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Dietary Supplementation of Bacillus subtilis Improves In Vitro Rumen Microbial Fermentation When Using Macadamia
Hu Liu1, Xiaoyan Deng1,2, Anmiao Chen1,2
1Zhanjiang Experimental Station, Chinese Academy of Tropical Agricultural Sciences, Zhanjiang 524013, China.
Microorganisms
|July 28, 2026
Summary
Supplementing Macadamia integrifolia husk (MIH) with Bacillus subtilis (BS) improves its digestibility and fermentation in goats. This study demonstrates BS enhances nutrient utilization, making MIH a potential alternative feed for ruminants.
Area of Science:
- Ruminant nutrition
- Animal microbiology
- Feed science
Background:
- Macadamia integrifolia husk (MIH) is an underutilized byproduct.
- Limited data exists on MIH's rumen fermentation and bacterial impacts.
- Bacillus subtilis (BS) is a potential feed additive for ruminants.
Purpose of the Study:
- To evaluate the effects of Bacillus subtilis (BS) on the in vitro rumen fermentation of Macadamia integrifolia husk (MIH).
- To assess the impact of BS supplementation on the rumen bacterial community structure in goats fed MIH.
Main Methods:
- In vitro fermentation using rumen fluid from goats.
- Four treatment groups: control (0 g/kg BS) and three BS inclusion levels (1.5, 3.0, 4.5 g/kg).
- Analysis of gas production, in vitro dry matter degradability (IVDMD), neutral detergent fiber (NDF), acid detergent fiber (ADF), volatile fatty acids (VFAs), and bacterial community composition.
Main Results:
- BS supplementation significantly improved gas production, IVDMD, NDFD, and ADFD at 48 hours.
- Ammonia-N, microbial protein, and VFA concentrations were quadratically affected by BS levels.
- Bacterial community analysis revealed significant shifts in the relative abundances of major phyla (Bacteroidota, Bacillota, Synergistota) and genera (e.g., Prevotella, Hoyesella) with BS supplementation.
Conclusions:
- Bacillus subtilis supplementation enhances the in vitro utilization of Macadamia integrifolia husk in goats.
- Improved feed utilization is linked to alterations in the rumen bacterial community structure.
- BS inclusion levels of 1.5 to 3.0 g/kg show promise for improving MIH as a ruminant feed.
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