| The black soldier fly, Hermetia illucens L, is a saprophagy beneficial insect. Originated from America, now it spreads all over the world where generally between 40°north and south of the equator. After starting the study in China recently, it now can be found in Guangxi, Guangdong, Yunnan, Taiwan, Hunan and Hubei etc.The black soldier fly larva can handle livestock manure and food waste, and black soldier fly larva contains high level of protein and fats, which makes it a good candidate for high quality animal protein source and energy feed.It is of great importance in treating environmental and resources issues through black soldier flies.This study was dedicated on the research of black soldier flies' digestive system. This investigation included that four-day-old black soldier fly larvae were fed on three diets(pig feed, food waste and swine manure, respectively) with different treatments(fermented vs. control). The larval survival rate, development time, average weight gain, the feed conversion ratio(FCR), the conversion efficiency of digested feed(ECD) and the eclosion rate were tested to determine the effect of different treatments, firstly.Secondly, the optimal conditions of using the Lowry method and the colorimetric method on larval protease and amylase activities testes were determined. Furthermore, the influence of sterilization of feed(pig feed and food waste) and larvae on the larval protease and amylase activities was tested with methods mentioned under its optimal condition. Last but not least, the 16 S r RNA analysis technology was used to test the effect of sterilization on the larval intestinal flora. Research results were as follows:(1) Compared to the control feeds, the fermented pig feed increased the survival rate of larvae 5.34%(p<0.05), fermented food waste no effect on the survival rate of larvae(p>0.05), pre-fermented swine manure will reduce the survival rate of larvae(p<0.05). Fermented food waste and swine manure increased larvae average weight gain by 0.0190 g, 0.0813 g(p<0.05). Fermented pig feed, food, waste,swine manure could reduce FCR by 0.426,0.272,0.163( p<0.05). Fermented pig feed and food waste could significantly increase ECD by 0.066,0.116(p<0.05), fermented manure had no effect on ECD(p>0.05).Fermented pig feed, food waste, swine manure could improve Blackwater fly the eclosion rate by 8.58%, 21.03%, 15.43%(p<0.05).(2)Taking 1.0 m L of the crude enzyme solution into 1.0 m L casein solution at a concentration of 2%.With the conditions of the concentration of disodium hydrogen phosphate-sodium dihydrogen phosphate buffer(p H 7.0) was 0.05 mol/L and the reaction temperature is 40 ?,the reaction taked 5 min. Then adding 2.0 m L of trichloroacetic acid(0.4 mol/L) to terminate the reaction,and using Folin-phenol assay to get OD values at 680 nm with a UV spectrophotometer. This was the best method to Blackwater fly larvae protease activity determination. In this study the larval protease were tested as 193.82 U/m L.(3)Taking 0.5 m L of the crude enzyme solution into 0.1 m L of starch solution at a concentration of 3%.With the conditions of the concentration of disodium hydrogen phosphate-sodium dihydrogen phosphate buffer(p H 7.0) was 0.05 mol/L and the reaction temperature is 40 ?,the reaction taked 8 min. Then using Iodine-starch law to get the OD values at 660 nm with a UV spectrophotometer. This was the best method to Blackwater fly larvae amylase activity determination. In this study the larval amylase activities were tested as 591.25 U/m L.(4)The larval protease activity can be influenced by the type of feed(p<0.05). We found that larvae fed on pig feed had higher protease activity while sterilization did not alter the results(p>0.05). However, amylase activity was related to both the type of feed and larval sterilization process(p<0.05). Larvae on pig feed and larvae without sterilization had higher amylase activity.(5)Intestinal flora of Blackwater fly larvae was influenced by the sterilization on the feed, of which larvae fed on the feed without sterilization had more species of intestinal flora.Among the SF-m-1, SF-m2, SF-m-3, SF-m-4, SF-p-1, SF-p-4 six-treated samples,Morganella was the main bacteria in the Blackwater fly intestinal flora, the proportion was 92.05%, 90.65%, 66.68%, 97.31%, 94.04%, 27.91%, respectively. Trabulsiella in sample SF-p-2 and SF-p-3 occupied larger proportion, respectively, 40.08%, 25.83%.Conclusion: The present study showed that fermented feed can significantly increase black soldier fly larval survival rate, FCR, ECD and eclosion rate respectively. Sterilized feed would not affect the activities of digestive enzymes, and disinfected larvae only reduced amylase activity. Feed sterilization would reduce the number of species Blackwater fly larvae intestinal flora. |
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