Redefining the requirement for total sulfur amino acids in the diet of barramundi (Lates calcarifer) including assessment of the cystine replacement value

This study was designed to confirm a previous estimate of the methionine (Met) and total sulfur amino acid (TSAA) requirement of juvenile barramundi (Lates calcarifer) (Coloso et al., 1999) with a view for further study. Triplicate groups of fish (initial weight: 18.3 g ± 1.5 g) were fed diets with graded levels of dietary Met (7.2–12.8 g kg−1 DM), centred around a previously reported requirement, and a constant dietary cystine (Cys) inclusion (5.9 g kg−1 DM) over a 42 day period. At the termination of the experiment, a significant linear increase (p<0.001) in %BW gain was observed in response to increasing dietary methionine, with no plateau in growth, suggesting the previous estimate of requirement may have been inadequate. A second experiment was designed to re-evaluate the Met/TSAA requirement in which a broader range of methionine inclusion levels were assessed (8.6–21.4 g kg−1 diet DM Met). Triplicate groups of fish (initial weight: 36.4 g ± 8.3 g) were fed the diets for a period of 49 days. A plateau and subsequent depression in growth, as well as significant (p<0.05) effects of dietary Met inclusion on %BW gain, feed conversion ratio (FCR) and protein retention efficiency (PRE) were observed at the conclusion of this experiment. The best fitting of nine nutrient response models, the Compartmental Model (R2=0.71), predicted a requirement for Met of between 10.5 (95% of maximum response) and 13.6 g kg−1 (99% of maximum response) in a diet with 592 g kg−1 CP and 6.6 g kg−1 Cys (17.1–20.2 g kg−1 TSAA; 1.8–2.3% CP Met +1.1% CP Cys). This TSAA requirement is equivalent to 43–51% of the lysine content of the diets. The applicability of this mode of expression and its relation to the ideal protein concept is discussed as is the application of different response models to the data. The impact of dietary Met:Cys ratio was also investigated with results suggesting at least 40% of dietary Met can be replaced with Cys without significantly affecting animal performance. It was concluded that disparity in the estimates of Met and TSAA requirement between this study and that of Coloso et al. (1999) was likely the result of a combination of model choice, experimental design and mode of expression of the requirements

Performance evaluation of the Pima™ point-of-care CD4 analyser using capillary blood sampling in field tests in South Africa

<p>Abstract</p> <p>Background</p> <p>Point-of-care CD4 testing can provide immediate CD4 reporting at HIV-testing sites. This study evaluated performance of capillary blood sampling using the point-of-care Pima™ CD4 device in representative primary health care clinics doing HIV testing.</p> <p>Methods</p> <p>Prior to testing, prescribed capillary-sampling and instrument training was undertaken by suppliers across all sites. Matching venous EDTA samples were drawn throughout for comparison to laboratory predicate methodology (PLG/CD4). In Phase I, Pima™ cartridges were pipette-filled with EDTA venous blood in the laboratory (N = 100). In Phase II (N = 77), Pima™ CD4 with capillary sampling was performed by a single operator in a hospital-based antenatal clinic. During subsequent field testing, Pima™ CD4 with capillary sampling was performed in primary health care clinics on HIV-positive patients by multiple attending nursing personnel in a rural clinic (Phase-IIIA, N = 96) and an inner-city clinic (Phase-IIIB, N = 139).</p> <p>Results</p> <p>Pima™ CD4 compared favourably to predicate/CD4 when cartridges were pipette-filled with venous blood (bias -17.3 ± STDev = 36.7 cells/mm³; precision-to-predicate %CV < 6%). Decreased precision of Pima™ CD4 to predicate/CD4 (varying from 17.6 to 28.8%SIM CV; mean bias = 37.9 ± STDev = 179.5 cells/mm³) was noted during field testing in the hospital antenatal clinic. In the rural clinic field-studies, unacceptable precision-to-predicate and positive bias was noted (mean 28.4%SIM CV; mean bias = +105.7 ± STDev = 225.4 cells/mm³). With additional proactive manufacturer support, reliable performance was noted in the subsequent inner-city clinic field study where acceptable precision-to-predicate (11%SIM CV) and less bias of Pima™ to predicate was shown (BA bias ~11 ± STDev = 69 cells/mm³).</p> <p>Conclusions</p> <p>Variable precision of Pima™ to predicate CD4 across study sites was attributable to variable capillary sampling. Poor precision was noted in the outlying primary health care clinic where the system is most likely to be used. Stringent attention to capillary blood collection technique is therefore imperative if technologies like Pima™ are used with capillary sampling at the POC. Pima™ CD4 analysis with venous blood was shown to be reproducible, but testing at the point of care exposes operators to biohazard risk related to uncapping vacutainer samples and pipetting of blood, and is best placed in smaller laboratories using established principles of Good Clinical Laboratory Practice. The development of capillary sampling quality control methods that assure reliable CD4 counts at the point of care are awaited.</p

Renewing and Rethinking Bilateralism after Brexit

This report emerged from a workshop in Brussels where Aston Centre for Europe staff presented research on the future of the UK’s bilateral relations after Brexit. The report itself examines the central policy challenges arising from the UK’s need to renew and rethink bilateral relations with key European countries after the UK has left the EU. The bilateral relationships selected for inclusion in this report reflect the variety of cross-cutting economic, security, and diplomatic concerns that characterize UK engagement with Europe after Brexit. UK relations with France, Germany, Spain, Turkey, and the Visegrad Four (V4; the Czech Republic, Hungary, Poland and Slovakia) are scrutinized to determine how far bilateralism is likely to address the first two policy challenges described above. The final chapter brings back in to focus the complicating factor of devolution, looking at how territorial governance arrangements elsewhere in Europe can provide lessons on conducting “paradiplomacy” with the EU

Postprandial plasma free amino acid profile and hepatic gene expression in juvenile barramundi (Lates calcarifer) is more responsive to feed consumption than to dietary methionine inclusion

The effects of dietary methionine (Met) supply on the postprandial pattern of plasma free amino acids and the differential expression of several genes associated with a number of sulfur amino acid and protein turnover pathways in the liver of juvenile barramundi (Lates calcarifer) was investigated. At the conclusion of a 49-day growth trial assessing the requirement for dietary Met, three treatments were selected (with deficient (DEF; 8.6 g kg−1), adequate (ADQ; 14.9 g kg−1) and excessive (EXC; 21.4 g kg−1)) levels of dietary Met, based on their respective growth responses. A peak occurred in plasma free Met at 2 h post-feeding in fish fed the DEF and ADQ diets and at 4 h post-feeding in fish in the EXC treatment. Liver samples collected at these timepoints, as well as those taken as a pre-feeding control, were analyzed for expression of genes involved in Met turnover (CGL, MAT-1, MAT-2a) and taurine biosynthetic pathways (CSAD, ADO, CDO), target of rapamycin inhibition (Redd-1), the somatotropic axis (GHR-II, IGFI, IGF-II) and protein turnover pathways (MUL-1, ZFAND-5). Markers of sulfur amino acid turnover were more significantly affected by time after feeding than by dietary Met level, suggesting production of these enzymes may be primarily regulated by the consumption of feed or protein, rather than by the dietary composition. Further, metabolised Met appeared likely to have been directed through S-Adenosylmethionine (SAM) dependent pathways, rather than converted to Cys, which may have contributed to the observed growth response. Both genes influencing the conversion of Met to SAM appear to be active at this lifestage in barramundi. Previously described markers of proteolytic pathways appear to be conserved in this species and we have confirmed that ZFAND-5 is a reliable biomarker of this process in barramundi. A number of important genes were investigated for the first time in this species and shown to be nutritionally regulated

Endogenous biosynthesis of n-3 long-chain PUFA in Atlantic salmon

A more efficient utilisation of marine derived sources of dietary omega-3 long-chain polyunsaturated fatty acids (n-3 LC PUFA) in cultured Atlantic salmon could, amongst other strategies, be facilitated by nutritional strategies that maximise endogenous n-3 LC PUFA synthesis. The objective of the current study was to quantify the extent of n-3 LC PUFA biosynthesis and the resultant effect on fillet nutritional quality in large, market size Atlantic salmon. Four diets were manufactured providing altered levels of dietary omega-3 substrate, namely 18:3n-3, and end-products, namely, 20:5n-3 and 22:6n-3. After 283 days of feeding, fish grew to in excess of 3000g and no differences in growth performance or biometrical parameters were recorded. An analysis of fatty acid composition and in vivo metabolism revealed that post-smolt Atlantic salmon have the potential to endogenously produce n-3 LC PUFA when provided with a substantial amount of dietary omega-3 substrate. Moreover, the extent of endogenous production resulted in fillet levels of n-3 LC PUFA comparable to fish fed a diet with added fish oil. Another major finding was that the presence of abundant dietary omega-3 substrate with the addition of dietary omega-3 end-product (i.e. fish oil) had a positive effect on final fillet levels of n-3 LC PUFA. This was likely the result of the preferential β-oxidation of dietary C18 n-3 PUFA resulting in an apparent conservation of n-3 LC PUFA from catabolism. Ultimately, this study highlights the potential for endogenous synthesis of n-3 LC PUFA to, at least partially, support a substantial reduction, in the amount of dietary fish oil in diets for market sized Atlantic salmon reared in seawater

The impact of dietary protein: lipid ratio on growth performance, fatty acid metabolism, product quality and waste output in Atlantic salmon (Salmo salar)

A common strategy for aquafeed manufacturers has been the utilisation of relatively large amounts of terrestrial, both animal and plant, oil sources to produce diets with a high energy content. The provision of high fat diets is aimed at promoting the utilisation of energy from lipid, thus increasing the amount of dietary protein used for tissue synthesis. However, in recent years the cost of marine sourced dietary lipids has risen, at the same time, farming operations are under increasing pressure to limit environmental degradation associated with nitrogenous waste effluent. Currently there is limited information available regarding the environmental and economic impacts of an altered dietary protein: lipid ratio in diets for large Atlantic salmon (Salmo salar) reared in seawater, presenting a potential impediment for nutritional based solutions. Accordingly the present study compared two isoenergetic diets with varied protein: lipid ratios via an assessment of growth, fatty acid utilisation, human nutritional quality, nitrogenous waste output and economic considerations. The trial diets were fed to the fish for the final 150 days of an on-farm grow-out period and resulted in minimal differences in fish growth, fatty acid utilisation and fillet quality. A decreased dietary protein: lipid ratio resulted in a more efficient protein utilisation both in terms of digestibility and assimilation into fish and, therefore, nitrogenous waste output was reduced. However, due to small differences in feed utilisation, the cost of fish production was numerically higher

Altered levels of shorter vs long-chain omega-3 fatty acids in commercial diets for market-sized Atlantic salmon reared in seawater – Effects on fatty acid composition, metabolism and product quality

There is a growing trend of ‘replacing’ long-chain omega-3 polyunsaturated fatty acid (n-3 LC PUFA) rich oils with C18 shorter-chain omega-3 polyunsaturated fatty acid rich oils in Atlantic salmon aquafeed formulations. n-3 LC PUFA, including 20:5n-3 and 22:6n-3, play contrasting physiological roles and are metabolised differently in comparison to C18 PUFA. Accordingly, the present study recorded the effect of replacing n-3 LC PUFA rich dietary fish oil with C18 n-3 PUFA rich camelina oil at two inclusion levels in commercial-like diets fed to market-sized Atlantic salmon. This assessment was achieved by an analysis of industry relevant production parameters including growth performance, fatty acid composition and metabolism, nutrient digestibility and consumer acceptance (liking and attribute analysis of fillet). The trial was conducted over the final 150 days of an on-farm grow-out period in seawater. The dietary replacement of n-3 LC PUFA with C18 n-3 PUFA resulted in a significant decrease in fillet n-3 LC PUFA and a poorer growth performance. However, in the absence of fish oil, the inclusion of camelina oil at high levels (40%) contributed to an improved n-6/n-3 ratio and partially ameliorated low dietary n-3 LC PUFA by providing added substrate for endogenous n-3 LC PUFA synthesis in comparison to a 20% camelina oil inclusion. Furthermore, consumer acceptance of Atlantic salmon was unaffected by the dietary addition of camelina oil

Atlantic Salmon (Salmo salar L.) Gastrointestinal Microbial Community Dynamics in Relation to Digesta Properties and Diet

To better understand salmon GI tract microbial community dynamics in relation to diet, a feeding trial was performed utilising diets with different proportions of fish meal, protein, lipid and energy levels. Salmon gut dysfunction has been associated with the occurrence of casts, or an empty hind gut. A categorical scoring system describing expressed digesta consistency was evaluated in relation to GI tract community structure. Faster growing fish generally had lower faecal scores while the diet cohorts showed minor differences in faecal score though the overall lowest scores were observed with a low protein, low energy diet. The GI tract bacterial communities were highly dynamic over time with the low protein, low energy diet associated with the most divergent community structure. This included transiently increased abundance of anaerobic (Bacteroidia and Clostridia) during January and February, and facultatively anaerobic (lactic acid bacteria) taxa from February onwards. The digesta had enriched populations of these groups in relation to faecal cast samples. The majority of samples (60&ndash;86&nbsp;%) across all diet cohorts were eventually dominated by the genus Aliivibrio. The results suggest that an interaction between time of sampling and diet is most strongly related to community structure. Digesta categorization revealed microbes involved with metabolism of diet components change progressively over time and could be a useful system to assess feeding responses.&nbsp

In vitro characteristics of an Atlantic salmon (Salmo salar L.) hind gut microbial community in relation to different dietary treatments

In this study, microbial community dynamics were assessed within a simple invitro model system in order to understand those changes influenced by diet. The abundance and diversity of bacteria were monitored within different treatment slurries inoculated with salmon faecal samples in order to mimic the effects of dietary variables. A total of five complete diets and two ingredients (plant meal) were tested. The total viable counts (TVCs) and sequencing data revealed that there was very clear separation between the complete diets and the plant meal treatments, suggesting a dynamic response by the allochthonous bacteria to the treatments. Automated ribosomal intergenic spacer analysis (ARISA) results showed that different diet formulations produced different patterns of fragments, with no separation between the complete diets. However, plant-based protein ingredients were clearly separated from the other treatments. 16S rRNA Illumina-based sequencing analysis showed that members of the genera Aliivibrio,Vibrio&nbsp;and Photobacterium&nbsp;became predominant for all complete diets treatments. The plant-based protein ingredient treatments only sustained weak growth of the genusSphingomonas. Invitro based testing of diets could be a useful strategy to determine the potential impact of either complete feeds or ingredients on major fish gastrointestinal tract microbiome members