Digestibility of canola meals in barramundi (Asian seabass; Lates calcarifer)

The influence of two different oil processing methods and four different meal origins on the digestibility of canola meals when fed to barramundi (Lates calcarifer) was examined in this study. The apparent digestibility coefficients were determined using the diet-substitution method with faeces collected from fish using stripping techniques. The protein content of the solvent extracted (SE) canola meals (370-423. g/kg DM) was higher than that of the expeller extracted (EX) canola meal (348. g/kg DM), but the lipid content was lower than that of the expeller extracted canola meal. Among the SE canola meals, the protein digestibility of the canola meals from Numurkah and Newcastle was similar (84.1% and 86.6% respectively), but significantly higher than that of the canola meal from Footscray (74.5%). The protein digestibility was lowest (63.1%) for the EX canola meal. The energy digestibility of the canola meals (43.1-52.5%) was similar to that of the lupin (54.8%) except for the lower of SE canola from Footscray (32.4%). The SE canola meals provide 276-366. g/kg DM of protein while that of the EX is only 220. g/kg DM. The digestible energy content of the SE canola meal Footscray (6.5. MJ/kg) was lower than the other canola meals (8.7-10.6. MJ/kg DM). This study shows that there can be significant variability in the digestibility of canola meals subject to potential processing and sourcing variables.&nbsp

Effects of canola meal on growth, feed utilisation, plasma biochemistry, histology of digestive organs and hepatic gene expression of barramundi (Asian seabass; Lates calcarifer)

The serial replacement of fish meal (anchovetta) by canola meal (CM) (100, 200, 300 g kg−1 as either solvent extracted (SE) CM or expeller extracted (EX) CM was undertaken to investigate the effects of increasing dietary CM levels on feed intake, growth, protein and energy retention, plasma biochemistry and the expression of a suite of hepatic genes in barramundi (Asian seabass; Lates calcarifer) over an eight week feeding trial. An additional diet using lupin kernel meal (LM) to replace the fish meal was also included as a comparative reference. Eight iso-digestible nitrogenous (423±29 g kg−1) and iso-digestible energetic (14.6±8 MJ kg−1 DM) diets were formulated. Each diet was randomly allocated to triplicate groups of fish in seawater tanks (600 L), and each tank was stocked with 15 fish (53.4±7.0 g). Fish were fed once daily (9:00–10:00) to apparent satiation, and uneaten feed was collected to determine feed consumption. The results showed that the survival, feed intake, growth, FCR, energy and protein retention of fish fed the diet containing SE CM were similar or even higher to those of fish fed the fish meal reference diet (FM) and the LM diet. Fish fed with the diet containing 300 g kg−1 SE CM did not show any changes in biochemistry and gene expression in a suite of detoxification genes. However, the diet with 300g kg−1 EX CM depressed feed intake, growth performance and increased feed conversion ratio (FCR). Transcription of genes involving in fatty acid synthesis and the TCA cycle were not changed by different diets. The down regulation of gene expression in certain detoxification genes (Lc CYP1A1, Lc CYP3A, Lc CYP2N and Lc GST) was observed in fish fed with the diet containing 300 g kg−1 EX CM compared to the FM control diet and other experimental diets. In general, the SE CM can be used up to 300 g kg−1 diet without negative performance effects or signs of clinical plasma biochemistry. By contrast the maximum acceptable level of the EX CM for barramundi was only 200 g kg−1. Higher inclusion level of the EX CM induced negative effects on growth performance, feed utilisation, plasma biochemistry and gene expression in relation to detoxification

Evaluation of canola meal as an aquafeed ingredient for barramundi (Asian seabass; Lates calcarifer)

Canola meal (CM) is one of many potential plant ingredients for fishmeal replacement in fish diets. Many fish species have performed good growth when fed with dietary CM. However, there is limited information for using this ingredient in barramundi. In order to use this ingredient for aquaculture feeds, the information such as nutritional value, nutrient digestibility and ingredient utilisation have to be provided. Therefore, the present study described in this thesis was carried out to: (1) characterise nutritional composition and determine nutrient and energy digestibility of four Australian CMs with respect to different origin and processing method; (2) assess effects of diets with serial inclusion levels of two different CMs regarding different processing methods (expeller and solvent extraction) on growth performance and feed utilisation; (3) examine effects of CMs on changes in plasma chemistry, histology of digestive, metabolic organs and hepatic gene expression. To achieve the above objectives, two experiments were undertaken. The first experiment (digestibility experiment) was designed with six diets (four CMs: three solvent extracted (SE) CMs from Newcastle, Footscray, Numurkah and one expeller extracted (EX) CM from Pinjarra), a diet with fishmeal (FM) as the sole protein and a diet based on lupin kernel meal (LM) were included as reference diets. Each CM test diet and LM diet were made by incorporation of 30 % of test ingredient and 70 % of basal mash (FM reference). Dry matter, protein, energy, amino acid and yttrium content of the diets, ingredients and faeces were analysed to enable the determination of the apparent digestibility of corresponding parameters. The second experiment (growth experiment) included eight dietary treatments each with three replicates, one FM reference diet (sole protein as fishmeal) (FM), one lupin (LM) diet (300 g/kg LM) and the CM diets (100, 200, 300 g/kg as either SE CM or EX CM). Performance indices such as feed intake, weight gain, DGC, FCR, protein and energy retention were determined. Following, an examination of the health effects and molecular responses of fish fed the CM containing diets compared to the FM and LM diets were also carried out. Plasma samples were analysed for biochemical parameters. The liver, kidney, caeca, distal intestine and stomach were used for histological analysis. For molecular expression, genes involved in fatty acid metabolism (FAS, SCD and FXR) and energy production pathways (CS and PDK) and others involved in detoxification (CYP1A1, CYP3A, CYP2N, GST, GHGPx and GPx) were examined using RT-qPCR. The relative expression level of each gene in each sample was determined by normalising the cycle threshold values for each gene to Ef1-α. Compositional analysis of the ingredients showed that the protein content of the SE CMs (370 to 423 g/kg DM) was higher than that of the EX CM (348 g/kg DM), but the lipid content was lower than that of the EX CM. Among the SE CMs, the protein digestibility of the CMs from Numurkah and Newcastle was similar (84.1 % and 86.6 % respectively), corresponding to that of the LM but significantly higher than that of the CM Footscray (74.5 %). The protein digestibility was the lowest (63.1 %) for the EX CM. The energy digestibility of the CMs (43.1 % to 52.5 %) was similar to that of the LM (54.8 %) except for the lower of the SE CM Footscray (32.4 %). The SE CMs provide 276 to 366 g/kg DM of digestible protein while that of the EX CM is only 220 g/kg DM. The digestible energy content of the SE CM Footscray (6.5 MJ/kg) was significantly lower than that of other CMs (8.7 to 10.6 MJ/kg DM). After an eight week culture period the feed intake, growth performance, and protein retention efficiency of fish fed with dietary CM levels were similar or even higher to those of fish fed the FM and the LM diets. The FCR is also similar or better than the control diets. The exception to this was for fish fed with the 300 g/kg EX CM diet. The diet containing 300 g/kg EX CM depressed growth performance, feed intake, and increased FCR. In general, the SE CM can be used up to 300 g/kg diet without negative growth effects while 200 g/kg is the maximum acceptable level of the EX CM for barramundi. Plasma biochemistry parameters were fairly similar among each of the dietary treatments. There were no modifications in the morphology of the liver, kidney, caeca, distal intestine or stomach of fish caused by any of the experimental diets. The expression of genes involved in fatty acid metabolism and TCA cycle was not influenced by fish fed with CM containing diets relative to the FM control and LM diets. However, fish fed with the diet containing 300 g/kg EX CM were shown to downregulate the expression of some genes acting in detoxification pathways (Lc CYP1A1, Lc CYP3A, Lc CYP2N and Lc GST), but not Lc GPx, Lc PHGPx and Lc GR. Overall, this study demonstrates that CM is a promising plant ingredient for FM replacement in barramundi based on determined digestible values and feed utilisation. However, implications regarding different origin and processing method importantly affect CM utilisation for barramundi

Complement receptor type 1 and 2 (CR1 and CR2) gene polymorphisms and plasma protein levels are associated with the Dengue disease severity

Abstract The pathological outcome of dengue disease results from complex interactions between dengue virus (DENV) and host genetics and immune response. Complement receptor types 1 and 2 (CR1 and CR2) mediate complement activation through the alternative pathway. This study investigated the possible association of genetic polymorphisms and plasma levels of CR1 and CR2 with dengue disease. A total of 267 dengue patients and 133 healthy controls were recruited for this study. CR1 and CR2 gene polymorphisms were analyzed by Sanger sequencing, while plasma CR1 and CR2 levels were measured by ELISA. The frequency of the CR1 minor allele rs6691117G was lower in dengue patients and those with severe dengue compared to healthy controls. Plasma CR1 and CR2 levels were decreased in dengue patients compared to healthy controls (P < 0.0001) and were associated with platelet counts. CR1 levels were lower in dengue patients with warning signs (DWS) compared to those without DWS, while CR2 levels were decreased according to the severity of the disease and after 5 days (T1) and 8 days (T2) of follow-up. CR2 levels were decreased in dengue patients positive for anti-DENV IgG and IgM and patients with bleeding and could discriminate DWS and SD from dengue fever patients (AUC = 0.66). In conclusion, this study revealed a reduction in CR2 levels in dengue patients and that the CR1 SNP rs6691117A/G is associated with the dengue severity. The correlation of CR2 levels with platelet counts suggests that CR2 could be an additional biomarker for the prognosis of severe dengue disease