| Feeding trials were conducted to determine the optimal dietaryprotein and protein to energy ratio (P/E) for Japanese seabass in twodifferent growth stage. Results of the study are presented as follows:1. Fish meal and casein were chosen as the main dietary protein sourceand five formulated diets with different protein levels (35%、40%、45%、50%and55%) were prepared to fed Japanese seabass (initialaverage weight34.15±0.33g and343.89±5.04g). For the initialaverage weight34.15±0.33g Japanese seabass, the experiment lastedfor eight weeks. There were no significant differences in the survivalrate (91.67%~96.67%) among dietary groups (P＞0.05). Withincreasing dietary protein level, the specific growth rate (SGR)increased, the SGR of fish in45%group was significantly higher thanthat in35%group (P<0.05), but there was no significant difference inthe40%,50%and55%groups (P>0.05). With increasing dietaryprotein level, the protein productive value (PPV) and proteinefficiency ratio (PER) increased, up to45%then decreased. Withincreasing dietary protein level, feed intake (FI) decreased. With theincrease of dietary protein level, the content of crude protein of wholebody increased but the crude fat and ash decreased. As dietary proteinincreasing, pepsin, trypsin and the glutamic-oxaloacetic transaminase（GOT）activity were increased, however, there was no difference inglutamic-pyruvic transaminase (GPT) activity (P＞0.05). For theinitial average weight343.89±5.04g Japanese seabass, the experimentlasted for ten weeks. There were no significant differences in thesurvival rate (75.00%~97.22%) among dietary groups (P＞0.05).With increasing dietary protein level, the specific growth rate (SGR)increased, SGR of fish in40%group was significantly higher thanthat in35%group (P<0.05), but there was no differences in45%, 50%and55%groups (P>0.05). The PER and PPV increased, thenstabilized. There were no significant differences in FI among dietarytreatments (P>0.05). There was no significant difference in wholebody moisture content (P>0.05). With increasing dietary proteinlevels, whole body protein and lipid all increased. As dietary proteinincreasing, pepsin, trypsin, GOP and GPT activity all were increased.Based on the indices of SGR, FE and PER, It is suggest that theoptimal dietary protein levels were45.73%~45.89%and40.23%forJapanese seabass with initial average weight34.15±0.33g and343.89±5.04g, respectively.2. Fish meal and casein were chosen as the main dietary protein source,fish oil and soybean oil were chosen as lipid source. Nine diets wereformulate to contain three protein levels (35%,40%,45%), each withthree lipid levels (8%,12%,16%)，so as to produce a range of P/Eratios (from24.3to34.5mg/KJ). Japanese seabass (initial averageweight34.29±0.42g and305.06±1.63g) were hand fed twice daily toapparel satiation. For the initial average weight34.29±0.42g Japaneseseabass, the experiment lasted for eight weeks. The SGR was better infish fed with high protein diets (40%,45%) than those fed with lowprotein diets (35%). Fish fed the diets with45%protein (12%and16%lipid) had the highest SGR, however, fish fed the diet with40%protein and8%lipid showed comparable growth, and had the similarFI, FE and PER (P<0.05). There was no significant difference insurvival rates (P>0.05). At the same lipid level, body protein contentsincreased with increasing dietary protein level, at the same proteinlevel, lipid contents increased with increasing dietary lipid level. Theactivities of GPT was better in fish fed with high protein diets (40%,45%) than those fed with low protein diets (35%), but GOT was notsignificantly influenced by dietary protein to energy ratio. At the samelipid level, condition factor (CF) decreased with increasing dietaryprotein level, but liver and body weight ratio (HSI) increased. For theinitial average weight305.06±1.63g Japanese seabass, the experimentlasted for ten weeks. Fish fed the diet with protein and lipid levels of45%and8%respectively had the best SGR (0.60%/day), but fish fed the diet with40%protein and12%lipid showed comparable growth(0.55%/day), and had higher FE, PER, PPV. No significantdifferences in percent survival were found among all groups (P>0.05).No significant differences in FI were found among dietary groups(P>0.05). At the same lipid level, body protein contents increasedwith increasing dietary protein level; at the same protein level, lipidcontents increased with increasing dietary lipid level. The activities ofGPT and GOT were better in fish fed with high protein diets (40%,45%) than those fed with low protein diets (35%). At the same lipidlevel, condition factor (CF) decreased with increasing dietary proteinlevel, but liver and body weight ratio (HSI) increased. In conclusion,it suggests that the diet containing40%protein,8%lipid with P/E of33.2mg/KJ and40%protein,12%lipid with P/E of29.1mg/KJ wereoptimal for Japanese seabass with initial averaged body weight34.29±0.42g and305.06±1.63g, respectively. |
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