Breathing Trouble: A Glimpse into the World of CRD in Poultry
India ranks second globally in egg production and fifth in poultry meat production. The Indian poultry market, despite being one of the largest globally, remains a developing sector due to its fragmented infrastructure, inconsistent biosecurity standards, and varying degrees of modernization across regions.

A significant portion of poultry production still relies on open housing systems, limited automation, and minimal veterinary oversight, especially among smallholder and backyard farmers. These conditions foster high disease prevalence, as poor sanitation, overcrowding, and lack of structured vaccination programs create ideal environments for the spread of infectious agents like Mycoplasma gallisepticum, E. coli, and coccidia. Consequently, the industry faces substantial economic losses through reduced productivity, higher mortality, increased medication costs, and trade restrictions. Bridging the gap between traditional practices and scientific poultry management is critical for improving flock health and sustaining long-term growth.

One Breath at a Time: Poultry Farmers Battle Chronic Respiratory Disease

Before any effective fight against Chronic Respiratory Disease (CRD) can begin, the poultry industry must first understand the enemy it faces. CRD is not just another seasonal illness—it’s a complex, persistent infection primarily caused by Mycoplasma gallisepticum, capable of silently spreading through flocks and leaving devastating economic consequences in its wake. Its symptoms often mimic those of other respiratory illnesses, making early detection a challenge. Without a clear understanding of its pathogenesis, transmission, and triggers, efforts to control CRD remain reactive and insufficient. Knowledge is the first line of defense—only with education, diagnosis, and structured prevention can farmers hope to break the cycle of recurring outbreaks. The battle against CRD must begin with awareness and be fought with science, vigilance, and unity across the industry.

Unmasking the Culprit: The Hidden Cause of CRD in Poultry

CRD is caused by Mycoplasma gallisepticum (MG), a wall-less bacterium that affects the respiratory tract of poultry. Secondary infections with Escherichia coli, Ornithobacterium rhinotracheale, and viral pathogens (NDV, IBV) often exacerbate disease severity.

Silent Spread: How CRD Continues to Lurk in Poultry Farms
CRD in poultry, caused by Mycoplasma gallisepticum, spreads through both horizontal and vertical transmission. Infected birds release the pathogen via respiratory secretions, contaminating air, water, feed, and equipment. Vertical transmission from breeder hens to chicks via eggs further fuels early infection. Recovered birds often remain silent carriers, shedding the organism under stress. This makes CRD hard to eradicate and highlights the need for strong biosecurity, breeder screening, and flock management to control its spread.

How CRD Takes Hold: Understanding the Disease’s Journey in Poultry
The pathogenesis of Chronic Respiratory Disease (CRD) in poultry begins when birds inhale aerosolized Mycoplasma gallisepticum, the primary causative agent. The pathogen adheres to the ciliated epithelial cells lining the upper respiratory tract, disrupting the mucociliary clearance mechanism. This allows the bacteria to colonize and multiply, triggering a chronic inflammatory response that leads to thick mucus secretion, tracheitis, and air-sacculitis. The damaged respiratory lining also becomes highly susceptible to secondary bacterial infections, particularly from E. coli, compounding respiratory distress and systemic illness.

In commercial poultry, stress factors such as poor ventilation, high stocking density, and concurrent viral infections (like IBV or NDV) can further exacerbate disease progression, resulting in reduced growth rates, poor feed conversion, decreased egg production, and increased mortality.

Signs & Symptoms with Postmortem (PM) Findings
CRD in poultry typically presents with a range of respiratory signs that can vary in severity based on age, immune status, and presence of co-infections. Common clinical signs include coughing, sneezing, nasal discharge, tracheal rales, conjunctivitis, reduced feed intake, stunted growth, and a noticeable drop in egg production in layers. Birds may also exhibit open-mouth breathing and watery eyes. In chronic stages, swelling of infraorbital sinuses and air-sacculitis becomes evident. On postmortem examination, the most consistent findings include thickened, cloudy air sacs (airsacculitis), catarrhal to caseous exudate in the trachea and bronchi, perihepatitis, pericarditis, and fibrinous pneumonia. In cases complicated by secondary infections like E. coli, lesions become more severe, showing a classic “CRD complex.”

Integrated Strategy to Fight CRD
An integrated CRD control strategy combines biosecurity, vaccination, early detection, nutritional support, and precision medication.

Preventive Phase: Reducing the Latent Load
Forlutin 10% (Tiamulin 10%) a high-quality feed additive by Stallen South Asia Pvt. Ltd. serves as the cornerstone for preventive management. Administering it to growers between 7 to 14 weeks of age or just before expected stress periods such as vaccination or peak lay helps reduce the latent load of Mycoplasma. This approach prepares the flock by lowering the pathogen load before the birds reach a vulnerable stage.

Outbreak Management: When Clinical Signs Appear
At the onset of clinical signs indicative of Mycoplasmosis, immediate action is required. Stalmicosin (Tilmicosin Phosphate 250mg) oral solution – a high-quality product manufactured by Stallen South Asia Pvt. Ltd. in its own manufacturing facility to ensure the highest Quality standards, administered via drinking water at 15–20 mg/kg body weight, is highly effective due to its deep lung penetration and prolonged action. This should be continued for 3 to 5 days but not exceeded.

Following the Stalmicosin course, a 24–48hour break should be observed before beginning treatment with Forlutin 80% (Tiamulin 80%) water soluble powder. A dosage of 25–50 mg/kg body weight for another 3 to 5 days helps eliminate residual Mycoplasma and prevents recurrence. Integrating these antimicrobials into a scheduled rotation can significantly reduce disease recurrence and resistance development.

Monitoring and Biosecurity: Supporting the Antimicrobial Strategy
Surveillance using PCR and ELISA tests at regular intervals is vital to detect Mycoplasma presence, especially during and after stress periods. Swab sampling and necropsy examinations for lesions such as air sacculitis or swollen joints provide further evidence. Strict biosecurity—enforcing all-in/all-out practices, staff segregation, and regular disinfection using NADCC, quaternary ammonium compounds, or glutaraldehyde—is essential to support the medical interventions.

References
1. Indian Journal of Veterinary Science & Poultry Health, 2023. Comparative Efficacy of Antibiotics in CRD.
2. Practical Poultry Guide, Vol 18, 2024 – Antimicrobial Resistance Trends in Poultry Pathogens.
4. McOrist et al. (2002) – Tilmicosin pharmacokinetics and tissue distribution in avian models.
5. Poultry Science Journal, 2022 – Mycoplasma Control Strategies in South Asia.

The gastrointestinal tract (GIT) health impacts poultry productivity. It is known to be the pillar of poultry success. The poultry microbiome has myriad functions which range from protection against pathogens and nutrients production, to host immune system development. Healthy poultry birds possess a natural resistance to infection. Since optimum performance and growth rate are central to animal production, the host-microbiome relationship remains integral.

A healthy gut ensures:

• Proper digestion and absorption of valuable feed nutrients
• Less wastage of nutrients
• Minimum foul odour.
• Provides resistance against entero-pathogens
• Checks mortality and morbidity losses
• Optimizes feed conversion ratio.

Figure 1 : The gastrointestinal tract of a chicken.

Apart from nutrient absorption and digestion, three important part of gut function are gut integrity, gut immunity, and gut microbiome. Intestinal integrity may be described as the intactness of the intestine in maintaining its structure and function or simply an unimpaired and sound intestine.

Gut integrity maintains a strong barrier of defense. Physical barriers protect against the entry of foreign materials and organisms into the bloodstream and access to other viscera thus helping intestinal integrity. On occasion due to improper nutrition or an unhygienic environment, when the load of foreign invaders increases these barriers are breached.

1. Mucus (Mucus: material secreted by intestinal cells) acts as a barrier to bacterial and fungal invasion.

2. Gut epithelial cells (enterocytes): These cells form a semi-permeable surface that selectively allows passage of fluid, electrolytes, and dissolved nutrients. Every epithelial cell in the digestive tract is part of a continuous physical barrier. When organisms and toxic agents damage epithelial cells, the integrity of this protective barrier is broken.

3. Fluid secretion: fluid having large amounts of water mixed with electrolytes. The fluid in the upper small intestine is protective and keeps bacteria in suspension and washes them downstream.

4. Vascular supply: supply under the gut epithelial layer serves to rapidly dilute and carry away any agents or chemicals (endogenous or exogenous) that may breach the mucosal barrier.

Gut integrity can be affected by physical barriers Stress factors, Feed toxins and toxicants, dietary factors, health status and gut microflora.

Gut Immunity: Poultry GIT can be considered an immune organ. GALT (Gut associated lymphoid tissue ) is a secondary immune organ and developed early stage in birds life.

Gut microbiome: Consists of species of bacteria, protozoa and fungi in the GIT.

Early life and Gut health
Early life care is an important factor in maximizing profits from broiler operations. Early nutrition mainly in the first 7 days of life for broilers may program the birds’ systems and set a pattern for growth and productivity. A larger percentage of early growth (upto 5 times the growth rate of other tissues) occurs in the digestive tract and those organs involved in digestion. If digestive growth is hampered during this period, overall growth rate may be compromised. Newly hatched chicks are more prone to gut infections as its natural defence is yet to be strengthened. So proper care should be taken during this period.

Functions of Gastrointestinal Tract

Role of Environment in Poultry Gut health:

Role of Dietary Factors in Improving Intestinal Integrity
1. Quality feed ingredients: Supplementation of quality feed ingredients helps in maintaining natural gut health. Mycotoxins which are present in most of feed raw materials like Aflatoxin, Fumonisins, T2, DON, Zearalenone, Ochratoxins affect the gut integrity thereby affecting the gut health and giving rise to bacterial issues like E coli and Clostridium which is directly correlated with the presence of multiple mycotoxins. .

2. Processed feed: Many incriminating factors of feed are destroyed due to processing.

3. Pelleted feed: Pelleting provides scope for utilization of high fibre feed resources. Use of steam- pelleted feed seems to be of value in maintaining gut health.

4. Feed additives: Like Anticoccidials and Ionophores Coccidiosis, a managemental disease, causes devastating losses to the poultry industry. Other feed additives which can help maintain gut health are organic acids, probiotics, prebiotics, mycotoxin binders etc.

Conclusion: To summarise, gastrointestinal tract is the key organ that converts feed to meat and eggs. It is largest organ exposed to foreign matters and serves as first line of defence. GIT is continuously exposed to multiple foreign materials and irritants. Regardless of the level of hygiene and biosecurity imposed at production level, poultry will be exposed to multiple infections and toxic agents through the feed and environment.

Aerobic and anaerobic bacteria, toxin-producing fungi, and protozoan parasites (coccidian) are challenging to be eliminated from poultry production units.

Because of the potential development of antibiotic resistant human pathogenic bacteria, the use of antibiotics, have come under increasing scrutiny and feed safety concerns in the food chain. Hence, today’s intensive animal agriculture industry must adapt to producing poultry and take care of holistic factors that affect gut health right from maintaining biosecurity ,early chick health and also by implementing nutritional strategies that would strengthen the gut health by securing gut integrity, gut immunity and gut microbiome .