Bacillus microorganisms are gram-positive, spore-forming bacteria. They are known for their resilience and adaptability. These qualities make some Bacillus species well suited for inclusion in direct-fed microbial (DFM) feed products to support improved rumen function in high-performing cattle diets. This article will highlight the key species and discusses their potential.

DFM products containing Bacillus species represent a promising strategy for enhancing ruminant health and performance. These bacteria thrive in a range of environments and can form highly resistant endospores, allowing them to withstand harsh conditions such as heat, pH extremes and dehydration. These valuable qualities make Bacillus species well suited for inclusion in ruminant diets as they have strong survivability through the feed processes and digestion.

Bacillus species can have various modes of actions, for example, enzymatic activity, antimicrobial effects and immunomodulation, etc., and as such, support digestive function and overall health (see Table 1 for summary of benefits).

By harnessing the capabilities of Bacillus species, DFM products enable ruminant producers to enhance feed efficiency and address the increasing demand for high-quality livestock products.

Three important Bacillus species show significant potential in this respect:

1. Bacillus pumilus plays a crucial role in the development of effective DFM formulations for ruminants. It produces extracellular enzymes, such as proteases, amylases and cellulases, which help break down complex feed components, improving nutrient digestion and absorption. Additionally, B. pumilus secretes bioactive metabolites that influence gut microbiota composition, fostering a balanced microbial ecosystem in the rumen.
2. Bacillus subtilis is widely recognized for its probiotic properties and well-established benefits in animal nutrition. As a spore-forming bacterium, B. subtilis can persist in the gastrointestinal tract, promoting gut health and enhancing immune function. It stimulates mucus production and antimicrobial peptide secretion, strengthening the gut barrier and protecting against pathogen colonization. Furthermore, B. subtilis improves feed conversion efficiency and nutrient utilization, leading to enhanced growth performance in ruminants.
3. Bacillus velezenis is known for its wide-ranging benefits in agriculture and animal nutrition. It produces a variety of antimicrobial compounds, including cyclic lipopeptides and bacteriocins, which inhibit the growth of harmful bacteria in the rumen. Additionally, B. velezenis has plant growth-promoting properties, aiding nutrient absorption and contributing to overall gut health in ruminants.

How can the feed industry harness the potential of Bacillus species?

Formulating a blend of Bacillus pumilus, Bacillus subtilis and Bacillus velezenis in DFM products for cattle provides a synergistic approach to enhancing rumen health and performance. By selecting strains with complementary properties, formulators can address various digestive challenges. However, it's essential to ensure that the chosen strains do not inhibit each other.

In microbial communities, including the gastrointestinal tract of animals, competition for resources and space is common among different bacterial species and strains. While Bacillus strains are known for their beneficial effects, they may also produce antimicrobial compounds – such as antibiotics, bacteriocins and secondary metabolites – that can inhibit each other. These compounds are survival mechanisms, enabling Bacillus strains to outcompete other microbes for nutrients and ecological niches.

Furthermore, antagonistic interactions can arise when strains secrete enzymes that target similar substrates or alter environmental conditions to favor one strain over another. This competition can lead to the inhibition or elimination of more susceptible strains, affecting the overall microbial balance within the rumen. Therefore, while Bacillus species offer significant benefits, the potential for inhibitory interactions highlights the complexity of microbial ecosystems and the importance of careful strain selection to ensure compatibility and effectiveness in probiotic or DFM formulations.

For more information, please contact Bryan Miller, technical business manager for Volac Inc., at bryan.miller@volac.com.

Table 1. Potential benefits of including Bacillus-based DFM products in cattle diets

References:

1. Cortes-Cuevas, A., Bolaños-Aguilar, E. D., de Oca-Jiménez, R. M., Cárdenas-García, A., & Sánchez-Mendoza, M. E. (2020). Bacillus velezensis: A valuable member of the bacillus genus for use in agriculture. Journal of Applied Microbiology, 129(5), 988-1002.
2. Hong, H. A., & Cutting, S. M. (2017). The use of bacterial spore formers as probiotics. FEMS Microbiology Reviews, 29(4), 813-835.
3. Abdel-Salam, M. S., & Tawfeek, M. I. (2018). Probiotic effects of Bacillus subtilis and Bacillus pumilus on growth performance, hematological parameters, and immune response of Nile tilapia (Oreochromis niloticus). Aquaculture Reports, 10, 16-21.
4. Soltan, M. A., Morsy, A. S., El-Zaiat, H. M., & El-Zaiat, M. A. (2019). Impact of Bacillus subtilis DSM 32315 on growth performance, nutrients digestibility, blood components, intestinal histology and growth-related genes expression in broilers. Animal Feed Science and Technology, 247, 207-216.
5. Zhang, X., Zhao, L., Cai, Y., Shi, N., Wang, Y., & Ren, Y. (2020). Bacillus velezensis: A novel probiotic promotes growth performance by modulating the intestinal microbiota in broiler chickens. Animals, 10(2), 321.