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Maina JN. A critical assessment of the cellular defences of the avian respiratory system: are birds in general and poultry in particular relatively more susceptible to pulmonary infections/afflictions? Biol Rev Camb Philos Soc 2023; 98:2152-2187. [PMID: 37489059 DOI: 10.1111/brv.13000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 07/01/2023] [Accepted: 07/07/2023] [Indexed: 07/26/2023]
Abstract
In commercial poultry farming, respiratory diseases cause high morbidities and mortalities, begetting colossal economic losses. Without empirical evidence, early observations led to the supposition that birds in general, and poultry in particular, have weak innate and adaptive pulmonary defences and are therefore highly susceptible to injury by pathogens. Recent findings have, however, shown that birds possess notably efficient pulmonary defences that include: (i) a structurally complex three-tiered airway arrangement with aerodynamically intricate air-flow dynamics that provide efficient filtration of inhaled air; (ii) a specialised airway mucosal lining that comprises air-filtering (ciliated) cells and various resident phagocytic cells such as surface and tissue macrophages, dendritic cells and lymphocytes; (iii) an exceptionally efficient mucociliary escalator system that efficiently removes trapped foreign agents; (iv) phagocytotic atrial and infundibular epithelial cells; (v) phagocytically competent surface macrophages that destroy pathogens and injurious particulates; (vi) pulmonary intravascular macrophages that protect the lung from the vascular side; and (vii) proficiently phagocytic pulmonary extravasated erythrocytes. Additionally, the avian respiratory system rapidly translocates phagocytic cells onto the respiratory surface, ostensibly from the subepithelial space and the circulatory system: the mobilised cells complement the surface macrophages in destroying foreign agents. Further studies are needed to determine whether the posited weak defence of the avian respiratory system is a global avian feature or is exclusive to poultry. This review argues that any inadequacies of pulmonary defences in poultry may have derived from exacting genetic manipulation(s) for traits such as rapid weight gain from efficient conversion of food into meat and eggs and the harsh environmental conditions and severe husbandry operations in modern poultry farming. To reduce pulmonary diseases and their severity, greater effort must be directed at establishment of optimal poultry housing conditions and use of more humane husbandry practices.
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Affiliation(s)
- John N Maina
- Department of Zoology, University of Johannesburg, Auckland Park Campus, Kingsway Avenue, Johannesburg, 2006, South Africa
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Heat stress in poultry with particular reference to the role of probiotics in its amelioration: An updated review. J Therm Biol 2022; 108:103302. [DOI: 10.1016/j.jtherbio.2022.103302] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 07/23/2022] [Accepted: 07/27/2022] [Indexed: 12/14/2022]
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Nguyen QM, Oza AU, Abouezzi J, Sun G, Childress S, Frederick C, Ristroph L. Flow Rectification in Loopy Network Models of Bird Lungs. PHYSICAL REVIEW LETTERS 2021; 126:114501. [PMID: 33798375 DOI: 10.1103/physrevlett.126.114501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 01/13/2021] [Accepted: 02/24/2021] [Indexed: 06/12/2023]
Abstract
We demonstrate flow rectification, valveless pumping, or alternating to direct current (AC-to-DC) conversion in macroscale fluidic networks with loops. Inspired by the unique anatomy of bird lungs and the phenomenon of directed airflow throughout the respiration cycle, we hypothesize, test, and validate that multiloop networks exhibit persistent circulation or DC flows when subject to oscillatory or AC forcing at high Reynolds numbers. Experiments reveal that disproportionately stronger circulation is generated for higher frequencies and amplitudes of the imposed oscillations, and this nonlinear response is corroborated by numerical simulations. Visualizations show that flow separation and vortex shedding at network junctions serve the valving function of directing current with appropriate timing in the oscillation cycle. These findings suggest strategies for controlling inertial flows through network topology and junction connectivity.
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Affiliation(s)
- Quynh M Nguyen
- Applied Math Lab, Courant Institute, New York University, New York, New York 10012, USA
- Physics Department, New York University, New York, New York 10003, USA
| | - Anand U Oza
- Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, New Jersey 07102, USA
| | - Joanna Abouezzi
- Applied Math Lab, Courant Institute, New York University, New York, New York 10012, USA
| | - Guanhua Sun
- Applied Math Lab, Courant Institute, New York University, New York, New York 10012, USA
| | - Stephen Childress
- Applied Math Lab, Courant Institute, New York University, New York, New York 10012, USA
| | - Christina Frederick
- Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, New Jersey 07102, USA
| | - Leif Ristroph
- Applied Math Lab, Courant Institute, New York University, New York, New York 10012, USA
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Lawson AB, Hedrick BP, Echols S, Schachner ER. Anatomy, variation, and asymmetry of the bronchial tree in the African grey parrot (Psittacus erithacus). J Morphol 2021; 282:701-719. [PMID: 33629391 DOI: 10.1002/jmor.21340] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 02/20/2021] [Accepted: 02/23/2021] [Indexed: 12/16/2022]
Abstract
The avian bronchial tree has a unique and elaborate architecture for the maintenance of unidirectional airflow. Gross descriptions of this bronchial arrangement have traditionally relied upon dissection and casts of the negative (air-filled) spaces. In this study, the bronchial trees of five deceased African grey parrots (Psittacus erithacus) were segmented from micro-computed tomography (μCT) scans into three-dimensional (3D) surface models, and then compared. Select metrics of the primary bronchi and major secondary branches in the μCT scans of 11 specimens were taken to assess left-right asymmetry and quantify gross lung structure. Analysis of the 3D surface models demonstrates variation in the number and distribution of secondary bronchi with consistent direct connections to specific respiratory air sacs. A single model of the parabronchi further reveals indirect connections to all but two of the nine total air sacs. Statistical analysis of the metrics show significant left-right asymmetry between the primary bronchi and the origins of the first four secondary bronchi (the ventrobronchi), consistently greater mean values for all right primary bronchus length metrics, and relatively high coefficients of variation for cross-sectional area metrics of the primary bronchi and secondary bronchi ostia. These findings suggest that the lengths of the primary bronchi distal to the ventrobronchi do not preserve lung symmetry, and that aerodynamic valving can functionally accommodate a wide range of bronchial proportions.
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Affiliation(s)
- Adam B Lawson
- Department of Cell Biology and Anatomy, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, Louisiana, USA
| | - Brandon P Hedrick
- Department of Cell Biology and Anatomy, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, Louisiana, USA
| | - Scott Echols
- The Medical Center for Birds, Oakley, California, USA
| | - Emma R Schachner
- Department of Cell Biology and Anatomy, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, Louisiana, USA
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York JM, Scadeng M, McCracken KG, Milsom WK. Respiratory mechanics and morphology of Tibetan and Andean high-altitude geese with divergent life histories. ACTA ACUST UNITED AC 2018; 221:jeb.170738. [PMID: 29180602 DOI: 10.1242/jeb.170738] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 11/21/2017] [Indexed: 12/31/2022]
Abstract
High-altitude bar-headed geese (Anser indicus) and Andean geese (Chloephaga melanoptera) have been shown to preferentially increase tidal volume over breathing frequency when increasing ventilation during exposure to hypoxia. Increasing tidal volume is a more effective breathing strategy but is also thought to be more mechanically and metabolically expensive. We asked whether there might be differences in the mechanics or morphology of the respiratory systems of high-altitude transient bar-headed geese and high-altitude resident Andean geese that could minimize the cost of breathing more deeply. We compared these two species with a low-altitude migratory species, the barnacle goose (Branta leucopsis). We ventilated anesthetized birds to measure mechanical properties of the respiratory system and used CT scans to quantify respiratory morphology. We found that the respiratory system of Andean geese was disproportionately larger than that of the other two species, allowing use of a deeper breathing strategy for the same energetic cost. The relative size of the respiratory system, especially the caudal air sacs, of bar-headed geese was also larger than that of barnacle geese. However, when normalized to respiratory system size, the mechanical cost of breathing did not differ significantly among these three species, indicating that deeper breathing is enabled by morphological but not mechanical differences between species. The metabolic cost of breathing was estimated to be <1% of basal metabolic rate at rest in normoxia. Because of differences in the magnitude of the ventilatory response, the cost of breathing was estimated to increase 7- to 10-fold in bar-headed and barnacle geese in severe hypoxia, but less than 1-fold in Andean geese exposed to the same low atmospheric PO2.
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Affiliation(s)
- Julia M York
- University of British Columbia, Department of Zoology, 6270 University Boulevard, Vancouver, BC, Canada V6T 1Z4
| | - Miriam Scadeng
- University of California San Diego, Department of Radiology, Center for Functional MRI, 9500 Gilman Drive 0677, La Jolla, CA, USA 92093
| | - Kevin G McCracken
- University of Miami, Department of Biology, Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Sciences, and Human Genetics and Genomics - Miller School of Medicine, Coral Gables, FL, 33146, USA
| | - William K Milsom
- University of British Columbia, Department of Zoology, 6270 University Boulevard, Vancouver, BC, Canada V6T 1Z4
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Maina JN. Pivotal debates and controversies on the structure and function of the avian respiratory system: setting the record straight. Biol Rev Camb Philos Soc 2016; 92:1475-1504. [DOI: 10.1111/brv.12292] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 06/17/2016] [Accepted: 06/27/2016] [Indexed: 12/19/2022]
Affiliation(s)
- John N. Maina
- Department of Zoology; University of Johannesburg; P.O. Box, 524, Auckland Park, Kingsway Johannesburg 2006 South Africa
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Unidirectional pulmonary airflow in vertebrates: a review of structure, function, and evolution. J Comp Physiol B 2016; 186:541-52. [DOI: 10.1007/s00360-016-0983-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 03/15/2016] [Accepted: 03/21/2016] [Indexed: 01/23/2023]
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Harvey EP, Ben-Tal A. Robust Unidirectional Airflow through Avian Lungs: New Insights from a Piecewise Linear Mathematical Model. PLoS Comput Biol 2016; 12:e1004637. [PMID: 26862752 PMCID: PMC4749316 DOI: 10.1371/journal.pcbi.1004637] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Accepted: 10/29/2015] [Indexed: 11/22/2022] Open
Abstract
Avian lungs are remarkably different from mammalian lungs in that air flows unidirectionally through rigid tubes in which gas exchange occurs. Experimental observations have been able to determine the pattern of gas flow in the respiratory system, but understanding how the flow pattern is generated and determining the factors contributing to the observed dynamics remains elusive. It has been hypothesized that the unidirectional flow is due to aerodynamic valving during inspiration and expiration, resulting from the anatomical structure and the fluid dynamics involved, however, theoretical studies to back up this hypothesis are lacking. We have constructed a novel mathematical model of the airflow in the avian respiratory system that can produce unidirectional flow which is robust to changes in model parameters, breathing frequency and breathing amplitude. The model consists of two piecewise linear ordinary differential equations with lumped parameters and discontinuous, flow-dependent resistances that mimic the experimental observations. Using dynamical systems techniques and numerical analysis, we show that unidirectional flow can be produced by either effective inspiratory or effective expiratory valving, but that both inspiratory and expiratory valving are required to produce the high efficiencies of flows observed in avian lungs. We further show that the efficacy of the inspiratory and expiratory valving depends on airsac compliances and airflow resistances that may not be located in the immediate area of the valving. Our model provides additional novel insights; for example, we show that physiologically realistic resistance values lead to efficiencies that are close to maximum, and that when the relative lumped compliances of the caudal and cranial airsacs vary, it affects the timing of the airflow across the gas exchange area. These and other insights obtained by our study significantly enhance our understanding of the operation of the avian respiratory system. Birds and mammals have similar metabolic demands and cardiovascular systems, but they have evolved drastically different respiratory systems. A key difference in birds is that gas exchange occurs in rigid tubes, through which air flows unidirectionally during both inspiration and expiration. How this unidirectional flow is generated, and the factors affecting it, are not well understood. It has been hypothesized that the unidirectional flow is due to aerodynamic valving resulting from the complex anatomical structure. To test this hypothesis we have constructed a novel mathematical model that, unlike previous models, produces unidirectional flow through the lungs consistently even when the amplitude and frequency of breathing change. We have investigated the model both analytically and computationally and shown the importance of aerodynamic valving for generating strong airflow through the lungs. Our model also predicts that the timing of airflow through the lungs depends on the relative compliances of the different airsacs that exist in birds. The lumped parameters approach we use means that this model is generally applicable across all birds.
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Affiliation(s)
- Emily P. Harvey
- Institute of Natural and Mathematical Sciences, Massey University Albany, Auckland, New Zealand
- * E-mail:
| | - Alona Ben-Tal
- Institute of Natural and Mathematical Sciences, Massey University Albany, Auckland, New Zealand
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