| Digestive enzyme, optimum protein levels and optimum energy levels of Gymnocypris przewalskii were determined in the Present study. The results obtained can be briefly summarized as follows:1.The Gymnocypris przewalskii(weight : about 300g) has taken as the research object in this study, the activities and distributions of trypsin, lipase and amylase in liver, pancreas,fore-intestine, mid-intestine and hind-intestine have been analyzed at emptiness, after feeding 2h, 4h, 6h and 8h.Results showed that: the secretion of trypsin, lipase and amylase in liver and pancreas were constant, stable and increased within a short period of time after feeding; The activities of three digestive enzyme in liver and pancreas were significantly lower than those in different parts of the digestive tract under neither emptiness nor feeding conditions. Analysis on activities of three digestive enzyme in different parts of the digestive tract before and after feeding demonstrated that the enzyme activity was higher in the mid- and hind-intestine than the fore-intestine, which indicated that protein, lipid and amylum in the fodder of Gymnocypris przewalskii were mainly digested in mid- and hind-intestine.2.An 8 week feeding trial was conducted to estimate the dietary protein requirement of juvenile Gymnocypris przewalskii(initial weight 16.43 g). Practical basal diets were used and seven diets were formulated to contain graded levels of protein(31%, 33%, 35%, 37%, 39%, 41% and 43%). Each diet was fed to triplicate groups of fish in a recirculating rearing system. Results showed that the specific growth rate(SGR) increased significantly with the increasing dietary protein levels(31-37%; p<0.05) and then no further increase was found(37-43%; p>0.05). Feed conversion ratio of fish showed decreased trend with increase of dietary protein levels, but no significant difference was found among treatments(p>0.05). Glutamic-oxalacetic transaminase(AST) activity, total cholesterol and triglyceride contents in serum were significantly increased but serum urea nitrogen content was decreased with increase of dietary protein levels(p<0.05). Based on the SGR data, dietary protein requirement of juvenile Gymnocypris przewalskii was 37.67% by broken-line regression analysis.3.An 8 week feeding trial was conducted to estimate the energy requirement of juvenile Gymnocypris przewalskii(initial weight 15.99±0.02 g). Practical basal diets were used and five diets were formulated to contain graded levels of energy(16.1k J/g,16.4k J/g,16.7k J/g,17.0k J/g and 17.3 k J/g). Each diet was fed to triplicate groups of fish in a recirculating rearing system. Results showed that the specific growth rate(SGR) first increased firstly significantly and then decreased significantly with the increasing dietary energy levels(16.1-16.7 k J/g, p>0.05), On the contrary Feed conversion ratio of showed a rising trend and then descended with increase of dietary energy levels(p<0.05).Condition fact of fish fed the 16.7 k J/g energy diet was significantly higher then that fish fed of other energy levels diet(p>0.05), but hepato somatic index, viscero somatic index and survival rate were not significantly affected by energy levels(p > 0.05). The levels of alanine amnotransferase, aspartate aminotransferse,glucose, total choleterol, triacylglyceride and low density lipoprotein cholesterin in serum decreased with the dietary energy levels; Globulin, total protion and high density lipoprotein cholesterin showed a rising trend and then descended with increase of dietary energy levels(p<0.05). Blood urea nitrogen of fish fed the 16.7 k J/g energy diet was significantly lower then that fish fed of other energy levels diet(p>0.05). Based on the SGR data, dietary energy requirement of juvenile Gymnocypris przewalskii was 16.67 k J/g by quadratic model. |
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