Effects of dietary housefly larvae (Musca domestica) on the growth performance, immunity and intestinal microbiota of Chinese soft-shelled turtle (Pelodiscus sinensis)

To determine the impacts of housefly larvae (Musca domestica) on the Chinese soft-shelled turtle (Pelodiscus sinensis), sixty-three turtles with an initial body weight of 65.33 +/- 7.35 g were randomly distributed into nine 120-L tanks to three diet groups (three replicates each group), each group containing 21 turtles: basal diet every day (PBD), housefly larvae fed once weekly (PFL7, six-day basal diet and one-day housefly larvae), housefly larvae fed every third day (PFL3, two-day basal diet and one-day housefly larvae). We investigated their growth performance, immunity and intestinal microbiota. We found that the weight gain and specific growth rate were significantly higher in the larvae-supplemented groups than in the PBD group (p < 0.05), whereas the lipid accumulation in the liver was lower. Expression levels of IgD and IgM (immune genes) were significantly increased in the gut samples of PFL7 group (p < 0.05). Meanwhile, the larvae supplementation influenced the composition and diversity of gut microbiota of turtles; the abundance of Bacillus and Bacteroides increased significantly. PICRUSt functional prediction indicated that both larvae-supplemented groups exhibited upregulation of genes involved in lipid metabolism and carbohydrate metabolism, and downregulation of genes associated with infectious and cardiovascular diseases. In conclusion, dietary supplementation of housefly larvae had positive effects on the growth, liver health, immunity and intestinal microbiota of P. sinensis, suggesting that housefly larvae are a promising dietary supplement for the Chinese soft-shelled turtle.