Evaluation of black soldier fly larvae reared on different organic substrates on nutrient digestibility and palatability in cats

This study aimed to evaluate the digestibility and palatability of cat diets by substituting poultry meals (PM) with black soldier fly larvae (BSFL) reared on different organic substrates. The experimental treatments are as follows; CON, a basal diet based on the PM; AF3, 3% PM substituted with BSFL reared on animal-based substrates; AF6, 6% PM substituted with BSFL reared on animal-based substrates; PF3, 3% PM substituted with BSFL reared on plant-based substrates; PF6, 6% PM substituted with BSFL reared on plant-based substrates.<italic> In vitro</italic> and <italic>in vivo </italic>methods were used in this study. The <italic>in vitro</italic> experiment simulated gastric digestion using pepsin and small intestinal digestion using bile and pancreatin, with 6 replicates per diet. The <italic>in vivo</italic> experiment used 30 and 16 mixed-sex cats to assess digestibility and palatability, respectively. Fecal samples were collected over 3 d for nutrient digestibility and palatability was assessed in a 1 d. In the <italic>in vitro</italic> experiment, the AF3 had higher <italic>in vitro</italic> ileal digestibility (IVID) of crude protein (CP) than the CON and PF6, and diets supplemented with BSFL groups had higher IVID of gross energy and ether extract (EE) than the CON. In the <italic>in vivo</italic> experiment, the AF3 showed higher CP digestibility than the CON, and diets supplemented with BSFL groups had higher EE digestibility than the CON. In palatability evaluation, the AF6 had a lower intake ratio than the CON. The 3% substitution of BSFL showed a significantly higher first sniffing bout than the 6% substitution in animal and plant-based substrates. Additionally, except for the CON, the AF3 exhibited a higher first sniffing bout than the other groups. In conclusion, the AF3 improved CP digestibility in both <italic>in vitro</italic> and <italic>in vivo</italic> experiments. Also, the AF3 did not show negative effects on palatability. Therefore, this result indicated that substituting 3% of PM with BSFL reared on animal-based substrate in cat diets was the most efficient alternative.