the transcriptions of Muc2 and Muc5b. Our results indicate that inclusion of high level of glucose in the diet of blunt snout bream could improve growth performance, nonspecific immunity, and increase the efficiency of protein, which is suggesting that high level of glucose could be used in feed production. However, the proportion of the specific formula of glucose using in feed needs further study.

Effect of high dietary starch levels on growth, hepatic glucose metabolism, oxidative status and immune response of juvenile largemouth bass, Micropterus salmoides

An experimental trial was conducted to investigate the effects of high dietary starch levels on growth, hepatic glucose metabolism enzyme, antioxidant capacity and immune responses of largemouth bass, Micropterus salmoides. Fish (initial body weight: 16.9 ± 0.24 g) were fed three isonitrogenous and isoenergetic semi-purified diets containing 5%, 10% and 20% wheat starch, respectively. The results indicated that fish fed 5% and 10% starch diets showed significantly better weight gain, specific growth rate (SGR), protein efficiency ratio (PER) and feed conversion ratio (FCR) compared with that fed 20% starch diet. Meanwhile, fish fed 20% starch diet had a significantly higher hepatic glycogen and muscle glycogen contents than those fed the other diets. The alanine amiotransferase (ALT) and aspartate transaminase (AST) activities, glucose and insulin contents in plasma increased significantly with dietary starch levels, whereas triglyceride content showed the opposite trend. In addition, the highest glucokinase (GK), pyruvate kinase (PK) and phosphofructokinase (PFK) activities in liver were also observed in fish fed 20% starch diet. However, both fructose-1,6-bisphosphatase (FBPase) and pyruvate carboxylase (PC) activities in liver decreased significantly as dietary starch levels increased. Moreover, the lower superoxide dismutase (SOD) and catalase (CAT), the higher malondialdehyde (MDA) contents in liver were observed in fish fed 20% starch diets. Compared to the 5% and 10% starch, the 20% starch could enhance the content of plasma nitric oxide (NO) and the activities of inducible nitric oxide synthase (iNOS) and alkaline phosphatase (ALP). Results demonstrate that the starch levels may affect growth performance and metabolic changes, which suggest that high-starch diets were inefficiently used as an energy source by M. salmoides juveniles. Excessive dietary starch contents could result in oxidative stress, suppress innate immunity, and thus affect the health status of M. salmoides.

Dietary carbohydrates improve oxidative status of common dentex (Dentex dentex) juveniles, a carnivorous fish species

Common dentex (Dentex dentex) is an appreciated carnivorous fish with high growth rate and life cycle adaptable to existing farming techniques. Since the use of carbohydrates is an economic and sustainable alternative for a protein-sparing effect, the study of how this macronutrient affects the welfare of carnivorous species must be studied. The aim of the present study was to evaluate the effects of different types and levels of carbohydrates on common dentex oxidative status. Nine isonitrogenous (43%) and isoenergetic (22MJkg^-1) diets were formulated combining three types (pregelatinized starch-PS, dextrin-Dx and maltodextrin-Mx) and three levels (12, 18 and 24%) of carbohydrates. The activities of catalase-CAT, superoxide dismutase-SOD, glutathione peroxidase-GPX, glutathione reductase-GR and glucose 6-phosphate dehydrogenase-G6PDH, SOD isoenzymatic profile, lipid peroxidation-LPO and protein oxidation-PO were determined in liver and white muscle. SOD and CAT were not affected. GPX in liver and white muscle and GR in liver increased at higher inclusion carbohydrates levels. The lowest levels of GR and G6PDH in both tissues and LPO in liver were observed in maltodextrin groups. No significant effects by carbohydrate source were observed in liver PO and white muscle LPO. Regarding carbohydrate level effect, 18% and 24% dietary inclusion level decreased LPO in white muscle and PO in liver. LPO in liver was also decreased at 24% inclusion level. Altogether, results indicate the use of carbohydrates as an alternative energy source does not produce negative effects on oxidative status of common dentex, on the contrary, even contribute to their oxidative protection.