Effects of dietary black soldier fly larvae on performance of broilers mediated or not through changes in microbiota

Abstract

A total of 40 one-day-old male Ross chickens were individually fed a commercial feed with either 0 or 8% of de-frosted larvae of black soldier flies (BSF; wet weight). We recorded daily body weights and feed intake of each chicken for a period of 13 days. After euthanasia, we visually scored masses of abdominal fat tissues, and lesions and quantity of fat in intestinal villi. We measured percentages of tibia ash. Larvae, their growing substrate, and the caecal content of the chickens were collected for further microbiota characterisation. Statistical analyses included analyses of variance, chi-square tests, partial least square regressions and mediation analyses. We did not observe any significant differences in the overall means of zootechnical measures and in the relative abundances of most bacterial families in the caeca of birds fed insect larvae or not. On the other hand, relative abundances of both Rhodobacteraceae and Bacillaceae were lowest in birds receiving larvae. We identified new, and confirmed previously published, modifications in the chicken phenotypes as gut microbiota composition varied. For example, we observed indirect changes in the average daily gain, feed conversion ratio, tibia ash percentage and abdominal fat score in relation with the introduction of larvae in the diet, changes mediated by the influence of the diet on the relative abundance of Bacillaceae. We suggested presence of Dysgonomonas in larvae and in the growing substrate (after the passage of BSF larvae) may be one of the mechanisms used by the larvae to transform manure because these bacteria have a fermentative metabolism producing acids and no gas.