| Silkworm pupae is a kind of high protein, high fat,high-quality feed raw materials, with high yield, wide sources, rich in unsaturated fatty acid. But also because of its high content of unsaturated fatty acid, in the actual application process is also sensitive to oxidation. Therefore, Tilapia(Oreochromis niloticus) was chosed as an experiment object for the following two aspects of research:1. Suitable replacement ratio of fresh silkworm pupae with fish meal Five isonitorgenous(crude protein 32%) and isolipidic(ether extract 5.5%) diets(based diet contained 8% fish meal) were formulated by replacing 0%(control),25%, 50%, 75% and 100% fish meal with silkworm pupae on the basis of a basal diet which contained 8% fish meal, they were named as SP0, SP25, SP50, SP75 and SP100 respectively. Each diet was fed to triplicate groups of 20 juvenile Tilapia with an initial weight of 44.40 ±0.41 g for 56 d. The results showed that:(1) Compared with SP0 group, weight gain rate(WGR) and specific growth rate(SGR) in SP50 group were increased by 16.18% and 8.37%(P<0.05), respectively, and feed conversion ratio(FCR) was decreased by 3.94%(P<0.05);no difference was found in viscerosomatic index among all groups(P>0.05). Protein efficiency ratio(PER) and protein retention rate(PRR) firstly increased and then decresed with increase of SP substitution proportion, and reached maximum in SP50 group, in which which were increased by 6.48% and 13.83% compared with SP0 group(P < 0.05), respectively; while lipid retention rate(LRR) followed contrary pattern as that of PER and PRR(P<0.05).(2) Replacement of FM with SP significantly decreased serum total cholesterol,triglyceride and glucose concents(P<0.05);serum lysozyme activity was the highest when the SP substitution proportion was 50%,but it significantly declined when the silkworm pupae substitution proporation was over 75%, concomitantly, it significantly increased serum serum aspartate transaminase and alanine transaminase activities(P<0.05).(3) Hepatic total antioxidant enzymes(T-AOC) went up first and then down as the increasement of dietary SP, and reached maximum in SP75 group, significantly higher than other group(P<0.05), except SP50 group(P>0.05); While hepatic malondildehyde(MDA) had opposite change with T-AOC, and achieved the minimum in SP50 group.(4) Intestinal protease and lipase activities were no significant differences when SP alternative proportion among 0 and 75%(P>0.05),intestinal Na+-K+-ATP activity first increased and then decreased, and had the maximum value in SP50 group, and SP100 group intestinal Na+-K+-ATP activity decreased 19.01% compared with control group(P<0.05).(5) Crude protein(CP), ash, total amino acids, essential amino acids contents of muscle of Tilapia decreased significantly with dietary SP increasing(P<0.05), while muscle ether extract(EE) content had no significant difference(P>0.05);Total amino acids and essential amino acids contents of muscle in SP 100 group decreased by 3.99% and 3.46% compared with SP0 group. As dietary SP levels increased,fatty acid C18:3n-3 and C20:5n-3 in muscle of Tilapia increased gradually and C18:2n-6 declined. Compared with SP0 group, C18:3n-3, C20:5n-3 contents in muscle of SP100 group improved 105.33% and 132.72% respectively. In conclusion, replacement of 50% fish meal with silkworm pupae can improve growth performance, protein retention rate and serum lysozyome activity of Tilapia, promots the absorption of nutrients, and has the functions of decreasing serum lipid, blood glucose and liver lipid. The replacement ratio of silkworm pupae in feed has better not more than 75%.2. Effects of oxidized silkworm pupae on growth inhibition of Tilapia and gut, liver and muscle tissue structure Three isonitorgenous(crude protein 32%) and isolipidic(ether extract 5.5%) diets by containing 4% fresh silkworm pupae and two degrees of oxidized silkworm pupae(aicd value 5.26, acid value 9.18) were formulated, they were named as FSP, Ox5.26, Ox9.18, respectively. Each diet was fed to triplicate groups of 20 juvenile Tilapia with an initial weight of 44.22 ±0.54 g for 56 d to investigated effects oxidized silkworm pupae on growth performance, foregut, liver histology and function of Tilapia.The results showed that:(1) Compared with FSP, fish fed oxidized silkworm pupae significantly decreased weight gain rate(WGR), specific growth rate and condition factor(P<0.05),but there were no significant differences were found in hepatosomatic index and viscerosomatic index(P<0.05).(2) Oxidized silkworm pupae significantly improved whole fish ether extract and lipid retention rate(P<0.05); Ox5.26 and Ox9.18 group protein retention rate and protein efficiency ratio significantly decreased compared with FSP group(P<0.05).(3)Villus density and muscular thickness of forgut were no significant difference among differernt group(P>0.05), but villus length in Ox5.26 and Ox9.18 was significantly decreased compared to FSP, and a slight decrease also observed in microvilli density.(4) Oxidized silkworm pupae significantly decreased intestinal Na+-K+-ATP activity compared to fresh silkworm pupae group(P<0.05),no significant difference was obersved in pepsin and intestinal protease activity among Ox5.26 and control group(P>0.05), but pepsin and intestinal protease activity of Ox9.18 significantly decresed compared to FSP group(P<0.05).(5) Histological examinations indicated that liver cell cord disappear, nuclear migration, and mitochondrial swelling of Tilapia in Ox5.26 and Ox9.18.(6) Hepatic total antioxidant enzymes and superoxide dismutase activity had no siginificant differences(P>0.05), but malondialdehyde(MDA) of Tilapia in Ox5.26 and Ox9.18 siginificantly higher than FSP(P<0.05).(7) Muscular histological examinations(HE staining) indicated that Ox9.18 appeared muscle cell atrophy.(8) Oxidized silkworm pupae signigicantly decreased muscule crude protein and ash content compared with FSP, ∑SFA and ∑MUFA contents in muscle of Ox9.18 group improved 3.75% and 15.70%, respectly, ∑n-3PUFA decreased by 37.28%. In conclusion: Oxidized silkworm pupae can inhibit growth, reduce gigestive enzymes and Na+-K+-ATP activity, and change the forgut, liver, muscular histological structure of Tilapia, and signigicantly improved liver MDA contents,with the increasing degree of oxidation, this negative impact is gradually increased.
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