A cow’s lungs are large, asymmetrical organs that fill most of the thoracic cavity, handling the massive oxygen demands of an animal that can weigh over 600 kilograms. Beyond keeping cattle alive, these organs turn up in surprisingly diverse contexts: neonatal intensive care units, tissue engineering laboratories, pet food manufacturing, and dinner tables across Southeast Asia and Latin America. The anatomy and immune biology of bovine lungs also make them unusually interesting to researchers, because cattle possess lung defense cells that humans lack entirely.
Lobe Structure and Airway Branching
The cow lung is not a mirror image of left and right. The right lung is significantly larger, and its internal architecture reflects that asymmetry. In Holstein cattle, the right lung contains a bilobed cranial lobe, a middle lobe, a caudal lobe, and an accessory lobe. The left lung is smaller, with a bilobed middle lobe and a caudal lobe. Both sides share the same four bronchiole systems branching off the main bronchi: dorsal, lateral, ventral, and medial. The right lung also has something the left does not, a tracheal bronchus that branches directly off the trachea before the main airway even divides.1PubMed. The bronchial tree and blood vessels of the cow (Holstein) lung
That tracheal bronchus is worth pausing on, because it is a feature cattle share with some other species but that humans do not normally have. It ventilates a portion of the cranial right lung independently. From a veterinary standpoint, this matters during intubation and when interpreting imaging, because a tube placed too deep can bypass the tracheal bronchus and leave part of the lung unventilated.
The overall lobation is more pronounced in cattle than in many other mammals. The fissures between lobes are deep, which means that infections or fluid accumulation can be surprisingly well-contained within a single lobe. This is part of why veterinary pathologists pay close attention to which lobes are affected when diagnosing pneumonia in cattle, as the pattern of involvement often points to the cause.
Oxygen Transfer in a Large Animal
Breathing is fundamentally a surface-area problem. Oxygen has to cross from the air in the alveoli into the blood in the surrounding capillaries, and the rate at which that transfer happens depends on how much membrane surface is available. In larger mammals, this becomes a scaling challenge. Research comparing wild and domestic mammals confirmed that pulmonary diffusing capacity scales almost linearly with body mass, while the maximum rate of oxygen consumption scales at a slower rate. The practical result is that larger animals need proportionally more lung diffusing capacity to move the same amount of oxygen per unit of body weight from air into blood.2Respiration Physiology. Design of the mammalian respiratory system. V. Scaling morphometric pulmonary diffusing capacity to body mass: Wild and domestic mammals
For cattle, this means a lung with an enormous combined alveolar surface area. The deep lobation and extensive branching of the bronchial tree help maximize the amount of tissue available for gas exchange. But this large, heavily perfused organ is also metabolically expensive to maintain and vulnerable to disease, which is part of why respiratory illness is such a persistent problem in the cattle industry.
A Unique Immune Defense Inside the Blood Vessels
One of the most distinctive features of cow lungs is a cell type that most people have never heard of: pulmonary intravascular macrophages, or PIMs. These immune cells sit directly on the inner lining of the lung’s capillaries, positioned to intercept bacteria and particles circulating in the blood. In many species, including cattle, PIMs are responsible for clearing blood-borne pathogens as they pass through the lung’s dense capillary network.3Regional Immunology. Immunological characterization of pulmonary intravascular macrophages
Humans do not have PIMs under normal conditions. In people, the liver handles most blood-borne particle clearance. In cattle, the lung shares this duty, which is a double-edged sword. PIMs are effective at grabbing bacteria out of the bloodstream, but when they engulf large numbers of pathogens, the resulting inflammatory response happens right inside the lung tissue. Research on infections with Actinomyces pyogenes (now reclassified as Trueperella pyogenes) showed that PIMs actively took up bacteria from the blood and contributed to the formation of abscess-like lesions in the lung.4PubMed. Pulmonary intravascular macrophages in the pathogenesis of bovine pulmonary lesions caused by Actinomyces pyogenes
PIMs in cattle have a distinctive surface coat made largely of lipoproteins, arranged in rows of globules along the outer surface of the cell membrane. This coat is sensitive to certain enzymes and drugs, including heparin and the anesthetic gas halothane, which can disrupt it.5PubMed Central. Ultrastructural response of pulmonary intravascular macrophages to exogenous oestrogen in the bovine lung That sensitivity has practical implications for veterinary anesthesia: when cattle are anesthetized with halothane, the disruption of PIM surface coats may alter how the lungs handle circulating particles and immune responses during surgery.
Why Pneumonia Is Such a Problem in Cattle
Pneumonia is one of the leading causes of death and economic loss in the cattle industry worldwide. The patterns of lung disease in cattle are varied and reflect different causes. Bacterial pneumonias alone include several distinct forms: bronchopneumonia, fibrinous pneumonia, pleuropneumonia, caseonecrotic pneumonia (with cheese-like dead tissue), aspiration pneumonia, and tuberculosis. On top of these, cattle develop two major patterns of interstitial pneumonia, where inflammation centers on the walls between the air sacs rather than the airways themselves. Parasitic lung infections caused by the lungworm Dictyocaulus viviparus add yet another pattern.6PubMed Central. Pathogenesis and pathology of bovine pneumonia
The diversity of these pneumonia types matters for diagnosis and treatment. A veterinarian examining a sick cow or inspecting a lung at slaughter can often narrow down the cause based on which lobes are involved, whether the damage is centered in the airways or the tissue between them, and whether the lesions are firm, fluid-filled, or necrotic. The cranioventral lobes, which are the parts of the lung closest to the front and bottom of the chest, are typically hit hardest in bacterial bronchopneumonia, while interstitial pneumonia tends to affect the lung more diffusely.
Even fetal and newborn calves are not spared. A case series from Alberta documented interstitial pneumonia with emphysema in beef calves that were either still in the womb or less than three days old. At autopsy, the lungs of affected calves appeared swollen with air trapped between tissue layers, and microscopic examination revealed inflammation of the tissue between the air sacs along with prominent clusters of immune cells around the small airways.7Veterinary Pathology. Interstitial pneumonia and lymphocytic bronchiolitis with interstitial emphysema of unknown cause in Western Canadian fetal and neonatal beef calves The cause of these cases remained unknown, which underscores how much remains to be understood about early-life lung disease in cattle.
Brisket Disease and High-Altitude Lungs
Cattle raised at high altitudes face a lung problem that has no real equivalent in lowland herds. When oxygen levels in the air drop at elevation, the blood vessels in the lungs constrict in response, a reflex meant to redirect blood flow toward better-ventilated areas of the lung. At high altitude, though, the entire lung is getting less oxygen, so the constriction becomes widespread and chronic. This drives up blood pressure in the pulmonary arteries and, over time, remodels the blood vessels themselves. The right side of the heart, which pumps blood through the lungs, eventually fails under the sustained pressure. Fluid accumulates in the brisket area of the chest, giving the condition its common name: brisket disease.8PubMed Central. High-altitude pulmonary hypertension in cattle (brisket disease): Candidate genes and gene expression profiling of peripheral blood mononuclear cells
Brisket disease is a naturally occurring form of hypoxic pulmonary hypertension, which makes affected cattle a valuable animal model for studying the same process that affects some humans living at altitude. Not all cattle are equally susceptible. Some breeds and bloodlines tolerate high altitude well, while others develop dangerously high pulmonary pressures within months of being moved to elevation. Ranchers in the western United States sometimes screen young cattle with pulmonary artery pressure testing before moving them to high-altitude pastures, culling animals whose pressures suggest they are at high risk.
Diagnosing Lung Disease in Living Cattle
For decades, veterinarians relied on stethoscopes and clinical observation to detect lung disease in cattle. Those tools are limited: by the time a cow is visibly sick enough for a stethoscope to pick up abnormal sounds, the disease may be advanced. Thoracic ultrasound has changed the game. The technique allows real-time visualization of the lung surface and underlying tissue, and it has proven more accurate than traditional auscultation or radiography for detecting both early and advanced respiratory disease in cattle.9PubMed Central. Thoracic Ultrasound in Cattle: Methods, Diagnostics, and Prognostics
In calves, ultrasound techniques have evolved to allow rapid screening of entire groups, which is critical in feedlot settings where bovine respiratory disease can sweep through hundreds of animals. The technique can distinguish between disease affecting the lower airways and disease limited to the upper respiratory tract, which helps guide treatment decisions. Several classification systems exist for grading the severity of ultrasound findings, though the lack of a single standardized approach remains a challenge in the field.10Journal of Veterinary Internal Medicine. Thoracic Ultrasonography in Calves: A Narrative Review of Techniques and Reporting Practices
Bovine Surfactant in Neonatal Medicine
Perhaps the most medically significant use of cow lungs has nothing to do with cattle at all. Premature human babies often lack sufficient surfactant, the slippery mixture of fats and proteins that coats the inside of the lungs and keeps the tiny air sacs from collapsing with each breath. Without it, preterm infants develop respiratory distress syndrome, a condition that was once a leading killer of premature babies. Surfactant extracted and modified from cow lungs became one of the breakthrough treatments for this condition.
Beractant, sold under the brand name Survanta, is a modified bovine lung extract. Its safety and effectiveness were established in four large controlled trials in the late 1980s involving over 1,200 premature infants.11PubMed. Two-year follow-up of infants treated for neonatal respiratory distress syndrome with bovine surfactant Studies of how bovine surfactant behaves once instilled into a premature baby’s lungs have shown that clearance and metabolism depend on the specific preparation used, meaning that different bovine surfactant products are not interchangeable from a pharmacological standpoint.12PubMed. Pharmacokinetics of bovine surfactant in neonatal respiratory distress syndrome
Head-to-head comparisons between different surfactant products continue. A randomized trial comparing poractant alfa (derived from porcine lungs) with a bovine lipid extract surfactant in very premature infants found no significant difference in the primary outcome of being alive and off the ventilator at 48 hours. Infants who received poractant alfa did spend fewer days on supplemental oxygen, though the clinical significance of that difference is debated.13PLoS ONE. Poractant alfa versus bovine lipid extract surfactant for infants 24+0 to 31+6 weeks gestational age: A randomized controlled trial The bottom line is that bovine-derived surfactants remain a standard treatment in neonatal intensive care around the world, and cow lungs are still a primary raw material for these life-saving drugs.
Heparin and Biochemical Extraction
Cow lungs have historically been a source of heparin sulfate, the anticoagulant compound used in medicine to prevent and treat blood clots. Heparitin sulfate (a related compound) extracted from beef lung tissue turns out to be more complex than a single substance. Fractionation of commercial batches has revealed at least four distinct mucopolysaccharides within what is sold as a single product.14Biochimica et Biophysica Acta (BBA) – General Subjects. Fractionation and properties of four heparitin sulfates from beef lung tissue This biochemical complexity matters for quality control and for understanding how different batches of heparin products may behave slightly differently in clinical use.
While porcine intestines have largely overtaken bovine lungs as the primary commercial source of heparin in recent decades, beef lung-derived heparin still has a role, particularly in regions where pork-derived products face religious or cultural restrictions. The shift toward porcine sources was driven partly by supply chain economics and partly by concerns about bovine spongiform encephalopathy (mad cow disease) in the 1990s, which led regulators to restrict certain bovine-derived medical products.
Decellularized Lung Scaffolds for Tissue Engineering
A more futuristic application involves stripping cow lung tissue of all its cells while preserving the underlying structural framework, the extracellular matrix. The goal is to create biological scaffolds that could eventually be reseeded with human cells to build transplantable tissue or to serve as platforms for drug testing. Researchers have established methods for decellularizing bovine lung tissue using four different protocols and have characterized the resulting hydrogels for their biochemical makeup and mechanical properties. Different decellularization methods produce scaffolds with distinct stiffness and elasticity, which matters because cells behave differently depending on the mechanical environment they are placed in.15ACS Applied Bio Materials. Different Decellularization Methods in Bovine Lung Tissue Reveals Distinct Biochemical Composition, Stiffness, and Viscoelasticity in Reconstituted Hydrogels
Bovine lungs are attractive for this work because they are large and readily available from slaughterhouses, making them a cheap and abundant raw material compared with human donor lungs. The research is still early-stage, but the vision is that bovine lung matrix could one day serve as the backbone for lab-grown human lung tissue.
Cow Lung as Food
In many culinary traditions, cow lung is a valued ingredient rather than waste. Indonesian cuisine, for example, features a rich diversity of offal-based dishes that have been shaped over centuries by local resources, religious customs, and economic constraints.16Journal of Ethnic Foods. Diversity of Indonesian offal-based dishes Lung appears in stews, curries, and grilled preparations across Southeast Asia, Latin America, and parts of Africa and Europe. It has a spongy texture that absorbs sauces and seasonings readily, which makes it popular in heavily spiced dishes.
In the United States, the sale of cow lung for human consumption has been banned by the USDA since 1971. The concern is that during the slaughter process, lung tissue can become contaminated with stomach contents, bacteria, and other material that is difficult to remove from the spongy tissue. This regulation is specific to human food; cow lungs are still widely used in pet food and animal feed in the U.S. The ban sometimes surprises immigrants from countries where cow lung is a common and inexpensive protein source, and it has been the subject of occasional petitions for reconsideration.
In countries where cow lung is sold for human consumption, it is typically one of the cheapest cuts available, making it an important protein source for lower-income households. Nutritionally, lung is high in protein, relatively low in fat compared with other organ meats, and contains meaningful amounts of iron.
Pet Food and Animal Feed
Where cow lung cannot be sold for human consumption, much of it ends up in the pet food supply chain. Freeze-dried beef lung is a common ingredient in commercial dog treats, and raw beef lung is used in both raw and processed pet food formulations. Research evaluating the protein quality of various raw and rendered animal by-product meals found that most raw animal meals, including beef lungs, exhibited moderate to high protein quality. Lysine bioavailability in raw animal meals ranged from 86 to 107 percent, and protein efficiency ratios ranged from about 2.8 to 4.0, which compares well against standard reference proteins.17Oxford Academic (Journal of Animal Science). Protein quality of various raw and rendered by-product meals commonly incorporated into companion animal diets
The appeal for pet food manufacturers is straightforward: beef lung is abundant, inexpensive, nutritionally decent, and dogs tend to find the flavor and texture appealing. Dehydrated lung treats have become a popular category in the premium pet treat market, often marketed as single-ingredient, high-protein snacks.
Occupational Risks of Processing Cow Lungs
For workers in slaughterhouses and meat processing plants, handling cow lungs and other organs comes with respiratory health risks that most consumers never think about. Slaughterhouse workers are exposed to bioaerosols, airborne particles that include bacteria, endotoxins, blood mist, and fragments of animal tissue. A study comparing slaughterhouse workers with a reference group found that respiratory symptoms like cough, breathlessness, phlegm production, and wheezing were roughly three to five times more common among the exposed workers. Lung function measurements also declined significantly after work shifts, and long-term lung function was lower in slaughterhouse workers even after adjusting for age, body size, and smoking status.18PubMed Central. Respiratory Disorders Among Workers in Slaughterhouses
The workers most at risk are those in the evisceration and offal-processing areas, where exposure to aerosolized biological material is highest. Protective measures such as adequate ventilation, respiratory masks, and limiting time in high-exposure areas can reduce the risk, but compliance and implementation vary widely across facilities and countries. This occupational hazard represents a less visible cost of the global meat industry that extends beyond the health of the animals to the health of the people who process them.