Fish oil replacement in starter, grow-out, and finishing feeds for farmed aquatic animals

As aquaculture production continues to grow, there will be an increased use of lipid resources (oils and fats) alternative to fish oil for feed production. The potential for the use of these alternatives varies depending on the feeds in which they are included according to the production phase of the animals to which they are being fed. In starter feeds, where rapid growth, high survival, and normal development are critical priorities, there will remain a need for the use of lipid resources high in omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA). Fish in this starter phase have a critical requirement for the n-3 LC-PUFA docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), and fish oils remain the only cost-effective source of these nutrients in the volumes required. However, the greatest demand for lipids is in those diets for the grow-out phase. Most studies on alternative lipid use with animals in this part of the production phase show positive outcomes, in that there are few studies where all the added fish oil cannot be replaced. There are some species, however, where potential replacement levels are suggested to be more conservative, and a general substitution level in this production phase of 75% has been suggested. One of the key effects noted across the grow-out phase is that all alternatives affect the flesh fatty acid characteristics by reducing the level of n-3 LC-PUFA. This issue has provoked the concept of finisher diets, whereby a high n-3 LC-PUFA content diet is fed in order to restore the desired meat fatty acid profiles. Studies examining this concept have found that the tissue triacylglycerol fatty acids were greatly modified and responded in a simple dilution process to the added oil fatty acid composition, whereas the fatty acids of tissue phospholipids were less influenced by dietary fatty acid makeup.<br /

Bioactive factors in microbial biomass have the capacity to offset reductions in the level of protein in the diet of black tiger shrimp, Penaeus monodon

A factorial experiment was conducted with black tiger shrimp (Penaeus monodon) juveniles to determine the effects of varying protein inclusion in the diet and also varying inclusion of a microbial biomass on growth, feed and nutrient utilization when fed in indoor laboratory conditions. The growth performance of the shrimp improved with increasing diet protein level. However, in the absence of the added microbial biomass, this growth performance plateaued at the 480. g/kg protein level. The addition of the microbial biomass improved growth at each inclusion level of both protein and microbial biomass. No plateau in growth was observed with the addition of the microbial biomass. Improvements in feed conversion were seen with increasing dietary protein levels and also the inclusion of the microbial biomass. Examination of the feed intake of each treatment supports that there was a combined effect of an increase in feed intake and improvements in feed conversion that contributed to the improvements in growth performance with the use of the microbial biomass, but the increases in dietary protein level largely influenced growth through improvements in feed conversion

Partial utilization efficiencies of protein and methionine by barramundi (Lates calcarifer) in response to dietary methionine source and form

An experiment was conducted with barramundi (Lates calcarifer) juveniles (initial weight 10.3 g ± 0.3 g) to examine the partial efficiency of utilization of methionine (Met) from intact protein (fishmeal or lupin protein concentrate) and a crystalline DL‐Met source. Fish were fed at one of three ration levels: Low (0.4 g/fish/day), Moderate (0.8 g/fish/day) and High (1.6 g/fish/day). Those fed the fishmeal‐based diet (Diet FML) at the highest ration level grew to an average weight of 37.3 ± 0.46 g, whereas those fed the Lupin Protein Concentrate (LPC)‐based diet fortified with all EAA (Diet LPCM) at the highest ration level grew to 25.4 ± 2.27 g. The weight of the fish fed the LPC diet with no additional Met (Diet LPC) even at the highest ration level declined over the course of the experiment resulting in a final weight of 9.2 ± 0.88 g, clearly demonstrating the impact of dietary Met deficiency. The partial efficiency of protein utilization was also significantly reduced when Met was limiting (a coefficient of 0.06, compared to 0.39 in the Met‐supplemented LPC diet). The results suggested that the partial efficiencies (coefficients) of both Met and protein utilization in diets where crystalline Met is the primary source of Met (Diet LPCM: 0.26 and 0.39 respectively) were significantly poorer than from an intact protein source (Diet FML: 0.89 and 0.67 respectively) when Met is provided in excess

The effect of taurine supplementation to a plant‐based diet for barramundi (Lates calcarifer) with varying methionine content

The effect of variable taurine inclusion (Tau) (1 g/kg DM to 15 g/kg DM) in the diet of juvenile barramundi (Lates calcarifer) on growth and nutrient utilization was investigated at three levels of dietary methionine (Met) supplementation. Diets were fed to juvenile barramundi (starting weight: 26.8 g) twice daily under a restricted pair‐fed regime for a period of 42 days. No significant effect of dietary Tau supply on growth or nutrient utilization was observed at any level of Met inclusion. Numerical variations suggested a positive effect of Tau provision at the mid‐level of supplementation (6–8 g/kg DM). The best‐fit response model (5‐SKM), fitted to the percentage body weight gain data of fish fed diets with an adequate level of Met, suggested a relatively weak pattern of response (R2 = 0.183) and predicted a Tau requirement of 5.47 g/kg DM (9.64 g/kg CP) similar to that reported for several other species. It was concluded that taurine appears to be conditionally essential to barramundi, whereby provision in the diet when sulphur amino acid supply is insufficient to meet biosynthetic demands may be beneficial, but that the predicted requirement is likely reasonably accurate for use as a minimum level of inclusion

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

A feed is still only as good as its ingredients: An update on the nutritional research strategies for the optimal evaluation of ingredients for aquaculture feeds

The choice of strategies used to assess ingredients can have a strong impact on the interpretation of their quality. In an attempt to standardize the assessment process, a structured approach using five steps for assessing the quality of ingredients was proposed over a decade ago. Since then, there has been considerable progress in the science of ingredient evaluation, and expectations from the users of those ingredients have also evolved. Two additional steps have emerged that formulators require to make appropriate decisions in the use of ingredients. Accordingly, a series of seven steps (and the order in which they should be done) to develop a comprehensive data set on ingredient quality is proposed; Step 1 Characterization, Step 2 Palatability, Step 3 Digestibility, Step 4 Utilization, Step 5 Immunological, Step 6 Processing Effects and Step 7 Product Quality Influences. Once these seven steps had been achieved, a formulator can make the appropriate choice as to whether to use any particular ingredient, and with what constraints to impose on their use. Without any one of these steps, the risk exposure substantially increases as the formulator needs to make assumptions, and this increases the risk of a feed failing in one or more specifications

A review of carotenoid utilisation and function in crustacean aquaculture

Crustaceans are cultured extensively around the world in intensive farming systems. High-performance formulated feeds have been developed for crustacean aquaculture, which are often supplemented with a number of natural and synthetic carotenoid sources. Studies over a number of years have consistently shown that dietary carotenoid supplementation is beneficial for crustacean aquaculture across a range of commercially relevant parameters. Most obvious is the effect on pigmentation, where carotenoid inclusion levels in feeds and duration of feeding diets with carotenoids have been optimised across many species to improve product colour, and subsequently quality and price. However, beneficial effects of carotenoid inclusion have increasingly been demonstrated on other parameters. This review updates the recent progress in our understanding of dietary carotenoid utilisation and storage, and the combined effects of diet, genetics and environment on crustacean pigmentation. In addition, the range of other physiological benefits this class of molecules brings to these animals is summarised. These include improvements in survival, growth, reproductive capacity, disease resistance and stress resistance. &copy; 2015 Wiley Publishing Asia Pty Ltd

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 &plusmn; 1.5 g) were fed diets with graded levels of dietary Met (7.2&ndash;12.8 g kg&minus;1&nbsp;DM), centred around a previously reported requirement, and a constant dietary cystine (Cys) inclusion (5.9 g kg&minus;1&nbsp;DM) over a 42 day period. At the termination of the experiment, a significant linear increase (p&lt;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&ndash;21.4 g kg&minus;1&nbsp;diet DM Met). Triplicate groups of fish (initial weight: 36.4 g &plusmn; 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&lt;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&minus;1&nbsp;(99% of maximum response) in a diet with 592 g kg&minus;1&nbsp;CP and 6.6 g kg&minus;1&nbsp;Cys (17.1&ndash;20.2 g kg&minus;1&nbsp;TSAA; 1.8&ndash;2.3% CP Met +1.1% CP Cys). This TSAA requirement is equivalent to 43&ndash;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

Effect of dietary saturated and monounsaturated fatty acids in juvenile barramundi Lates calcarifer

Barramundi (Lates calcarifer), a catadromous teleost of commercial interest, perform well when fed a wide range of dietary oils. However, the range of alternative oils now being explored is typically rich in saturated and monounsaturated fatty acids (SFA and MUFA). In this study, the response of juvenile barramundi (47.0 g per fish initial weight) fed isolipidic and isoenergetic diets with 82 g kg-1 added oil was tested. The experimental test diets had a 2 : 1 or 1 : 2 ratio of SFA to MUFA (SFA-D and MUFA-D, respectively) compared to a control diet (CTRL-D) fed for 8 weeks. The diets containing mostly olive oil (dietary MUFA-D) and mostly refined palm oil (dietary SFA-D) did not impact the growth performance or feed utilization parameters of the barramundi. The in vivo beta-oxidation activity was consistent with the dietary fatty acid composition, with the most dominant FA being heavily beta-oxidized. Together, the in vivo whole-body mass balance of fatty acids showed that n-3 long-chain polyunsaturated fatty acids (LC-PUFA) were most efficiently utilized in the SFA-D- and MUFA-D-fed fish. This study provides evidence that additional dietary MUFA and SFA are suitable lipid classes for juvenile barramundi and they are both equally efficient at sparing LC-PUFA from an oxidative fate.

Using near-infrared reflectance spectroscopy to predict the digestible protein and digestible energy values of diets when fed to barramundi, Lates calcarifer

This study examined the potential of using near-infrared spectroscopy (NIRS) to predict nutrient digestibility parameters (digestible protein and digestible energy) of compound diets when fed to barramundi. A series of 60 diets were assessed for their protein and energy digestibilities in a series of five experiments over a 5-year period from 2009 to 2014. Considerable variance was observed in the digestibility parameters of diets across the experiments, providing a suitable range in diet digestible protein and digestible energy values from which to develop a NIRS calibration. Samples of the same diets were also scanned using a diode array near-infrared spectrophotometer (DA-NIRS). The spectra were obtained by the DA-NIRS and were chemometrically calibrated against the digestible value data using multivariate analysis software. The results in terms of standard error of cross-validation (SECV), residual prediction deviation (RPD) and correlation coefficient (R2) show good relationships (R2 &gt; 0.8) between the predicted and observed parameters for both the digestible protein and digestible energy parameters assessed. This study therefore demonstrates that it is possible to use NIRS technology to provide rapid estimates of the digestible protein and digestible energy values of compound diets for barramundi in near real time.&nbsp