Inclusion of Black Soldier Fly Larval Oil in Ruminant Diets Influences Feed Consumption, Nutritional Digestibility, Ruminal Characteristics, and Methane Estimation in Thai‐Indigenous Steers

The objective of this study was to examine the impact of black soldier fly larval oil (BSFO) on feed consumption, nutritional digestibility, ruminal characteristics and methane (CH₄) estimation in Thai-indigenous steers. Four male Thai native steers (Bos indicus) weighing 383 ± 9.0 kg were used in this investigation. The experimental design employed was a 4 × 4 Latin square, involving four cattle assigned to four dietary treatments. These treatments included a basal diet (control group) and a concentrate diet containing varying levels of BSFO at 1%, 2% and 4% DM, respectively. Rice straw intakes, and total and nutritional intakes of organic matter (OM), ether extract (EE), neutral detergent fiber (and) and acid detergent fiber (ADF) decreased significantly and linearly with the amount of BSFO incorporated (p < 0.05). The digestibility of DM and OM changed quadratically (p < 0.05) across different BSFO inclusion doses, with the highest values of 65.6% and 69.0%, respectively. Furthermore, the addition of BSFO improved the EE digestibility (p < 0.05) when compared with the control group. The addition of various BSFO doses did not result in significant changes in ruminal pH, temperature, ammonia-nitrogen (NH₃-N) levels or blood urea-nitrogen (BUN) (p > 0.05). However, the introduction of increasing amounts of BSFO into the diet led to a reduction in protozoal populations (p < 0.01). When rumen fluid was sampled at 0 and 4 h after feeding, the 2% BSFO-treated group had a greater propionic acid level (p < 0.05) than the no-BSFO-fed group. The CH₄ estimate in the rumen of the steers exhibited notable variations among those administered different doses of BSFO (p < 0.05), with a linear decline observed as the oil dose increased. In conclusion, the inclusion of 2% BSFO in diets led to enhanced digestibility and higher propionic acid concentrations, along with reductions in protozoal population and CH₄ emissions.