Abstract
This study was conducted to substitute different ratios and substrates of black soldier fly larvae (Hermetia illucens larvae; HIL) to investigate the effect on cats. A total of 30 mixed-sex domestic cats (Felis domestica) with an initial body weight of 5.06 ± 0.89 kg were used in this experiment, which used an incomplete 5 × 5 replicated Latin square design. The experimental period was 10 d, with 7 d of diet adaptation followed by 3 d of dietary treatment. The dietary treatments were provided: 1) CON (basal diet), 2) HA3 (replacing 3% of the poultry meal (PM) in the basal diet with HIL fed on animal-based substrate), 3) HA6 (replacing 6% of the PM in the basal diet with HIL fed on animal-based substrate), 4) HP3 (replacing 3% of the PM in the basal diet with HIL fed on plant-based substrate) 5) HP6 (replacing 6% of the PM in the basal diet with HIL fed on plant-based substrate). The HA3 group showed significantly higher (P < 0.05) crude protein (CP) digestibility than the CON group. The groups replaced by HIL had significantly higher (P < 0.05) ether extract (EE) digestibility than the CON group. The Leu, Trp, Ser, and Asp digestibility were significantly increased (P < 0.05) in the groups replaced by HIL compared to the CON group. The HP6 group showed distinct (P < 0.05) unweighted UniFrac distances from all other groups and weighted UniFrac distances from the CON and HP3 groups. In addition, the CON group exhibited significant differences (P < 0.05) in weighted UniFrac distances compared to all treatment groups. In the abundance of microbiota, the HP6 group showed increased (P < 0.05) abundance of Bacteroidota, Sutterellaceae, Prevotellaceae, Muribaculaceae, and Akkermansia, while the CON exhibited higher (P < 0.05) levels of Firmicutes, Lactobacillaceae, and Lactobacillus. In conclusion, substituting PM with HIL in cat diets improved nutrient digestibility and beneficially modulated the gut microbiome. Replacing 3% of animal-based protein with HIL showed potential as a viable protein alternative in cat diets.