Infectious bronchitis (IB) is an immunologically controlled disease affected by the environment. In autumn, large temperature fluctuations and sudden changes in temperature can expose chicks to cold stress, making them susceptible to infection. This can cause economic losses for poultry farmers. Therefore, comprehensive prevention and control of IB in chicks during autumn is particularly important for poultry farmers. Below is a brief introduction to measures for preventing and controlling IB in flocks during the autumn brooding and rearing period.
一、Effects of IB infection during the brooding and rearing period
1, high mortality and culling
The nephropathogenic form of IB mainly affects chicks aged 20–50 days. The younger the age at onset, the higher the mortality rate, which can generally reach 25%. The disease course lasts approximately 3–4 weeks, and affected flocks may show long-term poor growth in the later stages.
2, low egg production rate
Reproductive-type infectious bronchitis can infect chickens throughout their lives. The virus can replicate in the oviducts, causing permanent damage to the oviducts of chicks and pullets. This can result in the “false layer” phenomenon, causing infected chickens to lay few eggs or, in severe cases, none at all.
3, delayed onset
Regardless of whether a flock is infected with the infectious bronchitis virus during the brooding or rearing period, the infection cannot be confirmed until the laying period. As a result, the substantial funds invested earlier do not generate corresponding economic returns, causing significant economic losses.
II. How to prevent infectious bronchitis in flocks during the autumn brooding and rearing period
1, strictly implement downtime management and eliminate pathogens
High-standard, strict downtime management can effectively eliminate infectious bronchitis pathogens and interrupt horizontal transmission between flocks, thereby reducing the pathogen load in the farm area and creating a suitable, healthy growing environment for the flock.
Experience has shown that after poultry houses are swept and washed, spraying or fumigating them with disinfectant can reduce pathogens by more than 90%. To improve disinfection effectiveness and achieve downtime, 2–3 different types of disinfectants should be used alternately during the downtime period. Before each subsequent disinfection step, the floors and items should be allowed to dry.
2, manage immunization precisely to improve antibody levels in the flock
Manage infectious bronchitis immunization properly to produce uniform, effective antibodies in the flock, establish a protective barrier for the flock, and reduce the incidence of infectious bronchitis. Immunization management should cover the following aspects:
（1）Select vaccine strains suitable for the farm and develop a corresponding immunization schedule.
Vaccine strain selection: Select strains suitable for the local area and the farm. The virulence of the strains should progress from mild to strong as the flock ages, and appropriate combinations of strains should be used to produce effective cross-protection.
Immunization age: The earlier, the better. Vaccination is usually administered at 1 days of age so that the vaccine strain can take hold. Live vaccines are used primarily to effectively produce mucosal antibodies and protect the respiratory mucosa, preventing infection of chicks by field strains. During the brooding and rearing period, the recommended ages for live infectious bronchitis vaccine administration are 1, 7, 21, 60, and 100 days of age.
(2) Choose the best immunization method to ensure effectiveness.
Intranasal and eye-drop administration: Provides reliable immunization, causes little immunization stress, and produces high antibody levels. It is generally the preferred method at 1, 7, and 21 days of age.
Spray: Saves labor, but requires healthy flocks and high-quality vaccines. If the flock has respiratory issues or the vaccine quality is poor, it can easily lead to severe secondary respiratory disease and secondary colibacillosis. It is generally used after 1 and 60 days of age.
Drinking water: Not recommended for infectious bronchitis vaccination. Drinking-water vaccination against infectious bronchitis produces few antibodies and cannot provide sustained, effective protection for the respiratory mucosa.
(3) Points to note in on-site vaccination management
Accurate vaccination: Ensure that every chicken is vaccinated during the vaccination process, with none missed. After vaccination, carefully inspect areas such as the floor, manure belts, and manure channels to ensure that no chickens were missed.
Accurate dosage: Before use, calibrate the vaccination bottle dropper to check that the dosage is accurate. Vaccination equipment should be disinfected promptly after use. For example, for eye-drop vaccination, the standard dose per drop is 0.03ml. To calibrate, add 3ml of diluent to the dropper bottle; ideally, the diluent should be used up exactly after 100 drops.
Timing is important. In addition to vaccinating chicks with live vaccines at 1 days of age, vaccination should be scheduled for a period when the flock has no respiratory disease, because vaccination can stimulate the upper respiratory tract mucosa and worsen respiratory disease.
3. Maintain a stable microenvironment inside the poultry house and prevent cold stress.
Cold stress during the autumn chick-rearing and growing period is one of the important factors that can cause infectious bronchitis in a flock. Cold stress should be managed appropriately at each stage:
The physiological regulatory functions of chicks aged 0－3 weeks are not fully developed, so the temperature should be kept suitable and stable. To prevent cold stress caused by excessive temperature fluctuations, the day-to-night temperature difference inside the poultry house should preferably be kept within 2℃. The boiler and heating controls can be adjusted to maintain a suitable, stable temperature in the poultry house.
4–6 weeks is a critical period for the flock to transition off supplemental heat. During this stage, the boiler is gradually taken out of use, and the flock’s own body heat is relied on to maintain the temperature inside the house. At the same time, the flock’s ventilation requirements gradually increase. The temperature and ventilation must be balanced: the temperature should be lowered steadily while meeting the flock’s ventilation requirements. Calculate the minimum ventilation required for the poultry house based on the flock’s needs, then determine the number of fans required using the exhaust capacity of each fan. Next, use a smoke test to determine how far to open the air inlets. Also apply the principle of adjusting temperature based on observing the birds, and regulate the temperature inside the house appropriately so the flock can transition off supplemental heat steadily.
4, Emergency Plan for Temperature Management in Special Weather Conditions
In autumn, temperatures can fluctuate sharply. At this time, three areas of work should be addressed:
（1）Adjust the size of the small windows and the angle of the deflectors, and use a smoke test to verify the direction of airflow. This prevents cold air from outside from blowing directly onto the chickens. Adjust the window openings and deflector angles based on the smoke test results to ensure that cold air entering the upper part of the chicken house is sufficiently preheated before descending, thereby preventing cold stress in the flock.
(2) Use a small-cycle ventilation setting. While maintaining the minimum ventilation rate, change the ventilation cycle setting from a large cycle (one cycle every 5 minutes) to a small cycle (one cycle every 2–3 minutes) to shorten the time cold air enters.
(3) Provide appropriate heating to the poultry house. Based on the flock’s condition and the poultry house temperature, heat the house to ensure the flock is at a suitable temperature.
During the season when infectious bronchitis diseases are prevalent in autumn, high-standard downtime management can reduce the infectious bronchitis pathogen load on the farm. Precise on-site vaccination management helps the flock develop uniform, effective antibodies and improve its resistance. Stable ventilation and temperature inside the poultry house help prevent cold stress and improve the flock’s condition. This helps ensure that chicks and pullets avoid infectious bronchitis virus infection and reach peak egg production smoothly.