Study On The Development Of Digestive System And Bait Conversion Strategy Of Micropterus Salmoides

Although the largemouth bass(Micropterus salmoides)industry has grown quickly recently,its ability to continue growing has been constrained by the issue of poor fry survival rates.In trying to comprehend the critical period for digestive system development,we examined the development of the digestive system and the activity of digestive enzymes in the early stage of G5 generation Micropterus salmoides(From Baiyong Aquatic Seed Co.).The developmental pattern of the digestive system and the influence of different weaning duration on the effect of switching was studied to develop a suitable switching strategy in order to improve the early survival rate of Micropterus salmoides and to provide a theoretical basis for the development of the industry.The main results are as follows:1.Histological observation of digestive system developmentThe histological method was used to observe the development of the digestive system of largemouth bass 1-45 DAH(Days after hatching).The results were as follows:2 The DAH digestive tract and digestive glands began to differentiate;the oropharyngeal cavity was closed;the esophagus was connected to the gastric cavity;the intestine was in the form of a straight tube behind the yolk sac;hepatocytes and hepatic blood sinuses appeared in the liver.4 Mucous cells appeared in the mucosal layer of the DAH oropharyngeal cavity and esophagus,taste buds appeared around the gill arch,and the intestine was curved.5 The DAH oropharyngeal cavity opened and feeding began;the oral valves appeared.6 The DAH yolk sac was completely absorbed and Gastric glands appeared;nuclear vacuoles appeared in the intestine,and the differentiation of the digestive system was basically completed.12-15 DAH The number of nuclear vacuoles cells in the intestine decreased.18 DAH The nuclear vacuoles in the intestine disappeared.It shows that largemouth bass has the ability of extracellular digestion of protein after 6 DAH,and the ability of extracellular digestion is enhanced after 12 DAH,and the extracellular digestion is perfected after 18 DAH,and it can consume artificial feeds.2.Changes of digestive enzyme activityThis investigation looked at how the Micropterus salmoides’ s trypsin,amylase,alkaline phosphatase,and lipase activities changed from 1 to 45 DAH.The discovery of the four digestive enzyme functions at 1 DAH.After that,there was a substantial increase in both TPS and LPS activity(P<0.05),with TPS peaking at 4 DAH and LPS peaking at 5DAH.This was linked to Micropterus salmoides feeding openly,which increased TPS for protein digestion after opening and LPS for nutrient absorption from the yolk sac.While the difference in AMS and AKP specific activity was not significant prior to feeding(P>0.05),it markedly rose after 6 DAH(P<0.05),showing that both of these enzymes were influenced by food and that the action of exogenous bait caused the increase in secretion.From 10-20 DAH the activity of the three digestive enzymes increased significantly(P<0.05),except for TPS activity which decreased significantly(P<0.05),and the digestive capacity increased at this stage.1-20 DAH the difference in the full activity of the four digestive enzymes was not significant(P>0.05),and after 20 DAH the full activity increased significantly(P<0.05).According to the histological results from 6 DAH,the gastric glands appeared and digestive capacity was enhanced after 12 DAH;also after12 DAH digestive enzyme activity was enhanced and extracellular digestion was dominant,allowing for weaning.3.Effect of the duration of the weaning on the effect of weaningIn terms of this study,four different groups were set up based on the results of histological and digestive enzyme activity tests: 12 DAH to start the weaning,four groups fed with a mixture of fenugreek and commercial feed for 4,8 and 12 days,and no the weaning,respectively.The experimental results were as follows;the survival rate increased,the deformation rate decreased,the specific growth rate did not differ significantly(P>0.05),the TPS,LPS and AKP ratio vitality increased effectively with the extension of the mixed feeding time(P<0.05),and the differences between the AMS groups was not significant(P>0.05).There was no significance difference in the deformation rate between the groups that were switched to food for 12 days and those that were not,and there was no significant difference in digestive enzyme intensities(P>0.05),indicating that the effect of switching to food for 12 days was the same as feeding biological baits.Therefore,it can be obtained that Largemouth bass diversion lasting 12 days is the best under this test condition.The test results showed Micropterus salmoides has perfected extracellular digestion after 18 DAH,and can achieve better results by starting to switch to feed to 12 DAH until24 DAH.