Research Progress on Copra Meal in Aquafeed

Abstract

The aquafeed industry is currently facing severe challenges such as increasingly tight supply and price fluctuations of traditional high-quality protein ingredients like fish meal and soybean meal. Therefore, actively exploring and developing new, stable, efficient, and sustainable feed protein sources to replace fish meal and soybean meal has become an urgent task and an important strategic direction for ensuring the sustainable development of the aquaculture industry. Copra meal is a widely available plant protein source with lower cost compared to fish meal and soybean meal, demonstrating good application potential. However, copra meal has disadvantages including low protein content, imbalanced amino acid profile, high crude fiber content, numerous anti-nutritional factors, and low digestibility. These issues can be addressed through certain treatments (e.g., fermentation or water soaking) to enhance its nutritional value. Currently, research on copra meal in aquafeed is still relatively scarce. To enable the broader and more effective application of this promising feed ingredient in aquafeed, this review systematically summarizes the current research progress on the nutritional characteristics, appropriate inclusion levels, processing improvement technologies, and the effects of copra meal on the growth and health of aquatic animals, aiming to provide references for promoting resource diversification and sustainable development in the aquafeed industry.

1. Introduction

As one of the fastest-growing food production sectors globally, aquaculture has become a significant source of animal protein. The Food and Agriculture Organization of the United Nations (FAO) predicts that global aquaculture production will reach 104.1 million tons by 2025, with an annual growth rate of 2.7%, and will for the first time contribute more than half of the global seafood production for direct human consumption. As the world’s largest aquaculture producer, China’s aquaculture industry continues to improve efficiency, driven by intensive and industrialized farming technologies, while also facing resource and environmental pressures such as rising feed costs, disease control, and effluent treatment [1]. Green and healthy farming has become a consensus. Consumer market demand for high-quality and safe aquatic products is driving China’s aquaculture industry towards accelerated high-quality and sustainable development.

Aquafeed is a crucial material foundation for the development of the aquaculture industry. Its nutritional quality and formulation rationality directly determine the growth rate, health status, survival rate, and ultimately the product quality and food safety of farmed aquatic products. Currently, fish meal and soybean meal, as the primary animal and plant protein sources in feed, face global supply pressures. On one hand, constrained by resource sustainability, climate, and environmental factors, the production growth of fish meal and soybean meal struggles to match the rapidly expanding demand for aquafeed, creating a structural shortage. On the other hand, market volatility and competitive demand collectively drive up the prices of fish meal and soybean meal, leading to continuously rising feed production costs. This dual dilemma significantly squeezes farming profit margins and poses a severe challenge to the stability and sustainable development of the industry chain. Therefore, finding a new feed protein source that is widely available, low-cost, and nutritionally rich has become a research focus and a critical challenge to be addressed in aquafeed [2].

Copra meal is the residue obtained after pressing or solvent extraction of oil from dried coconut kernel (copra), following the removal of the coconut husk. In many tropical regions, such as Central American countries, some African countries, and some Southeast Asian countries, the production of copra meal is substantial [3,4]. Copra meal is also known as coconut meal. The crude protein content of copra meal is around 20%, crude fat content about 8–11%, crude fiber content about 9–12%, and nitrogen-free extract content about 44.41% and is rich in B vitamins and relatively high in phosphorus [5,6,7]. It is cheaper than fish meal and soybean meal, possessing potential to replace them [8]. Not only can copra meal itself serve as a protein source in aquafeed, but certain active substances it is rich in also hold application potential in this field. The protein in copra meal mainly consists of 11S globulin and 7S globulin [9]. 11S globulin, the major protein in copra meal, accounts for 52.46% of the total protein and is a reliable source of bioactive peptides [10]. Studies on novel antioxidant peptides from copra meal protein and their mechanisms of action resulted in the identification of two novel antioxidant peptides, GMEEER and EEGER, from the 11S globulin of copra meal. Both exhibited significant activity in ABTS (2,2′-Azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)) and DPPH (2,2-Diphenyl-1-picrylhydrazyl) radical scavenging systems. Molecular docking combined with isothermal titration calorimetry (ITC) thermodynamic analysis revealed that synergistic hydrogen bonding and hydrophobic interactions constitute the core driving force for their radical scavenging, with the C-terminal arginine residue serving as a critical “anchor” that dominates the stable binding of the peptides to radicals [11]. Furthermore, research indicated that adding mannan oligosaccharides (MOSs) (obtained by hydrolyzing the mannan in copra meal with mannanase) to feed could effectively enhance the immunity and disease resistance of shrimp against pathogenic bacteria [12,13]. These studies collectively indicate the important role and significance of copra meal as a feed protein source in aquaculture.

However, copra meal also has certain drawbacks. Its available energy value is low. Among essential amino acids (EAAs), copra meal has high arginine content but is low in lysine and methionine. The fatty acids in copra meal are saturated. It contains high levels of anti-nutritional substances such as crude fiber, tannin, and phytic acid [5,6]. Therefore, to ensure the normal growth and health of animals, the inclusion level of raw (untreated) copra meal must be appropriate, or raw copra meal must undergo a series of treatments, or feed additives must be supplemented. Currently, methods such as fermentation and water soaking are employed to treat raw copra meal to improve its utilization. The contents of anti-nutritional substances like crude fiber, tannin, and phytic acid are significantly reduced in copra meal after fermentation and water soaking treatments. Fermentation treatment can also increase the absorbable nutrients in copra meal, elevating the levels of available amino acids and fatty acids [3], thereby promoting fish growth.

The application of copra meal in the livestock industry is already relatively common. It not only effectively replaces part of conventional grain ingredients like corn and soybean meal, significantly reducing feed costs, but also plays a practical role in conserving grain resources and alleviating the competition for grain between humans and livestock, making important contributions to improving the economic efficiency of livestock farming [14,15,16,17,18,19]. Replacing part of fish meal, soybean meal, and other protein ingredients with copra meal in feed can effectively reduce feed costs while ensuring normal animal growth. Research has shown that replacing 10% of barley grain and soybean meal with raw copra meal in the diet of Awassi lambs (Ovis aries) did not affect their growth performance, carcass quality, meat quality, or health status. Moreover, it reduced the feed cost from USD 428 in the control group to USD 390 (a decrease of approximately 9%), and the cost per unit of weight gain decreased from USD 2.63/kg to USD 2.21/kg (a reduction of approximately 16%) [18]. Similarly, in the diet of Nile tilapia (Oreochromis niloticus), partially replacing fish meal (365 g/kg in the control diet) with 680 g/kg of autoclaved copra meal reduced feed costs by 27% [20].

However, compared to its mature application in livestock, research, development, and practical application of copra meal in the field of aquafeed are noticeably lagging and relatively limited. This is partly due to differences in the digestive physiology of aquatic animals (especially fish, shrimp, and crabs) compared to terrestrial animals, making them more sensitive to factors such as protein quality, amino acid balance, fiber content, and anti-nutritional factors (ANFs) in feed ingredients. On the other hand, systematic research remains scarce regarding the appropriate inclusion levels of copra meal for different aquatic animals, treatment methods to improve its utilization, and the long-term effects of feeding on the growth and health of aquatic animals. This leads to industry apprehension about its application. Therefore, to fully tap the resource potential of copra meal and promote the diversification of aquafeed ingredients, this paper aims to systematically review recent research progress on the application of copra meal in aquafeed. The content will cover its nutritional characteristics, feeding effects on different aquatic animals, existing limitations, and improvement strategies, aiming to assess its technical feasibility and economic value in aquafeed, and provide a solid literature basis and theoretical reference for the future scientific, safe, and widespread application of copra meal in aquafeed, thereby assisting in cost reduction, efficiency improvement, and sustainable development of the aquaculture industry.

2. Methodology

In this review, the studies on copra meal were selected based on the following criteria to ensure a comprehensive and state-of-the-art summary (databases searched: Web of Science and Google Scholar; keywords used: copra meal or coconut meal; timeframes: 1995 to 2025):

(1) Relevance: Focus on studies related to nutritional characteristics, feeding effects on different aquatic animals, existing limitations, and improvement strategies of copra meal.

(2) Credibility: Priority given to peer-reviewed articles, authoritative reports (e.g., FAO publications), and high-impact journal papers.

(3) Timeliness: Emphasis on recent studies to reflect current advancements, while including seminal works for historical context.

3. The Application of Copra Meal in Aquafeed

3.1. Raw Copra Meal

The application of raw copra meal in aquafeed is shown in Table 1. Compared to fish meal and soybean meal, raw copra meal has the advantage of lower cost. In a study on milkfish (Chanos chanos) juveniles, after replacing 50% of the fish meal protein in the feed with copra meal protein (the control diet contained 19.78% fish meal), the juveniles still exhibited good growth performance, including faster growth rate and higher feed conversion ratio and protein efficiency ratio, while also effectively reducing feed costs [21]. In a feeding trial with tambaqui (Colossoma macropomum), when raw copra meal was mixed with the reference diet at a 30% ratio, it showed high protein digestibility and good energy and dry matter digestibility, outperforming several traditional ingredients like sorghum and wheat middlings; this indicates that raw copra meal is a promising feed ingredient, though its optimal inclusion level still requires further experimental verification [22]. In a Nile tilapia feeding trial where raw copra meal replaced soybean meal (soybean meal content in the control diet was 53.35%), the inclusion levels of raw copra meal in the feed were 0% (T1 group, control), 10% (T2 group), 20% (T3 group), and 30% (T4 group); results showed no significant differences in crude protein and true protein content of the fish meat among the groups; cholesterol content of the fish meat increased linearly with higher copra meal inclusion, while total polyunsaturated fatty acid content of the fish meat remained stable [23]. This indicates that appropriate inclusion of raw copra meal in feed does not reduce the nutritional value and eating quality of Nile tilapia.

In terms of protein and amino acids, compared to fish meal and soybean meal, raw copra meal has lower crude protein content and an uneven amino acid profile, particularly deficient in EAAs like lysine and methionine, though it is high in arginine [24]. Studies have shown that lysine content in copra meal is only 0.42%, methionine 0.27%, and tryptophan 0.15% [4,6]. Compared to fish meal, the contents of lysine, methionine, and threonine in copra meal are significantly lower, becoming its first, second, and third limiting amino acids, respectively. Therefore, the amino acid profile of copra meal struggles to meet the essential amino acid requirements of many fish species [25]. In a study on Nile tilapia, it has been found that when raw copra meal was used to replace fish meal and its inclusion level reached 30%, an imbalance existed in the essential amino acid profile, specifically, the contents of limiting amino acids such as lysine, methionine, and threonine fell below the requirements for Nile tilapia [26].

Regarding carbohydrates, although raw copra meal contains considerable carbohydrates, most belong to types not utilizable by fish, existing mainly as mannan (26%), galactomannan (61%), and cellulose (13%) [27]. These components can affect nutrient digestibility and utilization by encapsulating nutrients or increasing the viscosity of intestinal contents. In a study on Nile tilapia, compared to the control diet (containing 425 g/kg fish meal), feeding a diet containing 30% copra meal did not negatively affect the feed intake of Nile tilapia in the short term (10 days), but increased fecal output and may negatively impact water quality [28]. Another study on Nile tilapia showed that, compared to the control (384 g/kg fish meal), copra meal could partially replace fish meal, but due to the undigestible carbohydrates like crude fiber and mannan in the copra meal-containing diet passing directly through the intestine, it led to decreased digestible energy in the tilapia diet and increased fecal matter [29]. Most current studies on dietary fiber indicate that high fiber content in feed can bind with chyme in the gastrointestinal tract, preventing complete feed digestion, ultimately manifesting as lower nutrient digestibility, higher fecal excretion, and lower growth rate. Moreover, high concentrations of fiber in feed can lead to poor water stability of the feed [7]. Water stability, one of the physical indicators of feed, is commonly used to evaluate feed quality. Increased water stability is often strongly correlated with the retention rates of dry matter, crude protein, and crude fat in feed. The stronger the water stability, the more nutrients the feed can retain in water over a certain period. The high cellulose level in copra meal reduced water stability of the feed, leading to decreased retention of dry matter, protein, and lipid of the feed in water, and causing Nile tilapia fecal output to increase significantly by 4–45% compared to the control [29].

Raw copra meal also contains ANFs such as phytic acid and tannin, which can impair growth and health. Phytic acid can form chemical complexes that alter protein structure, reduce protein solubility, digestibility and activity, adversely affect intestinal epithelial cells, and decrease nutrient and energy availability, thereby inhibiting fish growth performance. Phytic acid can also form insoluble chelates with divalent metal ions like calcium, zinc, iron, magnesium, and copper, significantly reducing the bio-availability of these minerals. Furthermore, under acidic conditions, phytic acid can form insoluble complexes with basic amino acids like lysine, arginine, and histidine. These complexes resist hydrolysis by proteases, leading to decreased protein digestibility, reduced feed utilization efficiency, and growth depression [30]. A study on Atlantic salmon (Salmo salar) showed that adding phytase (750 OTU/kg) to a high-plant diet significantly improved growth performance, as well as phosphorus digestibility and retention in Atlantic salmon, with effects comparable to adding inorganic phosphorus, indicating the clearly negative effect of phytic acid on fish growth [31]. The high tannin content in raw copra meal also negatively affects feed palatability, feed intake, and nutrient absorption, thereby inhibiting fish growth. A previous study showed that being autoclaved at 120 °C for 30 min could significantly reduce tannin levels from 2.5% to 1.4% of copra meal, and it could contain autoclaved copra meal up to 68% in diets without any negative effects on growth performance or on flesh sensory characteristics of Nile tilapia [20].

In summary, although raw copra meal is cheaper than fish meal and soybean meal, for it to be well-utilized in the feed industry, especially in aquafeed, a series of physical, chemical, or biological treatments is necessary to meet the essential nutritional requirements of cultured animals, enabling its better application in feed.

Table 1. The application of raw copra meal in aquafeed.

Species	Initial Weight	Feeding Period	Diet Preparation	Main Results	References
Milkfish (Chanos chanos)	6.4–7.4 g	60 days	50% of the fish meal protein in the feed was replaced with copra meal protein (the control diet contained 19.78% fish meal).	When 50% of the fish meal protein in the feed was replaced with copra meal protein, the juvenile fish still exhibited good growth performance, while also effectively reducing feed costs.	[21]
Tambaqui (Colossoma macropomum)	86.52 ± 6.71 g	30 days	The copra meal is mixed with the semi-purified reference diet at a 30% ratio to prepare the test diet.	Tambaqui could effectively utilize copra meal protein.	[22]
Nile tilapia (Oreochromis niloticus)	10.3 ± 1.76 g	90 days	Copra meal was used to replace soybean meal in the feed at four inclusion levels (0%, 10%, 20%, and 30%), with the soybean meal content in the control diet being 53.35%.	Copra meal could be used as a safe ingredient in Nile tilapia feed and did not negatively affect the nutritional value of the fish meat.	[23]
Nile tilapia (Oreochromis niloticus)	50 g	9 days	Fish meal was replaced by 30% copra meal, while the remaining 70% of the formulation remained identical to the control basal diet.	When the inclusion level of copra meal reached 30%, the contents of limiting amino acids such as lysine, methionine, and threonine fell below the dietary requirements for Nile tilapia.	[26]
Nile tilapia (Oreochromis niloticus)	50 g	10 days	A total of four diets were formulated: a control group (based on fish meal), a copra meal group (30% inclusion), a palm kernel meal group (30% inclusion), and a soybean meal group (30% inclusion).	The inclusion of 30% copra meal in the diet did not negatively affect the feed intake of Nile tilapia, but it increased fecal production and might have adverse effects on water quality.	[28]
Nile tilapia (Oreochromis niloticus)	36.4 ± 0.72 g	10 days	The control diet used fish meal (384 g/kg) as the primary protein source, while the six test diets replaced fish meal with mixed oilseed meals (including cottonseed meal, soybean meal, copra meal, and groundnut meal), collectively providing approximately 80% of the total protein in the feed.	Diets containing copra meal include indigestible carbohydrates such as crude fiber and mannan, which pass directly through the intestine, resulting in reduced digestible energy in tilapia feed and increased fecal output.	[29]

Table 1. The application of raw copra meal in aquafeed.

Species	Initial Weight	Feeding Period	Diet Preparation	Main Results	References
Milkfish (Chanos chanos)	6.4–7.4 g	60 days	50% of the fish meal protein in the feed was replaced with copra meal protein (the control diet contained 19.78% fish meal).	When 50% of the fish meal protein in the feed was replaced with copra meal protein, the juvenile fish still exhibited good growth performance, while also effectively reducing feed costs.	[21]
Tambaqui (Colossoma macropomum)	86.52 ± 6.71 g	30 days	The copra meal is mixed with the semi-purified reference diet at a 30% ratio to prepare the test diet.	Tambaqui could effectively utilize copra meal protein.	[22]
Nile tilapia (Oreochromis niloticus)	10.3 ± 1.76 g	90 days	Copra meal was used to replace soybean meal in the feed at four inclusion levels (0%, 10%, 20%, and 30%), with the soybean meal content in the control diet being 53.35%.	Copra meal could be used as a safe ingredient in Nile tilapia feed and did not negatively affect the nutritional value of the fish meat.	[23]
Nile tilapia (Oreochromis niloticus)	50 g	9 days	Fish meal was replaced by 30% copra meal, while the remaining 70% of the formulation remained identical to the control basal diet.	When the inclusion level of copra meal reached 30%, the contents of limiting amino acids such as lysine, methionine, and threonine fell below the dietary requirements for Nile tilapia.	[26]
Nile tilapia (Oreochromis niloticus)	50 g	10 days	A total of four diets were formulated: a control group (based on fish meal), a copra meal group (30% inclusion), a palm kernel meal group (30% inclusion), and a soybean meal group (30% inclusion).	The inclusion of 30% copra meal in the diet did not negatively affect the feed intake of Nile tilapia, but it increased fecal production and might have adverse effects on water quality.	[28]
Nile tilapia (Oreochromis niloticus)	36.4 ± 0.72 g	10 days	The control diet used fish meal (384 g/kg) as the primary protein source, while the six test diets replaced fish meal with mixed oilseed meals (including cottonseed meal, soybean meal, copra meal, and groundnut meal), collectively providing approximately 80% of the total protein in the feed.	Diets containing copra meal include indigestible carbohydrates such as crude fiber and mannan, which pass directly through the intestine, resulting in reduced digestible energy in tilapia feed and increased fecal output.	[29]

3.2. Fermented Copra Meal

Fermented copra meal is a product obtained by inoculating raw copra meal with specific microbial strains for fermentation. Fermented copra meal can reduce the content of ANFs and fiber, and enhance nutrient bioavailability through fermentation. NDF (Neutral Detergent Fiber) is an important indicator measuring the content of structural carbohydrates such as total cellulose, hemicellulose, and lignin. In a study on broilers (Gallus gallus), okara mixed with copra meal, inoculated with Lactobacillus spp. and Clostridium butyricum, and supplemented with non-starch polysaccharide enzymes (NSPases) for solid-state fermentation significantly reduced NDF content. At low inclusion levels (1.25–2.5%), the fermented okara–copra meal mixture (FOCM) significantly improved the feed conversion ratio, intestinal morphology, and ileal microbiota, while the high dose (5%) offered no additional advantage and even showed a slightly negative trend [32]. In a study on the solid-state fermentation of copra meal, after fermenting raw copra meal with Aspergillus niger FSPL104, the β-mannanase activity in the fermented copra meal continuously increased, reaching a maximum of 4.79 U/g. This enzyme can specifically hydrolyze mannan, the main ANFs in copra meal (belonging to non-starch polysaccharides, also a major component of fiber). Concurrently, metabolomic analysis showed significant activation of the fructose–mannose metabolism pathway and the starch–sucrose metabolism pathway, further confirming the breakdown and utilization of structural carbohydrates (fiber) during fermentation [33].

A comparison of EAAs between raw and fermented copra meal is shown in

Table 2. Comparison of essential amino acids between raw and fermented copra meal.

	Raw Copra Meal	Fermented Copra Meal
Total Essential Amino Acids	7.44–8.02%	8.18%
Arginine	1.57–2.13%	1.86–2.15%
Histidine	0.35–0.39%	0.16–0.46%
Isoleucine	1.20–1.28%	1.89%
Leucine	0.66–1.26%	1.54%
Lysine	0.42–0.81%	0.59–1.04%
Methionine	0.24–0.29%	0.28–0.34%
Phenylalanine	0.77–0.91%	0.94–1.47%
Threonine	0.55–0.64%	0.49–0.74%
Tryptophan	0.14–0.15%	0.15–0.27%
Valine	0.92–1.03%	0.29–1.12%
References	[3,5,6,7,32]

. The application of fermented copra meal in aquafeed is shown in

Table 3. The application of fermented copra meal in aquafeed.

Species	Initial Weight	Feeding Period	Fermentation Strain	Diet Preparation	Main Results	References
Nile tilapia (Oreochromis niloticus)	1.07 ± 0.11 g	75 days	Saccharomyces cerevisiae	Fish meal was replaced by the fermented guar bean and fermented copra meal mixture at substitution rates of 0% (control; 200 g/kg fish meal), 25%, 50%, 75%, and 100%, respectively.	The fermented guar bean and fermented copra meal mixture could partially replace fish meal, but the substitution ratio should not exceed 25%.	[5]
Hybrid saline-tolerant tilapia (Oreochromis niloticus × Oreochromis mossambicus)	0.42 ± 0.07 g	60 days	Aspergillus niger	Fermented copra meal gradually replaced 0% (control; 47% soybean meal), 25%, 50%, 75%, and 100% soybean meal.	Fermented copra meal could safely replace 50% of soybean meal without causing negative effects on the growth, feed utilization, and health.	[34]
Saline tilapia (Oreochromis niloticus)	Not available	Not available	Rhizopus sp.	Fermented copra meal was added at four levels of 0%, 15%, 30%, and 45%.	The addition of 15% fermented copra meal to the feed had minimal adverse effects on the digestibility of the fish, making it the optimal substitution level.	[35]
Milkfish (Chanos chanos)	2.83 ± 0.14 g	84 days	Not available	Fermented copra meal was used to substitute soybean meal at inclusion levels of 0% (control; 300 g/kg soybean meal), 5%, 10%, 15%, 20%, and 25%.	The optimal inclusion level was determined to be 5%. Even at a level as high as 20%, the growth performance of the fish remained comparable to that of the control group.	[36]
Black Tiger Shrimp (Penaeus Monodon)	0.63 g	154 days	Aspergillus niger	Replacing 40% of fish meal protein with fermented copra meal (fish meal content in the control diet was 162 g/kg).	The growth performance of the shrimp was not affected.	[37]
Black Tiger Shrimp (Penaeus monodon)	0.38 ± 0.02 g	63 days	Not available	Fermented copra meal was used to replace 0% (control; 270 g/kg fish meal), 10%, 20%, 30%, and 40% of fish meal protein.	Fermented copra meal could safely replace up to 40% of fish meal protein in black tiger shrimp feed without negatively affecting the shrimp growth, feed efficiency, survival rate, and body composition.	[38]

. Existing studies on replacing fish meal or soybean meal with fermented copra meal in aquafeed indicate that, compared to raw copra meal, fermented copra meal can replace a higher proportion of fish meal or soybean meal. In a study on Nile tilapia, fermented guar meal and fermented copra meal (fermented by Saccharomyces cerevisiae) were mixed at a 3:1 ratio (referred to as FGCM); five isonitrogenous and isolipidic diets were formulated, replacing different proportions of fish meal with FGCM (FGCM-0 (0%, control; 200 g/kg fish meal), FGCM-1 (25%), FGCM-2 (50%), FGCM-3 (75%), and FGCM-4 (100%); the results showed that the upper limit for FGCM replacing fish meal in diets for Nile tilapia juveniles was 25%; beyond 25%, the growth, feed efficiency, digestibility, antioxidant status, and blood parameters of Nile tilapia significantly deteriorated [5]. In a study on hybrid saline-tolerant tilapia (Oreochromis niloticus × Oreochromis mossambicus), fermented copra meal was prepared by the solid-state fermentation of raw copra meal with Aspergillus niger; this fermented copra meal was used to replace 0% (control; 47% soybean meal), 25%, 50%, 75%, and 100% of soybean meal in the diet for feeding trial; the results showed that fermented copra meal could replace up to 50% of soybean meal without affecting growth and feed utilization [34]. In a feeding trial with saline tilapia (Oreochromis niloticus) juveniles, fermented copra meal was prepared by inoculating Rhizopus sp. for solid-state fermentation after high-temperature steam sterilization of raw copra meal; while ensuring a 20% fish meal content in all diets, this fermented copra meal was used to replace other plant-based ingredients (tofu waste, noodle waste, rice bran, cassava flour) in the diet; the results indicated that 15% fermented copra meal could be included in the diet without significantly reducing digestibility, but inclusion levels exceeding 15% significantly inhibited digestibility and were not recommended [35]. In a feeding trial with milkfish (Chanos chanos), fermented copra meal was added at 0% (control; 300 g/kg soybean meal), 5%, 10%, 15%, 20%, and 25% to replace soybean meal; the results showed that, in terms of growth, the optimal inclusion level of fermented copra meal in milkfish feed was 5%, but from an economic perspective, it could be increased to 20% [36]. In an experiment replacing 40% of fish meal protein (fish meal content in the control diet was 162 g/kg) in black tiger shrimp (Penaeus monodon) feed with fermented copra meal, the results indicated that fermentation treatment with Aspergillus niger increased the crude protein level, increased available free amino acid and free fatty acid levels, significantly reduced the concentration of a series of ANFs, improved the nutritional value and palatability of copra meal, and did not affect growth performance [37]. In another feeding trial with Penaeus monodon, fermented copra meal was used to replace 0% (control; 270 g/kg fish meal), 10%, 20%, 30%, and 40% of fish meal protein; the results showed that replacing 40% of fish meal with fermented copra meal did not affect the growth, feed efficiency, survival rate, or body composition of Penaeus monodon, indicating that fermented copra meal has good potential to replace fish meal in Penaeus monodon feed [38]. In summary, compared to raw copra meal, fermented copra meal has better nutritional value and is more suitable as a substitute for fish meal and soybean meal.

3.3. Water-Soaked Copra Meal

Water-soaked copra meal is obtained by soaking raw copra meal in water for a period. Water soaking can significantly reduce the content of inherent ANFs in copra meal and enhance the water stability of feed made with copra meal as an ingredient. The application of water-soaked copra meal in aquafeed is shown in

Table 4. The application of water-soaked copra meal in aquafeed.

Species	Initial Weight	Feeding Period	Diet Preparation	Main Results	References
Nile tilapia (Oreochromis niloticus) and silver barb (Barbonymus gonionotus)	Nile tilapia 800–900 g and silver barb 400–450 g	Not available	Not available	Water soaking treatment effectively improved the quality of copra meal by increasing its pH, reducing crude fiber content, enhancing water stability, lowering the levels of multiple anti-nutritional factors, and increasing the content of available carbohydrates.	[27]
Rohu (Labeo rohita)	3.64 ± 0.20 g	79 days	Experimental diets were made using either raw or water-soaked copra meal at levels of 20, 30, or 40% by replacing fish meal from the control diet (40% fish meal).	The inclusion level of water-soaked copra meal could be further increased to 30% without causing any negative impact on the fish growth performance.	[39]

. Experiments measuring the in vitro digestibility of copra meal treated by different physical methods showed that soaking copra meal in distilled water at a certain ratio (1:10 w/v) for 12 h significantly increased its pH, significantly reduced crude fiber content, enhanced its water stability, reduced the contents of ANFs like polyphenols, tannin, phytic acid and α-amylase inhibitors, and significantly increased in vitro carbohydrate digestibility (significantly effective for Nile tilapia) [27]. In a feeding trial with rohu (Labeo rohita), experimental diets were made using either raw or water-soaked copra meal at levels of 20, 30, or 40% by replacing fish meal from the control diet (40% fish meal); the results showed that 20% raw copra meal did not affect the growth of rohu, while the inclusion level of water-soaked copra meal could reach 30% [39]. Overall, compared to using raw copra meal as a feed protein source in aquafeed, water-soaked copra meal allows for a further increase in its inclusion proportion in feed, thereby helping to reduce aquafeed costs. At appropriate inclusion concentrations, it does not impair the growth of farmed fish. Water soaking is beneficial for the application of copra meal in aquafeed.

3.4. Copra Meal Treated by Other Methods

Existing treatment methods for raw copra meal also include physical methods such as microwave irradiation (non-ionizing radiation), γ-irradiation, electron beam irradiation (ionizing radiation), heat, and autoclaving. Such physical methods typically work by altering or breaking chemical bonds to modify originally unavailable components. Treating raw copra meal with physical methods like microwave irradiation (non-ionizing radiation), γ-irradiation, and electron beam irradiation (ionizing radiation) could effectively increase the amorphous structure, thereby enhancing enzymatic hydrolysis capability. It also reduced the internal crude fiber content of copra meal, increased available carbohydrate content, improved the nutritional value of copra meal, and enhanced animal feed utilization [27]. Furthermore, heat treatment at 95 °C for 30 min could effectively enhance the stability and functionality of coconut protein Pickering emulsions, mainly by inducing protein hydrophobic aggregation and improving interfacial wettability, which helps expand its application in the food industry [40]. Studies on utilizing heat treatment and calcium ions to modify copra meal protein similarly indicated the potential to develop a sustainable, edible, high internal phase Pickering emulsion (HIPPEs) using protein resources from waste copra meal. This emulsion possessed good rheological properties and structural stability, could expand the application of copra meal protein in the food industry, and provided new ideas for the high-value utilization of waste protein resources [41]. A previous study on Nile tilapia reported that it could contain autoclaved copra meal (autoclaved at 120 °C for 30 min) up to 680 g/kg in diets without any harmful effects on growth performance or on flesh sensory characteristics [20]. However, overall, although these physical methods are relatively effective in improving nutritional value, the required equipment is expensive, and the technology is relatively difficult to apply on a large scale in the aquafeed industry. Moreover, copra meal treated by these methods has not yet been extensively tested in feeding trials with many aquatic animals to study its usability.

4. Future Perspectives

With the growing global demand for sustainable, low-cost protein sources in aquaculture, copra meal, as a plant protein source with great potential, has attracted significant attention for its application prospects. The in-depth development and efficient utilization of copra meal in aquafeed should shift from a simple “alternative ingredient” mindset to a systematic development strategy integrating “quality control—nutritional balance—treatment improvement—health assessment—environmental consideration”.

First, strict control of raw material quality is essential. The nutritional composition of copra meal is significantly influenced by treatment methods. In the future, stricter quality standards need to be established, with monitoring throughout the process from origin and processing to storage, especially to prevent mycotoxin contamination issues caused by humid environments.

Second, nutritional balance and precise application can be achieved through scientific formulation. For example, the amino acid profile of copra meal is imbalanced. Synthetic amino acids can be directly supplemented to compensate for the deficiencies, or copra meal can be used in combination with other protein sources to achieve amino acid complementarity. Additionally, systematic nutritional evaluation is needed to precisely determine the appropriate inclusion level of copra meal in feed based on the physiological stages of different aquatic animals (e.g., herbivorous, carnivorous, and omnivorous fish), finding the optimal balance between cost reduction and ensuring growth performance.

Third, comprehensively apply various treatment technologies to enhance the nutritional value of copra meal. For instance, to overcome the issues of high fiber and ANF content in copra meal, treatment technologies such as heating, enzymatic hydrolysis, and fermentation can be employed.

Fourth, strengthen research on the impact of copra meal on intestinal health. High fiber and ANF content may negatively affect aquatic animals, especially fish with shorter intestines. Future research needs to pay more attention to the effects of copra meal and its processed products (e.g., fermented products, enzymatically hydrolyzed products) on intestinal morphology and structure, gut microbial composition and function, intestinal mucosal barrier functions, and intestinal metabolism.

Fifth, systematically assess the impact of copra meal on the aquaculture environment. Introducing a new feed protein ingredient must not only focus on its growth-promoting effects; a comprehensive evaluation of its impact on the aquaculture environment (water and sediment) is essential, such as nitrogen and phosphorus cycling, to reduce environmental load from the source. This is not only a key part of assessing its application feasibility but also an inherent requirement for promoting the green development of the aquaculture industry.

5. Conclusions

In summary, as a widely available and low-cost plant protein ingredient, copra meal shows considerable potential for partially replacing fish meal or soybean meal in aquafeed. However, its large-scale application still faces a series of scientific and technological challenges. Currently, systematic research, particularly in-depth evaluation for different aquatic animal species, growth stages, health status, and farming modes, remains insufficient. The nutritional deficiencies of raw copra meal are quite prominent (low protein content, imbalanced amino acid profile, low digestibility, high crude fiber content, numerous ANFs, among other drawbacks). Therefore, directly adding high proportions of raw copra meal to aquafeed often negatively affects the growth performance, feed conversion ratio, and even intestinal health of cultured animals, limiting its practical application value. Subjecting it to appropriate treatment is one of the important ways to significantly improve the nutritional value and feeding quality of copra meal, enabling its safer and more efficient application in aquafeed, which is beneficial for the development of the aquafeed industry. According to the current research status, it is highly recommended to use fermentation due to its high efficiency and economic benefits.