A feed pore-forming agent for constructing a digestible honeycomb structure and a soft pellet feed prepared using the same

Abstract

The present application belongs to the technical field of aquatic feed. More specifically, it relates to a feed pore-forming agent for constructing easily digestible honeycomb structure and soft granular feed prepared by the same. The pore-forming agent is composed of hydrophilic colloid, sodium bicarbonate, citric acid, starch and wheat bran, which can form a uniform and stable honeycomb-like microporous structure in the feed. The structure helps to improve the water hydration speed of the soft granules at room temperature, matches the short intestinal emptying cycle of the grass carp, reduces the physical digestion burden, and at the same time increases the enzyme action area and penetration channel, and improves the nutrient absorption efficiency. The cultivation test proves that the feed provided by the present application has high water floating rate and high feed utilization efficiency, which can significantly reduce the feed coefficient, improve the intestinal villus development of the grass carp, and synchronously improve the survival rate and economic benefit. In addition, the raw materials used in the pore-forming agent of the present application are safe, cheap and stable in source, the process is compatible with the existing production line, and the scale production can be realized without modification, which has outstanding industrialization prospect.

Description

Technical Field

[0001] This invention belongs to the field of aquaculture feed technology. More specifically, it relates to a feed pore-forming agent for constructing an easily digestible honeycomb structure and the soft pellet feed prepared therefrom. Background Technology

[0003] Threadfin bream and their closely related groups generally have short intestines and relatively low digestive enzyme activity. When feeding them with existing hard-particle extruded feed, the following drawbacks exist: First, the high hardness and density of the feed particles make it difficult for them to fully absorb water and soften during the short digestive tract time of threadfin bream, resulting in ineffective penetration and action of digestive enzymes, leading to incomplete nutrient absorption and a high feed conversion ratio. Second, the hard particles can easily cause physical friction and damage to the fragile intestinal wall mucosa, providing a channel for pathogen invasion. In addition, undigested feed accumulates and ferments in the hindgut, easily disrupting the intestinal flora balance and inducing diseases such as enteritis and ascites, severely restricting the survival rate and economic benefits of threadfin bream farming.

[0004] To address these issues, the industry has begun exploring the use of soft pellet feeds with higher water content (typically 20%–30%) to reduce physical irritation to the fish. However, the applicant has found that the internal microstructure of existing soft pellet feeds remains too dense, resulting in insufficient hydration rates. Given the typical rapid feeding and swallowing behavior of threadfin bream, the feed requires a considerable amount of time to soften into a digestible chyme state after entering the intestines. This is inconsistent with the extremely short intestinal emptying time of threadfin bream. In other words, current products only achieve "softening of the apparent physical properties" and do not achieve "digestibility at the physiological level," thus failing to fundamentally resolve the risk of enteritis in threadfin bream.

[0005] Soft pellet feed faces a dual technical bottleneck during processing: firstly, its processing temperature is relatively low (typically 85-95℃), failing to reach the high-temperature conditions required for full starch extrusion, making it difficult to form effective pores within the pellets using traditional extrusion processes; secondly, due to the high moisture content of soft pellet feed, the formulation requires a large amount of protein and fat, further compressing the space for starch addition, making it even more difficult to construct a loose, porous structure. Meanwhile, threadfin bream have a habit of feeding on surface food, placing clear demands on the buoyancy of the feed. However, existing soft pellet feeds, limited by low starch ratios and low-temperature processing, cannot form a stable porous floating structure through high starch addition and high-temperature extrusion, as hard pellet extruded feeds do.

[0006] In summary, under the dual constraints of low-temperature processing and low starch content, how to create a loose, porous structure within soft pellet feed that facilitates floating and rapid hydration has become a pressing technical challenge. Current technologies lack effective means for actively and directionally controlling the internal structure of feed pellets. Therefore, there is an urgent need to develop an innovative technical solution that can significantly improve the water absorption and softening efficiency of soft pellet feed while ensuring its forming performance. This would allow it to quickly form a digestible state easily digested by enzymes upon entering water or the intestines, truly meeting the short-term, high-efficiency digestion needs of species like threadfin bream, reducing their intestinal burden, and thus lowering the probability of inflammatory bowel disease. This would provide crucial nutritional support for the healthy and efficient aquaculture of threadfin bream. Summary of the Invention

[0007] The technical problem to be solved by the present invention is that existing aquatic feeds are not suitable for the short intestines and relatively low digestive enzyme activity of threadfin bream. The present invention provides a pore-forming agent suitable for soft pellet feed and the soft pellet feed prepared therefrom.

[0008] The first objective of this invention is to provide a pore-forming agent for pelleted feed.

[0009] A second objective of this invention is to provide the application of the aforementioned pore-forming agent.

[0010] A third objective of this invention is to provide a pelleted feed.

[0011] The fourth objective of this invention is to provide a soft pellet feed.

[0012] The fifth objective of this invention is to provide a method for breeding threadfin bream that can promote its growth and improve its survival rate.

[0013] The above-mentioned objective of this invention is achieved through the following technical solution:

[0014] This invention provides a pore-forming agent that can construct a uniform, stable, and interconnected honeycomb microporous structure inside feed, significantly improving the hydration rate at room temperature. This allows for efficient nutrient release and absorption of feed within the fish's short intestinal emptying cycle, thereby reducing the physical and metabolic burden on the intestines, improving intestinal tissue development, and ultimately enhancing feed utilization efficiency, growth performance, and survival rate. Therefore, this invention claims protection for the following: This invention provides a pore-forming agent for pelleted feed, comprising the following components by weight: 0.5-3 parts hydrophilic colloid, 1.5-2.0 parts sodium bicarbonate, 1.2-1.4 parts citric acid, 1.0-5.0 parts starch, and 2.0-3.0 parts wheat bran; the raw materials for preparing the hydrophilic colloid include *Gnaphalium affine*, *Gnaphalium affine*, *Gnaphalium affine*, and *Gnaphalium affine*; preferably, the mass ratio of *Gnaphalium affine*, *Gnaphalium affine*, *Gnaphalium affine*, and *Gnaphalium affine* is (1-4):(2-3):(0.5-1):(1-2).

[0015] Preferably, the pore-forming agent contains the following components by weight: 2-3 parts hydrophilic colloid, 1.5-2.0 parts sodium bicarbonate, 1.2-1.4 parts citric acid, 1.0-2.0 parts starch, and 2.0-3.0 parts wheat bran.

[0016] Preferably, the starch is pea starch and the wheat bran is wheat bran.

[0017] The hydrophilic colloid can be prepared using conventional hydrophilic colloid preparation processes.

[0018] As an alternative implementation, the hydrophilic colloid is prepared by mixing deer antler powder, sea cypress powder, agaric powder and draco powder, heating at 85~95℃, cooling to 28~32℃ and drying to obtain the hydrophilic colloid.

[0019] Specifically, the powdered deer antler seaweed, sea cypress, agaric, and dragon beard algae are powders that have passed through an 80-120 mesh (preferably 100 mesh) sieve.

[0020] Optionally, the drying is vacuum freeze drying.

[0021] Optionally, after drying, the material is pulverized and passed through a 100-mesh sieve to obtain a hydrophilic colloid.

[0022] This invention provides the application of the above-mentioned pore-forming agent in the preparation of feed.

[0023] Preferably, the feed is a soft pellet feed.

[0024] The present invention provides a pelleted feed containing the above-mentioned pore-forming agent.

[0025] The present invention provides a soft pellet feed containing the above-mentioned pore-forming agent.

[0026] As an alternative implementation, the aforementioned soft pellet feed, by weight, contains the following components: 70-90 parts protein feed, 9-19 parts energy feed, 0.5-1 part vitamins, 0.5-1 part minerals, 1.2-2.0 parts additives, and 1-5 parts of the aforementioned pore-forming agent.

[0027] Preferably, the protein feed is at least one of fish meal, soybean meal, chicken meal, and blood meal.

[0028] Preferably, the energy feed is at least one of high-gluten flour, fish oil, phospholipid oil, and wheat bran.

[0029] Preferably, the additive is choline chloride and calcium dihydrogen phosphate.

[0030] Optionally, the mineral includes at least one of zinc, manganese, copper, iron, cobalt, iodine, and selenium.

[0031] Optionally, the vitamins include vitamin A, vitamin D3, vitamin E, vitamin K3, vitamin B1, vitamin B2, vitamin B6, and vitamin B6. 12 It contains at least one of the following: Vitamin C, D-calcium pantothenate, nicotinamide, folic acid, D-biotin, and inositol.

[0032] As an alternative implementation, the aforementioned soft pellet feed contains the following per kilogram: 3.5 mg zinc, 2.2 mg manganese, 0.82 mg copper, 2.6 mg iron, 0.12 mg cobalt, 0.1 mg iodine, and 0.03 mg selenium.

[0033] As an alternative implementation, the aforementioned soft pellet feed contains, per kilogram: Vitamin A 750 IU, Vitamin D3 154 IU, Vitamin E 6 mg, Vitamin K3 1.86 mg, Vitamin B1 1.2 mg, Vitamin B2 1.2 mg, Vitamin B6 1.2 mg, and Vitamin B... 12 0.08 mg, Vitamin C 21 mg, D-calcium pantothenate 4.8 mg, Nicotinamide 9 mg, Folic acid 0.37 mg, D-Biotin 0.015 mg and Inositol 9 mg.

[0034] Preferably, the above-mentioned soft pellet feed contains the following components by weight: 50-60 parts fish meal, 20-30 parts soybean meal, 6-10 parts high-gluten flour, 2-6 parts fish oil, 1-3 parts phospholipid oil, 0.5-1 part vitamins, 0.5-1 part minerals, 0.2-0.5 parts choline chloride, 1-1.5 parts calcium dihydrogen phosphate, and 1-5 parts of the above-mentioned pore-forming agent.

[0035] Preferably, the soft pellet feed contains 2 to 4 parts (more preferably 3 parts) of the pore-forming agent by weight.

[0036] More preferably, the above-mentioned soft pellet feed contains, by weight, the following components: 55 parts fish meal, 25 parts soybean meal, 8 parts high gluten flour, 4 parts fish oil, 2 parts phospholipid oil, 0.5 parts vitamins, 0.5 parts minerals, 0.5 parts choline chloride, 1.5 parts calcium dihydrogen phosphate, and 3 parts of the above-mentioned pore-forming agent.

[0037] As an alternative implementation, the above-mentioned aquatic feed is produced by extrusion pelleting, with the extrusion temperature controlled at 85~95℃.

[0038] This invention provides a method for raising threadfin bream that can promote its growth and improve its survival rate, using the aforementioned soft pellet feed to raise threadfin bream.

[0039] The present invention has the following beneficial effects: This invention introduces a composite pore-forming agent composed of hydrophilic colloid, sodium bicarbonate, citric acid, pea starch, and wheat bran into soft pellet feed, successfully constructing a uniform, stable, and interconnected honeycomb microporous structure, significantly improving the feed's hydration rate in room temperature water. This structure allows the feed to rapidly soften into an easily digestible chyme state upon entering the water or the intestines of threadfin bream, effectively matching its extremely short intestinal emptying cycle. This fundamentally solves the technical bottleneck of existing soft pellet feeds, which are "soft on the surface but dense internally and hydrate slowly," greatly reducing the physical digestive burden on the intestines. Furthermore, this composite pore-forming agent imparts excellent buoyancy to the feed, satisfying the threadfin bream's surface feeding habits, and also avoids the problem of bottom sedimentation and water pollution, improving feed utilization efficiency.

[0040] Thanks to its honeycomb-like microporous structure, this structural improvement directly translates into significant physiological and economic benefits in aquaculture. The honeycomb structure provides digestive enzymes with a large working area and permeation channels, significantly improving the efficiency of nutrient digestion and absorption. Aquaculture experimental data confirms that this invention has high feed utilization efficiency, significantly reducing the feed conversion ratio of threadfin bream, resulting in healthier intestinal tissue morphology and significantly improved villus development; correspondingly, the survival rate of threadfin bream is significantly increased, leading to a qualitative leap in overall aquaculture benefits.

[0041] Furthermore, the raw materials for the pore-forming agent of this invention are all safe and low-cost materials with wide availability and stable supply. Its preparation process is highly compatible with existing feed processing procedures, and it can achieve continuous, large-scale, and stable production without structural modifications to mainstream production lines. It combines technological advancement with the convenience of large-scale promotion, and has excellent industrialization prospects and application value. Attached Figure Description

[0042] Figure 1 Cross-sectional observation results of different feeds (magnification of 15×, Figures A to E are cross-sections of feeds in Examples 1 to 5 respectively; Figures F to J are cross-sections of feeds in Comparative Examples 1 to 5 respectively).

[0043] Figure 2 Nine hours after feeding different diets to bream, the digestion of the diet in the digestive tract was observed. Detailed Implementation

[0044] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0045] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0046] This is a premixed feed for marine fish, manufactured by Guangdong Liankun Group Co., Ltd. Its ingredients include: Vitamin A, Vitamin D3, Vitamin E, Vitamin K3, Vitamin B1, Vitamin B2, Vitamin B6, and Vitamin B1. 12 Vitamin C, D-calcium pantothenate, nicotinamide, folic acid, D-biotin, inositol, zinc, manganese, copper, iron, cobalt, iodine, and selenium.

[0047] Commercially available California bass hard pellet feed is manufactured by Zhuhai Hengxing Feed Co., Ltd.

[0048] Deer antler seaweed ( Silvetia siliquosa ), sea cypress ( Polyopes polyideoides Okamura ), Qiongzhi ( Betaphycus gelatinae Dragon Beard Algae () Red Gracilaria Feeding Algae (This is a market purchase.)

[0049] In the following examples, the basic formula of the soft pellet feed (i.e., the soft pellet feed of Comparative Example 5) contains the following components by weight: 55 parts fish meal, 25 parts soybean meal, 8 parts high gluten flour, 4 parts fish oil, 2 parts phospholipid oil, 1 part marine fish premixed feed, 0.5 parts choline chloride, and 1.5 parts calcium dihydrogen phosphate.

[0050] Example 1: Porous soft pellet feed 1. A porous soft pellet feed formulation A porous soft pellet feed formulation, by weight, contains the following components: 55 parts fish meal, 25 parts soybean meal, 8 parts high-gluten flour, 4 parts fish oil, 2 parts phospholipid oil, 1 part marine fish premixed feed, 0.5 parts choline chloride, 1.5 parts calcium dihydrogen phosphate, and 3 parts composite pore-forming agent.

[0051] The composite pore-forming agent formulation contains the following components by weight: 3.0 parts hydrophilic colloid, 1.5 parts sodium bicarbonate, 1.2 parts citric acid, 1.0 part pea starch, and 2.0 parts wheat bran.

[0052] In this embodiment, the preparation process of the hydrophilic colloid is as follows: Take deer antler seaweed ( Silvetia siliquosa ), sea cypress ( Polyopes polyideoides Okamura ), Qiongzhi ( Betaphycus gelatinae ) and dragon's beard algae ( Red Gracilaria Feeding Algae The mass ratio of *Gnaphalium affine*, *Gnaphalium affine*, *Gnaphalium affine*, and *Gnaphalium affine* was 3:2.5:1:1. After washing, the samples were dried with hot air. The dried samples were then mixed and thoroughly pulverized, and passed through a 100-mesh sieve. The resulting powder was heated to 90±5℃ to fully rupture the seaweed cell walls, allowing the intracellular contents to flow out, resulting in a homogeneous sol state. After cooling to 30±2℃, the sol spontaneously formed a gel with high strength. Finally, the gel was freeze-dried in a vacuum freeze dryer, then pulverized and passed through a 100-mesh sieve to obtain the target hydrophilic colloid.

[0053] 2. Preparation method of porous soft pellet feed According to the formula, all components are thoroughly mixed, and water (28-30% of the mass of the mixed raw materials) is added. The mixture is then thoroughly mixed again, followed by extrusion pelleting using a twin-screw extruder, with the extrusion temperature controlled at 85-95℃. At this temperature, the hydrophilic colloid is fully hydrated and thickened, the starch is partially gelatinized, and sodium bicarbonate reacts rapidly with citric acid to produce a large amount of carbon dioxide gas. The gas is effectively encapsulated by the colloid-starch network, forming uniform and fine internal pores. After extrusion, soft pellet feed is obtained.

[0054] Example 2: Porous soft pellet feed The difference from Example 1 is that the composite pore-forming agent formulation is different.

[0055] The composite pore-forming agent formulation of this embodiment contains the following components by weight: 0.8 parts hydrophilic colloid, 2.0 parts sodium bicarbonate, 1.6 parts citric acid, 4.0 parts pea starch, and 2.5 parts wheat bran.

[0056] Example 3 Porous soft pellet feed The difference from Example 1 is that the composite pore-forming agent formulation is different.

[0057] The composite pore-forming agent formulation of this embodiment contains the following components by weight: 0.5 parts hydrophilic colloid, 1.8 parts sodium bicarbonate, 1.4 parts citric acid, 5.0 parts pea starch, and 3.0 parts wheat bran.

[0058] Example 4 Porous soft pellet feed The difference from Example 1 is that the proportion of raw materials for preparing the hydrophilic colloid in the composite pore-forming agent is different.

[0059] The hydrophilic colloid used in this embodiment was prepared by using raw materials, including *Gnaphalium affine*, ... and *Gnaphalium affine*, in a mass ratio of 4:3:0.5:1.

[0060] Example 5 Porous soft pellet feed The difference from Example 1 is that the proportion of raw materials for preparing the hydrophilic colloid in the composite pore-forming agent is different.

[0061] The hydrophilic colloid used in this embodiment was prepared by using raw materials, including *Gnaphalium affine*, ... and *Gnaphalium affine*, in a mass ratio of 1:2:1:2.

[0062] Comparative Example 1: Soft Pellet Feed The difference from Example 1 is that the composite pore-forming agent formulation is different.

[0063] The comparative example of the composite pore-forming agent formulation contains the following components by weight: 1.0 part sodium bicarbonate, 1.2 parts citric acid, 3.0 parts pea starch, and 2.0 parts wheat bran.

[0064] Comparative Example 2: Soft Pellet Feed The difference from Example 1 is that the composite pore-forming agent formulation is different.

[0065] The composite pore-forming agent formulation of this comparative example contains the following components by weight: 3.0 parts hydrophilic colloid, 1.5 parts sodium bicarbonate, 3.0 parts pea starch, and 2.0 parts wheat bran.

[0066] Comparative Example 3: Soft Pellet Feed The difference from Example 1 is that the composite pore-forming agent formulation is different.

[0067] The composite pore-forming agent formulation of this comparative example contains the following components by weight: 3.0 parts hydrophilic colloid, 1.5 parts sodium bicarbonate, 1.2 parts citric acid, and 2.0 parts wheat bran.

[0068] Comparative Example 4: Soft Pellet Feed The difference from Example 1 is that the composite pore-forming agent formulation is different.

[0069] The composite pore-forming agent formulation of this comparative example contains the following components by weight: 3.0 parts hydrophilic colloid, 1.5 parts sodium bicarbonate, 1.2 parts citric acid, and 3.0 parts pea starch.

[0070] Comparative Example 5: Soft Pellet Feed The difference from Example 1 is that no composite pore-forming agent was added.

[0071] The formulations of the composite pore-forming agents in each embodiment and comparative example are summarized in Table 1: Table 1. Formulations of composite pore-forming agents for each embodiment and comparative example (unit: parts by weight)

[0072] Note: "—" indicates that this component was not added.

[0073] Experimental Example 1: Verification of Feed Microstructure I. Feed Sample Observation Methods Feed samples were cut horizontally to expose their internal cross-sections. Cross-sectional micrographs of each feed sample were acquired at a standard height using 15x magnification.

[0074] II. Experimental Results Microscopic observation results of feed cross section are as follows Figure 1 As shown, the results indicate that: Example 1 Feed ( Figure 1 (Figure A): The particles have a typical loose and porous honeycomb structure with uniform pore size distribution, and have good water permeability. Example 2 Feed ( Figure 1(Figure B): The internal structure has relatively good porosity. Although the structural skeleton is slightly denser than that of Example 1, it is still significantly better than each of the comparative examples. Example 3 Feed ( Figure 1 (Figure C): It exhibits a macroscopically loose structure, but compared to Example 1, the microstructure is relatively denser, and the through-holes are not as good as in Example 1; however, it is still significantly better than each of the comparative examples. Example 4 ( Figure 1 (D diagram): The internal structure exhibits a porous structure, with a significantly larger pore size compared to Example 1, but still significantly superior to the other comparative examples; Example 5 ( Figure 1 (Figure E): The particles have a porous structure inside, although it is not as numerous and obvious as in Example 1, but it is still superior to the comparative examples; Comparative Example 1 Feed ( Figure 1 (F diagram): The particles are dense inside, and the porous structure is significantly less than that of Examples 1-5, with almost no cavities formed by gas expansion; Comparative Example 2 Feed ( Figure 1 (G diagram): The particles are dense inside with indistinct porous structures and lack cavities formed by gas expansion. Comparative Example 3 Feed ( Figure 1 (H diagram): The particles are dense inside, with indistinct porous structures and a lack of cavities formed by gas expansion; Comparative Example 4 Feed ( Figure 1 (Figure I): The particles are dense inside, with indistinct porous structures and a lack of cavities formed by gas expansion; Comparative Example 5 Feed ( Figure 1 (J figure): The internal texture of the particles is very dense, and the main observed features are micro-gaps, with a clear lack of interconnected pore structures that facilitate hydration and floating.

[0075] Conclusion: Only when the five pore-forming components (hydrophilic colloid, sodium bicarbonate, citric acid, pea starch, and wheat bran) are present in synergy can an ideal, easily digestible honeycomb structure be formed, resulting in a microstructure that combines high porosity, good water stability, and rapid disintegration. The absence of any one of these components leads to a dense, non-porous interior or an indistinct pore structure, failing to meet the efficient digestive requirements of the short intestine of threadfin bream.

[0076] Experiment Example 2: Floatability Test I. Experimental Methods Randomly select 100 feed pellets from each group and place them into 1000 mL beakers of water. After soaking for 1 hour, record the number of feed pellets that remain floating and calculate the buoyancy rate using the following formula: Floatability (%) = 100 × Number of feed particles remaining floating / 100 II. Experimental Results The results of the floating rate determination of each group of feeds are shown in Table 2. The results show that the feed of Example 1 exhibits excellent floating performance (floating rate of 100%). The floating rates of the feeds of Examples 2-5 also all reach above 75%. In contrast, the floating rates of all comparative feeds are significantly lower (≤35%), with the blank control group (Comparative Example 5) sinking completely with a floating rate of 0%. This result further verifies the key role of the synergistic effect of the five pore-forming components in the floating performance of the feed.

[0077] Table 2 Results of floating rate determination for each group of feed

[0078] Experiment Example 3: Feeding Experiment with Threadfin Fish I. Experiment Design and Management The experimental fish were threadfin bream from the Liankun pilot plant. Before the formal experiment, the fish were temporarily held in a large net cage (6m long, 4m wide, and 2m high). During the temporary holding period, they were artificially fed commercially available hard pellet feed for California bass twice a day (7:00 and 17:00). The domestication period lasted for 2 weeks.

[0079] Then, 270 healthy, vigorous, and uniformly sized threadfin bream (50±5.5g) were selected and randomly distributed into 9 rearing tanks (diameter: 0.63m, height: 1.22m), with 30 fish per tank. Three treatment groups were established, with each treatment group replicated three times. All groups were fed twice daily (7:00 and 17:00). The feeding times for each group were as follows: ① Hard Pellets Group: Commercially available California bass hard pellet feed; ② Ordinary soft pellet group: Ordinary soft pellet feed without added pore-forming agent (i.e., soft pellet feed of Comparative Example 5); ③ Porous soft pellet group: Porous soft pellet feed prepared in Example 1.

[0080] Feeding was done to the point of fullness, with precise weighing and recording of the amount of food given. The health status of the experimental fish was observed daily, and the weight and number of dead fish, as well as water quality indicators, were recorded. One-third of the water was changed daily. Continuous aeration was maintained throughout the rearing process, keeping the water temperature at 26-30℃ and dissolved oxygen >6 mg / L. The rearing cycle was maintained for 60 days.

[0081] II. Sample Collection and Testing (1) Growth performance index test After 60 days of rearing, the final body weight of the experimental fish was measured, and growth performance indicators were calculated.

[0082] Weight gain rate (WGR, %) = 100 × (final weight - initial weight) / initial weight Specific growth rate (SGR, % / d) = 100 × (ln final weight - ln initial weight) / number of days in the experiment Survival rate (SR, %) = 100 × number of fish at the end of the experiment / number of fish at the beginning of the experiment Feed conversion ratio (FCR) = Total feed intake / Weight gain of experimental fish (2) Intestinal anatomy Three fish were randomly selected for each replicate, and their hindgut tissue was collected, fixed with 10% neutral formaldehyde, and used for paraffin sectioning and histological analysis (HE staining). Morphological parameters such as muscle layer thickness, villus length, villus width, and villus number were measured.

[0083] (3) Gastric emptying time test In each replicate, intestinal dissections were performed at 3, 6, 9, 12, 15 and 18 h after the last feeding of the threadfin bream. One fish was randomly selected for dissection at each time point to monitor the digestion of feed from the stomach to the intestine and to record the gastric emptying time (i.e., no obvious feed residue in the stomach was considered empty).

[0084] III. Test Results 1. Results of growth performance test The growth performance of each experimental group is shown in Table 3. The results indicate that: Compared to the hard pellet group, both the ordinary soft pellet group and the porous soft pellet group significantly improved the weight gain rate and specific growth rate of threadfin bream, and significantly reduced the feed conversion ratio. p <0.05).

[0085] Compared with the ordinary soft particle group, the porous soft particle group with added pore-forming agent on the basis of soft particles showed a further significant improvement in growth performance indicators such as weight gain and survival rate, which were significantly higher than those of the ordinary soft particle group.

[0086] Table 3 Effects of different treatment groups on the growth performance of threadfin bream

[0087] Note: Different lowercase letters in the table indicate significant differences. P <0.05) 2. Results of intestinal villus characteristic test The intestine is the site of digestion and absorption of nutrients in fish, and it is also the first barrier for anti-nutritional factors and toxic substances in feed to enter the fish's body. The thickness of the intestinal muscle layer, the number and height of villi can affect the intestinal barrier, thereby affecting the various functions and health of the entire fish.

[0088] The effects of different treatment groups on the intestinal villus characteristics of threadfin bream are shown in Table 4. The results showed that compared with the hard particle group, the intestinal muscle layer thickness, villus length, villus width, and villus number of threadfin bream in the ordinary soft particle group all showed an increasing trend, but the differences did not reach the statistical significance level. p>0.05); and the above-mentioned intestinal morphology indicators of the porous soft granule group were significantly better than those of the hard granule group ( p <0.05), which is also significantly better than the ordinary soft particle group.

[0089] Table 4. Effects of different treatment groups on intestinal villus characteristics of threadfin bream

[0090] 3. Observation of the retention and disintegration of different feeds in the digestive tract Samples were taken 9 hours after feeding to observe the digestive condition of the threadfin bream after consuming different feeds. Figure 2 As shown, the results indicated significant differences in the stomach contents of the threadfin bream in each experimental group: intact, undigested feed particles were still visible in the hard pellet feed group; only a small amount of feed residue remained in the ordinary soft pellet feed group; while the porous soft pellet feed group was completely emptied, with no feed residue observed. Based on experimental observations, there were significant differences in the stomach emptying times among the hard pellet feed group, the ordinary soft pellet feed group, and the porous soft pellet feed group, which were 9 h, 12 h, and 18 h, respectively (as shown in Table 5).

[0091] Experimental results show that the physical properties of the feed (such as hardness and internal structure) significantly affect the gastric emptying rate of threadfin bream. Specifically, the addition of a pore-forming agent creates a honeycomb-like porous structure inside the soft pellet feed, which significantly shortens the gastric emptying time, thereby promoting feed digestion and nutrient absorption.

[0092] Table 5 Results of gastric emptying time measurement

[0093] In summary, ordinary soft pellet feed can effectively alleviate the mechanical damage to the intestines of threadfin bream caused by physical hardness; however, due to the short intestines of threadfin bream, if the hydration rate of soft pellets is too slow, nutrients will be emptied before full digestion, thus reducing feed utilization. The loose, porous structure design employed in this invention aims to improve the feed's water absorption capacity, accelerate the hydration process, and promote digestion and absorption. Experiments have demonstrated that adding 3% of the pore-forming agent of this invention can create an ideal porous structure in the feed, significantly improving the growth performance and survival rate of threadfin bream while protecting intestinal health.

[0094] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A pore former for a pellet feed, characterized by, The product contains the following components by weight: 0.5-3 parts hydrophilic colloid, 1.5-2.0 parts sodium bicarbonate, 1.2-1.4 parts citric acid, 1.0-5.0 parts starch, and 2.0-3.0 parts wheat bran; the raw materials for preparing the hydrophilic colloid include *Gnaphalium affine*, *Gnaphalium affine*, *Gnaphalium affine*, and *Gnaphalium affine*; preferably, the mass ratio of *Gnaphalium affine*, *Gnaphalium affine*, *Gnaphalium affine*, and *Gnaphalium affine* is (1-4):(2-3):(0.5-1):(1-2).

2. The pore forming agent of claim 1, wherein, By weight, it contains the following components: 2-3 parts hydrophilic colloid, 1.5-2.0 parts sodium bicarbonate, 1.2-1.4 parts citric acid, 1.0-2.0 parts starch, and 2.0-3.0 parts wheat bran.

3. The application of the pore-forming agent according to claim 1 or 2 in the preparation of pelleted feed; preferably, the feed is soft pelleted feed.

4. A pellet feed, characterized by, Contains the pore-forming agent as described in claim 1 or 2.

5. A soft pellet feed, characterized in that, Contains the pore-forming agent as described in claim 1 or 2.

6. The soft pellet according to claim 5, wherein By weight, it contains the following components: 70-90 parts protein feed, 9-19 parts energy feed, 0.5-1 part vitamins, 0.5-1 part minerals, 1.2-2.0 parts additives, and 1-5 parts pore-forming agent as described in claim 1 or 2.

7. The soft pellet according to claim 6, wherein The protein feed is at least one of fish meal, soybean meal, chicken meal, and blood meal.

8. The soft pellet feed according to claim 6, characterized in that, The energy feed is at least one of high-gluten flour, fish oil, phospholipid oil, and wheat bran; preferably, the additives are choline chloride and calcium dihydrogen phosphate.

9. The soft pellet feed according to claim 7 or 8, characterized in that, By weight, it contains the following components: 50-60 parts fish meal, 20-30 parts soybean meal, 6-10 parts high-gluten flour, 2-6 parts fish oil, 1-3 parts phospholipid oil, 0.5-1 part vitamins, 0.5-1 part minerals, 0.2-0.5 parts choline chloride, 1-1.5 parts calcium dihydrogen phosphate, and 1-5 parts of the pore-forming agent as described in claim 1 or 2.

10. A method of breeding of Gourami fish capable of promoting growth and enhancing survival rate of Gourami fish, characterized in that, Threadfin bream are cultured using the soft pellet feed described in any one of claims 5 to 9.

Images