| The growth curves were fitted and the growth stages were divided at different protein levels in crucian carp. Long-term effects of dietary protein levels and protein quality on growth performances, haematological parameters and compositions on crucian carp were studied and the protein requirements of juvenile and adult stage were obtained. The study was composed of three experiments and each of them was summarized respectively as follows.Experiment 1. Fitting and Analysis of the Growth Curves of Crucian carp(Carassius auratus Var. Pengze)at four protein levelsAbstract: The four protein levels diets of 31.97%(P1), 35.78%(P2), 38.79%(P3), 43.07%(P4) were fed the crucian carp of 1.85±0.17g weight for 285 days. Every two weeks they were weighed. After the experiment finished the growth curves of crucian carp from 0 to 41 weeks old were fitted and analyzed by using three kinds of nonlinear models (Gompertz, Logistic, von Bertalanffy). The results show that all the three models were preferably applicable for the growth curves and the correlated coefficients were above 0.99. In the models the von Bertalanffy model was the best and the correlated coefficients are above 0.997. Throught the fitting parameters of the von Bertalanffy model were analysized, the most weights of crucian carp at the four protein levels were 465.68g, 487.16g, 620.14g, and 575.30g respectively. The weights at the points of inflexion were 137.98g, 144.34g, 183.74g, and 170.46g respectively. The time at which the inflexion occurs is 28.33 week, 28.49 week, 33.11 week and 31.56 week respectively. The most weights, the inflexion weights and the inflexion week ages of P3 and P4 were far beyond the parameters of P1 and P2. The results showed that the high protein level diets could prolong the rapid growth stage of crucian carp. The growth speed of crucian carp was highly increased at first and then declines slowly. In the 0-18 weeks (the evaluated weight was 0.66-72.9g) the growth speed was highly increased. In the 18-34 weeks (the evaluated weight is 66.95-190.83g) the growth speed was slowly increased. After the 34 week (the evaluated weight is above 190.83g) the growth speed gradually declines. The growth speeds of the high protein level groups were higher than that of the low protein level groups. Based on the growth speed curves of Crucian carp, the growth process could be generally devided into the rapid growth speed duration (0-18 weeks, the evaluated weight is 0.66-72.9g ), the slow growth speed duration (18-34 weeks, the evaluated weight is 66.95-190.83g ), and the declining growth speed duration (after 34 week, the evaluated weight is above 190.83g).Experiment 2. Long-term effects of dietary protein levels on growth performance, haematological parameters and body compositions using high protein quality diets feed crucian carp (Carassius aruatus, Pengze)Abatract:A single factor feeding trial was made to determine the optimal dietary protein levels of crucian carp(initial body weight is 1.85±0.17g) at different stages. White fish meal, soybean meal, full-fat extruded soybean, spray-dried blood cells, and liver meal were used as the main dietary protein source to formulate four protein levels 31.97%(P1), 35.78%(P2), 38.79%(P3), 43.07%(P4)in 4% increments. Whole cultured process lasted for 283d and was divided to three stages. The first stage lasted 125d, the second stage lasted 111d, and the third stage lasted 49d.The results showed that there were significantly differences among groups in FI, FCR, PER, PR and ER in the whole precess of crucian carp (P<0.05). The FI, FCR, PER, PR of the low protein level groups(LPL) were higher than the high protein groups(HPL), but the ER was lower than HPL. It was no significantly difference in SGR. The muscle acid of HPLs were higher than the LPL, but there were no significant differences among groups. At the first stage, there were significantly differences among groups in WG, SGR, FI, FCR, PER, PR and ER (P<0.05). HPL could advance the growth and save the feed. At the second stage, There were respectively significant differences in FI, FCR, PR and ER, but not significantly in SGR and PER. FI of LPL was significantly higher than HPL, but not significantly in SGR, PER, FCR, PR and ER. The regression analysis showed at the first stage the optimum dietary protein level for supporting maximum specific growth rate(SGR) was 48.13%, and the maximum protein ratio(PR) was 24.47%. Dietary protein requirement was estimated at approximately 36% for better growth and better protein ratio at the first stage. We could not obtaine the protein level of the second stage and the third stage because the protein level was not enough.The dietary protein levels were no significant effect on body composition at the second stage and the third stage. The dietary protein levels were no significant effect on musle compositions. At the first stage the higher dietary protein levels could increase the body moisture content, decreased the fat and energy content significantly. Experiment 3. Eeffects of dietary protein levels on growth performance,haematological parameters and body compositions using low protein quality diets feed adult crucian carp (Carassius aruatus, Pengze)Abatract: A series of growth experiments were conducted to study the optimum dietary protein level of adult crucian carp(Carassius auratus Var. Pengze)(initial body weight is 51.56±0.13g)for a 144d feeding trial. Fish meal, soybean meal, rapeseed meal, and cottonseed meal is used as the main dietary protein source to formulate five protein levels 25.38%, 28.13%, 32.48%, 35.73%和38.64%in 4% increments. The results showed that weight gain(WG) and specific growth rate(SGR) of the fish fed the 35.73% protein diets was significantly higher than that of the fish fed 25.38%, 28.13%, 38.64% protein diets (P<0.05),but not significantly different from that of the fish feed the 32.48% protein diets (P> 0.05). With the increase of dietary protein the protein efficiency and protein ratio were decreased. There were respectively no significant differences in fish CF, VSI, HIS, and GSI between fish fed different diets. The dietary protein level that yield maximum growth was 33.78-33.95%based on parabolic curve model estimation of weight gain and feed efficiency. The results of haematological parameters analysis showed that There were respectively no significant differences in fish ALT, AST, TP, TG and Chol between fish fed different diets.Urea of the fish fed the 38.64% protein diet was significantly higher than that of the fish fed 25.38%protein diets ( P<0.05), but not significantly different from that of the fish feed the 28.13%, 32.48%, and 35.73% protein diets ( P>0.05).The results of body composition analysis showed that protein content in whole body increases with the increase in dietary protein level. 38.64% dietary protein group was significantly different ( P<0.05) to 38.64%dietary protein group, but not significantly different from that of the fish feed the 28.13%, 32.48% and 35.73 % protein diets (P>0.05). Moisture, fat and energy content in whole body were no significantly differences among groups. there were no significantly differences among groups in moisture, protein, crude lipid and ash contents in muscles ( P> 0.05). The energy content in muscle was the highest in 28.13% dietary protein group, which exhibited significantly higher than that of 25.38% dietary protein groups.
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