Feed for resisting bacterial enteritis of pelteobagrus fulvidraco and application thereof

Abstract

The invention belongs to the technical field of feed, and particularly relates to feed for resisting bacterial enteritis of pelteobagrus fulvidraco and application of the feed. By adding the corn protein enzymatic hydrolysate into the feed, the nutritional value of the feed can be remarkably improved, and breeding and feeding experiments prove that the corn protein enzymatic hydrolysate can effectively improve the growth performance of the pelteobagrus fulvidraco, promote the digestion and absorption efficiency of the pelteobagrus fulvidraco on protein, reduce nitrogen emission and improve the yield of the pelteobagrus fulvidraco. Therefore, the environmental pollution risk in the breeding process is reduced, and the disease resistance of the pelteobagrus fulvidraco is enhanced.

Description

Technical Field

[0001] This invention belongs to the field of feed technology, and more specifically, relates to feed for resisting bacterial enteritis in yellow catfish and its application. Background Technology

[0002] With rising consumption levels, yellow catfish, due to its lack of intramuscular bones, delicious taste, and reasonable price, has become a popular choice for consumers seeking upgraded products, leading to a continuous increase in its aquaculture volume, from approximately 420,000 tons in 2017 to 620,000 tons in 2023. Its pond-gate price is stable, typically exceeding the farming cost by 2-5 yuan / jin, resulting in significant economic benefits. However, in the past two years, feed raw material prices have generally risen sharply, and industry competition has intensified. How to optimize feed formulation costs to the greatest extent possible while maintaining production performance and disease resistance has become a focus of industry attention and research. In high-density yellow catfish farming, bacterial enteritis poses a significant threat, with particularly pronounced harm. This disease is mainly caused by opportunistic pathogens (such as Vibrio mimicus) that invade when the fish's immunity is weakened or water quality deteriorates. Typical symptoms in infected fish include swimming alone, darkening of body color, and red, swollen, and protruding anus. Dissection reveals severe congestion, inflammation, and swelling of the intestines, filled with yellow mucus or pus. The intestinal wall loses elasticity and may even become thin and perforated. Liver lesions are also common. This disease spreads rapidly, and once an outbreak occurs, it can cause a sharp decline in feed intake or even complete cessation of feeding within a short period, severely impacting fish growth rate and feed utilization. More fatally, the mortality rate of infected fish is extremely high, especially after stress (such as sudden weather changes, pond separation, or transportation), often resulting in explosive mortality and direct economic losses. Even those that survive recover slowly after infection, exhibiting inconsistent size and significantly affecting market time and commercial value. Repeated use of antibiotics not only increases costs and easily leads to drug resistance but also poses a risk of drug residues, threatening food safety and the sustainability of the aquaculture environment, and disrupting the pond's microecological balance, creating a vicious cycle of water quality deterioration and frequent disease outbreaks. Given that bacterial enteritis causes multi-dimensional damage to yellow catfish farming—high mortality, stunted growth, decreased quality, medication risks, and ecological destruction—there is an urgent need for a fish feed capable of resisting bacterial enteritis. Summary of the Invention

[0003] The purpose of this invention is to provide feed for resisting bacterial enteritis in yellow catfish and its application.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a feed for resisting bacterial enteritis in yellow catfish, which is composed of a basic feed and corn protein hydrolysate, wherein the amount of corn protein hydrolysate added is 5% to 7% of the mass fraction of the basic feed.

[0005] This invention adds a certain level of corn protein hydrolysate to the feed, which reduces the burden on the animal's gastrointestinal tract, improves gastrointestinal function, and enhances the ability of yellow catfish to resist bacterial enteritis. On the basis of promoting the accumulation of protein and fat in the body of yellow catfish juveniles, it reduces the incidence and mortality of enteritis in yellow catfish, increases the activity of immune enzymes in the intestine of yellow catfish, thereby improving the ability of yellow catfish to resist bacterial enteritis, and reduces the pollution in the water quality of yellow catfish breeding, thus enhancing its disease resistance.

[0006] Furthermore, the basic feed ingredients, calculated by weight parts, include: 18-20 parts fish meal, 14-16 parts chicken meal, 20-21 parts dehulled soybean meal, 5-6 parts soybean protein concentrate, 11-13 parts wheat flour, 6-7 parts soybean oil, 1-2 parts calcium dihydrogen phosphate, 1-2 parts microcrystalline cellulose, 7-9 parts carboxymethyl cellulose, 1-3 parts mineral element premix, 0.5-1.5 parts vitamin premix, 0.5-1.5 parts choline chloride premix, 0.005-0.015 parts butylated hydroxyanisole, 0.5-1 parts L-lysine salt, and 0.1-0.2 parts L-methionine.

[0007] The present invention also provides the application of the aforementioned feed in improving the disease resistance of yellow catfish.

[0008] Furthermore, the term "anti-disease" refers to resistance to diseases caused by Vibrio mimicry infection.

[0009] Furthermore, the disease caused by the Vibrio mimicry infection is bacterial enteritis.

[0010] The present invention also provides the application of the aforementioned feed in promoting the accumulation of protein and fat in yellow catfish.

[0011] The present invention also provides the application of the feed in reducing water pollution in yellow catfish farming.

[0012] Furthermore, the reduction of water pollution in yellow catfish farming includes reducing nitrogen emissions from yellow catfish.

[0013] The present invention has the following beneficial effects: This invention addresses the prominent pain points of high density, high disease incidence, and high mortality in yellow catfish farming. Breaking away from the traditional reliance on water conditioning drugs and defensive antibiotics (which easily lead to drug resistance and pollution), it innovatively proposes and implements a method to enhance the fish's own health and resistance by adding corn protein hydrolysate. It creatively integrates and solves the two fundamental problems of "feed" and "water." On the one hand, the corn protein hydrolysate has a high digestibility and utilization rate, significantly reducing the pollution of water quality and direct toxicity to the fish's liver and intestines by undigested nutrients (avoiding the risk of fishmeal spoilage and oxidation in feed). It improves water quality from the source and promotes liver and intestinal health, thereby systematically enhancing the yellow catfish's inherent disease resistance. This reduces yellow catfish morbidity and mortality, providing a scientifically sound and practical innovative approach for achieving healthy and efficient farming. Attached Figure Description

[0014] Figure 1 H&E staining diagram showing the effect of corn protein hydrolysate on the intestinal structure of juvenile yellow catfish.

[0015] Figure 2 The figure shows the effect of corn protein hydrolysate on the incidence and mortality of enteritis in juvenile yellow catfish after challenge with Vibrio mimicus.

[0016] Figure 3 H&E staining image showing the effect of corn protein hydrolysate on the intestine of juvenile yellow catfish after challenge with Vibrio mimicus.

[0017] Figure 4 H&E staining image showing the effect of corn protein hydrolysate on the liver of juvenile yellow catfish after challenge with Vibrio mimicus. Detailed Implementation

[0018] The present invention will now be described in detail with reference to specific embodiments, but these should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the following embodiments are conventional means well known to those skilled in the art, and the materials, reagents, etc. used in the following embodiments can be obtained commercially unless otherwise specified.

[0019] Example 1 I. Experimental Materials.

[0020] 1. Raw materials Corn protein hydrolysate (ECP) was purchased from Meinong Biotechnology (Leling) Co., Ltd.; fish meal from TASAOmega SA (USA); chicken meal from Chengdu Meiyide Biotechnology Co., Ltd.; soybean protein concentrate from Yihai Fangchenggang Soybean Industry Co., Ltd.; dehulled soybean meal from Luzhou Zhonghai Grain and Oil Industry Co., Ltd.; flour from Yihai Kerry Arawana Food Group Co., Ltd.; soybean oil from Suzhou Fuqianrun Food Co., Ltd.; butylated hydroxyanisole (BHA) from Henan Beixiang Trading Co., Ltd.; L-lysine salt and L-Met from Meihua Biotechnology Group Co., Ltd.; microcrystalline cellulose from Huzhou Linghu Xinwang Chemical Co., Ltd.; carboxymethyl cellulose from Shanghai Changguang Enterprise Development Co., Ltd.; vitamin A acetate, vitamin D3, DL-α-tocopheryl acetate, vitamin K3, vitamin B12, vitamin C acetate, and vitamin B6 were all purchased from Sichuan Provincial Animal Husbandry Science and Technology Group Co., Ltd.; choline chloride from Hebei Dazheng Feed Technology Co., Ltd.; and corn starch from Shaanxi Guowei Starch Co., Ltd.

[0021] 2. Experimental diet formulation The feed mainly consists of fish meal, chicken meal, soybean protein concentrate and soybean meal as the main protein sources, soybean oil as the main fat source, and vitamin and mineral premixes are added. Six feed formulas A to F are designed, as shown in Table 1.

[0022] Table 1: Feed Formulation Note: Each kilogram of mineral element premix contains: 0.86g of MnSO4·H2O, 133.34g of MgSO4·H2O, 9.29g of FeSO4·H2O, 2.49g of ZnSO4·H2O, 0.624g of CuSO4·5H2O, 1.72g of Ca(IO3)2, and 2.23g of Na2SeO3, filled to 1kg with corn starch.

[0023] Each kilogram of vitamin premix contains: 0.40g of vitamin A acetate (500,000 IU / g), 0.25g of vitamin D3 (500,000 IU / g), 30.51g of DL-α-tocopherol acetate, 2g of vitamin K3, 0.20g of vitamin B12, 0.75g of D-biotin, 0.16g of folic acid, 0.13g of thiamine nitrate, 12.06g of vitamin C acetate, 1.42g of niacin, 31.08g of inositol, 1.76g of D-calcium pantothenate, 1.13g of riboflavin, and 0.38g of vitamin B6, filled to 1kg with corn starch.

[0024] II. Experimental Setup.

[0025] 1. Experimental Grouping Using commercial diets for yellow catfish as the control group (Group A), the experimental groups (Groups B, C, D, E, and F) were fed diets containing 1.5%, 3%, 4.5%, 6%, and 7.5% ECP protein, respectively, to replace fishmeal. A total of 1440 yellow catfish with an initial body weight of approximately 5.6g were selected (no significant difference in initial body weight between groups, P>0.05) and randomly divided into 6 treatment groups, with 4 replicates per treatment group and 60 fish per replicate. The specific experimental design is shown in Table 2.

[0026] Table 2: Experimental Design 2. Growth and feeding management Animal experiments were conducted at the Dayi Aquatic Animal Nutrition Research Base. After purchasing and temporarily holding the fry for four weeks, 1440 healthy yellow catfish of uniform initial weight were selected and randomly assigned to 24 net cages, with 60 fish per cage. The feeding experiment lasted for 10 weeks, with feeding at full capacity at 5:00, 10:00, 18:00, and 22:00 daily. The amount of feed given each time was determined based on the fish's feeding behavior. Uneaten feed was collected 60 minutes after feeding, and the amount of uneaten feed was recorded to calculate the actual feed intake. Water temperature, pH, feeding rate, feed amount, and uneaten feed amount were recorded daily, and 20 cm of water was changed every two days.

[0027] 3. Digestion experiment After the growth and rearing management was completed, another 720 healthy yellow catfish weighing approximately 10g were selected and randomly divided into 6 treatment groups, with 4 replicates per treatment and 30 fish per replicate. The fish were fed 6 different diets. In addition to the diets of groups A, B, C, D, E, and F, 0.5% Cr2O3 was added as an indicator. Feeding was conducted once daily at 5:00, 10:00, 18:00, and 22:00 for a digestibility test lasting 12 days.

[0028] III. Testing Indicators

[0029] 1. Growth performance Survival rate (%) = Number of fish at the end of the experiment / Number of fish at the beginning of the experiment × 100.

[0030] Feed intake (g / tail) = Total feed intake (g / tail) - Total uneaten feed (g / tail).

[0031] Weight gain rate (g / tail) = Final weight of the test (g / tail) - Initial weight of the test (g / tail) / Initial weight of the test × 100.

[0032] Feed conversion ratio = feed intake (g / tail) / weight gain (g / tail).

[0033] Protein efficiency = weight gain (g / tail) / protein intake (g / tail).

[0034] Specific growth rate (% / d) = [ln final weight (g) - ln initial weight (g)] × 100 / number of days in the experiment.

[0035] Final weight (g / tail) = the weight of the animal after the end of the experimental period.

[0036] Feed efficiency = Weight gain of growing animal / Feed intake.

[0037] 2. Intestinal growth and development Intestinal tissue morphology: At 10 weeks (end of the experiment), 16 fish from each treatment were selected, dissected, and intestinal weight and length were measured. Intestinal body index, intestinal length index, and weight per unit length were calculated. Photographs of the visceral mass and intestine were taken (the influence of feces was excluded when measuring intestinal weight).

[0038] Intestinal body index (%) = Intestinal weight (g) / Body weight (g) × 100.

[0039] Intestinal length index (%) = Intestinal length (cm) / Body length (cm).

[0040] 3. Integrity of intestinal structure Intestinal sections: At the end of 10 weeks (excluding the influence of feces), intestinal samples were taken from 4 fish in each treatment to measure the height and width of folds and the thickness of the muscle layer; the samples were fixed in 4% paraformaldehyde for subsequent HE section preparation to observe cell structure and integrity.

[0041] 4. Protein digestion and absorption capacity Apparent digestibility and nitrogen emissions: Apparent protein digestibility of feed requires the collection of feed and fecal samples. After the diets for treatments A, B, C, D, E, and F were prepared, 200 g of feed was aliquoted into sample bags using the quartering method and stored at -20°C for testing. Feces were collected and stored at -20°C for testing. Approximately 10 g of feces was collected, dried to constant weight at 65°C, ground into powder, and stored at -20°C for testing. Crude protein content in feed and feces was determined using the Kjeldahl method, and Cr2O3 content was determined using the acid digestion colorimetric method. The calculation methods for apparent protein digestibility and nitrogen emissions are as follows:

[0042] Crude protein apparent digestibility (%) = 100 × (1 - F / D × Dcr / Fcr).

[0043] In the formula, D is the crude protein content in the diet; Dcr is the Cr2O3 content in the diet; F is the crude protein content in the feces; and Fcr is the Cr2O3 content in the feces. Cr2O3 = (a / M) × (V / 10000) × 100, where a = Cr2O3 content (ug) obtained from the optical density reading on the standard curve; M = sample mass (g); and V = diluted volume of feces after digestion (ml).

[0044] Nitrogen emissions per unit weight gain (g / kg) = FCR × N content in the diet × (1 - apparent digestibility of N) × 1000.

[0045] 5. Protein deposition ability Whole fish composition analysis: At the end of 10 weeks (24 hours without feeding to exclude the influence of feces), healthy fish of similar weight were selected from each replicate, weighed, and dried at 105℃. The crude protein, crude fat content, and amino acid composition of the experimental fish and the initial fish were measured, and the nutrient deposition efficiency was calculated. The calculation formula is as follows:

[0046] Protein deposition rate (%) = body protein gain (g / tail) / protein intake (g / tail) × 100.

[0047] Fat deposition rate (%) = Body fat gain (g / tail) / Protein intake (g / tail) × 100.

[0048] IV. Data Processing and Statistical Analysis.

[0049] Results are expressed as mean ± standard deviation. One-way ANOVA was performed using SPSS software. Multiple comparisons were performed when differences were significant. P < 0.05 was considered significant.

[0050] V. Experimental Results.

[0051] 1. Effects of enzymatic hydrolysis of corn protein on the growth performance of juvenile yellow catfish The effects of ECP on the growth performance of juvenile yellow catfish are shown in Table 3. There were no significant differences in initial body weight among the treatment groups (P>0.05). Compared with the control group (Group A), the juvenile yellow catfish fed with 6% ECP replacing fishmeal showed significantly improved final body weight (FBW), weight gain (PWG), specific growth rate (SGR), feed intake (FI), and feed efficiency (FE) (P<0.05), while the feed conversion ratio (FCR) was significantly reduced (P<0.05), indicating that 6% ECP replacing fishmeal effectively improves the growth performance of yellow catfish. Furthermore, the growth performance of the group fed with 7.5% ECP replacing fishmeal was not significantly different from that of the fishmeal group (P>0.05), suggesting that adding up to 7.5% ECP to the feed to replace fishmeal has no significant negative impact on the growth performance of yellow catfish.

[0052] Table 3: Effects of enzymatic hydrolysis of corn protein on the growth performance of juvenile yellow catfish Note: All data are expressed as mean ± standard deviation (4 replicates per treatment, 60 fish per replicate). Different lowercase superscripts in the same row indicate significant differences (P<0.05), while the same superscript indicates no significant differences (P>0.05). The same applies to the table below.

[0053] IBW: Initial weight (g / fish); FBW: Final weight (g / fish); PWG: Percentage gain (%); SGR: Specific growth rate (% / day); FI: Feed intake (g / fish); FE: Feed efficiency (%); FCR: Feed conversion ratio; SR: Survival rate (%).

[0054] 2. Effects of enzymatic hydrolysis of corn protein on intestinal growth and development of juvenile yellow catfish The effects of ECP on intestinal growth and development in juvenile yellow catfish are shown in Table 4. Compared with the control group (Group A), replacing fishmeal with 6% ECP or other proteins in the diet of juvenile yellow catfish significantly increased intestinal length (IL), intestinal length index (ILI), intestinal weight (IW), and intestinal weight index (ISL) (P<0.05), indicating that replacing fishmeal with 6% ECP can effectively promote intestinal growth and development in juvenile yellow catfish. Meanwhile, compared with Group A, replacing fishmeal with 7.5% ECP or other proteins also significantly increased intestinal length and intestinal length index (P<0.05), but had no significant effect on intestinal weight and intestinal weight index (P>0.05). In summary, in terms of promoting intestinal growth and development, the effect of 7.5% ECP as a substitute for fishmeal was slightly less than that of 6% ECP. However, overall, it indicates that using 7.5% ECP as a substitute for fishmeal will not have a significant negative impact on the intestinal growth and development of juvenile yellow catfish.

[0055] Table 4: Effects of enzymatically hydrolyzed corn protein on intestinal development-related indicators in juvenile yellow catfish Note: All data are expressed as mean ± standard deviation. IL: Intestinal length (cm); ILI: Intestinal length index (%); IW: Intestinal weight (g); ISI: Intestinal body index (%).

[0056] 3. Effects of enzymatic hydrolysis of corn protein on the intestinal structural integrity of juvenile yellow catfish The effect of ECP on the intestinal structural integrity of juvenile yellow catfish is shown in [reference needed]. Figure 1See Table 5. The results showed that, compared with the control group (Group A), replacing fishmeal with 6% ECP and other proteins in the diet of juvenile yellow catfish significantly increased the intestinal fold height, fold width, and muscle layer thickness (P<0.05), indicating that replacing fishmeal with 6% ECP effectively improved the intestinal structure and enhanced the integrity of juvenile yellow catfish. Similarly, compared with the control group without ECP, replacing fishmeal with 7.5% ECP and other proteins also significantly increased the intestinal fold height, fold width, and muscle layer thickness of yellow catfish (P<0.05), indicating that replacing fishmeal with 7.5% ECP can also promote intestinal development and integrity to some extent.

[0057] Table 5: Effects of enzymatic hydrolysis of corn protein on intestinal structure of juvenile yellow catfish Note: The units for fold height, fold width, and muscle layer thickness are μm, and all data are expressed as mean ± standard deviation (n=4).

[0058] 4. Effects of enzymatic hydrolysis of corn protein on the protein digestibility of juvenile yellow catfish The effects of ECP on the protein digestibility of juvenile yellow catfish are shown in Table 6. The results showed that, compared with the control group (Group A), replacing fishmeal with 6% ECP in the diet of juvenile yellow catfish significantly improved the apparent digestibility of crude protein (P<0.05) and significantly reduced nitrogen emissions per unit weight gain (P<0.05). This result indicates that replacing fishmeal with 6% ECP can effectively improve the digestibility and absorption efficiency of protein in juvenile yellow catfish and reduce nitrogen emissions, thereby reducing the environmental pollution risk during aquaculture.

[0059] Table 6: Effects of enzymatic hydrolysis of corn protein on the crude protein digestibility of juvenile yellow catfish Note: All data are expressed as mean ± standard deviation (n=4) 5. Effects of enzymatic hydrolysis of corn protein on nutrient deposition in juvenile yellow catfish The effects of ECP on the whole body composition and nutrient deposition of juvenile yellow catfish are shown in Tables 7 and 8. The results showed that adding 6% ECP to the diet significantly increased the crude protein and crude fat content of the whole fish (P<0.05), and also significantly increased the protein deposition rate and fat deposition rate of the whole fish (P<0.05), indicating that ECP helps promote the accumulation of protein and fat in juvenile yellow catfish.

[0060] Table 7: Effects of enzymatically hydrolyzed corn protein on the whole-body composition of juvenile yellow catfish Note: All data are expressed as mean ± standard deviation (n=8) Table 8: Effects of enzymatic hydrolysis of corn protein on nutrient deposition in juvenile yellow catfish Note: All data are expressed as mean ± standard deviation (n=8) Example 2: Effect of enzymatic hydrolysis of corn protein on the disease resistance of juvenile yellow catfish.

[0061] The experimental materials, data analysis, and experimental grouping were the same as in Example 1. Vibrio mimicry has been published in the article “Chen Cheng, Geng Yi, Wang Kaiyu, et al. Study on dynamic pathological damage and pathogen distribution of Vibrio mimicry in yellow catfish [J]. Southern Fisheries Science, 2017, 13(01):10-18.” The applicant promises to distribute the biological material to the public within twenty years from the date of application and to provide the means of obtaining the biological material.

[0062] Address: Sichuan Agricultural University, No. 211 Huimin Road, Wenjiang District, Chengdu, Sichuan Province.

[0063] I. Experimental setup.

[0064] 1. Challenge test After the growth and rearing management was completed, 48 yellow catfish of similar weight were selected from each treatment group. Each fish in each treatment group was intraperitoneally injected with 200 μL of 10 5 CFU / ml of Vibrio mimicry solution was used, and the PBS group was perfused with 200 μL of PBS solution. After 24 h of Vibrio mimicry induction treatment, the hindgut of 4 fish from each treatment was randomly selected and fixed with 4% paraformaldehyde solution for intestinal histological observation. The midgut of the remaining experimental fish was placed in sterile tubes and stored at -80℃ for the determination of intestinal inflammation, immunity, and antioxidant indicators.

[0065] 2. Morbidity and cumulative mortality of enteritis After dissection, the intestines were dissected, and the degree of redness, swelling, and bloating in the anterior, mid, and posterior intestines was scored out of 5. Mortality was calculated based on the enteritis score. Vibrio mimicry-induced mortality was recorded, and the cumulative mortality rate was calculated. The calculation formula is as follows:

[0066] Incidence of enteritis (%) = Average score of enteritis per fish / 5 (total score) × 100.

[0067] Cumulative mortality rate (%) = (Nd / Nt) × 100.

[0068] In the formula: Nd is the cumulative number of dead fish, and Nt is the initial number of fish.

[0069] 3. Organizational structure integrity From the remaining live fish, four fish were selected from each group for four replicates (close to average body weight), and sections of the intestine and liver were prepared. Intestinal sections: Cell structure and integrity were observed. Liver sections: Cell structure and integrity were observed.

[0070] 4. Immune system Non-specific immune markers were measured in the intestines of the remaining live fish: lysozyme (LZM), phenol oxidase (PO), acid phosphatase (ACP), and alkaline phosphatase (AKP).

[0071] II. Experimental Results.

[0072] 1. Effects of enzymatic hydrolysis of corn protein on the morbidity and mortality of enteritis in juvenile yellow catfish after challenge with Vibrio mimicus. The effects of ECP on the morbidity and mortality of enteritis in juvenile yellow catfish after Vibrio mimicry challenge are shown in [reference needed]. Figure 2 The results showed that compared with the control group (Group A), Vibrio mimicry significantly increased the morbidity and mortality of juvenile yellow catfish. However, after adding 6% ECP (by mass fraction) of protein to the diet of yellow catfish to replace fishmeal, the morbidity and mortality of enteritis in juvenile yellow catfish were significantly reduced (P<0.05), indicating that ECP can effectively alleviate the diseases of yellow catfish caused by Vibrio mimicry infection.

[0073] 2. Effects of enzymatic hydrolysis of corn protein on the structural integrity of intestinal and liver tissues in juvenile yellow catfish challenged with Vibrio mimicus. The effect of ECP on the intestinal structural integrity of juvenile yellow catfish is shown in [reference needed]. Figure 3 .like Figure 3 As shown, Vibrio mimicry caused crypt damage and inflammatory infiltration in the intestines of juvenile yellow catfish in the group without ECP. However, in the group with 6% ECP, no obvious damage was observed to the intestinal structure of the juvenile yellow catfish, and the degree of inflammatory infiltration in the intestinal tissue was significantly reduced. This indicates that ECP can maintain the integrity of the intestinal structure and reduce the inflammatory response.

[0074] The effect of ECP on the liver structural integrity of juvenile yellow catfish is shown in [reference needed]. Figure 4 .like Figure 4 As shown, no obvious pathological changes were observed in the liver tissue of yellow catfish in the group that was not injected with Vibrio mimicry. In the group injected with Vibrio mimicry, the liver tissue of the group without ECP showed pathological damage such as nuclear dissolution and cell vacuolation. However, in the group with 6% ECP, no obvious damage was observed in the liver tissue structure of yellow catfish, suggesting that ECP can protect the liver from damage caused by Vibrio mimicry infection.

[0075] 3. Effects of enzymatic hydrolysis of corn protein on intestinal immunity in juvenile yellow catfish The effects of ECP on the intestinal immunity of juvenile yellow catfish are shown in Table 9. Compared with the control group, the addition of 4.5% ECP to the diet resulted in the highest activity of alkaline phosphatase (AKP) in the intestine of juvenile yellow catfish; the addition of 3% ECP resulted in the highest activities of acid phosphatase (ACP) and phenol oxidase (PO); and the addition of 6% ECP resulted in the highest activity of lysozyme (LZM). These results indicate that the addition of ECP to the diet can effectively improve the intestinal immunity of juvenile yellow catfish and enhance their resistance to pathogens.

[0076] Table 9: Effects of enzymatically hydrolyzed corn protein on intestinal immune-active substances in juvenile yellow catfish after DSS challenge. Note: AKP is alkaline phosphatase (King's units / g prot), ACP is alkaline phosphatase (King's units / g prot), LZM is lysozyme (U / mg prot), and PO is phenol oxidase (ng / ml). All data are expressed as mean ± standard deviation (n=8).

[0077] Experiments have shown that, while keeping the protein level in the feed formulation constant, replacing fishmeal with 6% corn protein hydrolysate can significantly improve the production performance of yellow catfish and enhance its disease resistance.

[0078] It should be noted that when numerical ranges are mentioned in the claims of this invention, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. To avoid redundancy, the present invention describes preferred embodiments.

[0079] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0080] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A feed for resisting bacterial enteritis in yellow catfish, characterized in that, It is composed of a mixture of basic feed and corn protein hydrolysate, wherein the amount of corn protein hydrolysate added is 5% to 7% of the mass fraction of the basic feed.

2. The feed for resisting bacterial enteritis in yellow catfish as described in claim 1, characterized in that, The basic feed ingredients, calculated by weight, include: 18-20 parts fishmeal, 14-16 parts chicken meal, 20-21 parts peeled soybean meal, 5-6 parts soy protein concentrate, 11-13 parts wheat flour, 6-7 parts soybean oil, 1-2 parts calcium dihydrogen phosphate, 1-2 parts microcrystalline cellulose, 7-9 parts carboxymethyl cellulose, 1-3 parts mineral premix, 0.5-1.5 parts vitamin premix, 0.5-1.5 parts choline chloride premix, 0.005-0.015 parts butylated hydroxyanisole, 0.5-1 parts L-lysine salt, and 0.1-0.2 parts L-methionine.

3. The application of the feed according to claim 1 in improving the disease resistance of yellow catfish.

4. The application as described in claim 3, characterized in that, The term "disease resistance" refers to resistance to diseases caused by Vibrio mimicry infection.

5. The application as described in claim 4, characterized in that, The disease caused by Vibrio mimicry infection is bacterial enteritis.

6. The use of the feed according to claim 1 in promoting the accumulation of protein and fat in yellow catfish.

7. The application of the feed according to claim 1 in reducing water pollution in yellow catfish farming.

8. The application as described in claim 7, characterized in that, The reduction of water pollution in yellow catfish farming includes reducing nitrogen emissions from yellow catfish.

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