Expert Interview | Applications and Prospects of Bacillus velezensis Postbiotics in Animal Health

INTERVIEWEE LEE TZAI-TAI | COMPILED BY CHIANG YI-HSUAN

Prof. Lee Tzai-Tai, Ph.D. Distinguished Professor, 

Department of Animal Science, National Chung Hsing University

[ Abstract ]

Postbiotics have emerged as a frontier area of probiotic research, attracting considerable attention from the livestock and pet food industries in recent years. Bacillus velezensis has been identified as a promising candidate for postbiotic applications, owing to its exceptional environmental tolerance, prolific extracellular enzyme secretion, and multifaceted intestinal protective mechanisms. Drawing on recent field trial data and mechanistic research, this article examines the scientific basis of B. velezensis postbiotics, their efficacy across multiple livestock species, and their potential role in antibiotic-free farming transitions and the growing companion animal health market.

The global livestock industry is undergoing a profound transformation. The European Union's 2006 ban on growth-promoting antibiotics set a precedent that has since been followed by countries worldwide, placing antibiotic residues and antimicrobial resistance firmly at the center of animal production concerns. Taiwan's livestock sector faces this same reality: with characteristically high stocking densities and a hot, humid, and climatically variable environment, maintaining intestinal health and productive performance while reducing dependence on antimicrobials has become one of the most pressing challenges for both industry and academia. Against this backdrop, probiotics rose rapidly as a practical alternative, evolving from straightforward antibiotic substitution toward the more sophisticated paradigm of precision nutrition. The emergence of postbiotics—a concept that builds on and extends probiotic science—now offers this field a more stable and quantifiable scientific foundation.

Among the many probiotic genera, Bacillus spp. have established themselves as the preferred choice for livestock and feed applications, owing to their distinctive biological properties. Members of this genus form highly resilient endospores capable of surviving the high-temperature pelleting process central to commercial feed manufacturing, ensuring delivery of viable organisms to the animal. These endospores likewise retain their integrity under the acidic conditions of the stomach, the bile-salt-rich environment of the small intestine, and the variable pH encountered throughout the gastrointestinal tract—overcoming the fundamental limitation of conventional probiotics, which suffer substantial viable cell count losses during both processing and digestion. Bacillus velezensis is particularly notable for its prolific secretion of extracellular enzymes during fermentation—including proteases, amylases, and cellulases—conferring high degradation efficiency across a broad range of feed ingredients and agricultural by-products, and providing an abundant substrate base for postbiotic preparation.

The concept of postbiotics represents a departure from the traditional paradigm of evaluating probiotic efficacy solely on the basis of viable cell counts. As defined by the International Scientific Association for Probiotics and Prebiotics (ISAPP) in 2021, postbiotics are "preparations of inanimate microorganisms and/or their components that confer a health benefit on the host." Their active constituents are more precisely quantifiable and maintain greater process stability than live-cell preparations, being unaffected by temperature fluctuations, pH variability, or microbial culture aging—providing a more reliable basis for industrial quality control. The functional components of B. velezensis postbiotics encompass four principal categories: bioactive enzymes that facilitate the hydrolysis of macromolecular feed substrates; antioxidant peptides capable of scavenging reactive oxygen species and alleviating systemic oxidative stress; antimicrobial substances—most notably lipopeptides—that directly suppress the proliferation of pathogenic microorganisms; and cell wall components that stimulate intestinal epithelial cells to produce immunomodulatory cytokines, thereby activating innate immune responses. Together, these constituents form a comprehensive and synergistic intestinal protective system.

Intestinal health is fundamentally anchored in the integrity of the gut barrier. B. velezensis postbiotics upregulate the expression of tight junction proteins—including claudin, occludin, and zonula occludens-1 (ZO-1)—in intestinal epithelial cells, reinforcing paracellular sealing and effectively preventing the translocation of pathogens and toxins into systemic circulation, thereby reducing the risk of systemic inflammatory responses. Beyond barrier reinforcement, once colonizing the intestine, this strain continuously secretes cellulase complexes that degrade the non-starch polysaccharides (NSPs) of plant cell walls present in feed ingredients; the oligosaccharide products of this degradation in turn promote the proliferation of beneficial microorganisms such as lactic acid bacteria (LAB), establishing a positive feedback loop within the gut microbiota. The net result is the maximal utilization of dietary nutrients by the animal—the central objective of precision nutrition.

Systematic field trials have validated the broad-spectrum benefits of B. velezensis postbiotics across multiple livestock species, frequently yielding findings that exceed initial expectations. In laying hen trials, in addition to significant improvements in established gut health parameters, the research team unexpectedly observed a reduction in egg off-flavor—particularly the elimination of a characteristic fishy note—a phenomenon tentatively attributed to optimization of fatty acid metabolic pathways following gut microbiota remodeling. Preliminary industry testing has reported encouraging outcomes, and mechanistic studies are ongoing. The trials also documented a marked reduction in fecal stickiness, indicative of enhanced intestinal fermentation efficiency and carrying practical benefits for farm environmental management.

"The emergence of postbiotics provides a scientifically robust and more readily quantifiable foundation for advancing this goal."

Findings from swine trials were equally noteworthy. Following postbiotic supplementation, barn odor scores declined substantially. Mechanistic analysis indicates that this effect operates through two synergistic pathways: first, the antimicrobial activity of the postbiotic preparation effectively suppresses environmental putrefactive bacteria and coliform populations, reducing aberrant fermentation and associated gas production from organic substrates; second, the systemic improvement in intestinal health directly attenuates enteric release of ammonia (NH3) and hydrogen sulfide (H2S). The combined action of these two mechanisms produces a fundamental improvement in barn air quality. Taken together, these field observations affirm that the benefits of postbiotics are not confined to discrete performance metrics, but instead exert broad and far-reaching effects on overall animal physiology through the systematic enhancement of gut health.

As companion animal ownership rates continue to rise across Taiwan and pet owners increasingly seek premium health solutions, the market for canine and feline health products is expanding rapidly. B. velezensis postbiotics offer particular suitability for companion animal applications. Cats, as obligate carnivores, have exceptionally high demands for protein digestibility; the proteases present in the postbiotic preparation effectively assist protein hydrolysis, improve amino acid bioavailability, and concurrently reduce the malodorous compounds generated by fermentation of undigested protein in the hindgut, thereby improving fecal quality. For juvenile dogs and cats, whose intestinal enzyme systems are not yet fully developed, postbiotic supplementation provides immunomodulatory support that helps establish a more robust intestinal barrier and protective immune response during this critical developmental window, laying a foundation for long-term health. Extending the healthy lifespan of companion animals represents the most compelling value proposition in the pet health market.

Broader adoption of postbiotics in commercial livestock production will require the continued accumulation of systematic, multi-species trial data and the refinement of precise dosing protocols, enabling producers to apply these preparations with greater confidence and accuracy. Taiwan's substantial research foundation in antibiotic-free animal production provides a solid scientific basis and favorable industry conditions for the practical deployment of B. velezensis postbiotics at scale. As national policy progressively restricts the use of growth-promoting antibiotics, fully validated postbiotic products of this kind are well-positioned to serve as an indispensable tool for safeguarding animal health and sustaining productive performance—and a cornerstone of Taiwan's livestock industry's transition toward a more sustainable future.

• Postbiotic Mechanism of Action: Modulates gut microbiota composition, suppresses the proliferation of pathogenic bacteria, and maintains intestinal ecological balance.
• Intestinal Barrier Reinforcement: Upregulates tight junction protein expression to strengthen the intestinal mucosal barrier and reduce the risk of pathogen invasion.
• Research & Application: Efficacy validated across multiple field trials, with consistent and stable benefits demonstrated across diverse livestock species and production environments.