Encyclopedia
The current practice of decapod aquaculture involves the provision of juveniles with food such as natural diet, live feed, and formulated feed. Knowledge of nutrient requirements enables diets to be better formulated. By manipulating the levels of proteins and lipids, a formulated feed can be expected to lead to optimal growth in decapods. The use of formulated feed for decapods at a commercial scale is still in the early stages. This is probably because of the unique feeding behavior that decapods possess: being robust, slow feeders and bottom dwellers, their feeding preferences change during the transition from pelagic larvae to benthic juveniles as their digestive systems develop and become more complex.
- feed
- feeding diets
- macro-micronutrients
- feeding behavior
- pellet–decapod performances
1. Historical Developments in Cultivation
Decapods are valuable sources of aquatic food protein, and their fisheries and aquaculture support the economic growth of many coastal countries [1]. The increasing demand for seafood products has led to considerable interest in cultivating decapod species at a larger scale. The cultivation of decapods in various countries began during the 1980s with raising juveniles from the wild. In 2018, aquaculture reported a strong growth in decapod production, primarily of penaeid shrimp, crabs, and spiny lobsters (9.4 million tons), as compared with the previous year [2].
The success of decapod farming is dependent on the variety of diets [3][4][5][6,7,8]. Current practices of commercially decapod farming involve the provision of juveniles with food such as natural diet, live feed, and formulated feed [6][9]. The developments of a formulated feed for decapods begins with the use of fish oil (FO) and fishmeal (FM) as the main sources of lipids and proteins, with other ingredients such as wheat flour being the main source of carbohydrates (CHO). The inclusion of vitamins and minerals, probiotics, and other feed additives, when combined, satisfy the growth demand.
Current research into the development of decapod formulated feeds is geared towards the juvenile stage, but limited information is available on decapod groups in the adult stage. This is probably because of the unique feeding behavior that decapods possess: being robust [7][12], slow feeders [8][13] and bottom dwellers [9][14]. In addition, most published studies on commercially farmed decapod nutrition lack data on the physical characteristics of the feeds, such as water stability, palatability, and digestibility. Due to these issues, it is difficult to establish a standard feed formulation that focuses on physical pellet properties.
2. Decapod Feeding Biology
Decapods typically have two pairs of appendages (antennules and antennae) in front of the mouth and paired appendages near the mouth that function as jaws, which affects their feeding selection. Many decapod crustaceans are described as bottom feeders and scavengers that feed on dead animals that reside on the seafloor [10][15].
In addition, several species are restricted to certain environments that affect the feeding selection between species and between life stages [11][12][13][14][19,20,21,22].
Moreover, feeding preferences also change at different growth stages, for example, the pelagic larvae of many decapod groups such as shrimp and crabs are generally opportunistic, preying on anything suspended in the water, such as plankton (phyto- and zooplankton) [15][27].
2.1. Factors That Affect Feeding of Decapods
2.1.1. Biotic Factors
2.1.1. Biotic Factors
Biotic factors that affect feeding selection in decapods involve the sensory basis, which includes vision, chemoreception, mechanoreception, and electrosensory systems. In adult decapods such as prawns, shrimps, and crabs, vision is not as important as the other sensory systems since they are nocturnal [10][16][17][15,32,33]. At the same time, other decapods such as the tropical spiny lobster use chemoreception to locate food from the beginning of the juvenile stage since this species resides on the seafloor [18].
On the other hand, mechanoreception is defined as the ability of a decapod to detect and respond to mechanical stimuli such as touch, sound, and changes in pressure or posture in their surrounding environment. In decapods, mechanoreception is used to avoid predators or detect prey.
2.1.2. Abiotic Factors
Abiotic factors such as light and day length, temperature, water quality, and the physical properties of the food greatly affect decapod feeding responses. The presence of light is especially important in the decapod during larval stages because, compared with adult decapods, they are primarily nocturnal during the mature stage [19][39].
Meanwhile, water quality directly affects feeding responses in decapods. Decapod species depend on their chemical senses for foraging and social interactions, so a low water quality may result in a low feeding rate.
3. Nutritional Requirements of Juvenile Stages
In decapod feedings, protein, lipid, and carbohydrate (CHO) are described as the most important components of the nutrient classes, acting as the main sources of nutrients for embryonic development and growth [20]. Table 1 shows the macro- and micronutrients of different decapod groups during the juvenile stages.
In decapod feedings, protein, lipid, and carbohydrate (CHO) are described as the most important components of the nutrient classes, acting as the main sources of nutrients for embryonic development and growth [56]. Table 2 shows the macro- and micronutrients of different decapod groups during the juvenile stages.
| Decapod Group |
|---|
| Macronutrients |
|---|
| Micronutrients | Feed Additives | Reference | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Protein | Carbohydrates | Lipid Derivatives | Vitamin | Mineral | ||||||
| Lipid | Cholesterol | Fatty Acids | Carotenoid | |||||||
| Prawn | 47.3% | N/A | 7.5% | 0.5% | 3.0% EFA | Carophyll pink: 0.15% | 1.6% | 2.0% | Ethoxyquin, squid mantle muscle, L-a-phosphatidylcholine, crystalline amino acids, sodium alginate, tetra-sodium-pyrophosphatem, α-cholestane, α- cellulose | Glencross et al. (2002) [84] |
| Isonitrogenous feed 39% | 30.8–32.50% | 10.15–10.48% | N/A | n-3/n-6: 0.54–0.65 | N/A | 1.0% | 1.0% | Shrimp shell meal, corn grain | Kangpanich et al. (2017) [55] | |
| 39.18% | 35.47% | 6.91% | N/A | n-3/n-6: 0.69 EPA/DHA: 0.81 |
N/A | 1.0% | 2.5% | Soybean lecithin, choline chloride, cellulose, squid paste, calcium phosphate, beer yeast cell, spray dried blood powder | Li et al. (2020) [107] | |
| Shrimp | Isonitrogenous feed 21% dry weight | N/A | 77.1–85.9% | 3% | N/A | N/A | 2.5% | 2.0% | Soy lecithin, antifungic, antioxidant (ethoxyquin), Vitamin E | Martínez-Rocha et al. (2012) [108] |
| 30% | 42.1% | 6% | 0.5% | N/A | N/A | 1.0% | 4.7% | Lecithin, alpha cellulose, alginate, sodium hexametaphosphate | Velasco et al. (1998) [109] | |
| 35% | N/A | 8% | 0.2% | DHA: 0.5% ARA: 0.13% |
N/A | 2.0% | 0.5% | Calcium phosphate dibasic, lecithin, StayC | Samocha et al. (2010) [110] | |
| 32.1% | 48.1% | 5.84% | N/A | N/A | N/A | 8.53% | 8.53% | Soybean lecithin, alginic acid | Gonzalez-Galaviz et al. (2020) [111] | |
| 40.08–42.93% | 33.09–36.4% | 7.37–8.39% | 0.1% | N/A | N/A | 0.5% | 0.2% | Lecithin, alginate | Suresh et al. (2011) [41] | |
| 34.2% to 36.3% dry weight | 40.5% to 44.3% | 3.9% to 6.0% dry weight | N/A | N/A | N/A | 1.8% | 0.5% | Choline chloride, Stay-C 35% active | Galkanda-Arachchige et al. (2019) [46] | |
| 36% | N/A | 8% | 0.1% | N/A | N/A | 1.8% | 0.5% | Choline chloride, Stay-C250 mg/kg, CaP-diebasic, lecithin, chromium oxide | Fang et al. (2016) [112] | |
| 42.2% | N/A | 9.1% | 0.5% | N/A | N/A | 2.0% | 2.0% | Calcium phosphate, soya lecithin | Palma et al. (2008) [44] | |
| 39.7% | 30.7% | 9.45% | 0.16% | N/A | N/A | 0.28% | 0.28% | Krill meal, monocalcium phosphate, lecithin | Derby et al. (2016) [43] | |
| 34.8% protein in feed with soy meal and 29.3% protein in feeds with FM | 38.76% in feed with soy meal and 22.45% in feed with FM | 6.65% in feed with soy meal and 5.84% in feeds with FM | N/A | N/A | N/A | 0.93% in feed with soy meal and 0.85% in feed with FM | 0.93% in feed with soy meal and 0.85% in feed with FM | Soy lecithin, alginic acid, cellulose, antioxidant | Gil-Núñez et al. (2020) [47] | |
| 35.8% to 36.6% dry weight | 34.7% to 38.9% | 7.9% to 8.1% | 0.2% | N/A | N/A | 0.5% | 0.5% | Lecithin-soy, methionine, lysine, titanium dioxide | Weiss et al. (2019) [113] | |
| Isonitrogenous feed 40% dry weight | N/A | Isolipidic feed 9.00% dry weight | 0.02% | N/A | N/A | 1.2% | 1.0% | Lecithin powder 97%, amygluten | Moniruzzaman et al. (2019) [114] | |
| Isonitrogenous feed 35% dry weight | 31.93–32.78% | 8.18–8.63% lipid | N/A | ARA:1.68%; EPA: 2.87%; DHA: 4.66% |
N/A | 15% | 25% | Dicalcium phosphate, antifungal, antioxidant, lysine, methionine, garlic powder | Tazikeh et al. (2019) [115] | |
| Isonitrogenous feed 36% crude protein | N/A | 7.9–9.00% lipid | 0.11% | N/A | N/A | 0.25% | 0.25% | Antioxidant, antifungic agent, Vitamin C, choline chloride, | Gamboa-Delgado et al. (2019) [116] | |
| 37% | 38.32 to 38.88% | 10% | 0.5% | N/A | 1.46% (5% from 29.23% carotenoid extracted) |
1.0% | 1.0% | Monocalcium phosphate, cellulose | Simião et al. (2019) [48] | |
| Crayfish | Isonitrogenous with 39.02% to 39.74% dry weight | 41.38% to 44.00% dry weight | Isolipidic 7.03% to 7.53% dry weight | 12.6% to 12.9% dry weight | Saturated with 2.52% to 2.72% dry weight and unsaturated with 4.51% to 4.81% dry weight | N/A | N/A | Sodium (1.4% to 1.5%), Calcium (3.3%) & Iron (0.7% to 1.3%) | N/A | Volpe et al. (2012) [17] |
| Isonitrogenous (40% protein as-fed basis) | 28.33% | 7.03% | 0% | ARA: 1.09% EPA: 3.58% DHA: 7.94% |
N/A | 2.0% | 0.5% | Lecithin, dicalcium phosphate, Vitamin C, choline chloride | Thompson et al. (2003) [13] | |
| Crab | 44.85% to 46.73% dry matter | N/A | 7% and 12% lipid | 0.50% | DHA/EPA ratio between 2.2 and 1.2 at 7% and 12% lipid, respectively | N/A | 1.00% | 1.50% | Monocalcium phosphate, choline chloride, cellulose | Wang et al. (2021) [79] |
| Isonitrogenous with 43.64 to 46.08% dry weight | 17.2 kJ g−1 | Dietary lipid level of 8.52–11.63% (op timum 9.5%) |
0.8% | ARA: 0.5%; EPA: 6.9%; DHA: 6.1% |
N/A | 3.00% | 2.00% | Lecithin, sodium alga acid, squid paste, cellulose | Zhao et al. (2015) [117] | |
| Isonitrogenous feed with 45% crude protein | N/A | Isolipidic diets containing 9.5% oil (FO, lard, safflower oil, perilla seed oil or mixture oil | 0.8% | ARA: 0.5%; EPA: 14.1%; DHA: 11.7% |
N/A | 3.00% | 2.00% | Lecithin, sodium alga acid, squid paste, cellulose | Zhao et al. (2016) [51] | |
| 46.9% to 47.03% dry weight | N/A | Isolipidic feed ~8% dry weight | 0.50% | N/A | 0.009% β-carotene | 1.50% | 5.00% | Cellulose, dextrin, lecithin | Unnikrishnan and Paulraj (2010) [53] | |
| Isonitrogenous with 45% dry weight | N/A | Isolipidic with 10.8% dry weight | 0.50% | 0.13% ARA; 0.64–0.66% EPA & 0.37–0.38% DHA | 0.009% β-carotene | 1.50% | 5.00% | Cellulose, dextrin, lecithin | Unnikrishnan et al. (2010) [52] | |
| 32 to 40% dry weight | 17.2 MJ kg−1 | 6% or 12% dry weight | 0.1% | N/A | N/A | 1.50% | 0.50% | Seaweed, soy lecithin, dicalphos | Catacutan (2002) [50] | |
| Isonitrogenous 48.5% | N/A | 5.3 to 13.8% lipid dry weight | 1.0% | 0.36–0.4% ARA; 6.54–7.03% EPA; 2.29–2.81% | 0.01% Astaxanthin | 4.00% | 4.00% | Taurine, choline chloride, vitamin A, Vitamin D3, Vitamin E | Sheen and Wu (1999) [118] | |
| 46.6% protein dry weight | N/A | 8.6% lipid dry weight | 0.51% | N/A | 0.01% Astaxanthin | 4.00% | 4.00% | Taurine, choline chloride, vitamin A, Vitamin D3, Vitamin E | Sheen (2000) [119] | |
| 44.0–45.7% dry weight | N/A | 1.1% to 1.08% lipid dry weight | 0.5% dry weight | 0.2% ALA, 0.2% ARA, 0.2% DHA dry weight | 0.01% Astaxanthin | 4.00% | 4.00% | Taurine, choline chloride, vitamin A, Vitamin D3, Vitamin E | Sheen and Wu (2002) [120] | |
| Lobster | Isonitrogenous 53% dry weight | N/A | 10.04% | 2% | N/A | 1% Carophyll pin (8% astaxanthin) | 1.1% | 0.6% | Lecithin, Stay-C | Marchese et al. (2019) [18] |
| 25% and 35% protein | 23.75–24.73% | 6.2–7% | N/A | N/A | N/A | 5% | 5% | Vitamin C, Vitamin E, Calcium carbonate, dicalcium phosphate | Perera et al. (2005) [54] | |
| Decapod Group | Macronutrients | Micronutrients | Feed Additives | Reference | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Protein | Carbohydrates | Lipid Derivatives | Vitamin | Mineral | ||||||
| Lipid | Cholesterol | Fatty Acids | Carotenoid | |||||||
| Prawn | 47.3% | N/A | 7.5% | 0.5% | 3.0% EFA | Carophyll pink: 0.15% | 1.6% | 2.0% | Ethoxyquin, squid mantle muscle, L-a-phosphatidylcholine, crystalline amino acids, sodium alginate, tetra-sodium-pyrophosphatem, α-cholestane, α- cellulose | Glencross et al. (2002) [21] |
| Isonitrogenous feed 39% | 30.8–32.50% | 10.15–10.48% | N/A | n-3/n-6: 0.54–0.65 | N/A | 1.0% | 1.0% | Shrimp shell meal, corn grain | Kangpanich et al. (2017) [22] | |
| 39.18% | 35.47% | 6.91% | N/A | n-3/n-6: 0.69 EPA/DHA: 0.81 |
N/A | 1.0% | 2.5% | Soybean lecithin, choline chloride, cellulose, squid paste, calcium phosphate, beer yeast cell, spray dried blood powder | Li et al. (2020) [23] | |
| Shrimp | Isonitrogenous feed 21% dry weight | N/A | 77.1–85.9% | 3% | N/A | N/A | 2.5% | 2.0% | Soy lecithin, antifungic, antioxidant (ethoxyquin), Vitamin E | Martínez-Rocha et al. (2012) [24] |
| 30% | 42.1% | 6% | 0.5% | N/A | N/A | 1.0% | 4.7% | Lecithin, alpha cellulose, alginate, sodium hexametaphosphate | Velasco et al. (1998) [25] | |
| 35% | N/A | 8% | 0.2% | DHA: 0.5% ARA: 0.13% |
N/A | 2.0% | 0.5% | Calcium phosphate dibasic, lecithin, StayC | Samocha et al. (2010) [26] | |
| 32.1% | 48.1% | 5.84% | N/A | N/A | N/A | 8.53% | 8.53% | Soybean lecithin, alginic acid | Gonzalez-Galaviz et al. (2020) [27] | |
| 40.08–42.93% | 33.09–36.4% | 7.37–8.39% | 0.1% | N/A | N/A | 0.5% | 0.2% | Lecithin, alginate | Suresh et al. (2011) [28] | |
| 34.2% to 36.3% dry weight | 40.5% to 44.3% | 3.9% to 6.0% dry weight | N/A | N/A | N/A | 1.8% | 0.5% | Choline chloride, Stay-C 35% active | Galkanda-Arachchige et al. (2019) [29] | |
| 36% | N/A | 8% | 0.1% | N/A | N/A | 1.8% | 0.5% | Choline chloride, Stay-C250 mg/kg, CaP-diebasic, lecithin, chromium oxide | Fang et al. (2016) [30] | |
| 42.2% | N/A | 9.1% | 0.5% | N/A | N/A | 2.0% | 2.0% | Calcium phosphate, soya lecithin | Palma et al. (2008) [31] | |
| 39.7% | 30.7% | 9.45% | 0.16% | N/A | N/A | 0.28% | 0.28% | Krill meal, monocalcium phosphate, lecithin | Derby et al. (2016) [32] | |
| 34.8% protein in feed with soy meal and 29.3% protein in feeds with FM | 38.76% in feed with soy meal and 22.45% in feed with FM | 6.65% in feed with soy meal and 5.84% in feeds with FM | N/A | N/A | N/A | 0.93% in feed with soy meal and 0.85% in feed with FM | 0.93% in feed with soy meal and 0.85% in feed with FM | Soy lecithin, alginic acid, cellulose, antioxidant | Gil-Núñez et al. (2020) [33] | |
| 35.8% to 36.6% dry weight | 34.7% to 38.9% | 7.9% to 8.1% | 0.2% | N/A | N/A | 0.5% | 0.5% | Lecithin-soy, methionine, lysine, titanium dioxide | Weiss et al. (2019) [34] | |
| Isonitrogenous feed 40% dry weight | N/A | Isolipidic feed 9.00% dry weight | 0.02% | N/A | N/A | 1.2% | 1.0% | Lecithin powder 97%, amygluten | Moniruzzaman et al. (2019) [35] | |
| Isonitrogenous feed 35% dry weight | 31.93–32.78% | 8.18–8.63% lipid | N/A | ARA:1.68%; EPA: 2.87%; DHA: 4.66% |
N/A | 15% | 25% | Dicalcium phosphate, antifungal, antioxidant, lysine, methionine, garlic powder | Tazikeh et al. (2019) [36] | |
| Isonitrogenous feed 36% crude protein | N/A | 7.9–9.00% lipid | 0.11% | N/A | N/A | 0.25% | 0.25% | Antioxidant, antifungic agent, Vitamin C, choline chloride, | Gamboa-Delgado et al. (2019) [37] | |
| 37% | 38.32 to 38.88% | 10% | 0.5% | N/A | 1.46% (5% from 29.23% carotenoid extracted) |
1.0% | 1.0% | Monocalcium phosphate, cellulose | Simião et al. (2019) [38] | |
| Crayfish | Isonitrogenous with 39.02% to 39.74% dry weight | 41.38% to 44.00% dry weight | Isolipidic 7.03% to 7.53% dry weight | 12.6% to 12.9% dry weight | Saturated with 2.52% to 2.72% dry weight and unsaturated with 4.51% to 4.81% dry weight | N/A | N/A | Sodium (1.4% to 1.5%), Calcium (3.3%) & Iron (0.7% to 1.3%) | N/A | Volpe et al. (2012) [39] |
| Isonitrogenous (40% protein as-fed basis) | 28.33% | 7.03% | 0% | ARA: 1.09% EPA: 3.58% DHA: 7.94% |
N/A | 2.0% | 0.5% | Lecithin, dicalcium phosphate, Vitamin C, choline chloride | Thompson et al. (2003) [8] | |
| Crab | 44.85% to 46.73% dry matter | N/A | 7% and 12% lipid | 0.50% | DHA/EPA ratio between 2.2 and 1.2 at 7% and 12% lipid, respectively | N/A | 1.00% | 1.50% | Monocalcium phosphate, choline chloride, cellulose | Wang et al. (2021) [40] |
| Isonitrogenous with 43.64 to 46.08% dry weight | 17.2 kJ g−1 | Dietary lipid level of 8.52–11.63% (op timum 9.5%) |
0.8% | ARA: 0.5%; EPA: 6.9%; DHA: 6.1% |
N/A | 3.00% | 2.00% | Lecithin, sodium alga acid, squid paste, cellulose | Zhao et al. (2015) [41] | |
| Isonitrogenous feed with 45% crude protein | N/A | Isolipidic diets containing 9.5% oil (FO, lard, safflower oil, perilla seed oil or mixture oil | 0.8% | ARA: 0.5%; EPA: 14.1%; DHA: 11.7% |
N/A | 3.00% | 2.00% | Lecithin, sodium alga acid, squid paste, cellulose | Zhao et al. (2016) [42] | |
| 46.9% to 47.03% dry weight | N/A | Isolipidic feed ~8% dry weight | 0.50% | N/A | 0.009% β-carotene | 1.50% | 5.00% | Cellulose, dextrin, lecithin | Unnikrishnan and Paulraj (2010) [43] | |
| Isonitrogenous with 45% dry weight | N/A | Isolipidic with 10.8% dry weight | 0.50% | 0.13% ARA; 0.64–0.66% EPA & 0.37–0.38% DHA | 0.009% β-carotene | 1.50% | 5.00% | Cellulose, dextrin, lecithin | Unnikrishnan et al. (2010) [44] | |
| 32 to 40% dry weight | 17.2 MJ kg−1 | 6% or 12% dry weight | 0.1% | N/A | N/A | 1.50% | 0.50% | Seaweed, soy lecithin, dicalphos | Catacutan (2002) [45] | |
| Isonitrogenous 48.5% | N/A | 5.3 to 13.8% lipid dry weight | 1.0% | 0.36–0.4% ARA; 6.54–7.03% EPA; 2.29–2.81% | 0.01% Astaxanthin | 4.00% | 4.00% | Taurine, choline chloride, vitamin A, Vitamin D3, Vitamin E | Sheen and Wu (1999) [46] | |
| 46.6% protein dry weight | N/A | 8.6% lipid dry weight | 0.51% | N/A | 0.01% Astaxanthin | 4.00% | 4.00% | Taurine, choline chloride, vitamin A, Vitamin D3, Vitamin E | Sheen (2000) [47] | |
| 44.0–45.7% dry weight | N/A | 1.1% to 1.08% lipid dry weight | 0.5% dry weight | 0.2% ALA, 0.2% ARA, 0.2% DHA dry weight | 0.01% Astaxanthin | 4.00% | 4.00% | Taurine, choline chloride, vitamin A, Vitamin D3, Vitamin E | Sheen and Wu (2002) [48] | |
| Lobster | Isonitrogenous 53% dry weight | N/A | 10.04% | 2% | N/A | 1% Carophyll pin (8% astaxanthin) | 1.1% | 0.6% | Lecithin, Stay-C | Marchese et al. (2019) [18] |
| 25% and 35% protein | 23.75–24.73% | 6.2–7% | N/A | N/A | N/A | 5% | 5% | Vitamin C, Vitamin E, Calcium carbonate, dicalcium phosphate | Perera et al. (2005) [49] | |
4. Development of Formulated Feed for Juvenile Decapod
4.1. Type of Formulated Feed
There are two main types of feed processing technology that have been introduced in aquaculture: the extruded (pressured) pellet and the steam pellet. The extrusion technique involves the use of a feed extruder, whereby pellets are forced through a die using higher pressure and steam heat before being left to cool and having a vitamin and mineral premix added. The extrusion method is different from the steam pellet in that the extruder does not use any pellet binder to add adhesion to the particles [50][121], where they only expand through gelatinization of starch [51][122]. The gelatinization of starch helps to improve feed digestibility in decapods [52][125]. For this reason, the use of extruder feed is better than a steam pellet as it offers high stability and functional properties [53][124].
4.1.1. Dry Pellet
Dry pellets can be used in a variety of forms: dry-sinking pellet, extruded sinking pellet, and extruded floating pellet. Suitable feed ingredient selection, together with proper manufacturing procedures such as an extrusion or steaming process, ensures high-water stability pellets, which is the main criterion for producing high-quality feeds. Overall, dry-sinking pellets are more practical for bottom feeders [54] such as shrimp [55], prawns [50], lobsters [56], crayfish [8][39], and mud crabs [57]. Necessary for the creation of water-stable dry pellets are good binding agents and finely ground ingredients to ensure the maximum adhesion of the binder molecules.
4.1.2. Moist Pellet
Moist, or wet, pellets are soft pellets consisting of a combination of high-moisture ingredients and dry pulverized ingredients.
4.1.1. Dry Pellet
Dry pellets can be used in a variety of forms: dry-sinking pellet, extruded sinking pellet, and extruded floating pellet. Suitable feed ingredient selection, together with proper manufacturing procedures such as an extrusion or steaming process, ensures high-water stability pellets, which is the main criterion for producing high-quality feeds. Overall, dry-sinking pellets are more practical for bottom feeders [133] such as shrimp [134], prawns [121], lobsters [135], crayfish [13,17], and mud crabs [16]. Necessary for the creation of water-stable dry pellets are good binding agents and finely ground ingredients to ensure the maximum adhesion of the binder molecules.
4.1.2. Moist Pellet
Moist, or wet, pellets are soft pellets consisting of a combination of high-moisture ingredients and dry pulverized ingredients. The use of moist pellets led to high growth performance in juvenile rock lobsters (Jasus edwardsii) [127], freshwater crayfish [136], and green mud crabs [120]. Although the use of moist pellets is widely accepted among decapods, it is highly desirable to have the advantage of storage without the need for a refrigerator in order to prevent fungal growth and mold problems. This has led to the innovation of semi-moist pellets, which have been successfully developed at a laboratory scale. Compared to moist pellets, the moisture content of semi-moist pellets is lower, and under the permissible level to avoid yeast and mold growth, with the addition of chemical agents [137].
4.2. Pellet Characteristics Requirement
The use of moist pellets led to high growth performance in juvenile rock lobsters (Jasus edwardsii) [58], freshwater uccrayfish [59], and green mud crabs [48]. Although the use of moist pellets is widely accepted among decapods, it is highly desirable to have the advantage of storage without the need for a refrigerator in order to prevent fungal growth and mold problems. This has led to the innovation of semi-moist pellets, which have been successfully developed at a laboratory scale. Compared to moist pellets, the moisture content of semi-moist pellets is lower, and under the permissible level to avoid yeast and mold growth, with the addition of chemical agentdecapod farming has [60].
4.2. Pellet Characteristics Requirement
The success of decapod farming has highghlighted the importance of physical pellet characteristics, which directly emphasizes the significance of artificial or formulated diets to replace live and fresh foods. The success of formulated feed may be controlled by the moisture content in the diet, which directly affects the physical forms. The high moisture content in the pellets is often associated with nutrient leaching since it dissociates easily upon entering the water. Apparently, the low pellet stability and durability resulting from high moisture content may not be suitable for decapods, partly because some species are aggressive in handling food [61][138]. In addition, the proper storage and handling of feed products may be difficult to achieve, as is the case with wet pellets. Since wet pellets have a high moisture content, rapid spoilage, such as from mold problems, is unavoidable during long storage periods [62][139]. Other physical pellet attributes, such as the palatability, type of binder, water stability, and durability, as well as buoyancy, are important to avoid pellet disintegration from decapods’ strong mastication and from long exposure to water.
4.3. Current Status of Nutritional Research and Developments
Many studies have evaluated adjustments to decapod crustacean feeding formulations by reducing the dependency on FM (protein source) and FO (lipid source). Recent research has explored the use of protein and lipid sources from various sources: terrestrial animal-based materials, plant-based materials, insect meal, food waste, and fishery and aquaculture byproducts [63][11]. The use of these alternative sources is often evaluated through several reliable indicators such as the voluntary feed intake, feed conversion ratio (FCR), and protein efficiency ratio (PER) in determining the effectiveness of the feed. Feed that uses both FO and FM ingredients has confirmed efficiency in decapod performance in terms of FCR (1.8) and PER (2.8) [33][47], and, thus, they have been used as a baseline to develop a new feed formulation that uses other protein and lipid sources.
5. Conclusions
The importance of good pellet physical characteristics in decapod feeding cannot be overemphasized in order to ensure that decapods meet their nutrient needs. The current development of decapod formulated feeds is focused on the juvenile stage. However, the unique feeding behaviors of adult decapods (slow feeding, bottom dwelling, and aggression when handling feed) are major challenges to developing a high-quality pellet for adult decapods. A high-quality pellet not only depends on the binding agent, but also on the attractants that enhance palatability, as well as the correct proportion of nutrients to boost decapod performance. However, most studies published on decapod nutrition lack data on the physical qualities of the feed. Thus, it is difficult to establish a standard feed formulation that focuses on the physical pellet properties.
The importance of good pellet physical characteristics in decapod feeding cannot be overemphasized in order to ensure that decapods meet their nutrient needs. The current development of decapod formulated feeds is focused on the juvenile stage. However, the unique feeding behaviors of adult decapods (slow feeding, bottom dwelling, and aggression when handling feed) are major challenges to developing a high-quality pellet for adult decapods. A high-quality pellet not only depends on the binding agent, but also on the attractants that enhance palatability, as well as the correct proportion of nutrients to boost decapod performance. However, most studies published on decapod nutrition lack data on the physical qualities of the feed. Thus, it is difficult to establish a standard feed formulation that focuses on the physical pellet properties.
