| Three feeding trials were conducted at a salinity of30ppt to evaluate the effectsof different optimal dietary protein to energy(P/E)ratio and different levels of tyrosineor proline on the growth of Penaeus vannamei. The results obtained can be brieflysummarized as follows:1.An8-week feeding trial was conducted to estimate the optimal dietary proteinto energy(P/E)ratio for juvenile Litopenaeus vannamei(initial average weight0.46±0.01g). Twelve practical diets were used in the study, which contain four proteinlevels (35%,37%,39%and41%), and there were three lipid levels (6%,8%and10%)at each protein level. Each diet was randomly assigned to triplicate groups of30shrimps per tank (280L). The shrimps were homogeneously fed three times daily, andthe feeding rate was about5-8%. The results showed that shrimp which fed the dietwith39%protein and8%lipid had the best specific growth rate and weigh gain(WG)which showed the best protein to energy(P/E)ratio for juvenile Litopenaeus vannamei is26.11mg protein/kJ, and the value of DP/DE is105.69mg/kcal. Andincrease of dietary lipid level has not efficient protein-sparing effect. There was acertain role in promoting the growth of shrimp at a high protein level of each lipidlevel. The increase on dietary lipid level had no efficient protein-sparing effect. But atthe same protein level, the raising on lipid level within a certain range can acceleratethe growth of shrimp. No difference was observed in whole body and musclecomposition among dietary treatments. No significant difference was found incholesterol,triglycerides and total protein in the haemolymph among diets groups.2. An8-week feeding experiment was conducted to investigate the effects ofdifferent tyrosine levels on the growth performance, feed utilization and haemolymphindex of juvenile white shrimp which fed low-fishmeal diets. Six experiment dietswere prepared in the trial, each had a supplemented tyrosine levelsof0%(D-1),0.07%(D-2),0.15%(D-3),0.22%(D-4),0.29%(D-5)and0.37%(D-6)respectively. Diets were randomly assigned to triplicate groups of30shrimps(initialaverage weight0.71±0.01g) per tank (280L). The shrimps were homogeneously fedthree times daily, and the feeding rate was about5-8%. Shrimp fed the0.22%tyrosine-supplemented diets showed the highest weight gain, but there was nosignificantly difference among trials. No difference was observed in whole body andmuscle composition among dietary treatments. But with the increase of tyrosine infeed, the tyrosine in whole body rose accordingly. No significant difference was foundin triglycerides, total protein, cholesterol in the haemolymph among diets groups.The results of the present study demonstrated that adding tyrosine to the low-fishmealdiet did not have any positive effects on growth of juvenile white shrimp.3. An8-week feeding trial was conducted to investigate the effects of differentproline levels on the growth performance, feed utilization and haemolymph index ofjuvenile white shrimp which fed low-fishmeal diets. Six experiment diets wereprepared in the trial, each had a supplemented proline levels of0%(D-1),0.06%(D-2),0.11%(D-3),0.17%(D-4),0.22%(D-5)and0.28%(D-6) respectively. Each diet wasrandomly assigned to triplicate groups of30shrimps (initial average weight0.73±0.01g) per tank (280L). The shrimps were homogeneously fed three times daily, and the feeding rate was about5-8%. Shrimp fed the0.22%proline-supplementeddiets showed the highest weight gain, but there was no significantly difference amongtrials. No difference was observed in whole body and muscle composition amongdietary treatments. But with the increase of proline in feed, the proline in whole bodyrose accordingly. No significant difference was found in triglycerides, total protein,cholesterol in the haemolymph among diets groups. The results of the present studydemonstrated that adding proline to the low-fishmeal diet did not have any positiveeffects on growth of juvenile white shrimp. |
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