Fortifying BRD Defense: Harnessing Intestinal Health

By Dr. Sara Trojan

The beef industry has dedicated decades to combating bovine respiratory disease complex (BRD) through advanced vaccines, evolving antibiotic therapies, and improved management strategies. Despite these efforts, mortality rates continue to rise, making BRD a significant challenge impacting profitability and animal welfare. To complement traditional approaches, a more systemic method of BRD management through prevention — particularly at the intestinal level — offers an alternative tactic for disease control.

The Role of the Intestinal Microbiome

Over the past ten years, our understanding of the gastrointestinal microbiome in ruminants has significantly advanced, highlighting its crucial role in animal health and well-being. A robust intestinal microbiome is essential for:¹

• Efficient nutrient digestion and absorption
• Optimal immune function
• Protection against harmful pathogens and toxins

The microbiome acts as a defense mechanism, establishing a physical barrier that safeguards the intestinal tract. It also produces specialized metabolites that support the integrity of intestinal epithelial cells and aid in immunity.¹ These microbial ecosystems are highly dynamic, shaped by factors like microbial exposure at birth, dietary variations, environmental conditions, and management practices.² In cattle, the expansive surface area of the intestinal tract signifies numerous sites susceptible to insult.

Impact of Stress on the Microbiome

Stress can significantly compromise the microbiome, stemming from routine management practices such as:⁴

• Weaning
• Comingling
• Transportation
• Dietary changes
• Environmental challenges

Periods of reduced feed intake, often accompanying changes in routine, can also detrimentally affect the microbiome.⁵ When compromised, the integrity of the intestinal barrier is jeopardized, rendering both the tract and animal susceptible to pathogen invasion and colonization.¹ Loss of microbial balance activates the immune system, leading to an uncontrolled flux of bacteria and nutrients from the intestinal tract to systemic circulation. This results in reduced nutrient absorption and a greater propensity for systemic disease, commonly referred to as “leaky gut”.⁴

Systemic Effects of the Intestinal Microbiome

Beyond localized impacts, the intestinal microbiome influences other organ systems, including the brain, lung, mammary gland, and reproductive tract. In the BRD complex, bacteria and their metabolites can migrate from the intestinal tract to the lung via the bloodstream and lymphatic system.³ A robust intestinal microbial community produces short-chain fatty acids like butyric acid, which strengthens the mucosal epithelium of the lung and supports immune function.³ The development of leaky gut can initiate a systemic immune response, leading to whole-body insulin resistance.⁴ This resistance impairs the ability of immune cells within the respiratory tract to effectively uptake glucose, compromising the overall immune response.

Emerging Alternative Methods

Emerging alternative methods for BRD prevention and management emphasize a systematic approach, including targeted therapies and strategies that bolster immune function and intestinal health at the microbial level. Technologies in the nutraceutical field are rapidly advancing. Given the increasing understanding of the post-ruminal digestive tract's roles in animal health and productivity, there is merit in comprehending the application and science behind these compounds.

The nutraceutical market, operating with minimal regulation, has been heavily exploited in livestock and human health sectors. Skepticism regarding the efficacy of these compounds arises from sometimes-exaggerated claims and responses. Evaluation of nutraceutical compounds should encompass:

• Development of sound research
• Understanding of the mode and site of action
• Impacts on commensal microbial populations
• Compound stability in pelleting and processing conditions
• Liquid flowability and mixing properties
• Gastrointestinal stability
• Interactions with other antimicrobials

Conclusion

The BRD complex will persist in beef and dairy production until market forces significantly propel alternative management practices. The clear association between intestinal health and total animal health underscores the importance of embracing preventative technologies and practices targeting intestinal health management. These can play a crucial role in mitigating the severity, incidence, and economic impact of BRD on the industry.

Kemin's Approach to Intestinal Health and BRD 

The Kemin Beef team works to serve the industry with intestinal health tools and solutions that are proven through science to impact animal health and performance, and consequently, the producer's bottom line.

References

1.      Chase, C., & Kaushik, R.S. (2019). Mucosal immune system of cattle. Veterinary Clinics of North America: Food Animal Practice, 35, 431–451.2.     

2. Lima, S.F., & Bicalho, R.C. (2019). The Bos taurus maternal microbiome: Role in determining the progeny early-life upper respiratory tract microbiome and health. PLoS ONE, 14(3), e0208014.3.     

3. Welch, C.B., Ryman, V.E., Pringle, T.D., & Lourenco, J.M. (2022). Utilizing the gastrointestinal microbiota to modulate cattle health through the microbiome-gut-organ axes. Microorganisms, 10, 1391.4.     

4. Horst, E.A., Mayorga, E.J., & Baumgard, L.H. (2025). International symposium on ruminant physiology: Integrating our understanding of stress physiology. Journal of Dairy Science. In press. https://doi.org/10.3168/jds.2024-257945.     

5. Zhang, S., Albornoz, R.I., Aschenbach, J.R., Barreda, D.R., & Penner, G.B. (2013). Short-term feed restriction impairs the absorptive function of the reticulo-rumen and total tract barrier function in beef cattle. Journal of Animal Science, 91, 1685–1695.