Application Of Four Kinds Of Feeding Stimulants In Low Fish Meal Feed Of Yellow Catfish(Pelteobagrus Fulvidraco)

In this paper,the effects of Tryptophan,Trp;Mixed nucleotide,Mix-NT;dimethyl-β-propionatethiotine,DMPT and Betaine,Bet on growth performance,body composition,serum biochemistry,serum tissue antioxidant index,tissue digestive enzyme activity and foregut tissue structure of Yellow catfish were studied.The results and detailed experiments are as follows:1.The effects of four kinds of feeding stimulants on growth performance,body composition and serum biochemical indices of Yellow catfish fed with low fish meal720 juveniles of Yellow catfish with initial average weight of 1.38g±0.01 were selected and randomly divided into six groups with 4 replicates in each group.Thirty young Yellow catfish were fed every other for 56days.Four groups were fed with low fish meal diet,high fish meal diet and low fish meal diet,respectively.Four groups were added with1.8g/kg Tryptophan,0.4g/kg Mixed nucleotide,0.4g/kg Dimethyl-β-propiothetin and 6g/kg Betaine.Six experimental groups were labeled as low fish meal,high fish meal,Trp,Mix-NT,DM and Bet groups.The results showed that the total food intake of Yellow catfish in the four groups increased significantly(P < 0.05),among which the Trp group had the highest food intake,and the final total weight,final average weight,specific growth rate and weight gain rate of Trp were higher than those of other experimental groups,but they were not significant(P > 0.05).The Feed conwersion ration of each group and the high fish meal group were lower than those of the negative control group,but the difference was not significant(P > 0.05).In terms of morphological indexes,except for the viscera-body ratio in Trp group,which was significantly higher than that in high fish meal group,Mix-NT group and Bet group(P < 0.05),there was no significant difference in other physical indexes.There were no significant differences in dry matter,crude protein,crude fat and crude ash content among the experimental groups(P > 0.05).The serum albumin content of DMPT and Mix-NT group was the highest,and the serum albumin content of DMPT group was significantly higher than that of Mix-NT group(P < 0.05),but there was no significant difference between DMPT group and control group.Among the six experimental groups,the serum cholesterol content of the low fish meal group was thehighest,which was significantly higher than that of the other five groups(P < 0.05).The content of serum triglycerides in the high fish meal group was the lowest,and significantly lower than that in the other five groups(P < 0.05).The content of serum triglycerides in the Bet group was significantly lower than that in the Trp,DMPT and Mix-NT groups(P <0.05),and the content of serum triglycerides in the Trp,Mix-NT and Bet groups was significantly lower than that in the negative control group(P < 0.05).The serum LDL content in Trp group was significantly lower than that in other five groups(P < 0.05).The blood sugar content of high fish meal group was significantly higher than that of low fish meal group,Trp group,Mix NT group and DMPT group(P < 0.05),while that of Bet group was significantly higher than that of negative control group(P < 0.05).Among the four groups,serum total triiodothyronine levels in Trp and Mix-NT groups were significantly higher than those in the positive control group(P < 0.05).In summary,the results showed that adding Trp,Mix-NT,Bet and DMPT to the feed of low-fish meal yellow catfish could significantly improve the feed intake and growth performance of yellow catfish.Trp had the best effect on improving the growth performance of Yellow catfish,and could also reduce the content of low density lipoprotein in serum.Trp,Mix-NT and Bet can reduce the content of cholesterol and triglyceride in serum and promote fat metabolism of Yellow catfish.Trp and Mix-NT can also significantly reduce blood sugar content and increase serum total triiodothyronine content.2.Effects of four kinds of feeding stimulants on antioxidant capacity of serum and tissues of Yellow catfish in low fish meal dietAfter 56days of feeding experiment,11 yellow catfish were randomly fished from each tank.Blood samples were taken from tail vein and injected into 5.0 ml centrifugal tube.Serum was prepared by standing overnight at 4 C refrigerator and centrifugation for 10 minutes at 3 500 r/min.Serum was stored in refrigerator at-20 C for biochemical and antioxidant determination.The visceral mass,liver and intestine were dissected,and the liver,intestine and stomach tissues were separated and preserved at-80 C for antioxidant enzymes.The results showed that the total antioxidant capacity in intestine and serum of Bet group was the highest,and the total antioxidant capacity in intestine of Bet group was significantly higher than that of control group,Trp,Mix-NT and DMPT group(P < 0.05).The activity of superoxide dismutase in liver of DMPT group was significantly higher than that of negative control group(P < 0.05).The activity of superoxide dismutase in intestine of Trp and Bet group was higher than that of low fish meal group(P < 0.05).The activity of superoxide dismutase in serum of Trp,DMPT and Bet group was higher than that of controlgroup,but the difference was not significant(P > 0.05).The malondialdehyde content in liver and intestine of the four groups was lower than that of the low fish meal group.The malondialdehyde content in intestine of the four groups was significantly different from that of the low fish meal group(P < 0.05),while the malondialdehyde content in liver of the DMPT group was significantly lower than that of the low fish meal group(P < 0.05).There was no significant difference in malondialdehyde content between the two groups(P > 0.05).The results showed that adding Trp and Bet to the low fish meal diet of Yellow catfish could improve the intestinal antioxidant capacity and reduce the content of malondialdehyde in the intestine.Adding DMPT and Mix-NT to the low fish meal diet of Yellow catfish could improve the antioxidant capacity of the liver,and DMPT could also reduce the content of malondialdehyde in the liver.3.Effect of four kinds of feeding stimulants on digestive enzyme activity in tissues of Yellow catfishAt the end of 56-day feeding experiment,three yellow catfish were randomly selected from each tank and dissected separately.The stomach,liver and intestine were taken out and stored at-20 C for the determination of protease,amylase and lipase activities.The results showed that the intestinal trypsin activity of Mix-NT and Bet groups was significantly higher than that of the other four groups.The activity of intestinal amylase in Bet group was higher than that in DMPT and low fish meal group(P < 0.05).The amylase activity in liver of DMPT group was higher than that of control group,but the difference was not significant.The activities of intestinal lipase in Mix-NT and Bet groups were the highest,significantly higher than those in DMPT group and low fish meal group.The digestive enzymes activities of stomach tissues of Yellow catfish in each experimental group were the highest in Trp group.The activity of pepsinase in Trp group was significantly higher than that in high fish meal group and the other three groups(P < 0.05).The activity of gastric amylase in Trp group was significantly higher than that in low fish meal,high fish meal,DMPT,Bet and Mix-NT group(P < 0.05).The activity of gastric lipase in the four groups was significantly higher than that in the negative control group(P< 0.05).The activity of gastric lipase in Trp group was significantly higher than that in low fish meal group,high fish meal group,Mix-NT group and Bet group.(P<0.05).The results showed that the activities of protease,amylase and lipase in liver,stomach and intestine of Yellow catfish could be increased by adding four kinds of food substances to the feed of low fish meal.4.Effects of four kinds of feeding stimulants on the structure of foregut of Yellow catfishAt the end of the experiment,three yellow catfish were randomly selected from each tank,and the foregut was taken for paraffin section,and observed by HE staining light microscopy.The results showed that the muscle thickness of Trp and DMPT groups was significantly higher than that of control group and Mix-NT and Bet groups(P < 0.05).The thickness of muscle layer in Bet group was the lowest,which was significantly lower than that in high fish meal group,Trp and DMPT.The fold height of the high fish meal group was the lowest and significantly lower than that of the other five groups(P < 0.05).It was concluded that adding four different kinds of feeding stimulants to the low fish meal diet of Yellow catfish could increase the foregut fold height of Yellow catfish,and Trp,Mix-NT and DMPT could increase the foregut muscle thickness,improve the intestinal structure and promote digestion and absorption of Yellow catfish.In conclusion,it is recommended that Trp,Mix-NT or Bet should be added to the feed of low fish meal of Yellow catfish as feeding stimulants promotion in production practice.