Comparative Study On The Utilization Of Different Lysine And Methionine Sources By Channel Catfish(ictalurus Punctatus)

The present study was conducted to compare the supplemental effects of different lysine sources and methionine sources in lysine deficient and methionine deficient diets of channel catfish(Ictalurus punctatus). The study contained three sections:(1) Effects of different lysine sources on growth performance, pepsin activities and serum biochemical indices of channel catfish;(2) Comparative study on the utilization of different lysine sources by channel catfish;(3) Comparative study on the utilization of different methionine sources by channel catfish. The results were presented as follow:Exp. 1 Effects of Different Lysine Sources on Growth Performance, Pepsin Activities and Serum Biochemical Indices of Channel CatfishThe present study was conducted to compare the ability of utilizing crystalline L-lysine hydrochloride(Lys.HCl), crystalline L-lysine sulphate(Lys.H2SO4) and microcapsulated L-lysine hydrochloride(microcapsulated Lys) in diet of channel catfish.Five diets with iso-nitrogen and iso-energy were designed as positive control diet(5%fish meal, 15% soybean meal), negative control diet(2.5% fish meal, 0% soybean meal)without or with the addition of Lys.HCl, Lys.H2SO4 and microcapsulated Lys to obtain the same Lys level as positive control diet. Then the five diets were fed to channel catfish with an initial body weight of(54.4±0.1)g for 60 d to investigate the effects on growth performance, serum biochemical indices and protein digestive enzyme activities.The results showed that adding Lys.HCl or Lys.H2SO4 in diet had no significant effects on growth performance when compared with negative control(P>0.05). Fish fed microcapsulated Lys diet had a higher growth rate(GR)(+20.7%) and a lower feed conversion ratio(FCR)(–16.0%)(P<0.05) than that fed negative control diet, and had the similar GR and FCR as those of positive control(P>0.05). The addition of Lys.HCl,Lys.H2SO4 or microcapsulated Lys had no significant effects on activities of serum alanine transaminase(ALT), aspartate transaminase(AST), alkaline phosphatase(ALP)and intestine protease(P>0.05), but significantly increased protease activities in stomach(P<0.05), when compared with negative control. In addition, dietarymicrocapsulated Lys significantly increased protease activity in hepatopancreas(P<0.05). Results above showed that the growth performance of channel catfish can be improved by adding microcapsulated Lys, but not by adding Lys.HCl or Lys.H2SO4 in low Lys diet.Exp. 2 Comparative Study on the Utilization of Different Lysine Sources by Channel CatfishThis study was conducted to compare the effects of supplementation of crystalline L-lysine hydrochloride(Lys.HCl), crystalline L-lysine sulphate(Lys.H2SO4) and microcapsulated L-lysine hydrochloride(M-Lys) in lysine-deficient diet on growth and feed utilization of channel catfish. Five diets with isonitrogen and isoenergy were formulated as positive control diet(6% fish meal, 16% soybean meal), negative control diet(3% fish meal, 0% soybean meal) without or with the addition of Lys.HCl,Lys.H2SO4 and M-Lys to obtain the same lysine level as positive control diet. The five diets were fed to channel catfish with an initial body weight of(76.0±0.3)g for 8 weeks.The results showed that the addition of Lys.HCl or Lys.H2SO4 in diet had no significant effects on growth of the fish when compared with negative control(P>0.05). Fish fed M-Lys diet had a higher weight gain ratio(+11.0%) and a lower feed conversion ratio(–9.9%) than that fed negative control diet(P<0.05), and showed a similar growth as positive control(P>0.05). Lipid productive value of the three Lys addition groups were significantly higher than that of negative control(P<0.05). The improvement of protein productive value was only observed in M-Lys group(P<0.05), but not in Lys.HCl group or Lys.H2SO4 group(P>0.05), when compared with negative control. The measurement of serum total protein(TP), total free amino acids(TFAA) and transaminase activities in liver at the 0, 2nd, 4th, 6th, 8th h after feeding showed that all groups except negative control had the similar change model of serum TP level, that was TP level peaked at the4 th h after feeding; but for negative control, the peak was observed at the 6th h after feeding. The serum TFAA level of Lys.HCl group and Lys.H2SO4 group rose rapidly and reached the plateau at the 2nd h after feeding, while the TFAA of both control groups and M-Lys group rose slower and peaked at the 4th h after feeding. In groups of Lys.HCl and Lys.H2SO4, the activities of liver aspartate aminotransferase(AST) and alanine aminotransferase(ALT) peaked at the 2nd h, but in M-Lys group, the highest values of AST and ALT were delayed to the 6th, 4thh after feeding, respectively. Theabove results indicated that the supplementation of M-Lys rather than Lys.HCl or Lys.H2SO4 in lysine-deficient practical diet could improve the growth performance of channel catfish.Exp. 3 Comparative Study on the Utilization of Different Methionine Sources by Channel CatfishThis feeding trial was conducted using six test diets to examine the supplementation effects of different methionine(Met) sources on the performance of channel catfish. Six diets with isonitrogen and isoenergy were formulated as positive control diet [0.57% Met in dry matter(DM)], negative control diet(0.42% Met in DM)without or with the addition of DL-methionine(DL-Met), methionine hydroxy analogue free acid(MHA-FA), methionine hydroxy analogue calcium salt(MHA-Ca) and microcapsulated methionine(M-Met) to obtain the same Met level as positive control diet on an equal-sulfur basis. The six diets were fed to channel catfish with an initial body weight of(76.0±0.3)g for 8 weeks. The results showed that the addition of DL-Met or MHA-FA in Met-deficient diet had no significant effects on growth and feed conversion ratio(FCR) of the fish when compared with negative control(P>0.05). Fish fed MHA-Ca and M-Met diet had a higher weight gain rate and a lower FCR than that fed negative control diet(P<0.05), and showed a similar growth as positive control(P>0.05). The improvement of protein productive value and lipid productive value were only observed in MHA-Ca and M-Met group(P<0.05), but not in other Met supplentation groups when compared with negative control. The measurement of serum total protein(TP), total free amino acids(TFAA) and transaminase activities in liver at the 0, 2nd, 4th, 6th, 8th h after feeding showed that all groups had the similar change model of serum TP level. The serum TFAA level of all groups were peaked at the 4th h after feeding, but DI-Met group was significant lower than that of M-Met group at 6thh after feeding(P<0.05). In groups of DL-Met, the activities of liver aspartate aminotransferase(AST) and alanine aminotransferase(ALT) peaked at the 2ndh, for negative group, the highest values of AST and ALT were delayed to the 4th h, while MHA-FA, MHA-Ca and M-Met group delayed to the 6th h after feeding, respectively.The above results indicated that the supplementation of MHA-Ca and M-Met rather than DL-Met or MHA-FA in Met-deficient practical diet could improve the growth performance of channel catfish.