Monsoon Broiler Management: Mitigating Humid-Heat Stress

Dr. Sikander1, Dr. Pooja Kundu2 and Dr. N K Mahajan3
1M.V.Sc student, Department of Veterinary Pathology, LUVAS Hisar,
2Veterinary Surgeon, Department of Animal Husbandry & Dairying, Govt. of Haryana,
3Retd. Professor and Dean, LUVAS Hisar.

Monsoon brings a unique and formidable set of challenges for commercial poultry farming. As monsoon advances, ambient temperatures remain high while relative humidity level also increases, flocks face dangerous dual threat of severe humid-heat stress and a higher prevalence of systemic viral infection with respiratory manifestations – such as Infectious Bronchitis Virus (IBV), Newcastle Disease Virus (NDV), or Low pathogenic Avian Influenza (LPAI) and Multi Drug Resistance Avian pathogenic E coli (MDR-APEC). Unlike mammals, birds lack sweat glands and rely on panting (evaporative cooling) and behavioral mechanisms like seeking shade, gular fluttering and standing in cool areas to regulate their body temperature. When relative humidity increases defense mechanism fails entirely, the consequences extend far beyond a drop in performance. Humid- heat stress triggers systemic physiological disruptions that compromise the intestinal barrier, suppress the immune system, and open the floodgates for opportunistic infections and catastrophic mortality.

Effectively managing a poultry farm requires a proactive approach balancing environmental humidity control, intensive litter management, strict water sanitization, and precise nutritional adjustments.

1. Environmental &Ventilation Control
Primary challenge is no longer just cooling the air, but moving moisture away from the birds and preventing the shed from becoming hot and humid.
· Stocking Density: Maintain strict reduction in stocking density by 10% to 15% compared to winter baselines. Allowing extra floor space per bird is critical during high-humidity periods to minimize micro-climate heat accumulation between individuals.

· Ventilation and Operational Air Velocity: Ensure that fans are running at peak efficiency. In environmentally controlled (EC) sheds, maintain an air velocity of at least 2.5 to 3.0 meters per second directly across the birds. Because evaporative cooling drops in efficiency when relative humidity exceeds 70%, farmers must rely on the wind-chill effect (convective cooling) to strip heat from the birds’ bodies. Regularly check house manometers. Maintain static pressure within the optimal 0.08 to 0.12 inches of water column depending on house width. High static pressure indicates restricted air inlets (clogged pads), causing fan motors to overheat and air speed to drop. Low static pressure indicates structural air leaks (loose curtains or unsealed doors), which causes short-circuiting of air currents and dead air spaces.

· Evaporative Cooling Pads: On high humidity days when relative humidity exceeds 70–75%, turn off the water pumps to the pads completely. Running water over the pads when air is already saturated will not lower temperature; it will only increase humidity, exacerbating respiratory distress. Run exhaust fans at maximum capacity to maximize pure wind velocity. Clean pads regularly with descalants to remove dust and monsoon-induced mold or algae blooms.

· Internal Fogger Restrictions: For open-sided poultry houses, discontinue use of internal low-pressure foggers entirely during rainy or high-humidity days. Fogger droplets will fail to evaporate in mid-air, falling directly onto the litter, causing wet floors, severe ammonia release, and coccidiosis outbreaks. High-pressure systems (400–600 PSI) should only be cycled briefly if dry, hot spells occur.

2. Water Security & Quality Management
Warm, humid monsoon conditions cause rapid bacterial proliferation and heavy biofilm formation in pipeline networks. Since water consumption remains high, biological water security is critical.

· Water Acidification and Sanitization: Efficacy of chlorine-based sanitizers is fundamentally tied to pH. In alkaline water (pH above 7.5), chlorine converts primarily into hypochlorite ions (OCl-), which are highly inefficient at killing bacteria. By utilizing organic acidifiers (Formic, Propionic, or Citric acid) to maintain an optimized, acidic water pH of 5.5 to 6.5, chlorine converts instead into hypochlorous acid (HOCl). This active form is up to 80 times more effective at destroying bacterial cell walls, preventing water lines from becoming breeding grounds for E. coli and Salmonella.

· Water Temperature Regulation: Particularly during hot spells birds will reject water if it is too warm (more than 22°C). Overhead water storage tanks must be fully shaded, or completely insulated with glass wool or local materials like gunny bags. Flush water lines regularly during the day to clear standing warm water and deliver cool, clean water to the nipples.

· Water Line Biofilm Removal: Between bird batches, or as a quick preventative step, water lines must be deeply cleaned to break down slimy bacterial buildup (biofilm). To do this, fill the pipe system with a 1–2% mix of hydrogen peroxide stabilized with silver nitrate. Leave this solution sitting still in the pipes for 4 to 6 hours so it can chemically dissolve the organic matrix completely. Immediately after; flush the lines thoroughly with high-pressure fresh water to wash away all the loosened dirt and leftover chemicals before the new chicks arrive.

3. Nutritional Adjustments & Electrolyte Therapy
In humid weather, broilers voluntarily reduce feed intake to minimize the metabolic heat generated by digestion. Feed consumed must be nutrient-dense but easy to metabolize.

4. Operational Practices
Minimizing physical and physiological stress and preserving litter quality are vital to avoiding sudden spikes in mortality.

· Feeding Schedule: Do not feed the birds during hottest, most humid hours of the day (typically 11:00 AM to 4:00 PM). Shift feed distribution to early morning/late evening when ambient conditions are more favorable. This prevents the peak of metabolic digestion from coinciding with the peak of environmental stress.

· Intensive Litter Management: Litter management is highly critical. Wet, caked litter undergoes rapid anaerobic fermentation, releasing toxic ammonia gas (NH3). Ammonia damages the protective cilia in the bird’s respiratory tract, leaving them highly vulnerable to viral infections (IBV/NDV). Rake the litter regularly during dry periods, add agricultural gypsum or alum to control ammonia release, and immediately replace wet patches with dry, pre-treated rice husk or sawdust.

· Zero Disturbances: Avoid shifting birds, vaccinations, flock grading, litter raking, and mortality collection, or weighing during peak heat hours. Any forced physical activity compels the birds to generate more internal metabolic heat load, which can quickly trigger acute heat stroke and fatal cardiovascular arrest.

Key Dietary Implementations

5. Critical Emergency Protocol:
· Assess Humidity and Disable Water Inputs: Immediate Check the relative humidity. If it is above 70%, ensure all cooling pad pumps and internal foggers are turned off immediately. Introducing more water vapor into saturated air will accelerate mortality.

· Maximize Wind Velocity: Within 2 minutes.
Override automated fan settings and force all exhaust fans to operate at 100% capacity. Achieve maximum operational air velocity (greater than 3.0 m/s) to maximize heat dissipation via the wind-chill effect.

· Charge Water Lines with Electrolytes: Within 10 minutes.
Ensure that cool water (under 22°C) infused with highly concentrated electrolytes—specifically Potassium Chloride and Sodium Bicarbonate—is fully charged into the drinking lines to combat respiratory alkalosis.

· Enforce Absolute Shed Calm: Continuous
Cease all human movement inside the shed. Do not collect mortality, adjust curtains, or walk along the lines during the crisis, as forcing a heat-stressed bird to stand up can induce instant heart failure.

Summary for Monsoon Management: Successful monsoon poultry management requires a complete shift from evaporative cooling to heavy wind-chill ventilation, aggressive litter moisture controls, and feed protection against molds. Managing the farm proactively before seasonal humidity peaks eliminates induced physiological stress, secures optimal feed conversion ratios (FCR), and safeguards overall farm profitability.

Mr. Naresh Ravi, Project & Development Manager, 

KP Asli Sdn. Bhd, Malaysia I Poultry Enthusiast I WPSA Member

Figure 1.0- (left) Imagined paths of how much carbon we might release this century based on different choices about energy and how economies grow. (right) Predicted rises in temperature compared to the average from 1901-1960, based on which carbon release path we end up on. Image by Katharine Hayhoe, from the 2017 Climate Science Special Report by the U.S. Global Change Research Program.

The increasing menace of climate change profoundly challenges the resilience of environmentally controlled (EC) broiler houses—infrastructures that are precisely built to create an ideal environment for poultry growth. As we gaze into what lies ahead, apprehensions intensify regarding the ability of this EC broiler houses’ to weather the looming climatic challenges catalysed by escalating global temperatures. This year’s record-breaking average global temperatures, such as the unprecedented 17.01°C experienced on July 3, illuminate the reality of this threat —’ . Further, predictive climate models offer robust projections, foretelling a future dominated by more frequent and intense heatwaves if annual carbon emission keeps on increasing as shown in figure 1.0.

In this article, delve into practical strategies to minimize external heat entry, from roofing choices to sidewall materials, ensuring optimal poultry health even in adverse conditions. Additionally, we explore the techniques to efficiently remove internal heat and cool incoming air, a critical aspect as broiler size increases in regions like China and India. By journey’s end, you’ll be equipped with a robust understanding of the pressing need for climate-resilient broiler houses and the solutions available to usher in a new era of poultry farming.

1. Strategies to Reduce Heat Penetration in EC Broiler Houses

Heat mainly enters chicken houses in two ways: through radiation and conduction. Radiative heat involves the absorption of electromagnetic waves. A broiler house with a dark roof or sidewalls absorbs more radiant energy than one with lighter shades. Over time, this can increase internal temperatures, stressing birds and affecting growth rates.
Conduction happens when heat moves through a material due to temperature differences. For example, on hot days, a metal-roofed broiler house can get hot externally, transferring this heat inside and jeopardizing bird comfort and health.

Figure 1.1- Majority of the heat entering the house via radiation. Image by https://ssl.acesag.auburn.edu/poultryventilation/documents/InsulationPVP.pdf

– Roofing: The roof accounts for approximately 70% of the heat entering a broiler house. Choosing the right roofing material is vital. Insulated roofing can minimize solar heat on warm days, benefiting the birds. The efficiency of insulation is rated by its R-value, with higher values indicating better insulation. A commonly used option is 25mm of PU (polyurethane) roofing with an R-value of 6. If you opt for a non-insulated roof, adding an insulating layer in the ceilings can help. However, EC broiler house without any roof insulation or ceiling insulation puts tremendous pressure to the ventilation system as more heat enters the house. For example, a PU roof can maintain internal temperatures around 33.3°C, a notable improvement of 10% from 37.2°C with a non-insulated roof.

Figure 1.2- Example of PU roofing used in poultry farm.
Image by https://agro-house.astino.com.my/astino-swine-structure/

– Sidewalls: Account for the remaining 30% of heat entering the house.

Curtain: While curtain sidewalls are popular due to their cost-effectiveness and flexibility during emergencies, their insulation properties are limited (R-value= 1.5). For instance, during hot summer days, side curtains can let in a lot of heat, which may require additional ventilations to maintain the right temperature for the birds.

Figure 1.3- Example of curtain sided EC broiler house.

Image credit: https://www.taimeichina.com/pid18255954/Poultry-House-Curtain-Poultry-Side-Curtain.htm

Insulated side wall: Besides that, traditional fiberglass batt (R -Value 3.2) side wall insulation offers cost-effectiveness and fire resistance but may settle over time and is susceptible to moisture damage. Modern Spray Foam (R -Value 7.0) insulation ensures comprehensive coverage and acts as a moisture barrier, especially in its closed-cell variant. However, it can be more expensive and might emit VOCs. Structural Insulated Panels (R -Value 4.0) are pre-fabricated units that speed up construction and reduce thermal bridging, though they can be pricier and challenging to modify post-installation.

Figure 1.4 Fiber glass batt insulation.

Image credit: https://www.silvercote.com/products-and-systems/ag-by-silvercote/ag-for-chickens/

Figure 1.5 Spray foam insulation.

Image credit: https://www.agseal.com/commercial-spray-foam-insulation-products/

Figure 1.6 Structural Insulated Panels (SIPs).
Image credit: https://raycore.com/sips-structural-insulated-panels/

Brick wall : Bricks, including hollow bricks (R-Value 1.1), are a traditional and durable option for side walls. Hollow bricks have empty spaces within them, providing some insulation. While they are not as efficient as modern insulation materials, they offer long-lasting structural integrity. For instance, in areas prone to extreme weather conditions, hollow bricks can withstand the elements and contribute to temperature regulation inside the broiler house.

Figure 1.7 Brick wall EC Broiler House
Image credit: Syarikat Sin Long Heng Breeding farm Sdn.Bhd

2. Optimizing Internal Heat Removal
The EC Broiler house gets heat mainly from two aspects: the heat from outside environment which is about 10% and the chickens themselves produce 90% of the heat inside the house. After stopping as much outside heat as possible, we need to get rid of the heat inside. We can do this with good ventilation, like having enough fans capacity. If we don’t have enough fans, it can get too hot inside, even hotter than outside! This can make the chickens very uncomfortable. Ideally, the back of the house shouldn’t be more than 3°C hotter than the front. If it is, then the fans capacity or number of fans are not enough. Currently, our goal is to achieve a wind speed of 3 m/s inside the chicken house, as this will expedite heat removal and provide a wind chill effect for the chickens. However, will 3 m/s be sufficient in the foreseeable future?

In the Asia-Pacific region, there used to be a preference for smaller chickens, with many weighing under two kilograms. However, there’s a trend towards larger birds, especially in China and India. As countries improve disease control and purchasing power, they’re choosing to raise bigger chickens because it’s more efficient. But with bigger chickens and hotter weather, we might need even higher wind speed in the future .

3. Efficient Cooling of the Inflowing Air
Once the challenges of heat entering the chicken house and the removal of internal heat are tackled, it’s crucial to focus on cooling the incoming air. This task is carried out with the help of cooling pads. The farmer should select a cooling pad size that matches the house’s needs, it ensures a wind speed of the cooling pad is around 1.5 to 1.7 m/s to ensure optimum cooling efficiency which is about 75% to 80%.

For optimal pad cooling, it’s crucial to align the total pad area with the fan capacity. This ensures desired cooling efficiency and prevents exceeding a static pressure of 0.10 inches. A frequent error in cooling pad installations is insufficient pad area, leading to high static pressure and inadequate fan performance and cooling.

The true power of the cooling pad lies in its combined effect with tunnel ventilation. The goal is to reduce the incoming hot air to a point where, combined with the wind-chill from tunnel ventilation, the chicken feels as though they’re experiencing temperatures close to 21°C. For instance, if outside air is 35°C and the cooling pad reduces it by about 6.5°C, and tunnel ventilation provides an “effective temperature” drop of another 5.5°C, the chicken would perceive the temperature to be around 23°C  .

Diving deeper, let’s not forget that all cooling pads aren’t made equal. A cooling pad made of paper might absorb and release moisture differently than one made of plastic. It’s like having two different brands of air conditioners; each might need its own settings to work best. So, for a farmer, understanding the type of cooling pad in use is essential to get the best cooling results and keep the birds comfortable.

Figure 1.8- The mechanism of reducing the air that entering the EC chicken house with evaporative cooling pad

Conclusion
The events of 2023 emphasize the need for advanced designs to face rising global temperatures. By grasping heat dynamics and selecting the right materials, we can ensure the health of larger Broiler populations, especially in fast-changing regions like China and India. Adapting to climate change is crucial for the poultry industry’s sustainability.

References are available on request.

Dr. N.K. Mahajan
Prof. & Head (Retd), Department of Veterinary Public Health & Epidemiology,
Lala Lajpat Rai University of Veterinary & Animal Sciences, Hisar-125004 (Haryana, India)
First Choice Veterinary Diagnostic Lab, Safidon Road, JIND (Haryana)

Various infectious diseases affect broilers at different ages and cause economic losses due to heavy mortality, poor FCR and weight loss. Some of the important viral diseases are discussed here:

1. New Castle Disease
It is one of the most dreaded diseases of poultry as it can cause very heavy mortality at a very high speed. The disease is caused by a virus of paramyxovirus group and classified into many serotypes based on the virulence. Chicken is the natural host, but vast majority of birds are susceptible to infection including ducks and turkey.

Source:https://www.poultryhub.org/

Signs
Depression, prostration, loss of appetite, greenish/yellowish diarrhea, nervous signs like in- coordination, twitching of neck, heavy mortality in acute outbreaks.

Postmortem Lesions
Pin pointed hemorrhages at the tip of proventricular glands, hemorrhagic/ diphtheritic ulcers in the intestine and caecal tonsils.
Diagnosis
Typical postmortem lesions mentioned above are diagnostic.

Laboratory diagnosis:
hemagglutination (HA), hemagglutination Inhibition (HI) and ELISA tests can be employed for confirmation of antibody titers. Polymerase Chain Reaction (PCR) is done for confirmation of the virus.

Treatment and Prevention
Effective vaccines are available for prevention. F/ B1 / clone vaccine is given at the age of 4-5 days followed by LaSota vaccine at 21 days can protect the bird.
If challenge in the area is high, can also inject ND Killed vaccine along with first vaccine at 4/5-day Vaccination can be done if not done earlier at the time of outbreak also. Provide supportive therapy in the form of Cough syrup (@ 10 ml / 100 birds in drinking water – twice a day), Immunomodulators like Vit. E (@ 5 ml/ 100 birds) once a day for 3-4 days.

2. Infectious Bursal Disease
(Gumboro Disease)
Infectious Bursal Disease (IBD) is a highly contagious viral disease of young chicken causing serious economic losses, occurs mainly between 3-5 weeks of age in broilers. The virus targets the Bursa of Fabricius, an important part of immune system making the bird susceptible to other infections. Vaccination failures may happen due to the associated immuno-suppression.

Signs: Dullness, depression, stretch legs backwards, whitish diarrhea and death.

Mortem Lesions: Hemorrhages in the thigh and pectoral muscles, bursa enlarged, edematous and hyperemic with bloody or mucoid contents inside, bursa firm and atrophic in chronic form, kidney may show nephrosis and mottling.

Diagnosis: Bursal lesions are characteristic. Age of the birds affected and hemorrhages on muscles help in diagnosis. Confirmation can be done by PCR.

Prevention
Vaccines are available for prevention which can be done between 11-13 days of age or now such vaccines are available which can be given / injected even on first day at hatchery.

Treatment
Segregate the affected birds, provide electrolytes (@ 1g/ lt of water) and paracetamol. Use Disinfectants like Virkon-S for spray (@4g/ lt of water) and in drinking water (@ 1g / 4lt ),also provide Liver tonic and Immuno-modulators.

3. Avian Influenza
Highly Pathogenic Avian Influenza (HPAI) is a highly lethal systemic disease affecting vast majority of birds caused by the Influenza Type A virus. Because of the zoonotic as well as pandemic potential, the disease gained much public health importance. Water birds and migratory birds act as carriers and spread the infection.
Signs: Sudden, heavy and unusual mortality reaching almost 100% without any clinical signs, edema of face, cyanosis of comb and wattles in less fulminating cases, nervous disorders like tremors, torticollis and opisthotonos.

Post mortem lesions
Extremely variable depending on the severity. Hemorrhagic lesions (petechial to ecchymotic) on all the visceral organs, serous membranes, skin and muscles in acute cases.
Lungs pneumonic, enteritis, air sacculitis, splenomegaly.

Diagnosis
Sudden, heavy, unusual mortality (80-90%) create the suspicion. The disease is to be differentiated from the other fulminating diseases of chicken like Newcastle Disease, IB etc., disease can be confirmed from High Security Animal Disease Laboratory, Bhopal.

Treatment
There is no treatment and birds are to be destroyed and buried as per OIE norms.

4. Infectious Bronchitis
Infectious bronchitis is a disease of chickens only.
Clinical signs: The severity of IB infection is influenced by the age and immune status of the flock, by environmental conditions, and by the presence of other diseases. Labored breathing with some gasping in young chickens. Breathing noises are more noticeable at night.

(Source:https://bitchinchickens.com/)

Diagnosis
Post mortem lesions: Characteristic post mortem lesion is presence of bronchial plug on the bifurcation of bronchioles, heamorrhagic tracheitis and CRD due to complication with Mycoplasma.
Control & Prevention:
There is no specific treatment for infectious bronchitis. Antibiotics for 3-5 days may aid in combating secondary bacterial infections. Raise the room temperature by 5°F for brooding-age chickens until symptoms subside. For Prevention: Establish and enforce a biosecurity program. Vaccines are available which can be carried out in endemic farms on 4-5th day of age by Intra-nasal / Oral route.

5. Avian encephalomyelitis (AE)
It is an infectious viral disease affecting young chickens, quail and turkeys characterized by ataxia and tremors of head and neck.Baby chicks of 1 to 2 weeks age are most severely affected. AE is an egg-borne infection. Adult hens get symptomless infection.

(Source:https://poultrydvm.com/)
Signs: New born chicks show paralysis in the first week after hatching. Progressive ataxia and incoordination, tremors of the head and neck become evident especially after exciting the chicks, mortality rate vary from outbreak to outbreak

Post mortem lesions: No gross lesions are observed. Minute whitish/grayish spots in the muscles of gizzard in a few cases.

Diagnosis/ Prevention
Age of the birds and symptoms are helpful in establishing tentative diagnosis. Screening of breeding stock for infection by carrying out ELISA test for antibody titers and immunization of breeding stock prevent the transmission of virus through eggs.

6. Hydropericardium syndrome (HPS) and Inclusion body hepatitis (IBH):
These two conditions are caused by avian adeno group-1 viruses while fowl adenovirus group-1 serotype 4 is predominantly associated with HPS, most other serotypes cause IBH.

Source: https://www.msdvetmanual.com/

Hydropericardium syndrome is mainly seen in 3-8 week-old broiler chickens and is characterized by sudden death. The most characteristic lesion is hydropericardium. The pericardial sac is filled with a clear or straw coloured fluid. Because of the size of the heart and accumulation of fluid around and the texture, the heart of affected bird appears like litchi fruit and the condition is also referred to as litchi disease which is in fact, a misnomer. The liver may be enlarged and fatty with some hemorrhages. Mortality to the tune of 80% has been recorded.

The liver lesions are prominent in IBH: liver is enlarged and mottled in appearance with necrotic foci. Fatty changes may be seen in liver. Kidneys may be enlarged and filled with urates.

Diagnosis:
The disease can be diagnosed on the basis of clinical findings, postmortem changes primarily in liver, heart and kidneys. Lab confirmation by Serological tests and by virus isolation or PCR for the causative agent.

Prevention and control:
Killed vaccine can be carried out in endemic areas during first week of age along with strict biosecurity measures which can help to prevent the disease.

Treatment:
Provide Aflatoxin free feed, dilute the feed by adding more grains for 4-5 days.
Disinfectants like Safegaurd @ 1 ml / 6 lt of water during the outbreak.
Livertonics and Diuretics in double dose may be helpful.

Conclusion
Preventing important viral diseases in broilers is of utmost importance to maintain the health and productivity of your poultry flock. One crucial aspect of disease prevention is implementing rigorous biosecurity measures. This entails controlling access to your farm, disinfecting equipment and footwear, and carefully monitoring visitor interactions. Additionally, isolating and quarantining new birds before introducing them to the existing flock can prevent the spread of diseases. Furthermore, vaccination plays a pivotal role in disease prevention. Consult with a veterinarian to develop a vaccination schedule tailored to your specific needs and regional disease risks. Regularly clean and disinfect the poultry house, and ensure proper ventilation and temperature control. These proactive measures can significantly reduce the risk of viral diseases among your broiler chickens, ultimately ensuring their well-being and the success of your poultry operation.