Impact of dietary supplementation of black soldier fly larvae (Hermetia illucens L.) on nutrient digestibility, serum antioxidants, ruminal volatile fatty acids, and abundance of microbial dominant flora in goats

This experiment aimed to investigate the potential impact of supplementing different levels of black soldier fly (BSF) on growth performance, serum antioxidants, and ruminal microbiota of goats. Twenty-four native Anglo-Thai male goats (18.43 ± 0.76 kg) were distributed across 4 dietary treatments with 6 repetitions in each group. The control treatment (BSF0) did not include BSF, the other treatments (BSF5, BSF10, and BSF15) contained 5%, 10%, and 15% of BSF, respectively. Black soldier fly supplementation did not affect (<i>P</i> > 0.05) growth performance. With increasing supplementation levels, the digestibility of dry matter (DM) decreased linearly and quadratically (<i>P</i> < 0.05), while organic matter (OM) decreased linearly and quadratically (<i>P</i> < 0.05). The apparent digestibility of crude protein (CP) decreased linearly (<i>P</i> < 0.001), and neutral detergent fiber (NDF) and acid detergent fiber (ADF) decreased linearly and quadratically (<i>P</i> < 0.05). Serum malondialdehyde concentration showed a linear (<i>P</i> < 0.05) response at 0 h, while superoxide dismutase activity and 2,2-diphenyl-1-trinitrophenylhydrazine (DPPH) concentration exhibited linear responses (<i>P</i> < 0.05) at 4 h. Black soldier fly supplementation did not affect (<i>P</i> > 0.05) ruminal pH. In the BSF15 group, ruminal ammonia nitrogen (NH₃-N) concentration decreased quadratically (<i>P</i> < 0.001) at 0 h, and linearly (<i>P</i> < 0.05) at 2 and 4 h. Acetic acid decreased linearly (<i>P</i> < 0.05) at 2 and 4 h, propionic acid decreased linearly (<i>P</i> = 0.029) at 4 h. However, the concentration of butyric acid significantly increased (<i>P</i> < 0.05). Total volatile fatty acids (VFAs) were highest (<i>P</i> < 0.05) in the BSF5 group, equal in BSF0 and BSF10, and lowest (<i>P</i> < 0.05) in the BSF15 group. The supplementation of BSF did not affect (<i>P</i> > 0.05) Chao 1, Shannon, and Simpson. The most abundant phylum were Bacillota, Bacteroidota, and Candidatus Saccharibacteria, the most abundant genera were <i>Xylanibacter</i>, <i>Saccharibacteria</i>, <i>Butyrivibrio,</i> and <i>Ruminococcus</i>, and there was no statistical difference (<i>P</i> > 0.05) among the 4 treatments. In summary, supplementing with BSF did not affect the growth performance and ruminal microbiota of goats. It was noteworthy that the supplementation of BSF at 5% and 10% were beneficial, as they increased antioxidant levels and the concentration of short-chain fatty acids. In contrast, the supplementation of 15% BSF results in decreased digestibility, antioxidant levels, and VFA parameters. Therefore, we recommend limiting the addition of BSF in goat diets to no more than 10%.