| Feeding trials were conducted to explore the technology pathway on the decrease of fish meal levels in diets of Chinese soft-shelled turtle. The main studies included: (1) Effects of fermented soybean meal partly replacement for red fish meal on growth performance, physiological and biochemical indexes of Chinese soft-shelled turtle. (2) Effects of crystal lysine supplementation level in meat and bone meal based diet on growth performance, physiological and biochemical indexes of Chinese soft-shelled turtle. (3) Effects of different quality fish meals on growth performance, physiological and biochemical indexes of Chinese soft-shelled turtle. (4) Effects of the powder diet and extruded diet on growth performance, physiological and biochemical indexes of Chinese soft-shelled turtle. (5) Effects of yeast culture (DVAQUA) on growth performance and immunity of Chinese soft-shelled turtle. The results are briefly summarized as follows:1. A 120-day feeding experiment was conducted to investigate the effect of graded levels (0%, 3%, and 6%, replacing 0%, 6.38% and 12.77% red fish meal (RFM), refered to (Diet 1, Diet 2 and Diet3) of fermented soybean meal (FSM) on the growth performance, feed efficiency ratio, and immunity of soft-shelled turtle (initial mean body weight: 115.52±1.05g). The results showed that specific growth rate (SGR) and feed efficiency ratio (FER) of turtle fed Diet 2 was higher than that of turtle fed Diet 1, but there were no significant differences between the two groups (P>0.05). Nevertheless, feeding intake (FI), SGR and FER of turtle fed Diet 3 was significantly lower than that of fed Diet 1 and Diet 2 (P<0.05). Whole body of moisture, crude protein, crude lipid, and ash contents were not significantly affected by dietary treatments (P>0.05). There were no significant differences in hepatosomatic index (HSI), intraperitoneal index (IPI), viscerosomatic index (VSI), and body coefficent (BC). And no significant differences were observed in activities of pepsin, trypsin and amylase in pancreas, and amylase in intestine, the activities of glutamic-oxalacetic transaminase (GOT) and glutamate pyruvate transaminase (GPT) in serum and liver among 3 groups (P>0.05). Nevertheless, the uric acid (UA) in serum of soft-shelled turtle fed Diet 2 and Diet 3 were significantly lower than that of turtle fed Diet 1 (P<0.05). There were no significant differences in the activities of lysozyme (LSZ), total superoxide dismutase (T-SOD), alkaline phosphatase (AKP), and the content of complement C4 in serum of the turtles among 3 groups (P>0.05). It is concluded that FSM replaced 6.38% RFM could improve the growth performance, without inhibiting physiological and biochemical indexes, and non-specific immunity of turtle. Under the experimental conditions, the appropriate replacing level of FSM in diet containing 47% RFM was about 6.38%, and less than 12.77%.2. A 136-day feeding experiment was conducted to investigate the effects of replacing RFM with meat and bone meal (MBM) in the diet of soft-shelled turtle (initial mean body weight: 112.56±2.13g) with supplementation of crystal lysine on growth performance, feed utilization and digestive enzyme activities. Diet 1 was served as control without supplementation of crystal lysine, which of dietary fish meal content were 61%; Diet 2 was served as another control without supplementation of crystal lysine, which formulated with meat and bone meal to replaced 20% RFM; Diet 2 and Diet 3 were formulated with meat and bone meal to replaced 20% RFM, and the graged levels of crystal lysine were 0.1% and 0.2%, respectively. The total lysine contents in Diet 1 to Diet 4 were 3.59%, 3.50%, 3.60% and 3.71%, respectively. The results showed that survival rate (SR) of turtles was not significantly affected by addition of lysine (P>0.05). SGR, FER, and protein efficiency ratio (PER) of turtle increased with the increasing of crystal lysine supplementation. The best performance in SGR, FER, PER and productive protein value (PPV) were found in turtle fed Diet 4 with 0.2% lysine supplementation (P<0.05); the worst values were found in turtle fed Diet 2 without lysine supplementation (P<0.05). SGR, FER, and PPV of turtle fed Diet 4 with 0.2% lysine supplementation significantly higher than that of turtle fed Diet 4 on day 68 (P<0.05), but not significantly affected by the two treatments on day 136 (P>0.05). There were no significant differences in the whole-body content of moisture, crude protein and ash, HSI, and BC among 4 groups (P>0.05). And no significant differences were observed in activities of GOT and GPT in serum and liver among 4 groups (P>0.05). Nevertheless, the content of UA in serum of turtle fed Diet 4 supplemented with 0.2% crystal lysine were significantly lower than that of other 3 groups on day 68 (P<0.05). The results show that supplementation of crystal lysine could improve growth performance, and feed utilization in soft-shelled turtle fed MBM and fish meal based diets.3. A 160-day experiment was conducted to investigate the effect of different quality of red fish meal (RFM) and with or without supplementation of 300mg/kg vitamin E (VE) on the growth performance, physiological and biochemical indexes of soft-shelled turtle (initial mean body weight: 65.66±1.63g). Four experimental diets including: Diet 1 (white fish meal WFM, control), Diet 2 (high quality RFM replacing 38% WFM), Diet 3 (poor quality RFM replacing 38% WFM), Diet 4 (poor quality RFM replacing 38% WFM and supplemented with 300 mg/kg VE). The results showed that the highest survival rate (SR) was observed in turtle fed Diet 1 and Diet 2, while the lowest was found in turtle fed Diet 3 (P<0.05). The best performance in the FI and SGR was found in turtle fed Diet 1, significantly higher than the other treatments on day 160 (P<0.05), but SGR, FER, PER of turtle fed Diet 1 not significantly higher than that of fed Diet 2 on day 80 (P>0.05). The worst performance in the FI, SGR, FER, PER was found in turtle fed Diet 3, which was significantly lower than that of fed Diet 1 and Diet 2 (P<0.05). SGR, FER, PER of turtle fed Diet 4 with VE supplementation were significant higher than that of fed Diet 3 without VE supplementation (P>0.05). There were no significant differences in HSI, IPI, VSI, and BC in turtle fed Diet 1 and 2 (P>0.05), however, HSI and VSI in turtle fed Diet 3 were significant higher than that of turtle fed Diet 1 on day 160 (P<0.05). Nevertheless, the VSI in turtle fed Diet 4 with VE supplementation was significantly lower than that of turtle fed Diet 3 without VE supplementation on day 160 (P<0.05). The different quality of RFM did not significantly affect the activities of pepsin, trypsin and amylase in pancreas, and amylase in intestine of turtle among 4 groups (P>0.05). The activities of GOT,γ-glutamyl transpeptidase (γ-GT) in turtle fed Diet 2 were significantly higher than that of fed Diet 1 on day 80 (P<0.05), but significantly lower than that of turtle fed Diet 3 and Diet 4 (P<0.05). The activities of GOT, glutathione peroxidase (GSH-Px), T-SOD, and the content of UA in serum of turtle fed Diet 3 were significantly higer than that of turtle fed Diet 1, and the activities of LSZ and AKP in turtle fed Diet 3 were significantly lower that of turtle fed Diet 1 and Diet 2 on day 160 (P<0.05). Nevertheless, the activities of AKP in turtle fed Diet 4 with VE supplementation was significantly lower than that of turtle fed Diet 3 without VE supplementation on day 160 (P<0.05). It is concluded that different quality of RFM replacing WFM affected the growth performance and immunity in soft-shelled turtle on day 160, the high quality RFM could replace 38% WFM within 80 days; the poor quality RFM 38% replacing WFM supplemented with 300 mg/kg VE fed Chinese soft-shelled turtle have higher growth performance and survival rate than that of fed without VE supplementation.4. A 76-day feeding experiment was conducted to investigate the effect of different fish meal and production process on the growth performance, feed conversion ratio and whole-body composition of soft-shelled turtle (initial mean body weight: 381.46±10.30g). Three isonitrogenous and isoenergetic experimental diets were formulated to contain. Diet 1 (powder diet, 56% WFM + 10%RFM), Diet 2 (extruded diet, 56%WFM + 10%RFM), Diet 3 (extruded diet, 16%WFM + 50%RFM). The results showed that there was no significant difference in FI among 3 groups (P>0.05). FER and PER in turtle fed Diet 2 was significantly higher than that of turtle fed Diet 1 and Diet 3 (P<0.05). There were no significant differences in SGR and FER between Diet 3 and Diet 1, but the PER of turtle fed Diet 1 was significantly higher than that of fed Diet 3 (P<0.05). Nevertheless, the whole-body content of moisture, crude protein, crude lipid and ash, HSI, and BC in turtle were not significantly affected by dietary treatments (P>0.05). The results indicated that extrusion could improve feed utilization, and the RFM replacing with 71% WFM could be used in extruded diets of grown soft-shelled turtle.5. A 100-day feeding experiment was conducted to investigate the effects of yeast culture (YC, DVAQUA) on growth performance and immunity of soft-shelled turtle (initial mean body weight: 121.07±3.07g). Three isonitrogenous and isoenergetic experimental diets (Diet 1, Diet 2, and Diet 3) were formulated with supplementation of graded levels of YC (0, 0.075%, and 0.15%). The results showed that there were no significantly differences in FI, SGR among 3 groups (P>0.05), but SR of turtle fed Diet 3 was significant higher than Diet 1 group (P<0.05). The activities of LSZ, acid phosphatase (ACP) and the content of complement C3 in turtle fed Diet 3 with 0.150% DVAQUA supplementation were significantly higher than Diet 1 group (P<0.05). In addition, after 30 d artificial added stress reaction experiment, cumulative incidence of disease rate in turtle was significantly decreased with the increase of DVAQUA in diets, while SR of turtle was significantly increased (P<0.05). It is concluded that supplementation of DVAQUA to the diet did not significantly affect the growth performance, but 0.150% DVAQUA level could increase immunity and SR of Chinese soft-shelled turtle.
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