Research Of Dietary Lysine And Arginine Level On Growth,Digestive Physiology,Amino Acid Absorption And Utilization In Yellow Catfish,Pelteobagrus Fulvidraco

This study was undertaken to determine the regulation of digestion,absorption and utilization role treated both by arginine and lysine in diet of yellow catfish,Peletobagrus fulvidraco,as well as to determine the interaction between arginine(Arg)and lysine(Lys)in vivo and nutritional requirements.To achieve the aim,growth trials,digestive test and comparative slaughter trials in combination with analyzing growth performance,digestive enzymatic activities as well as AA transport vector gene expressions were carried out to give evidences for guiding the production of compound feed in yellow catfish scientifically.The completed experiments were introduced briefly as follows:1.A two-factor test design was applied to investigate the effect of different levels of Arg and Lys in diets on growth performance,serum free amino acids,body composition,tissue enzyme activities,amino acid content and the expression of amino acid transporter in tissues of yellow catfish.Two factors were arranged as 2.50%(low),3.12%(middle),3.74%(high)for Arg levels and 2.07%(low),2.61%(high)for Lys levels respectively.The results showed that:(1)The effect of diet Arg and Lys level on the growth performance in yellow catfish was not significant and no interaction was found between them(P>0.05).The diet Lys level had significant effects on the protein efficiency and feed coefficient of the yellow catfish(P<0.05).(1)The serum free amino acid level of yellow catfish(except Met)was mainly affected by the diet Arg level,which in middle Arg level groups were higher than the others.The effect of diet Lys level on serum free amino acid was not obvious(P>0.05).The diet level of Arg and Lys had interaction on serum free Met and Leu(P<0.05).(2)Crude fat of the whole fish and muscle in low diet Arg level groups were higher than high level groups(P<0.05).crude protein of muscle in middle and high level were higher than low Arg level of the diet.High Lys level groups were significantly higher than that in low level groups on whole fish crude fat,which was opposite on crude protein(P<0.05).(2)Trypsin activity in liver,stomach,pylorus and foregut and amylase activity in pylorus and foregut was significantly affected by Arg level,which in middle levels were higher than the others(P<0.05).The diet Lys high levels had stronger activity of stomach and foregut trypsin than low levels,which increased the activity stomach,pylorus and content amylase as well.There was an interaction viewed between Arg and Lys levels on foregut trypsin activity and pylorus lipase activity(P<0.05).(3)The middle level of diet Arg levels were higher than the others on the contents of Thr,Val and Lys in the yellow catfish(P<0.05).His、Arg、Thr、Val、Met、Ile were affected by the interaction with Arg and Lys level in the diet(P<0.05).(1)the order of y LAT1 gene expression was:pylorus,foregut,liver>midgut,stomach,hindgut(P<0.05).The order of B0AT1 gene expression was:pylorus,hindgut>foregut,midgut>stomach,liver(P<0.05).(2)The expression of y LAT1 in liver,stomach,foregut and hindgut were found higher value both in middle and high Arg levels than that in low levels(P<0.05).But the y+LAT1 of hidgut tissue was observed the lowest value in high Arg level groups.There was no interaction between the Arg and Lys levels found on the yellow catfish y LAT1 gene(P>0.05).Conclusion:The levels of Arg and Lys in diet can significantly affect the body composition and amino acid content of juvenile fish.Lys levels of the diet affected the protein efficiency and feed coefficient on yellow catfish significantly.Higher levels of Arg and Lys in feed can significantly enhance the enzyme activity of yellow catfish and increase serum free amino acid content.The expression levels of amino acid transporters(y LAT1,B0AT1)in different tissues existed difference.The stomach and foregut are the main expression sites of y LAT1.The expression level of y+LAT1 in stomach,foregut and hindgut tissues is mainly affected by diet Arg level,while Lys level mainly had effect on y+LATI in the stomach of stingray.expression.2.The dynamic changes of enzymatic activities and serum free amino acids in yellow catfish tissues at post-prandial were studied with different Arg levels(2.50%,3.12%,3.74%)and Lys levels(2.07%,2.60%).The results showed that:Serum free amino acids gradually increased to peak value within 6 hours after feeding,and then showed a downward trend.The activities of trypsin in liver,foregut and midgut decreased to the trough at 2h,4h and 6-8h,and rose to the peak at 4h,6-8h and 8h,respectively.Liver amylase activity peaked at 4-6 h after ingestion,while the foregut and midgut peaked at 6 h and 8 h post-prandial.The activity of arginase in liver was affected by Arg and Lys level,which were the same trend.It increased slowly within 4 hours after ingestion,then decreased rapidly to the valley at 2h,and slowly rose to a stable level.The liver trypsin activity in diet 3.12%Arg level and 2.61%Lys level were higher than other levels.The lipase activity of each tissue was affected by the level of Lys,which in 2.61%level was higher than 2.07%.Arginase activity of liver increased with rising levels of diet Arg and Lys.In conclusion:The serum free amino acid content and tissue enzyme activity were regularly changed by the feeding on yellow catfish and enzyme activities of different tissues were sequenced.The levels of Arg and Lys affected the tissue enzyme activity of yellow catfish before and after feeding.3.This experiment was carried out to investigate different proportions of dietary Arg/Lys on growth performance,body chemical composition,biochemical indices in serum,tissue digestive enzyme activities as well as amino acid deposition rate in body tissues of whole fish.(Method)All-male yellow catfish with initial body weight(2.34±0.05)g were randomly divided into eight groups with four repeats each(30 fish per replicate).The dietary Arg/Lys levels were designed as 2.19/2.61(1,control),1.74/2.08(11),1.75/3.02(111),2.63/2.08(IV),2.64/3.12(V),3.07/2.61(Ⅵ),2.19/3.65(Ⅶ)and 3.08/3.65(Ⅷ)respectively.Trial lasted for 10 weeks.The results indicated that:(1)FBW,BGW,WGR and SGR in VI was significantly higher than others(P<0.05),except that in V(P>0.05).The feed coefficient of group Ⅱ was significantly higher than other groups(P<0.05).(2)There was no apparent difference observed on total moisture,EE,ash in whole fish body among groups respectively(P>0.05).But crude protein inⅥ was significantly than that in Ⅱ,Ⅲ and the moisture in Ⅶ had the higher value than that in Ⅰ,Ⅱ.(3)There were no significant differences in serum biochemical parameters between the groups(P>0,05).(4)The activity of liver and intestinal trypsin in group Ⅰ was the highest,which was significantly higher than that in group Ⅵ～Ⅷ(P<0.05).Trypsin activity of stomach in Group Ⅱ to Ⅳ,which was higher than others(P<0.05).The highest value of intestine lipase activity was recorded in Group Ⅷ which was higher than that among group Ⅰ to Ⅲ obviously.The amylase activity either in group Ⅱ or Ⅲ was lower than that among group Ⅴ,Ⅶ and Ⅷ in intestine obviously(P<0.05).(5)The digestibility of dry matter ranged from 62.02%to 76.51%while the higher values were recorded among group II to VI.The digestibility of protein,lipid,energy among groups were calculated between 84.06%to 91.42%,85.22%～94.10%,68.15%～80.99%;Arg,Lys and total amino acids digestibility were between 84.83%to 95.01%,91.97%～96.66%and 92.80%～96.97%respectively.(6)The amino acid deposition rate of whole fish reached the highest value in accordance with the ratio of Arg/Lys as 1.20(P<0.05).In conclusion,different dietary Arg/Lys level had effects on growth performance,body chemical composition and amino acid deposition rate of whole fish in diet.The suitable ratio of Arg/Lys in the yellow catfish diet can improve the growth composition,digestive enzyme activity and apparent digestibility amino acid deposition rate.