New use of euglena powder in the breeding of misgurnus anguillicaudatus

Abstract

This invention discloses a novel application of Euglena gracilis powder in eel farming, relating to the field of eel farming technology. By adding Euglena gracilis powder to the basic eel feed formula, this invention can significantly promote eel growth, improve eel morphology indicators, reduce the levels of alanine aminotransferase (ALT), gamma-glutamyl transferase (γ-GT), and triglycerides (TG) in eel serum, and enhance the antioxidant effect of eels. Simultaneously, Euglena gracilis powder can also increase the activity of intestinal digestive enzymes in eels, promote the elongation of intestinal villi and the thickening of the intestinal wall, and increase the number of hepatic sinusoids. It also has an antibacterial effect against Aeromonas verrucosa, increasing the abundance of Proteobacteria and decreasing the abundance of Firmicutes bacteria in the eel intestine, thus promoting eel growth and farming.

Description

Technical Field

[0001] This invention relates to the field of eel farming technology, specifically to a new use of Euglena powder in eel farming. Background Technology

[0002] The swamp eel, also known as the mud eel, has tender and delicious flesh with few bones and thick meat. It typically lives in the muddy bottoms of rice paddies, streams, ponds, canals, and lakes. It is produced in many parts of China, with the Yangtze River basin, Liaoning, and Tianjin having the largest production areas. The typical production season is from June to October, with the fattest swamp eels caught between June and August. Swamp eels primarily feed on animal matter.

[0003] Euglena powder is produced by culturing Euglena indoors and outdoors, centrifuging them together with the Euglena culture medium, and then subjecting them to sterilization, spray drying, and sieving. Euglena powder is rich in nutrients such as vitamins, minerals, amino acids, unsaturated fatty acids, and chlorophyll, and is specifically effective in improving immune function.

[0004] Currently, research on aquatic product feed shows that Euglena powder is mainly used in the breeding of crayfish. For example, Chinese patent CN106616020A discloses an ecological feed that promotes crayfish growth and improves crayfish quality. Its raw materials include algae powder, which is one or a mixture of green algae powder, brown algae powder, dinoflagellate powder, Euglena powder, and golden algae powder. Its main function is to increase the weight gain rate, specific growth rate and feed intake of crayfish, and reduce the feed conversion ratio.

[0005] However, there are currently no reports on the application of Euglena powder in eel farming. Summary of the Invention

[0006] This invention provides a novel application of Euglena powder in eel farming, aiming to solve the problems existing in the aforementioned background technology.

[0007] To achieve the above-mentioned technical objectives, the present invention mainly adopts the following technical solutions:

[0008] In a first aspect, the present invention discloses the application of Euglena powder in the preparation of feed that promotes the growth of swamp eels and improves their body shape indicators.

[0009] In a preferred embodiment of the present invention, the Euglena powder improves the morphological index of the eel by increasing the visceral index of the eel.

[0010] Secondly, this invention discloses the application of Euglena powder in the preparation of antioxidant feed for eels to reduce alanine aminotransferase (ALT), γ-glutamyltransferase (γ-GT), triglycerides (TG) in the serum of eels.

[0011] In a preferred embodiment of the present invention, the amount of Euglena powder added per kilogram of the feed is 0.25-2g.

[0012] Preferably, the amount of Euglena powder added per kilogram of the feed is 708.64 mg.

[0013] Thirdly, this invention discloses the application of Euglena powder in the preparation of feed for improving the activity of digestive enzymes in the intestines of eels.

[0014] In a preferred embodiment of the present invention, the digestive enzymes include intestinal trypsin, intestinal amylase, and intestinal lipase; when preparing feed to enhance the intestinal trypsin activity of swamp eels, the amount of Euglena powder added per kilogram of the feed is 0.5-2g; when preparing feed to enhance the intestinal amylase activity of swamp eels, the amount of Euglena powder added per kilogram of the feed is 1g; when preparing feed to enhance the intestinal trypsin activity of swamp eels, the amount of Euglena powder added per kilogram of the feed is 1g.

[0015] Fourthly, this invention discloses the application of Euglena powder in the preparation of feed for promoting the elongation of small intestinal villi, thickening of the small intestinal wall, and increasing the number of hepatic sinusoids in eels.

[0016] Fifthly, this invention discloses the application of Euglena powder in the preparation of feed resistant to Aeromonas verrucosa.

[0017] Sixthly, this invention discloses the application of Euglena powder in the preparation of feed that increases the abundance of Proteobacteria and decreases the abundance of Firmicutes in the intestines of eels.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention, by adding Euglena powder to the basic formula feed for eels, can significantly promote the growth of eels, improve their body shape indicators, reduce the levels of alanine aminotransferase (ALT), gamma-glutamyl transferase (γ-GT), and triglycerides (TG) in the serum of eels, and enhance their antioxidant effects. Simultaneously, Euglena powder can also increase the activity of intestinal digestive enzymes in eels, promote the elongation of intestinal villi and the thickening of the intestinal wall, and increase the number of hepatic sinusoids. It also has an antibacterial effect against Aeromonas verrucosa, increasing the abundance of Proteobacteria and decreasing the abundance of Firmicutes in the eel's intestine, thus promoting the growth and cultivation of eels. Attached Figure Description

[0020] Figure 1 The graph shows the effects of different concentrations of Euglena scoparia powder on the growth performance and feed utilization of swamp eels. A represents the effect of different concentrations of Euglena scoparia powder on the final body weight of swamp eels; B represents the effect of different concentrations of Euglena scoparia powder on the weight gain rate of swamp eels; C represents the effect of different concentrations of Euglena scoparia powder on the specific growth rate of swamp eels; and D represents the effect of different concentrations of Euglena scoparia powder on the feed conversion ratio of swamp eels.

[0021] Figure 2 Line regression analysis of weight gain rate versus the amount of Euglena powder added to feed;

[0022] Figure 3 The effects of different concentrations of Euglena powder on the morphological indicators of swamp eels were investigated. Among them, A represents the effect of adding different concentrations of Euglena powder on the liver body index of swamp eels; B represents the effect of adding different concentrations of Euglena powder on the visceral body index of swamp eels; and C represents the effect of adding different concentrations of Euglena powder on the condition factor of swamp eels.

[0023] Figure 4 The study investigated the effects of Euglena scoparia powder on the activity of digestive enzymes in the intestine of swamp eels. Specifically, A represents the effect of different concentrations of Euglena scoparia powder on the activity of trypsin in the intestine of swamp eels; B represents the effect of different concentrations of Euglena scoparia powder on the activity of amylase in the intestine of swamp eels; and C represents the effect of different concentrations of Euglena scoparia powder on the activity of lipase in the intestine of swamp eels.

[0024] Figure 5 Intestinal sections of eels after being fed different amounts of Euglena powder;

[0025] Figure 6 Liver sections of eels after being fed different amounts of Euglena powder;

[0026] Figure 7 A graph showing the survival rate of swamp eels 72 hours after infection with Aeromonas versicolor;

[0027] Figure 8 Image showing the skin lesions of a yellow eel after infection with Aeromonas versicolor;

[0028] Figure 9 The graph shows the bacterial load in immune organs of eels after infection with Aeromonas versicolor; where A represents the Aeromonas versicolor bacterial load in the liver of different groups of eels after challenge; B represents the Aeromonas versicolor bacterial load in the kidney of different groups of eels after challenge; and C represents the Aeromonas versicolor bacterial load in the spleen of different groups of eels after challenge.

[0029] Figure 10 Image of an intestinal section of a yellow eel infected with Aeromonas versicolor;

[0030] Figure 11 This is a diagram based on phylum-level species analysis. Detailed Implementation

[0031] To better understand the present invention, the present invention will be further described in detail below with reference to the embodiments. However, the scope of protection of the present invention is not limited to the scope represented by the embodiments.

[0032] Unless otherwise specified, all raw materials used in this invention are conventional commercially available products. Unless otherwise specified, all methods used in this invention are conventional methods in the field. All substances used in this invention are of conventional usage quality.

[0033] Example 1: Experiment on feeding eels with Euglena powder

[0034] Three hundred healthy, smooth, and trained eel fry, each weighing 12 (±1) grams, were randomly divided into five groups, with three replicates per group and 20 eels per replicate. They were housed in 15 plastic boxes (length × width × height = 105 cm × 75 cm × 50 cm) for 60 days (August 20, 2023 – October 20, 2023). In addition to standard feeding methods, five experimental feeds were provided: 0, 0.25, 0.5, 1, and 2 g / kg of Euglena powder were added to the basal diet (~44% protein, ~4% crude fat), and the groups were labeled CR group, HS1 group, HS2 group, HS3 group, and HS4 group, respectively.

[0035] After the aquaculture was completed, experiments such as data measurement and statistics, enzyme activity determination, challenge immunization, and intestinal flora analysis were conducted to analyze the role of Euglena powder in the aquaculture process of swamp eels.

[0036] The conclusions are as follows:

[0037] 1. Effects of Euglena powder on the growth performance of swamp eels

[0038] Table 1. Effects of Euglena powder on growth performance and feed utilization of yellow eel.

[0039]

[0040] Note: No letter or the same letter in the same row indicates no significant difference (P>0.05), while different letters in the same row indicate significant difference (P<0.05).

[0041] As shown in Table 1 and Figure 1 As shown, adding different concentrations of Euglena gracilis powder to the feed had a highly significant impact on the growth performance of swamp eels. Compared with the control group (CR) swamp eels raised without Euglena gracilis powder, the experimental groups (HS1, HS2, HS3, and HS4) showed nearly twice the weight gain rate. However, higher concentrations of Euglena gracilis powder did not necessarily lead to better growth performance. The experimental group HS3 (1 g / kg) showed the highest weight gain rate, which began to decline in HS4 (2 g / kg), but was still significantly higher than that of the control group.

[0042] Using the weight gain rate of eels as the dependent variable (y) and the amount of Euglena powder added to the feed as the independent variable (x), a broken-line regression analysis was conducted, such as... Figure 2 As shown, the optimal addition amount of Euglena powder is 708.64 mg / Kg.

[0043] 2. Effects of Euglena powder on the morphology of swamp eels

[0044] Table 2. Effects of Euglena powder on the morphology of the yellow eel.

[0045]

[0046] The effects of adding Euglena powder to the feed on the body morphology parameters of swamp eels are shown in Table 2. Figure 3 From Table 2 and Figure 3 It was found that there were no significant differences in liver body mass index and fatness between CR and HS1, HS2, HS3, and HS4 (P>0.05). However, there were significant differences in liver body mass index between the control group and the experimental group.

[0047] 3. Effects of Euglena powder on enzyme activity in eels

[0048] Table 3 Effects of Euglena powder on serum biochemistry of yellow eel

[0049]

[0050]

[0051] Table 3 shows that increasing Euglena powder significantly affected ALT, GT, and TG levels. ALT and TG decreased with increasing dosage, while GT was lowest in group HS2 and increased in group HS3. The activities of other serum enzymes did not differ significantly.

[0052] Table 4. Effects of Euglena powder on the antioxidant properties of eel intestines, liver, and serum.

[0053]

[0054] Table 4 shows that with the addition of Euglena powder, there were significant differences in SOD levels in the intestine, liver, and serum, and its activity initially increased and then decreased, with the highest activity in group HS3. The MDA activity in the experimental groups was lower than that in the control group, with no obvious pattern among the experimental groups. The activity of CAT generally increased with increasing dosage.

[0055] And by Figure 4 It can be seen that the activities of digestive enzymes all showed a trend of first increasing and then decreasing, with the highest activity in the HS3 group. In APS, there was no significant difference between CR and HS1, but there were significant differences between CR and HS2, HS3, and HS4. In AMS, there was no significant difference between CR and HS1, HS2, and HS4, but there was a significant difference between CR and HS3. In LPS, there were significant differences between HS3 and CR, and between HS1, HS2, and HS4, but no significant differences among CR, HS1, HS2, and HS4.

[0056] 4. Analysis of intestinal and liver sections

[0057] Intestinal and liver sections were prepared from eels in the experimental group and four control groups. The results are as follows: Figure 5 , Figure 6 As shown.

[0058] Depend on Figure 5 It can be seen that, compared with the control group CR, the small intestinal villi of the eels in the experimental groups HS1, HS2, HS3 and HS4 gradually lengthened and the small intestinal wall thickened.

[0059] Depend on Figure 6 It can be seen that, compared with the control group CR, the number of hepatic sinusoids of eels gradually increased in the experimental groups HS1, HS2, HS3 and HS4.

[0060] 5. Research on the antibacterial infection ability of Euglena powder

[0061] Table 5. Survival rate of eels challenged with Aeromonas vilonis after 572 hours.

[0062]

[0063] The effects of adding different levels of Euglena powder to the feed on the survival rate of swamp eels are shown in Table 5. Figure 7 As shown in Table 5 and... Figure 7 It was found that 24 hours after injection of Aeromonas verrucosa, the mortality rate of eels in the control group reached 60%, while the mortality rate in the experimental group was only 30%. After 72 hours, the mortality rate of eels in the control group reached 90%, while the mortality rate of the experimental group with added Euglena powder was significantly reduced, with the mortality rate of the HS4 group being only 70%.

[0064] In addition, such as Figure 8 As shown, 24 hours after being challenged with Aeromonas versicolor, the eels exhibited symptoms such as drooling, white spots on their bodies, and swelling and redness of the hepatic hilum. Dissection revealed hepatomegaly, splenomegaly with hemorrhage, and intestinal hemorrhage. The experimental group showed less symptom severity compared to the control group.

[0065] Immediately after challenging the AV-infected eels, they were dissected, and the bacterial load in each group was recorded. Figure 9 As shown, the AV content in the liver, kidneys, and spleen showed a continuous decreasing trend, and the CR was significantly different from that in the experimental group, with the lowest AV bacterial load in the HS4 group. Further verification confirmed that adding Euglena powder to the feed significantly improved the survival rate of eels (P<0.05).

[0066] Immediately after the AV-infected eels were challenged, their intestines were dissected and sections were prepared, such as... Figure 10 As shown, the intestinal structure of the unchallenged AV-infected eels in the control group was intact, with neatly arranged villi. In contrast, the intestinal slices of the AV-infected eels in the control group showed broken villi and an incomplete intestinal structure. Comparing the intestinal slices from eels fed Euglena powder and challenged with AV, although the intestinal villi in the HS3 group were broken, their structure was more intact than that of the CR group. This indicates that Euglena powder has a protective effect against intestinal bacterial infections.

[0067] 6. Gut microbiota and transcriptome analysis

[0068] Based on phylum-level species analysis, the gut microbiota of eels in the experimental and control groups were examined, and the results were as follows: Figure 11 As shown, at the phylum level, the largest proportion of bacteria in the CR, HS1, HS2, HS3, and HS4 groups is Firmicutes, followed by Proteobacteria. Compared with CR, the addition of Euglena powder to HS2, HS3, and HS4 reduced the abundance of Firmicutes bacteria, while HS2 and HS3 increased the abundance of Proteobacteria bacteria.

[0069] Although embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the scope of the invention is not limited to the contents disclosed in the embodiments.

Claims

1. Application of Euglena powder in the preparation of eel farming feed, wherein the feed is used to reduce alanine aminotransferase (ALT), gamma-glutamyl transferase (γ-GT), and triglycerides (TG) in eel serum and to improve the antioxidant effect of eels; to increase the activity of digestive enzymes in the eel intestine; to promote the elongation of intestinal villi, thickening of the intestinal wall, and increase the number of hepatic sinusoids in eels; to resist Aeromonas verrucosa; and to increase the abundance of Proteobacteria and decrease the abundance of Firmicutes in the eel intestine. The amount of Euglena powder added per kilogram of the feed is 0.25-2g.

2. The application according to claim 1, characterized in that, The amount of Euglena powder added per kilogram of the feed is 708.64 mg.

3. The application according to claim 1, characterized in that, The digestive enzymes include intestinal trypsin, intestinal amylase, and intestinal lipase. When preparing feed to enhance the intestinal trypsin activity of swamp eels, the amount of Euglena powder added per kilogram of the feed is 0.5-2g; when preparing feed to enhance the intestinal amylase activity of swamp eels, the amount of Euglena powder added per kilogram of the feed is 1g; when preparing feed to enhance the intestinal lipase activity of swamp eels, the amount of Euglena powder added per kilogram of the feed is 1g.

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