Abstract:

[Objective] This study was conducted to assess the effects of dietary sodium chloride level on the growth performance as well as the microbial community diversity in the larval intestine and feeding substrate of black soldier fly （Hermetia illucens L.）. [Method] The black soldier flies fed with the diet without extra addition of sodium chloride was set as control group, and the ones fed with the diets added with 0.7% and 2.0% sodium chloride were set as experimental groups. The experimental period was from 6-day-old larvae to adult laying eggs. The indexes associated with growth performance and growth cycle of the flies fed with the diets containing different levels of sodium chloride were statistically analyzed, and 16S rDNA sequence analysis technique was used to characterize the changes of microbial communities in the larval intestine and feeding substrate. [Result] ①The body length, body weight （except for 9-day-old）, feed conversion rate, feed utilization rate, feed to weight gain ratio, larval fresh mass and total fresh mass gain, protein content, fat content, survival rate, pupation rate, eclosion rate, eclosion time, and oviposition time of the 0.7% sodium chloride addition group were not significantly （P>0.05） different from those of the control group. ②Compared with the control group, in the 2.0% sodium chloride addition group, both the body length and weight of the 9- to 18-day-old larvae were significantly （P<0.05） decreased; the feed weight loss rate and apparent digestibility were significantly （P<0.05） reduced; the feed conversion rate was significantly （P<0.05） increased; there was no significant （P>0.05） changes in feed utilization rate and feed to weight gain ratio; the fat content was significantly （P<0.05） elevated; the larval fresh mass, total fresh mass gain, and protein content had no significant （P>0.05） changes; the survival rate, pupation rate, and eclosion rate were significantly （P<0.05） decreased, and the eclosion time and oviposition time extended by 2 d （P<0.05）. ③In 0.7% sodium chloride addition group, at phylum level, the relative abundance of Proteobacteria in the larval intestine was decreased from 92.33% to 82.53%, and that of Firmicutes was increased from 6.55% to 14.88% compared with the control group; the relative abundance of Firmicutes in the feeding substrate was increased from 23.42% to 28.07%, while that of Bacteroidetes was decreased from 41.57% to 37.92%. At genus level, the relative abundance of Providencia in larval intestine was decreased from 79.90% to 76.92%, and that of Morganella and Enterococcus was decreased from 8.27% to 5.34% and increased from 4.98% to 6.62%, respectively; the relative abundance of Alcaligenes in the feeding substrate was increased from 2.73% to 12.10%, and that of Pseudomonadaceae_Pseudomonas was decreased from 3.59% to 1.46%. ④In 2.0% sodium chloride addition group, at phylum level, the relative abundance of Proteobacteria in the larval intestine was decreased from 92.33% to 59.13%, and that of Firmicutes was increased from 6.55% to 34.69% compared with the control group; the relative abundance of Bacteroidetes in the feeding substrate changed greatly, decreasing from 41.57% to 11.11%. At genus level, the relative abundance of Providencia in the larval intestine was decreased from 79.90% to 29.36%, and that of Morganella was increased from 8.27% to 27.23%; the relative abundance of Corynebacterium in the feeding substrate changed greatly, increasing from 0.01% to 6.90%. [Conclusion] Dietary addition of 0.7% sodium chloride had no affects on the growth performance of black soldier fly. While the addition of 2.0% sodium chloride in diet inhibited the larval growth and greatly affected the microbial communities in larval intestine and feeding substrate.

Key words: black soldier fly （Hermetia illucens L.）, growth performance, sodium chloride, microbial community