A Study On Protein Soucres Screen And Processing -Related Technics In Artificial Microdiet For Larvae Of Large Yellow Croaker (Pseudosciaena Crocea) And Tongue Sole (Cynoglossus Semilaevis)

The dissertation primarily reviewed advances of studies on microdiet processing technics and digestive physiology for marine fish larvae in recent years. Furthermore, a series of feeding experiments were conducted to investigate the effects of several protein sources and processing technics for large yellow croaker, Pseudosciaena crocea R. and tongue sole, Cynoglossus semilaevis G. The researches were conducted in indoor culture system (288L for large yellow croaker and 120L for tongue sole). Results of the present study are presented as follows:1. An 28-day feeding experiment was conducted in tanks to investigate the effects of different protein sources on the survival, growth performance in large yellow croaker (Pseudosciaena crocea) larvae (17 days after hatching, with initial average wet weight 8.84±0.28 mg (mean±SD)). Three approximately isonitrogenous and isoenergetic microbound diets (Diet1-Diet3) were formulated with different protein sources proportion. Commercial diet (Diet4) (manufactured by Ri qing Co.) and live prey (LP used in fingerling production) were used as control diets. The results showed that there were no significant differences in survival among the fish groups (P>0.05), except for the Diet2. The final body weight and specific growth rates (SGRs) of fish fed Diet3 (191.8mg, 12.3%day^-1) was not significantly difference from Diet4 (185.2mg, 12.2%day^-1) (P>0.05). They were both significantly higher than Diet1 and LP groups. The body composition analysis showed that the crude protein of fish fed Diet3 (58.9 %) was not significantly different from Diet4 (P>0.05), but significantly higher than the other diets (P<0.05). The fish fed experimental diets had higher crude lipid content than the control diets. While the ash of the fish fed LP diet (24.3 %) was significantly higher than other groups (P<0.05). These results indicate that the protein sources proportion in Diet3 was better compared with Diet1 and Diet2.2. A 30-day feeding experiment was conducted in tanks to investigate the effects of dietary fish protein hydrolysate levels on the growth, survival and body composition of large yellow croaker (Pseudosciaena crocea Richardson) larvae (12 days after hatchery, with initial average weight 1.6±0.18 mg). Five practical diets were used in the present study. Four microdiets (MD), with fish protein hydrolysate (FPH) replacing 0%, 25%, 50% and 75% of fish meal protein, were formulated. The frozen copepods was used as a control diet. The results showed that dietary FPH levels significantly influenced the growth, survival and body composition of large yellow croaker larvae. With increasing dietary FPH, the specific growth rates (SGRs) and survival of large yellow croaker significantly decreased (P<0.05). While the survival (32.6%) in fish fed the diet with 25% FPH replacing fish meal was significantly higher than other groups (P<0.05), but was not significantly different from that of the control diet group (P>0.05). The SGR (9.0%day^-1) in fish fed the diet with 25% FPH replacing fish meal protein was not significantly different from the 0% FPH group. The body composition analysis showed that with increasing FPH, the whole body dry matter, crude protein and crude lipid significantly decreased (P<0.05). Analysis of whole body fatty acid showed that with increasing dietary FPH, DHA and EPA in fish body significantly decreased(P<0.05). Results from this study indicated that a proper replacement of fish meal with FPH in the microdiet of large yellow croaker larvae will improve survival, and excessive FPH will result in poor growth and low survival of the larvae. Maybe, there is a better level of FPH from 0% to 25% to replace fish meal in the diet.3. An 30-day feeding experiment was conducted in tanks to investigate the effects of four different stuff particle size on the survival, growth performance and specific activity of digestive enzymes in large yellow croaker (Pseudosciaena crocea) larvae (13 days after hatching, with initial average wet weight 1.7±0.11 mg (mean±SD)). Four approximately isonitrogenous and isoenergetic microbound diets were formulated with different stuff particle size (Diet1^-100μm, Diet2-71μm, Diet3-48μm and Diet4<25μm). Commercial diet (Diet5) (Com, manufactured by Ri qing Co.) and live prey (LP used in fingerling production) were used as control diets. The results showed that the water stability was improved with decreasing the stuff particle size reduction. The survival of fish fed Diet3 (34.6%) was significantly higher than Diet2(29.3%) and Diet1(18.7%)(P<0.05), and there were no significant differences in survival among fish fed Diet3, Diet4 (34.9%) and LP (P>0.05). The changes of the final wet weights (FWs) and specific growth rates (SGRs) among different tested groups followed the similar pattern as that of survival rates. However, fish fed Diet3 diet had a significantly higher BW (36.3 mg) and SGR (10.2 % day) than those in fish fed LP (25.7 mg, 9.0 % day ^-1) (P<0.01). The results of digestive enzyme showed that fish fed Diet3 diet had significantly higher (P<0.05) specific activity of brush border membranes enzymes, alkaline phosphatase ( 829.1 mU mg^-1prot. ) and aminopeptidase N(163.6 mU mg^-1prot.)than the fish fed Diet1 and LP(P<0.05), but not different from Diet4. These results indicated that the stuff particle size processed to less than 48μm was proper for larval large yellow croaker.4. An 30-day feeding experiment was conducted in tanks to investigate the effects of four different stuff particle size on the survival, growth performance and specific activity of digestive enzymes in tongue sole (Cynoglossus semilaevis Günther) post-larvae [24 days after hatching (DAH), with initial average wet weight 22.4±6.65mg (mean±S.D.)]. Four approximately isonitrogenous and isoenergetic microbound diets were formulated with different stuff particle size (Diet 1^-100μm, Diet 2-71μm, Diet 3-48μm and Diet 4<25μm). Commercial diet (Diet5) (manufactured by Riqing Co.) and live prey (LP, Artemia nauplii) were used as control diets. The results showed that the water stability was improved with decreasing the stuff particle size. There were no significant differences in survival between the fish fed Diet4 (29.3%) and Diet5 (35.2%), but fish fed other three experimental artificial diets had significantly lower survival than Diet5. LP groups obtained the significantly highest survival (54.5%) than other groups (P<0.01). The specific growth rates (SGRs) of fish fed Diet3 (6.9%·day^-1) was significantly higher than fish fed Diet1 (6.2%·day^-1) and Diet2 (6.7%·day^-1) (P<0.05), but was not different from the fish fed Diet4 (6.9 %·day^-1) (P>0.05). Correspondingly, the LP groups had the best growth compared with other artificial diet group. At 54 DAH, the fish fed Diet3 had significantly higher trypsin secretory level (56.6%) than Diet1 (43.5%) (P<0.05), but was not significantly different from Diet4 (P>0.05). The specific activity of leucine aminopeptidase N (LAP) on intestinal brush border membranes (BBM) in fish fed Diet5 was significantly higher than Diet1, but was not different from other three artificial diet groups. The results of alkaline phosphatase specific activities on BBM at 54 DAH increased with the reduction of stuff particle size (P<0.05). These results indicated that the smaller particle size, the higher growth. However, taking account the cost of processing, less than 48μm stuff particle size was suggested for post larval tongue sole.5. An 30-day feeding experiment was conducted in tanks to investigate the effects of four different binders (2% in microdiet) on the survival, growth performance and specific activity of digestive enzymes in large yellow croaker (Pseudosciaena crocea) larvae (13 days after hatching, with initial average wet weight 1.7±0.11 mg (mean±SD)). Four approximately isonitrogenous and isoenergetic microbound diets were formulated with carrageenan (Car), sodium carboxymethyl cellulose (CMS), sodium alginate (SA) and gelatin (Gelatin) as binders, respectively. Live prey (LP used in fingerling production) was used as control diets. The results showed that there were no significant differences in survival among fish fed Car (31.4%), SA (29.9%), Gel (28.9%) and LP (33.1%) diets (P>0.05). Moreover, the survival of Car and SA groups were both significantly higher than the fish fed CMS (18.0%) diet and Cont. (23.3%) diet (P<0.05). The changes of the final wet weights (FWs) and specific growth rates (SGRs) among different tested groups followed the similar pattern as that of survival rates. However, the fish fed Gel diet had a significantly lower FW (29.5mg) and SGR (9.5%day ^-1) than those in fish fed Car and SA diets. The body composition analysis showed that the crude protein of the fish fed Car diet (64.7%) was not significantly different (P>0.05) from SA diet and Gel diet, and significantly higher than CMS diet (P<0.05). While the ash of the fish fed LP diet was significantly different from other groups. There were no significant differences between the fish fed Car diet and SA diet in specific activities of digestive enzyme. Fish fed CMS diet had significantly lower (P<0.05) specific activity of brush border membranes enzymes, alkaline phosphatase, and aminopeptidase N than the other groups, which showed the relatively worse maturation of the intestinal digestive process. These results indicate that carrageenan and sodium alginate are suitable binders compared with gelatin and sodium carboxymethyl cellulose in microdiet of larval large yellow croaker.6. A 30-day feeding experiment was conducted in tanks to investigate the effects of four different binders (2% in microdiet) on the survival, growth performance and specific activity of digestive enzymes in tongue sole (Cynoglossus semilaevis Günther) post-larvae [24 days after hatching (DAH), with initial average wet weight 22.4±6.65mg (mean±S.D.)]. Five approximately isonitrogenous and isoenergetic microbound diets (MBD) were formulated with carrageenan (Car), sodium carboxymethyl cellulose (CMS), sodium alginate (SA), gelatin (Gel) as binders, respectively, and a diet with no special binder as a control. A commercial diet (RQ Com., manufactured by Marubeni Nisshin Feed Co., Ltd.) was used as other tested diet, and Artemia nauplii was used as live prey control. The results showed that the survival of the fish fed SA (31.3%) diet was significantly higher than CMS (21.8%), Car (10.8%) and control (21.8%) diets (P<0.05), but significantly lower than the live prey (54.5%) diet (P<0.05). The results of growth followed the similar pattern as that of survival although there were no significant differences in SGR among fish fed the diets of SA, CMS, Gel, the control and commercial diets (7.2, 6.8, 7.0, 6.9, and 7.3% day ^-1) (P>0.05). However, fish fed Car diet had a significantly lower SGR (5.9%day ^-1) than those in fish fed other diets. Percentages of secreted amylase of fish in artificial diets were not significantly different, but fish fed artificial diets had significantly higher secreted amylase than live prey group. Percentage of secreted trypsin of fish fed SA diet (54.9%) was relatively higher compared with other binders, and not significantly different from commercial and live prey treatments. However, trypsin in fish fed Car diets (29.3%) was significantly lower than other groups. Specific activities of alkaline phosphatase (AP) in the intestine, AP and on brush border membranes (BBM) in fish fed SA (264.6, 1882.8 and 187.2 mU mg^-1 prot.) diet were relatively higher compared with other binders. These results indicate that sodium alginate is one of suitable binders compared with carrageenan, sodium carboxymethyl cellulose and gelatin in microdiet of post larval tongue sole.7. An 28-day feeding experiment was conducted in tanks to investigate the effects of three microdiets with different processing technics on the survival, growth performance and specific activity of digestive enzymes in large yellow croaker (Pseudosciaena crocea) larvae (16 days after hatching, with initial average wet weight 4.1±0.26 mg (mean±SD)). Three approximately isonitrogenous and isoenergetic microdiets (Diet1, Diet2 and Diet3) were formulated with different characters. Commercial diet (Diet4) (manufactured by Ri qing Co.) and Live prey (LP used in fingerling production) were used as control diets. The results showed that there were no significant differences in survival among fish fed Diet2 (26.7%), Diet3 (27.0%) and Diet4 (29.8%) diets (P>0.05). However, fish fed Diet1 (20.8%) had significantly lower survival rate than Diet4. Fish fed LP had the highest survival rate (42.4%) in all the groups (P<0.05). However, the best growth came from the fish fed Diet3 (57.1mg-43 DAH ), which was significantly higher than any other groups (P<0.01) although the feed intake of Diet3 at the start of experiment was the lowest one. The secreted trypsin specific activitie of fish fed Diet3 (66.4 %) was significantly higher than Diet1, Diet2 and LP groups (P<0.05) at 44 DAH. The specific activity of brush border membranes enzymes, aminopeptidase N increased followed the same pattern as change of growth.The fish fed Diet3 had the higher specific activity of brush border membranes enzymes compared with other groups. These results indicate that MCD (Diet3) is desirable microdiet of larval large yellow croaker and deserved to further study.