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Effects of feed processing method (extrusion and expansion-compression pelleting) on water quality and growth of rainbow trout in a commercial setting
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To determine the effects of feed processing method (extrusion or expansion followed by compression pelleting) on feed physico-chemical characteristics, fecal stability, water quality, and growth performance in rainbow trout, three types of feed pellets (expanded sinking, EpS; extruded sinking, ExS; extruded floating, ExF) were prepared, analyzed, and fed to juvenile rainbow trout (initial weight = 285.8 ± 15.2 g) at three feeding rates based on feeding rate curves developed at Snake River Farm (Buhl, Idaho) (median rates [%BW] for feeding rate 1, 0.85; feeding rate 2, 0.95; feeding rate 3, 1.05) for 124 days. Results showed that all feeds had similar chemical composition, but the degree of starch gelatinization (as % of starch) was significantly higher in ExS (90.01 ± 0.26) and ExF (84.82 ± 0.63) than in the EpS (9.09 ± 0.41) feed, which led to extruded feeds having much higher water stability, fecal durability, and lower phosphorus discharge. The ExF feed produced better growth (% increase; 154.4 ± 18.5) and feed conversion (1.06 ± 0.06) compared to EpS (126.3 ± 12.4 and 1.26 ± 0.14) and ExS (121.7 ± 7.8 and 1.22 ± 0.04) in rainbow trout. Growth (% increase) improved as feeding rate increased (feeding rate 1, 125.6 ± 10.3; feeding rate 2, 140.8 ± 16.0), but further improvements were not observed at the highest feeding rate (feeding rate 3, 135.9 ± 22.8). The present study is the first to show that the extrusion process not only produces pellets having better quality than the expansion-compressed pelleting method but also improves fecal size and durability in water, and therefore, use of extruded feeds has the potential to improve waste collection and removal and reduce contribution to pollution in effluent.
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... However, these effects vary depending on the species [45]. Another downstream benefit of extruded feed is improved faecal durability in water, which allows for easier waste collection [46]. Overall, these features enable lower feed consumption and reduced operational issues for equivalent animal productivity. ...
... The comparative studies summarised in Table 4 encompass a variety of species, including tilapia, rainbow trout, carp and gilthead sea bream, among others, and cover different aspects of growth performance, feed utilisation and physiological impacts. Notably, extruded feeds have consistently been shown to significantly improve dry matter and energy digestibility, which equates to benefits in terms of higher weight gain, better FCRs and improved nutrient retention across several species [23,[46][47][48]. ...
... In addition, water and heat penetration promote the swelling of fibrous components and partial unfolding and denaturation of proteins. Steam is typically introduced to raise the moisture content to ~16% and the temperature to ~85°C [46]. Riaz and Rokey report that at least 30% starch pregelatinisation should occur throughout the pre-conditioning process to ensure effective extrusion [58]. ...
To sustain the expanding volume of aquaculture production, there is significant demand for an affordable supply of energy and nutrients to aquatic species. High-quality feed is essential to ensure the productivity, sustainability and economic viability of aquaculture systems. Over the past 30-40 years, extrusion technology has emerged as an efficient method to produce high-quality feed with enhanced functional attributes, such as digestibility, palatability, buoyancy and water stability. This review provides a comprehensive overview of the current state-of-the-art in aquafeed extrusion, highlighting the mechanisms underpinning extrusion technology, challenges for industrial production and future opportunities in this field. Through bibliometric analysis, we examine the evolution of aquaculture feeding techniques and their impact on feed quality and fish growth performance. Comparisons between pelletised and extruded feeds highlight advancements in extrusion methods, which offer superior nutrient retention and feed conversion efficiency. We elucidate the scientific principles of feed extrusion, including the effects of temperature , moisture and mechanical energy on feed properties. Despite significant progress, key challenges remain for the production of extruded feed, such as ingredient variability, operational complexity, diverse product requirements and waste management. Conversely, we explore opportunities for extrusion technology, emphasising predictive characterisation, extrusion modelling, and AI-driven quality control. The review concludes with a perspective of the industrial context, discussing the commercial drivers for aquafeed milling, insights from industry stakeholders and future directions for commercial research and development. This review offers researchers, technologists and industry stakeholders a comprehensive understanding of the current landscape, challenges and future prospects for extruded aquafeed production.
... A more sustainable alternative is extruded pellets (EP), which offer long-term cost efficiency and reduced ecological impact (Espinoza-Ortega et al. 2024;Lee et al. 2016;Welker et al. 2018). EP has demonstrated advantages such as improved digestibility, better nutrient retention, and reduced organic waste emissions. ...
This study applies the fixed-effects threshold model (FETM) to examine nonlinear dynamics and threshold effects in Korean finfish aquaculture using panel data from 2010 to 2023. The analysis identifies a critical threshold in current biomass (log-transformed 13.9483, approximately 1,142,010 fish), beyond which the marginal productivity of stocking density declines due to resource competition, oxygen depletion, and metabolic stress. Among key production inputs, feed input exhibits the highest elasticity (0.4717), confirming its dominant role in production efficiency, whereas water temperature shows a significant negative elasticity (-1.3301), highlighting the adverse impact of rising water temperatures on fish growth and survival. Additionally, many finfish aquaculture regions in Korea face severe constraints due to overuse of water surface areas, leading to diminishing marginal returns and heightened ecological stress. These findings highlight the urgent need for comprehensive environmental assessments, real-time monitoring systems, and adaptive management strategies to enhance sustainable aquaculture practices. Particularly, optimizing stocking densities based on the identified current biomass threshold and implementing spatial planning policies can balance ecological sustainability and production efficiency. This study demonstrates the effectiveness of FETM in detecting nonlinear relationships and production thresholds in aquaculture systems, providing insights for evidence-based policymaking and sustainable resource management aligned with global sustainability goals.
... Hot-extrusion is performed at temperatures above 100°C forming floating diets for surface feeders such as, O. niloticus; cold extrusion identifies at ambient temperatures producing sinking pellets for bottom dwelling finfish including Clarius gariepinus(Choton et al., 2020).Were et al. (2021), demonstrated benefits of hot extrusion processing of feeds in reducing microbial interferences in insect and larval meal replacement of FM diet for Nile tilapia and African catfish.Extrusion cooking affects nutritional quality of diet at various degrees. In its beneficial aspect, in addition to destruction of antinutrient factors, extrusion diets contain gelatinized starch, improved soluble dietary fiber; increasing its digestibility to fish and feed physical properties in water(Welker et al., 2018;Glencross et al., 2011). On the contrary, depending on extrusion conditions heat susceptible vitamins can be lost, with protein-sugar reactions at high extrusion temperatures deteriorating feed nutrient profiles(Singh et al., 2007). ...
Fish foods are known for their long standing health benefits to humans.Feed qualityenhancement provides an opportunity to improve sustainable aquaculture productions contributing to matchable fish demandsand consequent consumer gain.Preparation of balanced, cost effective feed based on the nutrition and health needs of fish is thus an essential precondition. Forcost-compliant production, diets must be formulated based on accurate apportionment of essential nutrients and energy gains according tofundamental needs of the species. Present study describes dietary requirements of finfish in terms of proteins, amino acids, lipids, constituent fatty acids, carbohydrates, and energy. The work also evaluates importance of feed processing in improvingdietary parameters for sustainable quality aquaculture productions.
... Extrusion feed processing is being extensively used in the fish feed industry to obtain compound feed pellets with functional physical properties like density with varying sinking velocities in seawater and high water stability (Sørensen, 2012;Welker et al., 2018). Recently, the effect of extruded pellets' physical properties on rumen environment variables and post-prandial starch appearance in the duodenum was studied in vivo (Larsen et al., 2019). ...
... Therefore, they will allow us to facilitate the development of novel sustainable feeds by the industry and to enhance the management of environmental impacts. In the fish species mostly farmed in the Mediterranean Sea, such as gilthead seabream and European seabass, the use of sustainable feedstuffs from seafood trimming and processing and aquafeed manufacture (extrusion) has already been adopted to improve the feed conversion rate while minimizing the environmental impact [44,45]. ...
IMTA is one of the most innovative and sustainable farming systems, exhibiting the best technique available in rearing aquatic organisms belonging to different positions along the trophic levels. In the literature and in legislation, the environmental benefits of IMTA protocols have been extensively recognized, mainly for its capability to reduce the ecological footprint of intensive aquaculture systems and concretely address the Sustainable Development Goal no. 14 (SDG 14). However, lesser attention is given to the assessments of its role in enhancing the zootechnical performance, animal welfare, and flesh quality of the species involved. To the best of our knowledge, this is the first review that aims to offer a systematic analysis of the existing literature on the main commercial motivations that could draw the attention of stakeholders, including consumers and fish farmers, towards a greater social acceptability and implementation of the IMTA system on a large scale. The findings suggest that, beyond its environmental advantages, IMTA systems can positively influence the productivity, growth, survival, feed efficiency, and animal health and welfare (AH&W), as well as the nutritional quality of the harvested species, thus offering significant economic and market value both in terms of Environmental, Societal and Governance (ESG) parameters and One Health.
... The conditioned feed mixture is subjected to the pelleting process, where it is compressed through dies to form pellets of a specific size. Pelleting enhances feed stability, reduces waste, and facilitates ease of handling [41]. However, the high temperatures involved in pelleting may not always be effective in eliminating mycotoxins, and there is a risk of recontamination during the cooling and storage phases. ...
The aim of this review is to provide an assessment of mycotoxin contamination in fish feed. Focusing on major mycotoxins including aflatoxins, fumonisins, ochratoxins, trichothecenes, and zearalenone, the paper explores their diverse impacts on fish health, from growth inhibition to immunosuppression. It meticulously examines the sources of mycotoxin contamination in fish feed, addressing raw ingredients, storage conditions, and feed manufacturing processes. The review emphasizes the critical role of adherence to Good Agricultural Practices (GAP) and Good Manufacturing Practices (GMP) in preventing mycotoxin risks. Additionally, the paper elucidates mitigation strategies, encompassing the use of mycotoxin-binding feed additives, feed formulation optimization, and technological advancements for early detection. This comprehensive overview serves as a valuable resource for aquaculture practitioners, researchers, and policymakers aiming to enhance the safety and sustainability of fish production amidst mycotoxin challenges.
Apparent digestibility coefficients (ADCs) of dry matter, crude protein, crude lipid, energy, essential amino acids, and fatty acids in extruded pellets containing various fish meals were determined for olive flounder (Paralichthys olivaceus). Eight extruded pellet diets were prepared to contain different fish meals (herring fish meal, anchovy fish meal, mackerel fish meal, sardine fish meal-A, sardine fish meal-B, tuna fish meal, pollock fish meal-A, and pollock fish meal-B) designated as HM, AM, MM, SM-A, SM-B, TM, PM-A, and PM-B, respectively. Chromic oxide (Cr2O3) was used as an inert indicator at a concentration of 0.5 % in the diet. Feces were collected from triplicate groups of fish (151 ± 4.0 g) using a fecal collection column attached to the fish rearing tank for 4 weeks. Dry matter ADCs of the MM, SM-A, SM-B, and PM-A diets were higher than those of all the other dietary groups, and the lowest digestibility of dry matter was observed in the PM-B diet. Fish fed the MM, SM-A, and PM-A diets showed significantly higher ADC of protein than those fed the AM, SM-B, TM, and PM-B diets. Lipid ADC of PM-B was significantly lower than that of the other diets. Energy ADCs of fish fed the MM, SM-A, and PM-A diets were significantly higher than those of the other diets. The availability of essential amino acids in the MM, SM-A, and PM-A diets were generally higher than that of the other fish meal diets, while TM showed the lowest values among all the experimental diets. ADCs of fatty acids in the AM, MM, SM-A, and PM-A diets were generally higher than those of fatty acids in the other diets, and the lowest values were recorded for the PM-B diet. These results provide information on the bioavailability of nutrients and energy in various fish meals which can be used to properly formulate practical extruded feeds for olive flounder.
A factorial experimental design (5×3×2) was used to investigate the effects of non-starch polysaccharide binding agents on physical properties of single-screw extrusion. Extrusion cooking trials were performed with an ingredient blend for yellow perch, fortified with five non-starch polysaccharide binding agents including three plant-origin gums (guar, wheat gluten, carboxymethyl cellulose (CMC)) and two microbial-origin exopolysaccharide gums (xanthan and pullulan), with three levels of gum inclusion (3,
6, and 10%), and two levels of screw speed (100 and 150 rpm). Effects of the independent variables on extrudate characteristics were extensively analyzed and included density, expansion ratio, water absorption and solubility indices, pellet durability, and color. Increasing gum level from 3 to 10% led to a considerable increase in unit density of extrudates for xanthan, guar, wheat gluten, CMC, and pullulan by 39.6%, 21%, 11.4%, 30%, and 19.7%, respectively. The minimum (357 kg m-3) and maximum (607 kg m-3) bulk densities were observed for the diets produced with 6% guar at 150 rpm and 10% xanthan at 100 rpm, respectively.
The mean values of expansion ratio for the diets containing exopolysaccharide gums were slightly smaller than those of the other diets. Increasing gum inclusion level increased the expansion ratio of the extrudates using xanthan, wheat gluten and pullulan but reduced the expandability of diets used guar gum; increased levels did not change the expansion ratio of extrudates containing CMC. At the highest levels of gum inclusion and screw speed, both pullulan and wheat gluten gums provided better expandability of the feed extrudate. Exopolysaccharide gums resulted in extrudates with significantly higher pellet durability and water solubility indices. Overall, the addition of 6 to 10% non-starch exopolysaccharides could improve the pellet durability of aqua feed extrudates. A future study investigating the effects of feed composition and additional extrusion processing conditions on the physical parameters of these products in aquafeeds would be appropriate.
Aquaculture is now recognized as a viable and profitable enterprise worldwide. As aquaculture technology has evolved, the push toward higher yields and faster growth has involved the enhancement or replacement of natural foods with prepared diets. In many aquaculture operations today, feed accounts for more than one-half the variable operating cost. Therefore, knowledge of nutrition and practical feeding of fish is essential to successful aquaculture.
This book is not written exclusively for scientists but also for students, practicing nutritionists, and aquaculturists. It covers the known nutrient requirements and deficiency effects for different fishes, and digestion and metabolism of nutrients and energy. It discusses nutrient sources and preparation of practical and research feeds. It gives directions for conducting fish nutrition and feeding experiments. Feeding practices for salmonids, channel catfish, tilapias, shrimps and hybrid striped bass are presented.
Since the first edition of this book was printed, the National Research Council of the National Academy of Sciences has revised the nutrient requirements for fish. These revisions are in the present edition. Other additions to this revised edition are chapters on nutrition and fish health, and bioavailability of nutrients. Each original chapter has been meticulously revised and updated with new information. Aquaculture is a dynamic area and new technologies are being introduced continuously; therefore, some of the material discussed in this revised edition may become obsolete quickly. Nonetheless, the material presented has been thoughtfully selected and updated to make it of maximum use to persons whose interests range from general aquaculture to animal nutrition to feed manufacture.
The potential of defatted soybean meal (SBM) as a protein source in high energy diets (extruded soft-dry pellets, SDP) was studied with rainbow trout of about 5g. The SDP contained respectively 0, 20, 30, 40, and 50% SBM, or 25% SBM plus 15% corn gluten meal (CGM) as a substitute for fish meal. The digestibility of SBM nutrients in SDP was determined using a reference diet and test diets which were formulated to contain both the reference diet and SBM in a ratio of 70:30, 60:40, and 50:50, respectively.The combination of 25% SBM with 15% CGM produced the best growth, while inclusion of SBM up to 50% did not reduce growth or protein utilization efficiency compared to the control diet. However, feed efficiency was slightly lower in SBM supplemental diets caused by the undigestible carbohydrate portion of SBM. The digestibility of protein, starch, and energy of SBM was 91, 54, and 80%, respectively, rather unaffected by the SBM levels in the formulation.It was concluded that SBM can be included up to 50% in SDP, replacing up to 91% of fish meal, supporting excellent growth and feed performance. A combination of 25% SBM and 15% CGM was confirmed to be an effective alternative protein source for rainbow trout.