Comparative lobe-specific histomorphometric evaluation of pulmonary architecture, fibrosis, and alveolar macrophage distribution in swine raised under different management systems

Vet World Vol.19 January-2026 Article - 30

Research Article

Veterinary World, 19(1): 415-432

https://doi.org/10.14202/vetworld.2026.415-432

Nattawat Chaiyawong¹, Napat Praditwattanakit², Surachai Chamsodsai², Pichaya Jumnongprakhon³, Ittipon Phoungpetchara³, and Charkriya Promsuban^3,4

1. Siriraj Integrative Center for Neglected Parasitic Diseases, Department of Parasitology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.

2. Faculty of Medical Science, Naresuan University, Phitsanulok, 65000, Thailand.

3. Department of Anatomy, Faculty of Medical Science, Naresuan University, Phitsanulok, 65000, Thailand.

4. Center of Excellence in Medical Biotechnology, Faculty of Medical Science, Naresuan University, Phitsanulok, 65000, Thailand.

Background and Aim: Swine housing and management systems strongly influence respiratory health through their effects on air quality, ventilation, and environmental exposure. However, quantitative, lobe-specific evidence describing how different management systems affect pulmonary microarchitecture remains limited. This study aimed to compare alveolar structure, fibrosis, collagen deposition, and alveolar macrophage distribution in swine raised under hygienic, beta-agonist-free rearing, and free-range systems.

Materials and Methods: Fifteen clinically healthy male crossbred (Large White × Landrace) swine were allocated to three management systems (n = 5 per group): hygienic, beta-agonist-free rearing, and free-range. Lung samples were collected from the right cranial, middle, and caudal lobes following humane slaughter. Sections were stained with Masson’s trichrome for collagen visualization. Quantitative histomorphometric analyses included alveolar wall thickness, alveolar space area, fibrosis distribution (%), semi-quantitative fibrosis score, collagen intensity (mean gray value) in bronchial hyaline cartilage, and alveolar macrophage density (AMD). Image analysis was performed using ImageJ, and observers were blinded to group allocation. Data were analyzed using one-way analysis of variance with Tukey’s post hoc test (p < 0.05).

Results: Marked lobe-specific differences were observed among management systems. Swine raised under beta-agonist-free rearing exhibited significantly thicker alveolar walls, reduced alveolar space area, higher fibrosis distribution and scores, increased collagen accumulation, and elevated AMD, particularly in the middle and caudal lobes. In contrast, free-range swine demonstrated thinner alveolar septa, wider alveolar spaces, lower fibrosis indices, and reduced macrophage infiltration, indicating preserved pulmonary architecture and reduced inflammatory remodeling. The hygienic group consistently showed intermediate values across most parameters, reflecting balanced structural adaptation under controlled housing conditions.

Conclusion: Swine management systems are associated with distinct patterns of pulmonary structural and immunological adaptation. Beta-agonist-free rearing was linked to early fibrotic remodeling and increased immune activation, whereas free-range management supported structural preservation and lower inflammatory burden. This study provides the first quantitative, lobe-specific histomorphometric comparison of pulmonary remodeling across different swine management systems, offering valuable insights for welfare-oriented and sustainable livestock production strategies.

Keywords: alveolar macrophages, histomorphometry, pulmonary fibrosis, swine housing systems, lung remodeling, Masson’s trichrome staining.

How to cite this article: Chaiyawong N., Praditwattanakit N., Chamsodsai S., Jumnongprakhon P., Phoungpetchara I., Promsuban C. Comparative lobe-specific histomorphometric evaluation of pulmonary architecture, fibrosis, and alveolar macrophage distribution in swine raised under different management systems. Vet World. 2026;19(2):415–432.

Received: 18-11-2025 Accepted: 06-01-2026 Published online: 31-01-2026

Corresponding author: Charkriya Promsuban E-mail: charkriyap@nu.ac.th

DOI: 10.14202/vetworld.2026.415-432

Copyright: Chaiyawong, et al. This article is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http:// creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.