| Monopterus albus has rich nutrition,delicious taste,high edible and medicinal value,and broad market prospects.It is widely distributed in China and has also been widely cultivated.At present,the annual production of Monopterus albus in China is about 310000 tons.The feed for Monopterus albus is usually made from chilled fish and fish meal as the main protein source.With the decline of global fishery resources,it is urgent to find other protein sources to replace chilled fish and fish meal.China is rich in cottonseed.Many experiments have proved that cottonseed meal can be used as a part of the protein source of conventional fish feed instead of fish meal.The processed cottonseed has high protein content and few anti nutritional factors,which is a good protein source.However,whether it can be used in Monopterus albus feed has not been reported yet.Therefore,this experiment first explored the effect of different water temperatures on the activity of Digestive enzyme of Monopterus albus,and obtained better breeding water temperature,Under this water temperature condition,dephenol cottonseed protein was added to the muscle amino acid composition of Monopterus albus to form a complex instead of fish meal,and additives were added to reduce the negative impact of cottonseed protein replacing fish meal.The main research results are as follows:1.Effect of water temperature on Digestive enzyme activity of Monopterus albusMonopterus albus was cultured at 6 ℃,16 ℃,26 ℃,28 ℃ and 32 ℃ respectively,and its Digestive enzyme activity was measured.Result:(1)The protease activity of each tissue in the 26 ℃ group was significantly higher than that of other temperature groups;The activity of Amylase in all tissues was significantly higher than that in other temperature groups at 26 ℃,except Hepatopancreas at 28 ℃;The lipase activity was highest at 26 ℃,significantly higher in the stomach and foregut at 26 ℃ than in other temperature groups,and significantly higher in the hindgut at 16,28,and 32 ℃ groups.(2)The activity of Digestive enzyme in foregut was significantly higher than that in other tissues.The results showed that the main digestive activity of Monopterus albus was in the foregut,the activity of Digestive enzyme was high at 26 ℃,and the digestive capacity was good,which was suitable for the feeding and growth of Monopterus albus.2.Effect of replacing fish meal with cottonseed protein complex on feeding Monopterus albus for 60 daysUsing cottonseed protein complex as a substitute for 25%,50%,and 100% fish meal in a basic feed containing 50% fish meal,and supplementing the corresponding substitute group with additives mainly composed of enzyme preparations,the Monopterus albus(8.774± 0.023g)was fed for 60 days.The results showed that:(1)growth first increased and then decreased with the increase of the substitute ratio.Regression analysis using specific growth rate as an indicator showed that the appropriate substitution ratio was 27.47% without additives and 42.70% with additives added;(2)As the substitution ratio increases,the visceral body index and liver body index decrease,while the plumpness first increases and then decreases;The whole fish and liver crude fat significantly increased,while muscle crude fat first decreased and then increased.Additives can reduce the whole fish fat and increase liver fat.Whole fish crude protein first increases and then decreases,muscle crude protein decreases,and liver crude protein increases;(3)The muscle texture decreases with increasing substitution ratio,and supplementation with additives can alleviate this downward trend;(4)The total Essential amino acid content in muscle reached the highest when 50% of the substitution was made,and the Essential amino acid and four delicious amino acids content under all substitution ratios were higher than those in the control group.The liver amino acid content increased with the increase of substitution ratio.In the ratio of muscle Saturated fat acid(SFA): Monounsaturated fatty acid(MUFA): Polyunsaturated fatty acid(PUFA),when MUFA is 100% replaced,it is lower than other groups.EPA,DHA,totalω-3 Unsaturated fat all showed a downward trend with the increase of substitution ratio,while ω-6 Unsaturated fat acid is the opposite.The trend of liver EPA and DHA is consistent with that of liver and muscle,ω-3/ ω-6 shows a downward trend.(5)The liver metabolism and antioxidant function of Monopterus albus were not significantly affected by 50% or less substitution,but the immune function began to show negative effects when the substitution reached 50% or less without supplementation with additives;(6)Digestive enzyme in Hepatopancreas decreased with the increase of substitution ratio,protease in stomach,foregut and hindgut increased with the increase of substitution ratio,lipase decreased with the increase of substitution ratio,and additives would increase the activity of various Digestive enzyme;(7)When the substitution ratio is 100%,the liver cell nucleus deviates severely and partially disappears;The villus height,Microvillus length,and Lamina propria thickness of the foregut and hindgut all increased first and then decreased.The villus height,Microvillus height,and Lamina propria thickness of the 100% replacement group were significantly lower than those of the other groups.(8)Effect on Gut microbiota of Monopterus albus Results: 25% replacement will increase the richness and diversity of Gut microbiota;In the phyla level,the abundance of each phyla in the 25% substitution group was more uniform,and the abundance of Pseudomonadota and Fusobacteria increased compared with the control group,while the abundance of Bacillota decreased.When 50% substitution with additives,the abundance of intestinal Fusobacteria mainly increased;At the genus level,compared with the control group,the abundance of Cetobacterium increased significantly when 25% substitution was used,while the abundance of Cetobacterium decreased significantly when 100% substitution was used,and the abundance of segmented filamentous fungi increased significantly.The abundance of Cetobacterium increased while that of Clostridium in the narrow sense decreased when the additive was replaced by 50%;At the genus level,there are 2dominant species with 25% substitution,of which the highest score is Bacillus Bacillaceae,50%substitution of supplementary additives group has no dominant species,and there are 7 dominant species with no additives group,of which Lactic acid bacteria and Streptococcaceae have high scores,and the dominant species with 100% substitution is Clostridium;KEGG analysis showed that the functional abundance of each group was mainly concentrated in six aspects such as metabolism,and the highest abundance was observed when each pathway was replaced by 25%.The results indicate that replacing fish meal in moderation is beneficial for the growth of Monopterus albus,and supplementing additives can increase the replacement ratio.The substitutable amounts for raising Monopterus albus for 60 days without supplementation and supplementation with additives are 27.47%and 42.70%,respectively.3.Effect of replacing fish meal with cottonseed protein complex on feeding Monopterus albus for 120 daysUsing cottonseed protein complex in a base material containing 50% fish meal and supplementing additives to replace 25%,50%,and 100% fish meal,the Monopterus albus(8.774 ± 0.023g)was fed for 120 days to basically meet the market specifications.Result:(1)The growth of Monopterus albus showed a trend of first increasing and then decreasing with the increase of substitution ratio,and the suitable substitution amount was 14.19% using specific growth rate as an indicator for regression analysis;(2)The liver body index and plumpness of Monopterus albus were not significantly affected at 50% substitution or below;(3)There was no difference in muscle moisture,and except for 100% substitution,there was no difference in ash content between the other groups and the control group.The 100%substitution group was significantly higher than the control group.Crude fat decreases with an increase in substitution ratio,while crude protein first increases and then decreases with an increase in substitution ratio.It reaches its highest level at 25% substitution,and the control group is lower than the other groups;(4)The rate of muscle dripping loss first decreases and then increases with the increase of substitution ratio,and 50% substitution and below do not cause significant negative effects;(5)Replacing 50% of the Monopterus albus did not significantly affect liver metabolism and antioxidant function,and replacing 25% of the Monopterus albus did not significantly affect immune function;The ultrastructure of 100%replacement ratio showed that the liver of Monopterus albus was damaged,the gap between hepatocytes was increased,and the structure of Endoplasmic reticulum in cells became loose.The results showed that the cottonseed protein complex with a substitution ratio of less than50% had no significant negative effects on the meat quality,antioxidant activity,and liver tissue structure of Monopterus albus.The substitution ratio of 50% could lead to a decrease in the growth and immunity of Monopterus albus.The appropriate substitution amount for feeding Monopterus albus albus for 120 days was 14.19%.Conclusion: The highest activity of Digestive enzyme was found in Monopterus albus when the water temperature was 26 ℃.Replacing fish meal with cottonseed protein complex can replace 42.70% of fish meal in short-term farming and 14.19% in long-term farming. |
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