Beyond Biosecurity: Building Health-Oriented Livestock Systems to Reduce Disease Risk

Preventing infectious disease remains one of the primary goals of livestock practice. Biosecurity protocols are an essential component of herd and flock health programs, helping reduce opportunities for pathogen introduction. However, disease outbreaks continue to occur even in production systems with stringent biosecurity measures, highlighting the importance of addressing additional factors that influence disease susceptibility¹. 

For practicing veterinarians, this emphasizes the need to look beyond pathogen exclusion alone. Animal housing, stocking density, stress, environmental conditions, and management practices all influence immune competence and disease resilience. A health-oriented production system aims to make good health an inherent feature of the production environment rather than relying primarily on interventions after disease risk has increased^1,2. 

Recognizing the Limits of Biosecurity 

Biosecurity remains fundamental to disease prevention, but it cannot completely eliminate the possibility of pathogen introduction. Even indoor commercial production systems with high biosecurity standards have experienced incursions of highly pathogenic avian influenza, demonstrating that no biosecurity program is infallible¹. 

Once infectious agents enter intensive production facilities, certain characteristics of these systems may accelerate disease transmission. High animal density facilitates rapid spread between susceptible animals, while genetically similar populations can create favorable conditions for widespread outbreaks and pathogen evolution³. 

Veterinarians should therefore view biosecurity as one component of a broader preventive health strategy rather than the sole defense against infectious disease. 

Management Factors That Influence Disease Risk 

Several management practices directly influence animal health and immune function. 

Stocking Density 

Overcrowding increases opportunities for pathogen transmission while limiting the expression of normal behaviors. High stocking densities have also been associated with impaired welfare, reduced mobility, and increased occurrence of conditions such as footpad dermatitis in broilers^1,4. 

Appropriate space allowances help support normal behavior, improve comfort, and may contribute to better overall health by reducing stress-related immune suppression¹. 

Stress Reduction 

Stress has important physiological consequences that can impair immune competence and increase susceptibility to disease¹. 

Common on-farm stressors include: 

• Crowding 

• Mixing unfamiliar animals 

• Feed restriction 

• Thermal discomfort 

• Inadequate bedding 

• Limited environmental enrichment 

• Improper handling 

• Noise 

Addressing these factors can support both animal welfare and herd health while reducing pressures that predispose animals to infectious disease¹. 

Allowing Natural Behaviors 

Production environments that prevent animals from performing highly motivated natural behaviors may contribute to chronic stress. Poor environmental enrichment and barren housing conditions can interfere with normal behavioral expression, particularly in pigs, where the inability to root, explore, or manipulate materials may increase stress responses^1,5. 

Providing housing that supports species-specific behaviors should therefore be considered an integral component of preventive herd health planning. 

Environmental Management Matters 

Environmental quality extends beyond cleanliness alone. 

Poor ventilation, elevated ammonia concentrations, and excessive airborne dust have been identified as risk factors for respiratory disease¹. Maintaining appropriate air quality should therefore be incorporated into routine herd health assessments alongside vaccination protocols, nutrition, and biosecurity audits. 

Similarly, minimizing unnecessary mixing of animals may reduce both stress and opportunities for disease introduction within production groups¹. 

Practical Clinical Insights 

When evaluating herd health, veterinarians may benefit from assessing management practices alongside traditional disease investigations. 

Consider reviewing: 

• Stocking density and available space 

• Ventilation and indoor air quality 

• Sources of chronic stress 

• Grouping and mixing practices 

• Availability of environmental enrichment 

• Housing conditions that support normal behavior 

Addressing these factors may strengthen herd resilience and reduce conditions that favor disease transmission while complementing existing biosecurity measures. 

Conclusion 

Disease prevention requires more than preventing pathogen entry. Production systems that minimize chronic stress, avoid overcrowding, maintain good environmental conditions, and support normal animal behavior create conditions that are more conducive to good health. For practicing veterinarians, integrating these principles into routine herd health programs offers an opportunity to strengthen disease prevention while supporting both animal welfare and sustainable livestock production. 

References 

1. Stevenson P. Links between industrial livestock production, disease including zoonoses and antimicrobial resistance. Animal Research and One Health. 2023 Aug;1(1):137-44. https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/aro2.19?download=true 

2. Laxminarayan, R., Duse, A., Wattal, C., Zaidi, A. K. M., Wertheim, H. F. L., Sumpradit, N., Vlieghe, E., Hara, G. L., Gould, I. M., Goossens, H., Greko, C., Bigdeli, M., Tomson, G., Woodhouse, W., Ombaka, E., Peralta, A. Q., Qamar, F. N., Mir, F., & Cars, O. (2013). Antibiotic resistance—The need for global solutions. The Lancet Infectious Diseases, 13(12), 1057–1098. https://doi.org/10.1016/S1473‐3099(13)70318‐9 

3. Espinosa R, Tago D, Treich N. Infectious diseases and meat production. Environmental and Resource Economics. 2020 Aug;76(4):1019-44. https://pmc.ncbi.nlm.nih.gov/articles/PMC7399585/pdf/10640_2020_Article_484.pdf 

4. EFSA AHAW Panel (EFSA Panel on Animal Health and Welfare), Nielsen SS, Alvarez J, Bicout DJ, Calistri P, Canali E, Drewe JA, Garin‐Bastuji B, Gonzales Rojas JL, Schmidt CG, Herskin MS. Welfare of broilers on farm. EFSA journal. 2023 Feb;21(2):e07788. https://efsa.onlinelibrary.wiley.com/doi/pdfdirect/10.2903/j.efsa.2023.7788?ref=ctrlalt-del.com 

5. Martínez-Miró S, Tecles F, Ramón M, Escribano D, Hernández F, Madrid J, Orengo J, Martínez-Subiela S, Manteca X, Cerón JJ. Causes, consequences and biomarkers of stress in swine: an update. BMC veterinary research. 2016 Aug 19;12(1):171. https://link.springer.com/content/pdf/10.1186/s12917-016-0791-8.pdf