Potential, Implications and Solutions Regarding the Use of Rendered Animal Fats in Aquafeeds

Problem statement: In the past, aquafeeds were comprised largely of fish meal and fish oil derived from marine reduction fisheries. In addition to being highly palatable and readily digested by cultured fishes, these feedstuffs were historically inexpensive sources of protein, energy and essential nutrients. However, increasing cost and concerns over safety and sustainability have greatly incentivized the transition from fish meal and oil to alternative sources of protein and lipid for aquafeed formulation. Fish oil replacement is proving more difficult than originally anticipated, particularly for marine carnivorous species. Approach: If complete fish oil replacement is not a viable goal for fish nutritionists and aquafeed manufacturers, at a minimum, we must strive for judicious use of limited marine-derived resources. In the present review, we explore the opportunities of using rendered fats as alternatives to marine-derived fish oils in aquaculture feeds, beginning with a discussion of the products themselves before reviewing the most recent literature and concluding with a discussion of the future of these products in aquafeed formulations. Results: Rendered fats have not been as intensively evaluated in aquaculture nutrition as grain and oilseed-derived lipids, although a number of recent publications on the subject suggest increasing interest in the use of rendered products in aquafeeds. Conclusion: Poultry fat, beef tallow, pork lard and to a lesser extent, yellow/restaurant grease and catfish oil, have been investigated individually or in combination with other lipids in feeds for a broad range of cultured taxa with generally acceptable results

Evaluation of Natural-Source Vitamin E, RRR-α-Tocopheryl Acetate, as a Micronutrient in Sunshine Bass Feed

A variety of vitamin E isomers can be used in the manufacture of animal feeds, though the efficacy of these sources varies. Our purpose was to evaluate natural-source vitamin E, RRR-a-tocopheryl acetate (NSVE), as an alternative to synthetic vitamin E, all-rac-a-tocopheryl acetate (SYNE), in the diets of sunshine bass (female white bass Morone chrysops X male striped bass M. saxatilis). Our specific objectives were to evaluate graded levels of NSVE in terms of meeting the vitamin E requirement of sunshine bass and to address the physiological and economic suitability of NSVE by direct comparison with SYNE. Five isocaloric, isonitrogenous, semipurified diets were prepared and supplemented with NSVE at 0, 10, 20, or 30 mg/kg or SYNE at 30 mg/kg. Each dietary treatment was fed to fish in four replicate tanks, each housing 10 juvenile sunshine bass (mean weight = 25.1 g) in a recirculating system. One-way multiple analysis of variance (MANOVA) indicated that significant differences among treatment groups (Wilks’ λ = 0.006) were most greatly attributable to differential survival, growth, food conversion ratio, and liver aldehyde concentration. Fish fed diets containing NSVE at less than 22 mg/kg (as-fed concentration, or 20 mg/kg supplemental dietary treatment) exhibited significantly lower survival (≤65% versus ≥92%) and weight gain (≤359% versus ≥591%), impaired food conversion ratio (2.9 versus ≤1.9), and evidence of heightened liver tissue oxidation (aldehyde, 0.62 nmol/g of tissue versus ≤0.22 nmol/g). Fish fed diets containing an NSVE as-fed concentration of 22 mg/kg or more exhibited performance equivalent to those fed the SYNE control within all parameters. Accordingly, we conclude that NSVE is as effective as SYNE, but at lower concentrations, and that it may be of greater value as a micronutrient source for aquaculture feeds

Fatty Acid Profiles Distinguish Channel Catfish From Three Reaches of the Lower Kaskaskia River and its Floodplain Lakes

Despite the increasing use of fatty acids (FAs) as biomarkers in aquatic food web analysis, little information is available regarding differences in FA profiles of fish among habitat types in river-floodplain ecosystems. The objectives of this study were to 1) test whether the FA profiles of channel catfish (Ictalurus punctatus) differed among three reaches of the lower Kaskaskia River and its floodplain lakes, and 2) to compare FA profiles among muscle, liver, and adipose fin tissues collected from these fish. Profiles differed significantly among sites, especially between upper and lower river sites, and between river channel and oxbow lake sites, suggesting differences in FA availability for channel catfish occupying different habitats and river reaches in the Kaskaskia River system. Specifically, the essential FAs 18:2n-6 and 18:3n-3 increased in catfish tissues from upstream to downstream reaches, which could reflect increased floodplain connectivity and decreasing impoundment effects downstream. Ratios of n-3 to n-6 FAs were higher in fish from oxbow lakes, perhaps suggesting increased use of autochthonous production in the floodplain relative to the main river channel. Muscle and adipose fin FA profiles exhibited similar location-related trends, whereas liver FA profiles were markedly different from the other tissue types. These results suggest that adipose fin tissue samples may be a viable, less-invasive alternative to muscle tissue for analysis of FA profiles in channel catfish. Our study supports the use of tissue FA profiles in identifying habitat utilization by channel catfish, and perhaps habitat-specific energy contributions to riverine consumers. Furthermore, our work highlights floodplain habitat as a potential source of essential n-3 FA and the associated importance of maintaining river-floodplain connectivity to support aquatic food webs

Influence of Grow-Out Feed Fatty Acid Composition on Finishing Success in Nile Tilapia

The fatty acid (FA) composition of cultured finfish can be tailored by transitioning fish reared on alternative lipid-based, low long-chain polyunsaturated FA (LC-PUFA) content grow-out feeds to high LC-PUFA finishing feeds based on fish oil (FO) before harvest. To determine whether the FA composition of the grow-out feed influences finishing success in Nile tilapia Oreochromis niloticus, coconut (CO), grapeseed (GO), linseed (LO), and poultry (PO) oils were evaluated in grow-out feeds with respect to production performance and responsiveness to finishing. The production performance of Nile tilapia was unaffected by application of the various feeding regimes, indicating that this species can effectively utilize CO, GO, LO, PO, and FO in aquafeeds. Implementation of the alternative lipid sources was associated with altered fillet FA composition. Although the differences were not significant in all cases, the levels of FO-associated FAs (e.g., 20:5[n-3] and 22:6[n-3]) were elevated among finished groups relative to their unfinished counterparts. However, the effect of finishing on fillet LC-PUFA content was relatively minor given the considerable retention of LC-PUFAs observed in unfinished groups. The patterns of fillet FA profile change in Nile tilapia appear to support a hypothesis of selective FA metabolism in this species. Our results suggest that attempts to enhance the FA composition of Nile tilapia fillets via finishing may be best served by providing a grow-out feed high in saturated and monounsaturated FAs and low in medium-chain polyunsaturated FAs

Fatty Acid Profiles are Biomarkers of Fish Habitat Use in a River-Floodplain Ecosystem

Fatty acid (FA) analyses of fish tissues offer the potential to gain new knowledge of habitat or forage-specific energy inputs to fishes in river-floodplain ecosystems, although limited information exists regarding among-habitat differences in FA biomarkers. The goal of this study was to determine if differences in fish FA profiles among main channel and connected and disconnected floodplain lakes exist in large river-floodplain systems. Bluegill Lepomis macrochirus FA profiles were generated to assess differences among two reaches of the Illinois River, USA, and its connected and disconnected floodplain lakes and determine whether FA signatures could be used to reclassify fish to their source habitat. Bluegill FA profiles differed among habitats and river reaches, including differences in levels of individual FAs (e.g., 18:2n-6, an indicator of allochthonous inputs, was higher among main channel fish) and FA groupings (e.g., n-3:n-6 FA ratio, an indicator of aquatic primary productivity, was higher among floodplain lake fish), which enabled [87.5% reclassification accuracy of fish to their source environment. We demonstrated that bluegill FA profiles differed among reaches and laterally among river channel and floodplain habitats, suggesting that FA profiles can be used to infer recent habitat use and habitat-specific foraging of fishes in large river-floodplain ecosystems

Thoughts for the Future of Aquaculture Nutrition: Realigning Perspectives to Reflect Contemporary Issues Related to Judicious Use of Marine Resources in Aquafeeds

In recent decades, aquaculture nutrition research has made major strides in identifying alternatives to the use of traditional marine‐origin resources. Feed manufacturers worldwide have used this information to replace increasing amounts of fish meal and fish oil in aquafeeds. However, reliance on marine resources remains an ongoing constraint, and the progress yielded by continued unidimensional research into alternative raw materials is becoming increasingly marginal. Feed formulation is not an exercise in identifying "substitutes" or "alternatives" but rather is a process of identifying different combinations of "complementary" raw materials—including fish meal, fish oil, and others—that collectively meet established nutrient requirements and other criteria for the aquafeed in question. Nutrient‐based formulation is the day‐to‐day reality of formulating industrially compounded aquafeeds, but this approach is less formally and explicitly addressed in aquaculture research and training programs. Here, we (re)introduce these topics and explore the reasons that marine‐origin ingredients have long been considered the "gold standards" of aquafeed formulation. We highlight a number of ways in which this approach is flawed and constrains innovation before delving into the need to assess raw materials based on their influence on aquafeed manufacturing techniques. We conclude with a brief commentary regarding the future funding and research landscape. Incremental progress may continue through the accumulation of small insights, but a more holistic research strategy—aligned with industry needs and focused on nutrient composition and ingredient complementarity—is what will spur future advancement in aquaculture nutrition.This article also appears in: World Fisheries Da

Chemical and Electrical Approaches to Sedation of Cobia: Induction, Recovery, and Physiological Responses

To support the growing interest in marine fisheries research in areas such as biotelemetry, tagging, and tracking, we assessed the ability of various sedatives to facilitate this research in juvenile cobias Rachycentron canadum (∼300 g), namely, tricaine methanesulfonate (MS-222; 150 mg/L), carbon dioxide (CO2; ∼750 mg/L), eugenol (60 mg/L), benzocaine (150 mg/L), and pulsed-DC electrosedation (100 V, 30 Hz, 25% duty cycle, 5-s exposure). Induction times (CO2 [z] \u3e benzocaine [y] \u3e eugenol [y] \u3e MS-222 [y] \u3e electrosedation [x]), recovery of equilibrium (CO2 [z] \u3e eugenol [z] \u3e MS-222 [y] \u3e benzocaine [y] \u3e electrosedation [x]), and responsiveness to tactile stimulus (eugenol [z] \u3e MS-222 [y] \u3e benzocaine [y] \u3e CO2 [xy] \u3e electrosedation [x]) differed significantly among the sedative treatments (treatments with the same letters are not significantly different). Total handling time from initial sedative exposure to recovery differed among the sedatives as well (CO2 [z] \u3e eugenol [y] \u3e benzocaine [x] \u3e MS-222 [x] \u3e electrosedation [w]), with cumulative means ± SEs of 5.9 ± 0.2 min for CO2, 4.1 ± 0.2 for eugenol, 2.7 ± 0.2 min for benzocaine and MS-222, and 1.0 ± 0.2 min for electrosedation. Physiological responses differed significantly over time, with transient increases in plasma cortisol, glucose, osmolality, and lactate that were resolved within 6 h. The overall magnitude of the physiological responses differed among sedatives, depending on the response variable; however, in each case, CO2 elicited the greatest response. Although variations in induction and recovery times were observed, it is likely that these differences can be reasonably accommodated within the context of typical research by adjusting the sedative treatments or allowing for longer induction and recovery times as needed

Temporal Dynamics of Lipid and Fatty Acid Characteristics of Gulf Menhaden, \u3ci\u3eBrevoortia patronus\u3c/i\u3e in the Northern Gulf of Mexico

Gulf Menhaden, Brevoortia patronus, in the northern Gulf of Mexico support a large commercial fishery and are thought to play an important trophic role in the coastal ecosystem. The temporal dynamics of both fatty acid and oil content have a direct impact on the value of Gulf Menhaden to predators and to the fishery. In this work, we describe how oil content of Gulf Menhaden varies with season, sex, age, condition, and tissue and investigate how fatty acid composition of mature (137.5 mm FL) female tissues varies with season, month, and tissue type. We found pronounced temporal (January to October) variation in mean oil content ranging from 0.062 to 0.579 mg g−1 that exhibited a significant (p \u3c 0.001) seasonal pattern. We observed significant differences in oil content between tissue (muscle vs. ovary) of mature females and these exhibited a significant seasonal contrast, indicating that females were provisioning eggs in the fall. PERMANOVA analysis indicated the existence of significant differences (p \u3c 0.001) in the composition of fatty acids of muscle tissue collected in different months. Mean eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and long chain polyunsaturated fatty acid (LC-PUFA) levels exhibited significant seasonal differences (p \u3c 0.05), and in the case of DHA and LC-PUFA, both exhibited mean tissue-specific differences (p \u3c 0.05). This work indicates that the value of Gulf Menhaden as prey and a fishery resource in the region varies during the year and we propose that trophic models of the Gulf of Mexico ecosystem should account for this variation

Saturated Lipid Sources in Feeds for Sunshine Bass: Alterations in Production Performance and Tissue Fatty Acid Composition

Feeds rich in saturated (SFAs) and monounsaturated fatty acids (MUFA) appear to maximize the retention of long-chain polyunsaturated fatty acids (LC-PUFA) in the fillets of sunshine bass (female white bass Morone chrysops × male striped bass M. saxatilis). To determine whether different sources of SFA and MUFA have equivalent effects on tissue fatty acid (FA) profile change, coconut (CO) and palm oils(PO) were evaluated as partial and complete substitutes for fish oil (FO) in feeds for juvenile sunshine bass. After 8 weeks of culture, the production performance of all groups was within the acceptable range for sunshine bass; however, weight gain was significantly reduced within the 100%-CO group. Partial replacement of FO with CO or PO resulted in significant alteration of fillet FA profiles, and these changes were exacerbated in the complete-FO-replacement groups. The LC-PUFA were disproportionately enriched in the fillets of fish fed the reduced or FO-free feeds, whereas dietary surpluses of 12:0 and 14:0 (CO-based feeds) and 16:0 (PO-based feeds) were not reflected in any of the tissues analyzed. Rather, the levels of the SFA elongation–desaturation products (i.e., 18:0 and 18:1[n-9]) were elevated, particularly within liver lipid, suggesting enhanced FA biotransformation activity among fish fed higher levels of either alternative lipid source. Based on tissue FA composition, PO and CO appear to be approximately equivalent in terms of fillet LC-PUFA retention. However, the digestibility and utilization of these feedstuffs must be further investigated to maximize the ability of PO and CO to (partially or completely) replace FO in sunshine bass feeds

Towards achieving circularity and sustainability in feeds for farmed blue foods

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